ADVANCED RADIO TELECOM CORP
424B1, 1997-02-04
CABLE & OTHER PAY TELEVISION SERVICES
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<PAGE>
PROSPECTUS
                                  $135,000,000
 
                                     [LOGO]
                          135,000 UNITS CONSISTING OF
                             14% SENIOR NOTES DUE 2007
           AND 2,025,000 WARRANTS TO PURCHASE SHARES OF COMMON STOCK
                               ------------------
 
    Advanced Radio Telecom Corp. ("ART" or the "Company") is hereby offering
(the "Offering") 135,000 units (the "Units"), each consisting of $1,000
principal amount of 14% Senior Notes due 2007 (the "Notes") and 15 warrants
(collectively, the "Warrants"), each Warrant representing the right to purchase
1.349 shares of common stock (the "Common Stock") of the Company. The Notes and
the Warrants will not be separable until the earliest of (i) August 15, 1997,
(ii) a Change in Control (as defined) of the Company and (iii) such date as the
Underwriters may, in their discretion, deem appropriate (the "Separation Date").
At the closing of the Offering, the Company will use approximately $51.6 million
of the net proceeds thereof to purchase a portfolio of Pledged Securities (as
defined), initially consisting of U.S. government securities, that will provide
funds sufficient for payment in full of interest on the Notes through February
15, 2000 and that will be pledged as security for repayment of principal of the
Notes. See "Use of Proceeds." The Notes will mature on February 15, 2007.
Interest on the Notes will be payable, at a rate of 14% per annum, semiannually
in arrears on February 15 and August 15 of each year, commencing August 15,
1997. See "Description of Notes." The Notes will be redeemable at the option of
the Company, in whole or in part, at any time on or after February 15, 2002 at
the redemption prices set forth herein, plus accrued and unpaid interest, if
any, to the date of redemption. In addition, in the event that the Company
receives net proceeds from the sale of its Common Stock in one or more Equity
Offerings (as defined) or investments by one or more Strategic Equity Investors
(as defined) on or prior to February 15, 2000 (other than in connection with a
Change in Control of the Company), the Company may, at its option, use all or a
portion of any such net proceeds to redeem up to a maximum of 25% of the
initially outstanding aggregate principal amount of the Notes at a redemption
price equal to 114% of the principal amount thereof, plus accrued and unpaid
interest, if any, to the redemption date; PROVIDED that not less than 75% of the
initially outstanding aggregate principal amount of the Notes remains
outstanding following such redemption. See "Description of Notes -- Redemption
- -- Optional Redemption." Upon the occurrence of a Change in Control, the Company
is obligated to make an offer to purchase all outstanding Notes at a price of
101% of the principal amount thereof, plus accrued and unpaid interest, if any,
to the date of purchase. See "Description of Notes -- Certain Covenants --
Change in Control." There can be no assurance that the Company will have
sufficient funds available at the time of any Change in Control to purchase all
Notes tendered. See "Risk Factors."
 
    The Notes will represent senior obligations of the Company and will be
unsecured, except for the pledge by the Company of the Pledged Securities. The
Notes will rank PARI PASSU in right of payment with all existing and future
unsecured, senior indebtedness of the Company and will rank senior in right of
payment to any future subordinated indebtedness of the Company. At September 30,
1996, on a pro forma basis after giving effect to the Offering, the Common Stock
Offering (as defined) and the application of the net proceeds therefrom, the
aggregate amount of indebtedness of the Company (excluding the Notes) was
approximately $3.1 million, which consisted of the EMI Note (as defined) and the
Equipment Note (as defined), all of which ranked PARI PASSU with the Notes.
However, $1.6 million of such indebtedness constituted secured indebtedness
which will effectively rank senior to the Notes with respect to the assets
securing such indebtedness. Although the Indenture (as defined) will limit the
ability of the Company and its subsidiaries to incur additional indebtedness,
including senior indebtedness, the Indenture will permit the Company to incur a
substantial amount of secured indebtedness, including vendor indebtedness and
indebtedness under the Credit Facility (as defined), which, if incurred, will
effectively rank senior to the Notes with respect to the assets securing such
indebtedness. See "Risk Factors -- Possible Incurrence of Substantial Secured
Indebtedness," "Description of Notes--Ranking" and "Description of Certain
Indebtedness."
 
    Each Warrant will entitle the holder thereof, subject to certain conditions,
to purchase 1.349 shares of Common Stock at an exercise price of $.01 per share,
subject to adjustment under certain circumstances. Upon exercise, the holders of
Warrants will be entitled, in the aggregate, to purchase 2,731,725 shares of
Common Stock, representing 12.0% of the outstanding Common Stock on a
fully-diluted basis on the date hereof, after giving effect to the Offering and
the CommcoCCC Acquisition (as defined). The Warrants will be exercisable at any
time on or after August 15, 1997. Unless earlier exercised, the Warrants will
expire on February 15, 2007. See "Description of Warrants."
 
    There is no existing trading market for the Units, the Notes or the
Warrants, and the Company does not intend to list the Units, the Notes or the
Warrants on any securities exchange or for quotation on the Nasdaq National
Market. The Common Stock is quoted on the Nasdaq National Market under the
symbol "ARTT." On January 31, 1997, the closing price of the Common Stock on the
Nasdaq National Market was $10.75 per share. See "Risk Factors -- Absence of
Public Market; Possible Volatility of Stock Price."
 
    SEE "RISK FACTORS" BEGINNING ON PAGE 13 FOR A DISCUSSION OF CERTAIN FACTORS
WHICH SHOULD BE CONSIDERED BY PROSPECTIVE PURCHASERS OF THE UNITS OFFERED
HEREBY.
                             ---------------------
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
  AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION, NOR HAS
    THE SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES
      COMMISSION PASSED UPON THE ACCURACY OR ADEQUACY OF THIS
       PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL
       OFFENSE.
 
<TABLE>
<CAPTION>
                                                 PRICE TO           UNDERWRITERS'          PROCEEDS TO
                                                PUBLIC(1)            DISCOUNT(2)            COMPANY(3)
<S>                                        <C>                   <C>                   <C>
Per Unit.................................          100%                  3.5%                 96.5%
Total....................................      $135,000,000           $4,725,000           $130,275,000
</TABLE>
 
(1) Plus accrued interest, if any, on the Notes from February 6, 1997.
(2) The Company has agreed to indemnify the Underwriters against certain
    liabilities, including liabilities under the Securities Act of 1933, as
    amended (the "Securities Act"). See "Underwriting."
(3) Before deducting expenses payable by the Company estimated at $1,250,000.
                         ------------------------------
 
    The Units are being offered by the Underwriters, subject to prior sale,
when, as and if delivered to and accepted by the Underwriters, subject to
approval of certain legal matters by counsel for the Underwriters and certain
other conditions. The Underwriters reserve the right to withdraw, cancel or
modify such offer and to reject orders in whole or in part. It is expected that
delivery of the Units will be made in New York, New York on or about February 6,
1997.
                         ------------------------------
MERRILL LYNCH & CO.                             CIBC WOOD GUNDY SECURITIES CORP.
                         ------------------------------
 
                The date of this Prospectus is February 3, 1997.
<PAGE>
                         [INSIDE FRONT COVER GATE FOLD]
 
                     [MAP OF U.S. DISPLAYING ADVANCED RADIO
                     TELECOM CORP.'S 38 GHz SERVICE AREAS.]
<PAGE>
                        [GRAPHIC DISPLAYING 38 GHz LINKS
                        BETWEEN METROPOLITAN FIBER RING,
              OFF-FIBER NET BUILDINGS AND ON-FIBER NET BUILDINGS.]
 
IN CONNECTION WITH THIS OFFERING, THE UNDERWRITERS MAY OVER-ALLOT OR EFFECT
TRANSACTIONS WHICH STABILIZE OR MAINTAIN THE MARKET PRICE OF THE SECURITIES
OFFERED HEREBY AT LEVELS ABOVE THAT WHICH MIGHT OTHERWISE PREVAIL IN THE OPEN
MARKET. SUCH STABILIZING, IF COMMENCED, MAY BE DISCONTINUED AT ANY TIME.
<PAGE>
                               PROSPECTUS SUMMARY
 
    THE FOLLOWING SUMMARY SHOULD BE READ IN CONJUNCTION WITH, AND IS QUALIFIED
IN ITS ENTIRETY BY, THE MORE DETAILED INFORMATION, INCLUDING "RISK FACTORS" AND
THE HISTORICAL AND PRO FORMA FINANCIAL STATEMENTS AND THE NOTES THERETO,
APPEARING ELSEWHERE IN THIS PROSPECTUS. UNLESS OTHERWISE INDICATED, ALL
INFORMATION IN THIS PROSPECTUS GIVES EFFECT TO (I) THE COMPLETION OF THE
ACQUISITION OF TELECOM (AS DEFINED) BY THE MERGER (THE "MERGER") OF A
WHOLLY-OWNED SUBSIDIARY OF ADVANCED RADIO TECHNOLOGIES CORPORATION WITH AND INTO
TELECOM EFFECTED IN OCTOBER 1996, (II) THE CONVERSION (THE "CONVERSION") OF ALL
OUTSTANDING SHARES OF PREFERRED STOCK OF ART INTO SHARES OF COMMON STOCK OF ART
EFFECTED IN NOVEMBER 1996, (III) THE AMENDMENT OF THE COMPANY'S CERTIFICATE OF
INCORPORATION TO CHANGE ITS NAME FROM ADVANCED RADIO TECHNOLOGIES CORPORATION TO
"ADVANCED RADIO TELECOM CORP." ("ART" OR THE "COMPANY"), AND (IV) COMPLETION OF
THE INITIAL PUBLIC OFFERING OF 2,300,500 SHARES OF COMMON STOCK EFFECTED IN
NOVEMBER 1996 (THE "COMMON STOCK OFFERING"). AS USED IN THIS PROSPECTUS, THE
TERMS "ART" OR THE "COMPANY" REFER EITHER TO ART ON A STAND-ALONE BASIS OR ON A
COMBINED BASIS WITH ITS WHOLLY-OWNED SUBSIDIARY, ART LICENSING CORP. ("ART
LICENSING" AND, FORMERLY, TELECOM) AS THE CONTEXT MAY REQUIRE. SEE "THE
COMPANY." SEE "GLOSSARY" FOR THE DEFINITIONS OF CERTAIN TERMS AND ACRONYMS USED
HEREIN.
 
                                  THE COMPANY
 
    Advanced Radio Telecom Corp. ("ART" or the "Company") provides wireless
broadband telecommunications services using point-to-point microwave
transmissions in the 38 GHz band of the radio spectrum. The Company is seeking
to address the growing demand for high speed, high capacity digital
telecommunications services on the part of business and government end users who
require cost effective, high bandwidth local access to voice, video, data and
Internet services. Upon completion of its pending acquisition of 129 38 GHz
wireless broadband authorizations (the "CommcoCCC Assets") from CommcoCCC, Inc.
("CommcoCCC"), the Company will own, manage or have a right to use on a long-
term basis a total of 233 authorizations (which are also referred to herein as
"licenses") granted by the Federal Communications Commission (the "FCC")
covering an aggregate population of approximately 156 million in 169 U.S.
markets. ART's footprint will allow it to provide 38 GHz wireless broadband
services in 47 of the top 50 markets and 82 of the top 100 markets. Presently,
the Company owns, manages or has a right to use on a long-term basis 104
licenses (exclusive of the CommcoCCC Assets) that allow it to provide 38 GHz
wireless broadband services in 81 markets. See "Risk Factors -- Risk of
Non-Consummation of CommcoCCC Acquisition and Other Acquisitions; Commco
Option," "Business -- 38 GHz Wireless Broadband Licenses and Authorizations" and
"-- Agreements Relating to Licenses and Authorizations -- CommcoCCC
Acquisition." During 1996 the Company installed over 370 radio links (single
path point-to-point microwave connections), including approximately 80
revenue-generating radio links installed and operated by the Company and an
additional 99 radio links installed for other carriers.
 
    The ability to access and distribute information quickly has become critical
to business and government users of telecommunications services. The rapid
growth of local area networks ("LANs"), Internet services, video
teleconferencing and other data intensive applications is significantly
increasing the volume of broadband telecommunications traffic. The inability of
the existing infrastructure to meet this demand is creating a "last mile"
bottleneck in the copper wire networks of the incumbent local exchange carriers
("LECs"). This increasing demand, together with changes in the regulatory
environment, is creating an opportunity to offer cost effective, high capacity
last mile access using both wireline and wireless solutions. See "Business --
Telecommunications Industry Overview."
 
ART'S WIRELESS BROADBAND SERVICES
 
    The Company is positioned to solve the need for broadband last mile
services, linking end users to facilities of LECs, competitive access providers
("CAPs"), competitive local exchange carriers ("CLECs"), inter-exchange carriers
("IXCs") and Internet service providers ("ISPs"). The Company is also positioned
to link cell sites of mobile communications service providers and to link
metropolitan area network sites using 38 GHz technology. The Company's wireless
broadband links deliver high
 
                                       3
<PAGE>
quality voice and data transmissions at a level of performance which exceeds the
performance of copper based networks and is a viable alternative to fiber optic
based networks. The Company provides point-to-point wireless digital circuits
ranging in capacity from DS-1 (1.544 megabits per second ("Mbps"), capable of
carrying 24 simultaneous voice conversations) to DS-3 (45 Mbps, capable of
carrying 672 simultaneous voice conversations). The Company believes that it
generally owns or manages sufficient 38 GHz bandwidth to satisfy the anticipated
service requirements of its target customers in each of the Company's existing
markets and the additional 88 markets to be acquired under the CommcoCCC
Agreement (as defined). See "Business -- ART's Wireless Broadband Services."
 
    The Company intends initially to market its services as a carrier's carrier
in order to leverage ART's carrier customers' sales forces, channels of
distribution and customer bases. The Company believes that its services will be
attractive to carrier customers which do not currently have broadband networks
that reach the majority of their customers. For example, the Company has entered
into a strategic distribution agreement (the "Ameritech Strategic Distribution
Agreement") with Ameritech Corp. ("Ameritech") for delivery of the Company's
wireless broadband services throughout Ameritech's midwest operating region and
for certain large customers located outside its region. Ameritech has initiated
the sale of ART's wireless broadband services on a limited basis, and the
Company expects that full-scale rollout will begin in the first quarter of 1997.
See "Business -- Strategic Alliances -- Ameritech Strategic Distribution
Agreement."
 
    The Company believes that a number of factors provide it with certain
significant competitive advantages in offering broadband last mile services,
including:
 
    - The characteristics of 38 GHz technology (high data transfer rates,
      significant channel capacity, rapid deployment, easy installation, very
      high transmission quality and efficient network design) are ideal for the
      provision of last mile services. See "Business -- 38 GHz Technology."
 
    - The Company deploys capital efficiently because of the
      installation-to-meet-demand and redeployable nature of the Company's
      wireless broadband equipment, as compared to the significant upfront cost
      for installation of fiber based networks.
 
    - As one of the first 38 GHz service providers, the Company enjoys a
      time-to-market advantage and is therefore well-positioned to capture a
      large percentage of early adopters, which are generally among the heaviest
      users. The Company believes it is one of only two 38 GHz service providers
      currently offering commercial services.
 
    - The Company is forging strategic alliances with major telecommunications
      carriers, equipment vendors and technology development companies, thus
      gaining access to important channels of distribution and early deployment
      of advanced technologies.
 
    - The broad scope of the Company's footprint enables it to offer wireless
      broadband services targeting much of the United States's addressable
      business market.
 
    - The Company's network management operational support system provides
      24-hour, seven-days-a-week network monitoring and management.
 
    - The Company is developing proprietary Geographic Information Systems
      ("GIS") that provide ART with 3-D digital modeling of all of its markets,
      including all building and landscape features, to reduce the time and
      expense of engineering its proposed radio locations. These systems will
      allow the Company to determine line of site for proposed links, produce a
      list of tenants in the buildings serviceable from such locations and
      integrate this information with its marketing databases.
 
                                       4
<PAGE>
BUSINESS STRATEGY
 
    The Company is seeking to capitalize on its broad footprint of 38 GHz
authorizations to become a leading provider of wireless broadband solutions to a
diverse group of traditional and emerging telecommunications service providers
and end users. See "Business -- Business Strategy." The Company has begun to
implement the following strategic initiatives to achieve this objective:
 
    - CAPITALIZE ON BROAD SPECTRUM POSITION. The Company's spectrum assets
     provide it with the foundation on which to create a large scale commercial
     network of 38 GHz wireless broadband operations. The Company plans to
     continue to build out its infrastructure and to intensify its marketing
     effort in its market areas in order to exploit the value inherent in its
     spectrum assets. See "Business -- Agreements Relating to Licenses and
     Authorizations."
 
    - ESTABLISH AND EXPAND KEY STRATEGIC ALLIANCES. The Company plans to utilize
     strategic alliances to bundle its services with those of its partners, to
     provide for alternative distribution channels and to gain access to
     technological advancements. The Company has established and will seek to
     continue to establish key strategic alliances with major service providers,
     equipment manufacturers and systems integrators. Under the Ameritech
     Strategic Distribution Agreement, Ameritech is targeting certain sales
     objectives and has agreed to spend internally up to $7.0 million on its
     sales and marketing of ART's services. Ameritech owns a 5.0% beneficial
     equity interest in the Company as of January 14, 1997. The Company also has
     agreements with Harris Corporation, Farinon Division ("Harris") for
     marketing ART's 38 GHz services to PCS providers and with GTE Corporation
     for installation, field servicing and network monitoring. See "Business--
     Strategic Alliances."
 
    - MARKET INITIALLY AS A CARRIER'S CARRIER. The Company intends to initially
     market its services as a carrier's carrier in order to leverage ART's
     carrier customers' sales forces, channels of distribution and customer
     bases. The Company's initial target customers include LECs, CAPs/CLECs,
     IXCs, ISPs and mobile communications service providers. The Company
     believes that its services are particularly attractive to carrier customers
     who do not currently have broadband networks capable of reaching the
     majority of their customers.
 
    - PROACTIVELY IDENTIFY OFF-NET MARKET OPPORTUNITIES FOR CARRIER CUSTOMERS.
     ART utilizes its proprietary database tools, such as GIS, to analyze a
     particular carrier's network and identify high density off-net customer
     locations. The GIS database is then used to pre-clear off-net buildings for
     line of site, distance and network design alternatives. After a critical
     mass of sites has been pre-qualified, the Company is able to proactively
     market to the carrier access to such customer premises and pursue a "team
     selling" approach to end users. Utilizing this proactive approach with
     multiple carriers is expected to allow the Company incrementally to build a
     custom-designed wireless hub network in each of its target markets.
 
    - PURSUE OPPORTUNITIES TO PROVIDE VALUE-ADDED SERVICES. The Company will
     also market services such as data, video-conferencing, high resolution
     imaging and video on demand directly to end users in conjunction with
     system integrators, telecommunications equipment manufacturers and other
     service providers. The Company also plans to offer point-to-multipoint
     wireless broadband services and may also decide to offer switched-data
     services to end users who desire a single source telecommunications
     solution.
 
    - MAINTAIN COMPETITIVE ADVANTAGES THROUGH TECHNOLOGY ADVANCEMENTS. As 38 GHz
     microwave radios begin to be produced in large volumes with modern
     manufacturing techniques, the Company believes that the cost of such
     equipment will decline, thereby allowing the Company to meet anticipated
     price competition in its markets. In addition, through the Company's
     internal technology development efforts, as well as on-going participation
     in equipment manufacturers' research and development activities, the
     Company continuously seeks to reduce costs by designing equipment that
     allows it to more efficiently utilize its spectrum. For example, the
     Company anticipates taking delivery of 38 GHz OC-3 radios SONET compatible
     (155 Mbps) within 18-24 months.
 
                                       5
<PAGE>
CUSTOMERS AND APPLICATIONS
 
    The Company began deploying its links principally on a trial basis in
November 1995 and has since been hiring its staff, building its internal
infrastructure and developing its marketing plans and relationships with
potential customers. The Company has generated only nominal revenues from its
operations to date and has recently begun to finalize plans to roll out its
services on a wide-scale basis. Currently, the Company is providing or has
received orders to provide wireless broadband services to LECs, CAPs/ CLECs,
ISPs and mobile communications service providers, and is in the process of
becoming a qualified vendor to all the major IXCs. The Company currently
provides services to carriers such as Ameritech, Bell Atlantic NYNEX Mobile, MFS
Communications Company, Inc./WorldCom, Inc., UUNet, DIGEX, Incorporated,
Electric Lightwave, NEXTLINK Communications LLC, American PCS, L.P., Western
Wireless, Commonwealth Telephone, Public Interest Network, Chadwick Telephone,
CGX Telecom, CAIS, Inc. and Brooks Fiber Properties, Inc., among others. See
"Business--Customers and Applications."
 
38 GHZ TECHNOLOGY
 
    The 38 GHz band provides for the following additional advantages as compared
to other spectrum bands and wireline alternatives:
 
    - HIGH DATA TRANSFER RATES.  The total amount of bandwidth for each 38 GHz
      channel is 100 MHz, which exceeds the bandwidth of any other present
      terrestrial wireless channel allotment and supports full broadband
      capability. For example, one 38 GHz DS-3 link at 45 Mbps today can
      transfer data at a rate which is over 1,300 times the rate of the 33.3
      Kbps dial-up modem, which is the fastest dial-up modem currently in
      widespread commercial use, and over 350 times the rate of the fastest
      integrated services digital network ("ISDN") line currently in use (128
      Kbps). In addition to accommodating standard voice and data requirements,
      45 Mbps data transmission rates allow end users to receive real time, full
      motion video and 3-D graphics at their workstations and to utilize highly
      interactive applications on the Internet and other networks.
 
    - SIGNIFICANT CHANNEL CAPACITY.  Because 38 GHz radio emissions have a
      narrow beam width, a relatively short range and in most instances the
      capability to intersect without creating interference, 38 GHz service
      providers can efficiently reuse their bandwidth within a licensed area,
      thereby increasing the number of customers to which such services can be
      provided. Management believes that by using technology currently employed
      by the Company it can serve virtually all of its addressable service
      market.
 
    - RAPID DEPLOYMENT.  38 GHz technology can be deployed considerably more
      rapidly than wireline and other wireless technologies, generally within 72
      hours after obtaining access to customer premises. In contrast to the
      relative ease of installing a 38 GHz transmission link, extending fiber or
      copper-based networks to reach new customers requires significant time and
      expense. In addition, unlike providers of point-to-point microwave service
      in most other spectrum bands, a 38 GHz license holder can install and
      operate as many transmission links as it can engineer in the licensed area
      without obtaining additional approvals from the FCC. This is a substantial
      advantage over other portions of the microwave radio spectrum that must be
      licensed on a link-by-link basis and that cannot commence service until
      frequency coordination has been completed.
 
    - EASE OF INSTALLATION.  The equipment used for 38 GHz point-to-point
      applications (I.E., antennae, transceivers and digital interface units) is
      smaller, less obtrusive and less expensive than that used for microwave
      equipment applications at other frequencies, making it less susceptible to
      zoning restrictions. In addition, 38 GHz equipment can be easily
      redeployed to meet changing customer requirements.
 
    - VERY HIGH TRANSMISSION QUALITY.  The Company's wireless broadband services
      are engineered to provide 99.999% availability, with better than a 10-13
      (unfaded) bit error rate. This level of availability exceeds the
      performance of copper based networks and is a viable alternative to fiber
 
                                       6
<PAGE>
      based networks. When measured as the total amount of time "out of service"
      over a year, 99.999% availability equates to less than six minutes per
      year of down-time, compared to a range of four hours to 44 hours of
      historical performance of similar copper-based LEC circuits.
 
    - ADDITIONAL ADVANTAGES OVER OTHER PORTIONS OF RADIO SPECTRUM.  At
      frequencies above 38 GHz, point-to-point applications become less
      practical because attenuation increases and the maximum distance between
      transceivers accordingly decreases. Additionally, the FCC has specified
      the use of many portions of the spectrum for applications other than
      point-to-point, such as satellite and wireless cable services, and,
      accordingly, these portions of the radio spectrum often are not available
      for point-to-point applications.
 
RECENT DEVELOPMENTS
 
    There have been a number of recent corporate developments at ART, including:
 
    - AMERITECH ROLLOUT ANNOUNCEMENT.  Ameritech has initiated the sale of ART's
      wireless broadband services on a limited basis, and the Company expects
      that full-scale rollout will begin in the first quarter of 1997. Ameritech
      will rely on ART for the provision of high speed door-to-door connectivity
      of voice, data and video to customers in the Midwest. See
      "Business--Strategic Alliances."
 
    - MASTER SERVICE AGREEMENTS WITH CAPS/CLECS AND ISPS.  In September and
      October 1996, ART entered into various master service agreements with a
      number of CAPs/CLECs and ISPs, including NEXTLINK Communications LLC,
      DIGEX, Incorporated, CAIS, Inc., Microwave Partners d/b/a Astrolink
      Communications, Inc., American PCS, L.P., Message Center Management, Inc.,
      GST Telecom, Inc., and Brooks Fiber Properties, Inc. The Company's master
      service agreements contain the terms by which customers will place future
      orders. The terms which are outlined in these agreements include volume
      discounts, approximate geographic location of links needed and
      representative pricing. Although a master service agreement is not a take
      or pay commitment, it lays the groundwork for future orders by a preferred
      customer and is utilized to facilitate the issuance of purchase orders by
      a customer without any additional negotiations. See "Business--Strategic
      Alliances."
 
    - WORLDCOM AGREEMENT.  In November 1996, ART entered into an agreement with
      WorldCom, Inc. ("WorldCom") to supply trial broadband links to connect
      WorldCom sites in the New York City metropolitan area. Assuming successful
      completion of the trial and evaluation process, the Company anticipates
      that it will be able to enter into broader contractual relationships with
      WorldCom; however, there can be no assurance that the Company will be able
      to do so. WorldCom acquired MFS Communications, Inc. on December 31, 1996.
 
    - TELEPORT CONTRACT.  In October 1996, ART entered into an installation
      services agreement pursuant to which ART acted as a sub-contractor to
      Teleport Communications Group ("TCG" or "Teleport") to provide
      transmission facilities construction services. As of December 31, 1996,
      all of such construction services had been substantially completed. See
      "Business--Strategic Alliances."
 
    - ICG AGREEMENT.   In October 1996, ART entered into a services agreement
      (the "ICG Agreement") with ICG Telecom Group, Inc. and Pacific & Eastern
      Digital Transmission Services, Inc., pursuant to which the Company will
      have an exclusive right, as against third parties, to use for a five-year
      term ten 38 GHz wireless broadband authorizations covering an aggregate
      population of approximately 13 million in or around the California cities
      of Beverly Hills, Los Angeles, Palm Springs, Riverside, Santa Barbara, San
      Bernardino, Santa Monica, San Diego, Santa Ana and Ventura. In addition,
      the services agreement grants to the Company a right of first refusal with
      respect to the purchase of such authorizations, subject to limited
      exceptions. The services agreement may be renewed for successive one-year
      terms totalling five additional years upon expiration of its initial term.
      See "Business--Agreements Relating to Licenses and Authorizations--ICG
      Agreement."
 
                                       7
<PAGE>
                                  THE OFFERING
 
THE UNITS
 
<TABLE>
<S>                                 <C>
Units Offered.....................  135,000 Units, each consisting of $1,000 principal
                                    amount of 14% Senior Notes due 2007 and 15 Warrants,
                                    each Warrant representing the right to purchase 1.349
                                    shares of Common Stock of the Company. The Notes and the
                                    Warrants will not be separable until the earliest of (i)
                                    August 15, 1997, (ii) a Change in Control of the Company
                                    and (iii) such date as the Underwriters may, in their
                                    discretion, deem appropriate (the "Separation Date").
Use of Proceeds...................  To fund capital expenditures, including the purchase of
                                    equipment and the acquisition of certain spectrum
                                    rights, and for general corporate purposes, including
                                    the funding of operating cash flow shortfalls,
                                    technology development and acquisitions of additional
                                    spectrum rights and, potentially, related businesses. At
                                    the closing of the Offering, the Company will use
                                    approximately $51.6 million of the net proceeds to
                                    purchase the Pledged Securities. The amount of the net
                                    proceeds used to purchase Pledged Securities may vary
                                    depending upon the then current interest rates on U.S.
                                    government securities. See "Use of Proceeds" and
                                    "Description of Notes -- Security."
THE NOTES
Notes Offered.....................  $135,000,000 aggregate principal amount of 14% Senior
                                    Notes due 2007.
Maturity Date.....................  February 15, 2007.
Interest Payment Date.............  Cash interest on the Notes will be payable semiannually
                                    in arrears on February 15 and August 15 of each year,
                                    commencing August 15, 1997.
Security..........................  At the closing of the Offering, the Company will use a
                                    portion (approximately $51.6 million) of the net
                                    proceeds thereof to purchase a portfolio of Pledged
                                    Securities that will provide funds sufficient for
                                    payment in full of interest on the Notes through
                                    February 15, 2000 and that will be pledged as security
                                    for repayment of principal of the Notes. Proceeds from
                                    the Pledged Securities will be used by the Company to
                                    make interest payments on the Notes through February 15,
                                    2000. See "Description of Notes -- Security." The
                                    Pledged Securities will be held by the Collateral Agent
                                    under the Pledge Agreement (in each case, as defined)
                                    pending disbursement.
Mandatory Redemption..............  None.
Optional Redemption...............  The Notes will be redeemable at the option of the
                                    Company, in whole or in part, at any time on or after
                                    February 15, 2002 at the redemption prices set forth
                                    herein, plus accrued and unpaid interest thereon, if
                                    any, to the date of redemption. In addition, in the
                                    event that the Company receives net proceeds from the
                                    sale of its Common Stock in one or more Equity Offerings
                                    or investments by one or more Strategic Equity In-
                                    vestors on or prior to February 15, 2000 (other than in
                                    connection with a Change in Control of the Company), the
                                    Company may, at its option, use all or a portion of any
                                    such net proceeds to redeem up to a maximum of 25% of
                                    the initially outstanding aggregate principal amount of
                                    the Notes at a redemption price equal to 114% of the
                                    principal amount thereof, plus accrued and unpaid
                                    interest thereon, if any, to the date of redemption;
</TABLE>
 
                                       8
<PAGE>
<TABLE>
<S>                                 <C>
                                    PROVIDED that not less than 75% of the initially
                                    outstanding aggregate principal amount of the Notes
                                    remains outstanding following such redemption. See
                                    "Description of Notes -- Redemption -- Optional
                                    Redemption."
Change in Control.................  Upon the occurrence of a Change in Control, the Company
                                    is obligated to make an offer to purchase all
                                    outstanding Notes at a price of 101% of the principal
                                    amount thereof, plus accrued and unpaid interest
                                    thereon, if any, to the date of purchase. See
                                    "Description of Notes -- Certain Covenants -- Change in
                                    Control." There can be no assurance that the Company
                                    will have sufficient funds available at the time of any
                                    Change in Control to purchase all Notes tendered. See
                                    "Risk Factors -- Risk of Inability to Satisfy Change in
                                    Control Offer."
Ranking...........................  The Notes will represent senior obligations of the
                                    Company and will be unsecured, except for the pledge by
                                    the Company of the Pledged Securities. The Notes will
                                    rank PARI PASSU in right of payment with all future
                                    unsecured, senior indebtedness of the Company and will
                                    rank senior in right of payment to any future
                                    subordinated indebtedness of the Company. At September
                                    30, 1996, on a pro forma basis after giving effect to
                                    the Offering, the Common Stock Offering and the
                                    application of the net proceeds therefrom, the aggregate
                                    principal amount of indebtedness of the Company
                                    (excluding the Notes) was approximately $3.1 million,
                                    which consisted of the EMI Note and the Equipment Note,
                                    all of which ranked PARI PASSU with the Notes. However,
                                    $1.6 million of such indebtedness constituted secured
                                    indebtedness which will effectively rank senior to the
                                    Notes with respect to the assets securing such indebted-
                                    ness. Although the Indenture will limit the ability of
                                    the Company and its subsidiaries to incur additional
                                    indebtedness, including additional senior indebtedness,
                                    the Indenture will permit the Company to incur a
                                    substantial amount of secured indebtedness, including
                                    vendor indebtedness and indebtedness under the Credit
                                    Facility, which, if incurred, will effectively rank
                                    senior to the Notes with respect to the assets securing
                                    such indebtedness. See "Risk Factors -- Possible
                                    Incurrence of Substantial Secured Indebtedness,"
                                    "Description of Notes" and "Description of Certain
                                    Indebtedness."
Certain Covenants.................  The Indenture will contain certain covenants which,
                                    among other things, will restrict the ability of the
                                    Company and its Restricted Subsidiaries (as defined) to
                                    (i) incur indebtedness, (ii) pay dividends or make
                                    distributions in respect of the Company's capital stock
                                    or make certain other restricted payments, (iii) create
                                    certain liens, (iv) enter into certain transactions with
                                    affiliates or related persons, (v) conduct certain
                                    businesses or (vi) sell certain assets. In addition, the
                                    Indenture will limit the ability of the Company to
                                    consolidate, merge or sell all or substantially all of
                                    its assets. These covenants are subject to important
                                    exceptions and qualifications. See "Description of Notes
                                    -- Certain Covenants."
THE WARRANTS
Warrants..........................  2,025,000 Warrants which, when exercised, would entitle
                                    the holders thereof to purchase, in the aggregate,
                                    2,731,725 shares of Common Stock (the "Warrant Shares"),
                                    representing 12.0% of the outstanding Common Stock on a
                                    fully-diluted basis on the date hereof, after giving
                                    effect to the Offering and the CommcoCCC Acquisition.
</TABLE>
 
                                       9
<PAGE>
<TABLE>
<S>                                 <C>
Registration Rights...............  The Company will be required under the terms of the
                                    agreement pursuant to which the Warrants are issued (the
                                    "Warrant Agreement") to use its best efforts to cause to
                                    become effective under the Securities Act no later than
                                    August 15, 1997 a shelf registration statement (the
                                    "Warrant Shelf Registration Statement") covering the
                                    issuance and resale, to the extent applicable, of the
                                    Warrant Shares upon exercise of the Warrants. Subject to
                                    certain "black-out" periods, the Company will also be
                                    required to use its best efforts to maintain the
                                    effectiveness of the Warrant Shelf Registration
                                    Statement until the expiration or exercise of all
                                    Warrants. See "Description of Warrants -- Registration
                                    of Warrant Shares" and "Risk Factors -- Ability to
                                    Exercise Warrants."
Separation Date...................  The Notes and the Warrants will not be separable until
                                    the earlier of (i) August 15, 1997, (ii) a Change in
                                    Control of the Company and (iii) such date as the
                                    Underwriters may, in their discretion, deem appropriate.
Exercise..........................  Each Warrant will entitle the holder thereof, subject to
                                    certain conditions, to purchase 1.349 shares of Common
                                    Stock at an exercise price of $.01 per share, subject to
                                    adjustment under certain circumstances. The Warrants
                                    will be exercisable at any time on or after August 15,
                                    1997 and prior to the expiration of the Warrants, as set
                                    forth below. The exercise price and number of shares of
                                    Common Stock issuable upon exercise of the Warrants will
                                    be subject to adjustment from time to time upon the
                                    occurrence of certain changes with respect to the Common
                                    Stock, including certain distributions of shares of
                                    Common Stock, issuances of options or convertible
                                    securities, and dividends and distributions. A Warrant
                                    does not entitle the holder thereof to receive any
                                    dividends paid on shares of Common Stock. See
                                    "Description of Warrants."
Expiration........................  February 15, 2007.
</TABLE>
 
    For additional information concerning the Units, the Notes, the Warrants and
the Common Stock, and the definitions of certain capitalized terms used above,
see "Description of Units," "Description of Notes," "Description of Warrants"
and "Description of Capital Stock."
 
                           CIBC FINANCING COMMITMENT
 
    The Company has entered into agreements with certain investors (the "CIBC
Investors") which provide for the issuance of $50.0 million of Senior Secured
Notes due 1998 (the "Senior Secured Notes") at any time, at the Company's
option, until February 10, 1997 (the "CIBC Financing Commitment"). Upon
completion of the Offering, the CIBC Financing Commitment will terminate, and,
accordingly, the Company will not issue the Senior Secured Notes in such event.
See "Description of Certain Indebtedness -- CIBC Financing Commitment."
 
                                  RISK FACTORS
 
    See "Risk Factors" beginning on page 13 for a discussion of certain factors
that should be considered by prospective purchasers of the Units offered hereby.
Certain statements contained in this Prospectus constitute "forward-looking
statements" within the meaning of the Private Securities Litigation Reform Act
of 1995. Such forward-looking statements involve known and unknown risks,
uncertainties and other factors that may cause the actual results, performance
or achievements of the Company, or industry results, to be materially different
from any future results, performance or achievements expressed or implied by
such forward-looking statements. Given these uncertainties, prospective
investors are cautioned not to place undue reliance on such forward-looking
statements. See "Risk Factors" and "Special Note Regarding Forward-Looking
Statements."
 
                                       10
<PAGE>
                SUMMARY HISTORICAL AND PRO FORMA FINANCIAL DATA
 
    The following table presents unaudited summary historical and pro forma
financial data which were derived from, and should be read in conjunction with,
the audited financial statements of the Company and the notes thereto, the
unaudited condensed consolidated financial statements of the Company and the
notes thereto, and the unaudited pro forma condensed consolidated financial
statements of the Company and the notes thereto, included elsewhere in this
Prospectus. The pro forma financial data are not necessarily indicative of what
the actual financial position and results of operations of the Company would
have been as of and for the nine months ended September 30, 1996 and for the
year ended December 31, 1995, nor do they purport to represent the Company's
future financial position and results of operations.
 
<TABLE>
<CAPTION>
                                                          YEAR ENDED DECEMBER 31, 1995    NINE MONTHS ENDED SEPTEMBER 30,
                                                                                                       1996
                                                         -------------------------------  -------------------------------
                                                         HISTORICAL (1)  PRO FORMA (2)    HISTORICAL (1)  PRO FORMA (2)
                                                         -------------  ----------------  -------------  ----------------
<S>                                                      <C>            <C>               <C>            <C>
STATEMENT OF OPERATIONS DATA:
Service revenue........................................   $     5,793     $      5,793     $   125,013     $    125,013
Non-cash compensation expense..........................     1,089,605        1,089,605       7,504,452        7,504,452
Depreciation and amortization..........................        15,684        2,408,559         504,462        2,299,118
Interest and financing expense.........................       131,540       32,658,543       1,396,943       26,577,589
Net loss...............................................     3,234,843       34,633,966      20,378,377       44,713,113
Pro forma net loss per share of Common Stock (3).......   $      0.30     $       1.75     $      2.15     $       2.43
Pro forma weighted average number of shares of Common
 Stock outstanding (3).................................    10,912,338       19,846,172       9,470,545       18,404,379
 
OTHER FINANCIAL DATA:
EBITDA (4).............................................   $(2,007,568)    $ (2,007,568)    $(9,978,993)    $ (9,978,993)
Capital expenditures...................................     3,585,144        3,585,144       7,864,110        7,864,110
</TABLE>
 
<TABLE>
<CAPTION>
                                                                    AS OF
                                                              DECEMBER 31, 1995      AS OF SEPTEMBER 30, 1996
                                                              ------------------  -------------------------------
                                                                HISTORICAL (1)    HISTORICAL (1)  PRO FORMA (2)
                                                              ------------------  -------------  ----------------
<S>                                                           <C>                 <C>            <C>
BALANCE SHEET DATA:
Working capital surplus (deficit)...........................     $ (3,008,510)     $(20,700,673)  $   75,455,289
Property and equipment, net.................................        3,581,561       11,019,217        11,019,217
FCC licenses, net...........................................        4,235,734        4,276,780        99,991,780
Total assets................................................        9,876,559       20,541,997       258,520,252
Short-term debt.............................................               --        9,275,179                --
Long-term debt (including current portion)..................        6,450,000        3,107,422       108,768,695
Total stockholders' equity (deficit)........................         (312,860)      (2,995,212)      116,666,949
</TABLE>
 
- ------------------------------
 
(1) The historical summary financial data of the Company reflects the Merger of
    ART and Telecom, which occurred on October 28, 1996. The Merger was
    accounted for as a reorganization of entities under common control which is
    similar to that of a pooling of interests.
 
(2) The unaudited summary financial data under the caption "Pro Forma" are
    presented as if the following transactions had occurred as of the beginning
    of the respective periods for the Statement of Operations Data and Other
    Financial Data and as of the balance sheet date for the Balance Sheet Data:
    (i) the sale by the Company of 2,300,500 shares of Common Stock offered in
    the Common Stock Offering in November 1996 at a price of $15.00 per share,
    after deducting the underwriting discount and offering expenses; (ii) the
    Conversion in November 1996; (iii) fees and expenses of approximately $6.4
    million related to the CIBC Financing Commitment, including the issuance of
    the First CIBC Warrants (as defined) to purchase 300,258 shares of Common
    Stock, which financing commitment is assumed to be replaced by the issuance
    of the Notes in the Offering; (iv) the receipt of $1.6 million (out of a
    total of $4.0 million) in cash proceeds from the September Bridge Financing
    (as defined) in October 1996; (v) the application of the net proceeds from
    the Common Stock Offering to repay the March Bridge Notes, the CommcoCCC
    Notes and the September Bridge Notes (in each case, as defined), which
    repayment occurred in November 1996, and the November 1996 payment of $3.0
    million of the total $6.0 million consideration to acquire the 50% ownership
    interest of ART West held by Extended (in each case, as defined); (vi) the
    exercise of the Ameritech Warrant (as defined) to purchase an aggregate of
    318,374 shares of Common Stock in December 1996; (vii) the sale by the
    Company of 135,000 Units offered in the Offering assuming $135.0 million of
    gross proceeds, after deducting (a) the estimated underwriting discount and
    offering expenses, (b) the cash used to purchase the Pledged Securities of
    approximately $51.6 million and (c) the value ascribed to the Warrants of
    approximately $29.3 million (the value was based on an assumed value of
    $10.75 per share of Common Stock, an exercise price of $.01 per share and an
    issuance of Warrants to purchase an aggregate of
 
                                       11
<PAGE>
    2,731,725 shares of Common Stock); (viii) the use of $3.0 million of net
    proceeds from the Offering to fund the balance of the ART West purchase
    price; and (ix) the consummation of the acquisition by the Company of the
    CommcoCCC Assets in exchange for 6,000,000 shares of Common Stock at an
    assumed value of $10.75 per share plus related estimated expenses.
 
(3) Pro forma net loss per share is computed based on the loss for the period
    divided by the weighted average number of shares of Common Stock outstanding
    during the period including the issuance of 2,300,500 shares of Common Stock
    issued in the Common Stock Offering, the Conversion, the issuance of
    potentially dilutive instruments issued within one year prior to the Common
    Stock Offering at exercise prices below the initial public offering price of
    $15.00 per share (in measuring the dilutive effect, the treasury stock
    method was used), the issuance of the 318,374 shares of Common Stock to
    Ameritech and the issuance of 6,000,000 shares of Common Stock in connection
    with the CommcoCCC Acquisition.
 
(4) EBITDA represents loss before interest and financing expense (net of
    interest income), income tax expense, depreciation and amortization expense,
    non-cash compensation expense and non-cash market development expense.
    EBITDA is not intended to represent cash flows from operating activities, as
    determined in accordance with generally accepted accounting principles.
    EBITDA should not be considered as an alternative to, or more meaningful
    than, operating income or loss, net income or loss or cash flow as an
    indicator of the Company's performance. EBITDA has been included because the
    Company uses it as one means of analyzing its ability to service its debt,
    because a similar measure will be used in the Indenture with respect to
    computations under certain covenants and because the Company understands
    that it is used by certain investors as one measure of a company's
    historical ability to service its debt. Not all companies calculate EBITDA
    in the same fashion and therefore EBITDA as presented may not be comparable
    to other similarly titled measures of other companies.
 
                                       12
<PAGE>
                                  RISK FACTORS
 
    IN ADDITION TO THE OTHER INFORMATION CONTAINED IN THIS PROSPECTUS, THE
FOLLOWING RISK FACTORS SHOULD BE CONSIDERED CAREFULLY IN EVALUATING AN
INVESTMENT IN THE UNITS OFFERED HEREBY. CERTAIN STATEMENTS CONTAINED IN THIS
PROSPECTUS CONSTITUTE "FORWARD-LOOKING STATEMENTS" WITHIN THE MEANING OF THE
PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995. SUCH FORWARD-LOOKING
STATEMENTS INVOLVE KNOWN AND UNKNOWN RISKS, UNCERTAINTIES AND OTHER FACTORS THAT
MAY CAUSE THE ACTUAL RESULTS, PERFORMANCE OR ACHIEVEMENTS OF THE COMPANY, OR
INDUSTRY RESULTS, TO BE MATERIALLY DIFFERENT FROM ANY FUTURE RESULTS,
PERFORMANCE OR ACHIEVEMENTS EXPRESSED OR IMPLIED BY SUCH FORWARD-LOOKING
STATEMENTS. GIVEN THESE UNCERTAINTIES, PROSPECTIVE INVESTORS ARE CAUTIONED NOT
TO PLACE UNDUE RELIANCE ON SUCH FORWARD-LOOKING STATEMENTS. SEE "SPECIAL NOTE
REGARDING FORWARD-LOOKING STATEMENTS."
 
                         BUSINESS AND REGULATORY RISKS
 
LIMITED OPERATIONS; HISTORY OF NET LOSSES
 
    Although the Company's business commenced in 1993, the Company has generated
only nominal revenues from operations to date. The Company's primary activities
have focused on the acquisition of wireless authorizations, the hiring of
management and other key personnel, the raising of capital, the acquisition of
equipment and the development of operating systems. Prospective investors have
limited operating and financial data about the Company upon which to base an
evaluation of the Company's performance and an investment in the Units offered
hereby. The Company's ability to provide commercial service on a widespread
basis and to generate positive operating cash flow will depend on its ability
to, among other things, (i) deploy its 38 GHz technology on a market-by-market
basis, (ii) attract and retain an adequate customer base, (iii) develop its
operational and support systems and (iv) acquire appropriate sites for its
operations. See "Business -- Business Strategy." Given the Company's limited
operating history, there can be no assurance that it will be able to achieve
these goals, to develop a sufficiently large revenue-generating customer base,
to service its indebtedness or to compete successfully in the telecommunications
industry.
 
    The development of the Company's business and the deployment of its services
and systems will require significant capital expenditures, a substantial portion
of which will need to be incurred before the realization of significant
revenues. Together with the associated start-up operating expenses, these
capital expenditures will result in negative cash flow until an adequate revenue
generating customer base is established. For the year ended December 31, 1995
and the nine-month period ended September 30, 1996, the Company reported net
losses of $3.2 million and $20.4 million, respectively. From inception through
September 30, 1996, the Company reported net losses of $23.7 million. See
"Management's Discussion and Analysis of Financial Condition and Results of
Operations." The Company currently expects capital expenditures of approximately
$35.0 million in 1997 as the development and expansion of its wireless broadband
business continues. The Company expects to generate significant operating and
net losses for at least the next several years. There can be no assurance that
the Company will develop an adequate revenue-generating customer base or will
achieve or sustain profitability in the future.
 
EMERGING MARKET; UNCERTAIN ACCEPTANCE OF 38 GHZ SERVICES
 
    The Company has only recently begun to market its wireless broadband
services to potential customers and has generated only nominal revenues to date.
The provision of wireless broadband services on 38 GHz frequencies represents an
emerging sector of the telecommunications industry, and the demand for such
services is uncertain. Market acceptance may be adversely affected by historical
perceptions of the unreliability and lack of security of previous microwave
technologies using frequencies other than 38 GHz. The Company expects that
substantial marketing effort, time and expense will be required to stimulate
initial demand for the Company's wireless broadband services. See "Business --
38 GHz Technology." There can be no assurance that substantial markets will
develop for 38 GHz wireless broadband services, or, if such markets were to
develop, that the Company would be able to attract and maintain a sufficient
revenue-generating customer base or operate profitably.
 
                                       13
<PAGE>
    The Company's success in providing wireless broadband services is subject to
certain factors beyond the Company's control. These factors include, without
limitation, changes in general and local economic conditions, availability of
equipment, changes in telecommunications service rates charged by other service
providers, changes in the supply and demand for wireless broadband services,
competition from wireline and wireless operators in the same market area,
changes in the federal and state regulatory schemes affecting the operation of
wireless broadband systems (including the enactment of new statutes and the
promulgation of changes in the interpretation or enforcement of existing or new
rules and regulations) and changes in technology that have the potential of
rendering obsolete the Company's wireless broadband equipment. In addition, the
extent of the potential demand for wireless broadband services in the Company's
market areas cannot be estimated with certainty. There can be no assurance that
one or more of these factors will not have an adverse effect on the Company's
financial condition and results of operations.
 
RISK OF NON-CONSUMMATION OF COMMCOCCC ACQUISITION AND OTHER ACQUISITIONS; COMMCO
OPTION
 
    On July 3, 1996, the Company entered into an agreement (as amended, the
"CommcoCCC Agreement") to acquire the CommcoCCC Assets from CommcoCCC (the
"CommcoCCC Acquisition") in exchange for 6,000,000 shares of Common Stock. See
"Business -- Agreements Relating to Licenses and Authorizations -- CommcoCCC
Acquisition." The CommcoCCC Acquisition is subject to various conditions
including receipt of FCC and other approvals (including approval under the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, if required), receipt by
CommcoCCC of an opinion as to the tax-free nature of the transaction, minimum
population coverage requirements for the authorizations of ART and CommcoCCC,
accuracy of representations and warranties except for breaches that do not have
in the aggregate a material adverse effect, no pending or threatened material
litigation and other customary closing conditions. On January 27, 1997, the FCC
granted its consent to the CommoCCC Acquisition, but periods for judicial and
administrative review have not expired. There can be no assurance that all such
conditions will be satisfied. After consummation of the CommcoCCC Acquisition, a
stockholder of CommoCCC may have the right, subject to certain conditions, to
acquire up to 12 authorizations from the Company pursuant to the Commco Option
(as defined). Exercise of the Commco Option would reduce the number of
authorizations owned by the Company and might adversely affect development of
the Company's business. See "Business -- Agreements Relating to Licenses and
Authorizations -- CommcoCCC Acquisition." In order to satisfy the minimum
population coverage requirements, the Company will be obliged to complete the
acquisitions of certain spectrum rights from ART West and TeleCom One (as
defined), or, in the event it cannot complete one or more of such acquisitions,
to acquire, manage or obtain the right to use on a long-term basis other
spectrum rights; however there can be no assurance that the Company will be able
to do so. The Company's acquisition agreements with ART West and TeleCom One are
also subject to various conditions and consequently there can be no assurance
that all such conditions can be satisfied. See "Business--Agreements Relating to
Licenses and Authorizations."
 
    If the Company were unable to complete the CommcoCCC Acquisition for any
reason, the Company's footprint could be considerably smaller than planned, and
the expected development of the Company's business could be materially adversely
affected.
 
COMPETITION
 
    The telecommunications services industry is highly competitive. The Company
has only recently begun to market its wireless broadband services to potential
customers and is currently providing services on a limited basis. In each market
area in which the Company is authorized to provide services, the Company
competes or will compete with several other service providers and technologies.
The Company expects to compete primarily on the basis of wireless broadband
service features, quality, price, reliability, customer service and rapid
response to customer needs. The Company faces significant competition from other
38 GHz providers and incumbent LECs, such as the Regional Bell Operating
Companies ("RBOCs"). The Company may also compete with CAPs/CLECs, other
wireless service
 
                                       14
<PAGE>
providers, cable television operators, electric utilities, LECs operating
outside their current local service areas and IXCs. There can be no assurance
that the Company will be able to compete effectively in any of its market areas.
See "Business -- Competition."
 
    COMPETITION FROM 38 GHZ SERVICE PROVIDERS.  The Company faces competition
from other 38 GHz service providers, such as WinStar Communications, Inc.
("WinStar") and BizTel Communications, Inc. ("BizTel," which is an affiliate of
TCG), within its market areas. In many cases, one or both of these service
providers hold licenses to operate in other portions of the 38 GHz band in
geographic areas which encompass or overlap the Company's market areas. In
certain of the Company's market areas, other 38 GHz service providers may have a
longer history of operations, a larger geographic footprint or substantially
greater financial resources than the Company. WinStar commenced its 38 GHz
operations approximately one year prior to the Company, has raised significant
capital and has the competitive advantages inherent in being the first to market
38 GHz services. In addition to WinStar and BizTel, several dozen smaller
entities have been granted 38 GHz authorizations in geographic regions in which
the Company plans to operate. In January 1997, WinStar acquired the 38 GHz
licenses of one such entity, Milliwave L.P. ("Milliwave"). Due to the relative
ease and speed of deployment of 38 GHz technology, the Company could face
intense price competition and competition for customers from other 38 GHz
service providers.
 
    The Company also faces potential competition from new entrants to the 38 GHz
market, including LECs and other leading telecommunications companies. The NPRM
(as defined) contemplates an auction of certain spectrum assets, including the
lower fourteen proposed 100 MHz channels (which are similar to those used by the
Company) and four proposed 50 MHz channels in the 38 GHz spectrum band, which
have not been previously available for commercial use. See "-- Government
Regulation." On December 31, 1996, the FCC announced that it had adopted an
order that partially lifted the freeze on the processing of new applications,
which should result in the grant of additional authorizations to other 38 GHz
applicants. The grant of additional authorizations by the FCC in the 38 GHz
band, or other portions of the spectrum with similar characteristics, could
result in increased competition and diminish the value of the Company's existing
38 GHz authorizations. The Company believes that, assuming that additional
channels are made available as proposed by the NPRM, additional entities having
greater resources than the Company could acquire authorizations to provide 38
GHz services. See "Business -- Government Regulation -- Federal Regulation --
FCC Rulemaking."
 
    OTHER WIRELESS COMPETITORS.  The Company may also face competition from
other terrestrial wireless services, including 2 GHz and 28 GHz "wireless cable"
systems (MMDS and LMDS), 18 GHz point-to-point microwave services (DEMS), FCC
Part 15 wireless radio devices, and other services that use existing
point-to-point microwave channels on other frequencies. Motorola Satellite
Systems, Inc. has filed an application with the FCC for a global network of
satellites in the 37.5-40.5 GHz band and the 47.2-50.2 GHz band, which is
proposed to be used for broadband voice and data services. Other companies have
filed applications for global broadband satellite systems in the 28 GHz band. If
developed, these systems could also present significant competition to the
Company.
 
    The FCC is planning to hold an auction for 28 GHz spectrum in all markets
for the provision of high capacity wireless cable systems. These auctions are
expected to take place in 1997. The 2 GHz wireless cable spectrum may also
provide competition for metropolitan wireless broadband services. At present,
wireless cable licenses are used primarily (if not exclusively) for the
distribution of video programming, and have only a limited capability to provide
two-way communications needed for wireless broadband telecommunications
services, but there can be no assurance that this will continue to be the case.
 
    According to press reports and FCC records, Associated Communications Group,
affiliates and joint venture partners (collectively, "ACG") hold licenses in the
18 GHz band in 31 markets. Press reports indicate that ACG plans to use fixed
wireless service to provide voice, data, Internet and videoconferencing
services.
 
                                       15
<PAGE>
    The FCC has allocated a number of spectrum blocks for use by wireless
devices that do not require site or network licensing. A number of vendors have
developed such devices that may provide competition to the Company for certain
low data-rate transmission services.
 
    In January 1997, the FCC allocated 300 MHz of spectrum in the 5 GHz band for
unlicensed devices to provide short-range, high-speed wireless digital
communications. These frequencies must be shared with incumbent users without
causing interference. Although the allocation is designed to facilitate the
creation of new wireless local area networks (and thus might not be competitive
to the Company's services), it is too early to predict what kind of equipment
might ultimately be manufactured and for what purposes it might be utilized.
 
    COMPETITION FROM INCUMBENT LECS.  The Company also faces significant
competition from incumbent LECs, irrespective of whether they provide 38 GHz
services. Incumbent LECs have long-standing relationships with their customers,
generally own significant PCS or cellular assets, have the potential to
subsidize competitive services with revenues from a variety of businesses and
benefit from favorable federal and state policies and regulations. Regulatory
decisions and recent legislation, such as the Telecommunications Act of 1996
(the "Telecommunications Act"), have partially deregulated the
telecommunications industry and reduced barriers to entry into new segments of
the industry. In particular, the Telecommunications Act, among other things, (i)
enhances local exchange competition by preempting laws prohibiting competition
in the local exchange market, by requiring LECs to provide fair and equal
standards for interconnection and by requiring incumbent LECs to provide
unbundling of services and (ii) permits an RBOC to compete in the inter-LATA
long distance service market once certain competitive characteristics emerge in
such RBOC's service area. The Company believes that this trend towards greater
competition will continue to provide opportunities for broader entrance into the
local exchange markets. However, as LECs face increased competition, regulatory
decisions are likely to provide them with increased pricing flexibility, which
in turn may result in increased price competition. There can be no assurance
that such increased price competition will not have a material adverse effect on
the Company's results of operations.
 
    A number of companies are developing enhancements to increase the
performance of LECs' legacy copper networks. These generally come under the
description of digital subscriber line products, such as ADSL (asymmetrical
digital subscriber line), HDSL (high-speed digital subscriber line) and VDSL
(video digital subscriber line). There can be no assurance that the Company will
be able to compete effectively with these enhancements.
 
    OTHER COMPETITORS.  The Company may compete with CAPs/CLECs for the
provision of last mile access and additional services in most of its market
areas. However, the Company believes that many CAPs/CLECs may utilize 38 GHz
transmission links primarily to augment their own service offerings to IXCs and
end users, and that the Company is well positioned to provide such 38 GHz
services to CAPs/ CLECs. However, there can be no assurance that CAPs/CLECs will
utilize the Company's 38 GHz services or that CAPs/CLECs will not seek to
acquire their own 38 GHz licenses or use the 38 GHz licenses of other licensees.
Furthermore, the ability of CAPs/CLECs to compete in the local exchange market
is limited by lack of parity with LECs in number portability, dialing parity and
interconnection. The Telecommunications Act requires the FCC and the states to
implement regulations that place CAPs/ CLECs on a more equal competitive footing
with LECs. To the extent these changes are implemented, CAPs/CLECs may be able
to compete more effectively with LECs. However, there can be no assurance that
CAPs/CLECs or 38 GHz service providers, such as the Company, will be able to
compete effectively for the provision of last mile access and other services.
 
    The Company may also face competition from cable television operators
deploying cable modems, which provide high speed data capability over installed
coaxial cable television networks. Although cable modems are not widely
available currently, the Company believes that the cable industry may support
the deployment of cable modems to residential cable customers through methods
such as price subsidies. Notwithstanding the cable industry's interest in rapid
deployment of cable modems, the Company
 
                                       16
<PAGE>
believes that in order to provide broadband capacity to a significant number of
business and government users cable operators will be required to spend
significant time and capital in order to upgrade their existing networks to the
next generation of hybrid fiber coaxial network architecture. However, there can
be no assurance that cable television operators will not emerge as a source of
competition to the Company.
 
    The Company may also face competition from electric utilities, LECs
operating outside their current local service areas, IXCs and other providers.
These entities provide transmission services using technologies which may enjoy
a greater degree of market acceptance than 38 GHz wireless broadband technology
in the provision of last mile broadband services. In addition, the Company may
face competition from new market entrants using wireless, fiber optic and
enhanced copper based networks to provide local service.
 
    Many of the Company's competitors have long-standing relationships with
customers and suppliers, greater name recognition and greater financial,
technical and marketing resources than the Company. As a result, these
competitors may be able to more quickly develop and exploit new or emerging
technologies, adapt to changes in customer requirements or devote greater
resources to the marketing of their services than the Company. The consolidation
of telecommunications companies and the formation of strategic alliances and
cooperative relationships in the telecommunications and related industry, as
well as the development of new technologies, could give rise to significant new
competitors to the Company. In such case, there can be no assurance as to the
degree to which the Company will be able to compete effectively.
 
GOVERNMENT REGULATION
 
    The telecommunications services offered by the Company are subject to
regulation by federal, state and local government agencies. At the federal
level, the FCC has jurisdiction over the use of the electromagnetic spectrum
(I.E., wireless services) and has exclusive jurisdiction over all interstate
telecommunications services, that is, those that originate in one state and
terminate in another state. State regulatory commissions have jurisdiction over
intrastate communications, that is, those that originate and terminate in the
same state. Municipalities may regulate limited aspects of the Company's
business by, for example, imposing zoning requirements and requiring
installation permits. See "Business -- Government Regulation."
 
    The Company is licensed by the FCC as a common carrier provider of
facilities-based local telecommunications services. For many of its intrastate
services, the Company will need to seek authorizations from the states and, in
most cases, file tariffs. The Company is in the process of filing tariffs for
some of its services with the FCC and with certain state authorities on an
ongoing basis. Certain of its proposed services have not yet been permitted in
most states. Although the Telecommunications Act requires the states to open up
all of the Company's services to competition, there can be no assurance that
this will occur on a timely basis. Challenges to its applications for
authorizations or its tariffs by third parties could cause the Company to incur
substantial legal and administrative expenses and time delay in implementing its
business plan. Although many of the Company's applications for FCC
authorizations were subject to challenge, the Company nonetheless was granted
authorizations for a majority of its applications. The Company's remaining
applications were either dismissed, voluntarily or involuntarily, or are
currently pending before the FCC.
 
    Twenty of the Company's applications were dismissed by the FCC because they
overlapped either with authorizations granted to third parties or with third
party applications that held superior rights by virtue of the timing of their
filing. Five of the Company's applications were dismissed voluntarily by the
Company because they could not be granted under FCC policies. In one instance,
the geographic area sought was larger than that permitted by the FCC's September
1994 Policy Statement. In the other four instances, the dismissed applications
overlapped with each other and thus could not be granted under then-existing FCC
policies. None of the dismissals will impact the financial condition or
operations of the Company because they have not been included in the Company's
business plan. Some of the pending applications propose use of the same channel
in part of the same geographic area as one or
 
                                       17
<PAGE>
more applications filed by third parties and therefore could not be granted
under the FCC rules generally prohibiting the grant of mutually-exclusive
applications. All of the pending applications are subject to the freeze on the
grant of additional authorizations pending completion of the NPRM, which
proposes dismissal of all such applications. The Company's business plans do not
assume that any of these pending applications will be granted. The Company does
not believe that a failure to grant these applications will impair its ability
to operate. See "Business -- Government Regulation."
 
    In its provision of local wireless broadband services, the Company currently
is not subject to rate regulation by the FCC, but is subject to regulation by
most states. Additionally, the Company is required to comply with all applicable
local zoning and other laws governing the installation and operation of its
wireless broadband networks.
 
    Changes in existing laws and regulations, including those relating to the
provision of wireless local telecommunications services via 38 GHz licenses, or
any failure or significant delay in obtaining necessary regulatory approvals,
could have a material adverse effect on the Company. On November 13, 1995, the
FCC released an order barring the acceptance of new applications for 38 GHz
authorizations. On December 15, 1995, the FCC announced the issuance of a notice
of proposed rulemaking (the "NPRM"), pursuant to which it proposed to amend its
current rules to provide for, among other things, (i) the adoption of an auction
procedure for the issuance of authorizations in the 38 GHz band, including a
possible auction of the lower fourteen proposed 100 MHz channels (which are
similar to those used by the Company) and the lower four proposed 50 MHz
channels in the 38 GHz band that have not been previously available for
commercial use and the possible auction of the unlicensed areas in the upper
fourteen 100 MHz channels, (ii) licensing frequencies using predefined
geographic service areas ("Basic Trading Areas"), (iii) the imposition of
substantially stricter construction requirements for authorizations that are not
received pursuant to auctions as a condition to the retention of such
authorizations and (iv) the implementation of certain technical rules designed
to avoid radio frequency interference among licensees. In addition, the FCC
ordered that those applications subject to mutual exclusivity with other
applicants or placed on public notice by the FCC after September 13, 1995 would
be held in abeyance pending the outcome of the NPRM and might then be dismissed
(the "freeze"). On December 31, 1996, the FCC announced that it had adopted an
order that partially lifted the freeze on the processing of pending
applications. Among other actions, the order provides that the FCC will process
certain amendments filed before December 15, 1995 that have the effect of
eliminating mutual exclusivity among pending applications, which is likely to
result in the grant of additional authorizations to 38 GHz applicants other than
the Company.  Final rules issued in connection with the NPRM may require that 38
GHz service providers share the 38 GHz band with satellite services. Motorola
Satellite Systems, Inc. ("Motorola Satellite") has filed an application with the
FCC with respect to a global network of satellites to be used to provide
broadband voice and data services. See "-- Other Wireless Competitors." Motorola
Satellite proposes to use 38 GHz frequencies for transmissions from space to
earth. If permitted by the FCC, satellite transmissions in the 38 GHz
frequencies could adversely effect the Company's existing operations or its
future expansions by creating interference or by causing the FCC to impose power
and other limitations upon the Company's transmissions. The Motorola Satellite
application would require the FCC to change certain rules in order to be
granted, and the Company expects that a number of years would elapse before any
such system would be launched. The extent of the adverse impact upon the
Company's operations if the Motorola Satellite application were to be granted in
its current form is unknown. However, there can be no assurance that the
Company's operations would not be adversely affected.
 
    There can also be no assurance that the final rules (if any) issued in
connection with the NPRM will resemble the rules proposed in the NPRM, and there
can also be no assurance that any proposed or final rules will not have a
material adverse effect on the Company. Statutes and regulations which may
become applicable to the Company as it expands could require the Company to
alter methods of operations at costs which could be substantial or otherwise
limit the types of services offered by the Company.
 
                                       18
<PAGE>
    The Company manages the systems of ART West, DCT (as defined), TeleCom One
and CommcoCCC (during the pendency of certain acquisitions) pursuant to
management agreements. In addition, the Company recently entered into the ICG
Agreement and a services agreement with Microwave Partners. See "Business --
Agreements Relating to Licenses and Authorizations." The Company believes that
the provisions of these management and lease agreements comply with the FCC's
policies concerning licensee control of FCC-licensed facilities. Because the 38
GHz service is a new service, however, there is no FCC precedent addressing the
limits of such management arrangements for this service. No assurance can be
given that the management arrangements or proposed acquisitions will, if
challenged, be found to satisfy the FCC's policies or what modifications, if
any, may need to be made to satisfy those policies. If the FCC were to void or
require modifications of the management arrangements, the operations of the
Company could be adversely affected.
 
RISK OF FORFEITURE, NON-RENEWAL AND FLUCTUATION IN VALUE OF FCC LICENSES
 
    Upon completion of the CommcoCCC Acquisition, the Company will own, manage
or have a right to use on a long-term basis a total of 233 licenses that will
allow it to provide 38 GHz wireless broadband services in 169 U.S. markets. The
Company currently owns, manages or has a right to use on a long-term basis 104
licenses (exclusive of the CommcoCCC Assets) that allow it to provide 38 GHz
wireless broadband services in 81 markets, 73 of which are owned by the Company,
19 of which are managed by the Company through the Company's interests in or
arrangements with other companies, and 12 of which the Company has the right to
use on a long-term basis. Under the current FCC rules, the recipient of a
license for 38 GHz microwave facilities is required to construct facilities to
place the station "in operation" within 18 months of the date of grant of the
authorization. Although under current FCC regulations the term "in operation" is
not defined beyond the requirement that the station be capable of providing
service, the industry custom is to establish at least one link between two
transceivers in each market area for which an authorization is held. In the
event that the recipient fails to comply with this construction deadline, the
license is subject to forfeiture, absent an extension of the deadline. All of
the 104 licenses that the Company owns, manages or has a right to use on a
long-term basis (exclusive of the CommcoCCC Assets) have met the FCC's
construction deadline. Under the terms of the CommcoCCC authorizations and the
Company's management agreement with CommcoCCC, the Company has met the
construction deadline for 76 licenses and must meet the construction deadline
for the remaining 53 licenses between mid-April and mid-August 1997. The Company
believes that, in light of current FCC practice, extensions of construction
periods are highly unlikely. Although the Company believes that it can meet the
construction deadline for all of the CommcoCCC licenses within applicable time
limits, there can be no assurance that it will be able to do so or that the
Company will be able to comply with whatever more stringent construction
requirements the FCC ultimately adopts as a result of the NPRM. As a result,
some of the Company's licenses could be subject to forfeiture, which could have
a material adverse effect on the Company's development and results of
operations. In addition, pursuant to rules that became effective August 1, 1996,
if a station does not transmit operational traffic (not test or maintenance
signals) for a consecutive period of twelve months at any time after
construction is complete, or if removal of equipment or facilities renders the
station incapable of providing service, the license is subject to forefeiture,
absent a waiver of the FCC's rules. Although this rule has not been interpreted
by the FCC, it is possible that it could be applied in such a way that could
cause one or more of the Company's licenses to be subject to forfeiture. See
"Business -- Government Regulation" and "-- 38 GHz Wireless Broadband Licenses
and Authorizations."
 
    The FCC's current policy aligns the expiration dates of all 38 GHz licenses
so that all licenses expire concurrently. Licenses can be renewed for a period
not to exceed ten years. All of the 38 GHz licenses owned or to be acquired by
the Company will expire in February 2001. Although the Company currently
anticipates that its licenses will be renewed based upon the FCC's custom and
practice in connection with other services which have established a presumption
in favor of licensees that have complied with regulatory obligations during the
initial license period, there can be no assurance that all
 
                                       19
<PAGE>
or any of the licenses will be renewed upon expiration of their initial terms.
In the event that the FCC does not renew one or more of the licenses, the
Company's business and results of operations could be materially adversely
affected.
 
    The Company plans to use its licenses to develop wireless broadband systems
in all of its market areas. In addition, a limited secondary market exists for
38 GHz licenses, and the Company may from time to time purchase such licenses.
The value of licenses held or acquired hereafter by the Company will depend upon
the success of the Company's wireless broadband operations, fluctuations in the
level of supply and demand for such licenses and the telecommunications
industry's response to the availability and efficacy of wireless broadband
systems. In addition, federal and state regulations limit the ability of
licensees to sell their licenses. Assignments of licenses and changes of control
involving entities holding licenses require prior FCC and, in some instances,
state regulatory approval and are subject to restrictions and limitations on the
identity and status of the assignee or successor. These regulatory restrictions
on transfer of licenses may adversely affect the value of the Company's
licenses.
 
POTENTIAL RIGHTS TO FOREIGN LICENSES
 
    Entities in which the Company has a substantial interest have applied or
intend to apply for licenses to provide wireless broadband services in Canada
and in various Western European countries. Although the Company currently
expects that, if licenses are obtained, these entities will be financed on a
stand-alone basis without recourse to the Company, there can be no assurance
that such entities will have access to financing on acceptable terms or at all.
See "Business -- Foreign Markets."
 
    In October 1996, ART entered into a binding letter of intent with Advantage
Telecom, Inc. ("ATI"), a Canadian company which has applied for licenses to
provide 38 GHz service in the 66 major markets in Canada covering a population
of at least 21 million people. Upon consummation of the transactions described
in the letter of intent, ART will hold a substantial direct and indirect
minority interest in ATI and will be a party to a services agreement with ATI
pursuant to which ART will construct and operate radio systems based upon any
licenses that may be granted to ATI and subject to control by ATI. The Company
incurred costs of approximately $300,000, and ATI is responsible for securing
any additional funding necessary to construct the radio systems. Due to current
uncertainty in Canada's licensing policy, there can be no assurance that ATI
will be granted these licenses or that, if licenses are granted, ATI will obtain
the funding necessary to construct the radio systems.
 
    On September 29, 1996 the Company entered into a shareholders agreement with
Trond Johannessen, pursuant to which the Company anticipates eventually
obtaining licenses and offering its wireless broadband services through separate
subsidiaries in the 17 countries comprising the European Union. The Company has
caused or will cause to be formed subsidiaries in Sweden, the United Kingdom and
Italy for this purpose. Under the shareholders agreement, in consideration for
services to be rendered and his proportionate share of the formation costs, Mr.
Johannessen is entitled to receive a 20% interest in the initial shareholdings
in certain of the subsidiaries in each country, prior to significant funding of
each subsidiary. The Company has no further commitment to fund any such
subsidiary. Mr. Johannessen is also a consultant to the Company, for which he
receives monthly payments of $10,000 plus expenses. The Company is seeking but
has not yet received any operating licenses, strategic alliances or customer
commitments in Europe. Although each member nation of the European Economic
Community is required pursuant to a directive of the European Commission to open
its telecommunication markets to competition over the next several years, the
timing and extent of a relaxation in entry barriers and the degree of
cooperation from the incumbent service providers in such areas as
interconnection to customers and the public networks is unknown. There can be no
assurance that the Company, through such subsidiaries, will be able to acquire
the licenses necessary in each European country, to finance and or implement its
business plan or to operate in any country on a profitable basis.
 
                                       20
<PAGE>
MANAGEMENT OF GROWTH
 
    The Company is currently experiencing a period of rapid growth and is
pursuing a business plan that, if successfully implemented, will result in
expansion of its operations and the provision of 38 GHz services on a widespread
basis over the next two to five years. The Company's success will depend on its
ability to manage growth effectively, to enhance its operational and financial
control and information systems and to attract, assimilate and retain additional
qualified personnel. Failure by the Company to meet the demands of customers and
to manage the expansion of its business and operations could have a material
adverse effect on the Company's development and results of operations.
 
LINE OF SIGHT; ROOF RIGHTS; OTHER LIMITATIONS
 
    Wireless broadband services over 38 GHz frequencies require a direct line of
sight between two transceivers comprising a link and are subject to distance and
rain attenuation. The maximum length of a single link is generally limited to
three to five miles, and, as a result, intermediate links (or "repeaters") are
required to permit wireless broadband transmission to extend beyond this limit.
In the absence of a direct line of sight, repeaters may be required to
circumvent obstacles, such as buildings in urban areas or hills in rural areas.
In addition, in areas of heavy rainfall, the intensity of rainfall and the size
of raindrops can affect the transmission quality of 38 GHz services.
Transmission links in these areas are engineered for shorter distances and
greater power to maintain transmission quality. The use of intermediate links to
overcome obstructions or rain fade increases the cost of service. While these
increased costs may not be significant in all cases, such costs may render
wireless broadband services uneconomical in certain circumstances.
 
    Due to line of sight limitations, the Company currently installs its
transceivers and antennas on the rooftops of buildings and on other tall
structures. Line of sight and distance limitations generally do not present
problems in urban areas due to the ability of the licensee to select
unobstructed structures from which to transmit and the concentration of
customers within a limited area although the Company may have to install
intermediate links. Line of sight and distance limitations in non-urban areas
can arise due to lack of structures with sufficient height to clear local
obstructions. The Company has generally been able to construct intermediary
repeater links and other solutions to reduce line of sight and distance
limitations in urban and non-urban areas; however, in a minority of instances
the Company has encountered line of sight and distance limitations that could
not be solved economically. In such instances, sales to certain potential
customers have been or in the future may be adversely affected, and, in some
cases, the Company may determine to provide certain services on terms that are
uneconomical in the near term as a result of these limitations. While the effect
on the financial condition and results of operations of the Company resulting
from such cases has been minimal to date, there can be no assurance that such
limitations will not have a material adverse effect on the Company's future
development and results of operations.
 
    In order to obtain the necessary access to install its transceivers and
antennas, the Company generally must secure roof rights from the owners of each
building or other structure on which its equipment is installed. Failure to
obtain roof rights in a timely fashion may cause potential customers to use
alternative providers of 38 GHz services or to refrain from using 38 GHz
services altogether. There can be no assurance that the Company will succeed in
obtaining the roof rights necessary to establish wireless broadband services to
all potential customers in its market areas on favorable terms, if at all, or
that delays in obtaining such rights will not have a material adverse effect on
the Company's development and results of operations.
 
    The relative significance of the size of a market area served depends on the
concentration within that area of potential customers. The Company's market
areas were defined by the Company in preparing its FCC applications for 38 GHz
licenses. The definitions of these areas were based on the Company's analysis of
the then existing local demographic characteristics in each market, such as
concentrations of employees and income levels. In certain of the Company's
market areas, other 38 GHz service providers have larger geographic footprints
or greater bandwidth. To the extent that the
 
                                       21
<PAGE>
Company's authorizations do not track the appropriate growth and development
patterns of potential customers within its market areas or that other 38 GHz
providers have greater geographic coverage or more bandwidth, the Company may
have a competitive disadvantage.
 
RELIANCE ON EQUIPMENT SUPPLIERS; LACK OF INDUSTRY STANDARDS
 
    The Company currently purchases the majority of its telecommunications
equipment pursuant to an agreement with P-Com, Inc. ("P-Com") and also has
entered into an equipment purchase agreement with Harris. Any reduction or
interruption in supply from either supplier could have a disruptive effect on
the Company. Although six manufacturers currently produce or are developing
equipment that will meet the Company's current and anticipated requirements, no
industry standard or uniform protocol currently exists for 38 GHz equipment.
Consequently, a single manufacturer's equipment must be used in establishing a
link and generally will be used across an entire market area. As a result, the
failure of the Company to procure sufficient equipment produced by a single
manufacturer for service in a particular market area could adversely affect the
Company's results of operations. See "Business -- Strategic Alliances."
 
DEPENDENCE ON THIRD PARTIES FOR MARKETING AND SERVICE
 
    The Company is partly dependent upon third parties for marketing its
services and maintaining its operational systems. The Company entered into the
Ameritech Strategic Distribution Agreement, which allows Ameritech to resell the
Company's 38 GHz services to customers within Ameritech's midwestern region and
to major Ameritech customers nationwide. The Company also has agreements with
subsidiaries of GTE to provide field service and network monitoring and a joint
marketing agreement with Harris. The failure of any of these third parties to
perform or the loss of any of these agreements could have a material adverse
effect on the Company's results of operations or its ability to service its
customers. The Company plans to enter into sales and marketing agreements with
other companies, and the failure to successfully implement these agreements
could have an adverse effect on the Company's development and results of
operations. See "Business -- Strategic Alliances."
 
ACQUISITION OF ADDITIONAL BANDWIDTH IN SELECTED AREAS
 
    Although the Company believes the 38 GHz authorizations it owns, manages,
has agreed to acquire or has the long-term right to use are sufficient in each
of its markets to implement its current business strategy, the Company may seek
to acquire or lease additional authorizations to expand its geographic footprint
or to enhance its ability to provide service to its current target market or
customers it may target in the future. The Company is unable to apply for
additional licenses as the FCC has generally suspended the acceptance of new
applications subject to resolution of the NPRM. The Company does not believe
that the FCC's suspension will have a material effect on the Company's financial
condition, results of operation and plans of expansion since the Company's
business plan does not depend on the grant of new licenses. See "Business --
Government Regulation." However, the Company believes that additional channels
may become available by virtue of (i) the obligations of other 38 GHz service
providers as common carriers to make their services available, (ii) applications
currently being processed by the FCC and (iii) FCC auctions of and adoption of
other licensing procedures for additional 38 GHz authorizations. Nevertheless,
there can be no assurance that access to additional 38 GHz authorizations will
be acquired on favorable terms, if at all. See "Business -- Business Strategy,"
"-- 38 GHz Wireless Broadband Licenses and Authorizations" and "-- Government
Regulation."
 
NEW SERVICES; TECHNOLOGICAL CHANGE
 
    The telecommunications industry has been characterized by rapid
technological advances, changes in end user requirements, frequent new service
introductions, evolving industry standards and decreases in the cost of
equipment. The Company expects these changes to continue, and believes that its
long-term success will increasingly depend on its ability to exploit advanced
technologies and anticipate or adapt to evolving industry standards. There can
be no assurance that (i) the Company's wireless broadband services will not be
outmoded by technology or services now existing or developed and
 
                                       22
<PAGE>
implemented in the future, (ii) the Company will have sufficient resources to
develop or acquire new technologies or to introduce new services capable of
competing with future technologies or service offerings, (iii) the Company's
inventory of equipment will not be rendered obsolete or (iv) the cost of 38 GHz
equipment will decline as rapidly as that of competitive alternatives. See
"Business."
 
DEPENDENCE ON KEY EMPLOYEES
 
    The success of the Company is dependent, in part, on its ability to attract
and retain qualified technical, marketing, sales and management personnel,
especially the Company's executive officers. Competition for such personnel is
intense, and the Company's inability to attract and retain additional key
employees or the loss of one or more of its current key employees could have a
material adverse effect on the Company's business and results of operations. The
Company has employment agreements with each of its officers. See "Management."
 
                                FINANCIAL RISKS
 
SIGNIFICANT CAPITAL REQUIREMENTS; NEED FOR ADDITIONAL FINANCING
 
    Management anticipates that, based on its current plan of development,
assuming that no material new acquisitions are consummated, the net proceeds of
the Offering and the remaining net proceeds of the Common Stock Offering, after
the use of approximately $3.0 million to complete the acquisition of certain
spectrum rights and $2.4 million to pay expenses related to the CommcoCCC
Acquisition, when consummated, will be sufficient to fund the operations and
capital requirements of the Company at least through December 31, 1997. See "Use
of Proceeds." Management also believes that the Company's future capital needs
will continue to be significant, and management intends to seek additional
sources of financing, including the Credit Facility. See "Management's
Discussion and Analysis of Financial Condition and Results of
Operations--Liquidity and Capital Resources" and "Description of Certain
Indebtedness--Proposed Credit Facility." The Company expects capital
expenditures of approximately $35.0 million in 1997 as the development and
expansion of its wireless broadband business continues. The Company expects to
generate significant operating losses for at least the next several years. The
Company will require substantial investment capital for the continued
development and expansion of its wireless broadband operations, the continued
funding of related operating losses, and the possible acquisition of additional
licenses, other assets or other businesses. From its inception through September
30, 1996, the Company reported a net loss of $23.7 million. In addition, if (i)
the Company's plan of development or projections change or prove to be
inaccurate, (ii) the proceeds from the Offering, together with other existing
financial resources, prove to be insufficient to fund the operations and capital
requirements of the Company through December 31, 1997, (iii) the Company
completes any material acquisitions, other than those now under contract, or
buys spectrum at auction or (iv) the Company accelerates implementation of its
business plan, the Company may be required to obtain additional financing
earlier than December 31, 1997. See "Management's Discussion and Analysis of
Financial Condition and Results of Operations." There can be no assurance that
the Company will be able to obtain any additional financing, including the
Credit Facility, or, if such financing is available, that the Company will be
able to obtain it on acceptable terms. In the event that the Company fails to
obtain additional financing when required, such failure could result in the
modification, delay or abandonment of some or all of the Company's development
and expansion plans. Any such modification, delay or abandonment is likely to
have a material adverse effect on the Company's business, which could adversely
affect the value of the Common Stock, the Notes and the Warrants and may limit
the Company's ability to make principal and interest payments on its
indebtedness.
 
POSSIBLE INCURRENCE OF SUBSTANTIAL SECURED INDEBTEDNESS
 
    The Notes will represent senior obligations of the Company and will be
unsecured, except for the pledge by the Company of the Pledged Securities. The
Notes will rank PARI PASSU in right of payment with all existing and future
unsecured, senior indebtedness of the Company and will rank senior in right of
payment to any future subordinated indebtedness of the Company. At September 30,
1996, on a pro
 
                                       23
<PAGE>
forma basis after giving effect to the Offering and the Common Stock Offering,
and the application of the net proceeds therefrom, the aggregate principal
amount of indebtedness of the Company (excluding the Notes) was approximately
$3.1 million, which consisted of the EMI Note and the Equipment Note, all of
which ranked PARI PASSU with the Notes. However, $1.6 million of such
indebtedness constituted secured indebtedness which will effectively rank senior
to the Notes with respect to the assets securing such indebtedness. Although the
Indenture will limit the ability of the Company and its subsidiaries to incur
additional indebtedness, including senior indebtedness, the Indenture will
permit the Company to incur a substantial amount of secured indebtedness,
including vendor indebtedness and indebtedness under the Credit Facility, which,
if incurred, will effectively rank senior to the Notes with respect to the
assets securing such indebtedness. In addition, the Indenture will permit the
subsidiaries of the Company (including any subsidiary holding all or any part of
the Company's FCC licenses and authorizations) to guarantee the indebtedness of
the Company under the Credit Facility on a secured basis (consistent with
applicable FCC rules), which guarantees and security interests would effectively
rank senior in right of payment to the Notes. In such a case, if the Company or
any such subsidiary were to become insolvent or be liquidated or if any of such
secured indebtedness were to be accelerated, the holders of such secured
indebtedness would be entitled to payment in full out of the assets securing
such indebtedness prior to payment to holders of the Notes. If the lenders party
to, or the holders of, any such secured indebtedness were to foreclose on the
collateral securing the Company's obligations to them, there can be no assurance
that there would be sufficient assets remaining after payment of all such
secured indebtedness to satisfy the claims of holders of the Notes in full. See
"Description of Notes -- Certain Covenants" and "Description of Certain
Indebtedness."
 
LEVERAGE; ABILITY TO SERVICE INDEBTEDNESS
 
    Following the Offering, the Company will be leveraged and will have certain
restrictions on its operations. As of September 30, 1996, on a pro forma basis
after giving effect to the Common Stock Offering and the Offering, the use of
the proceeds therefrom, and completion of the CommcoCCC Acquisition, all as if
they had occurred on that date, the Company would have had approximately $108.8
million of total indebtedness (which is net of $29.3 million allocated to the
Warrants) and stockholders' equity of approximately $116.7 million. See
"Capitalization."
 
    The indebtedness expected to be incurred by the Company as a result of the
Offering will have several important consequences to the holders of the
Company's securities, including, but not limited to, the following: (i) a
substantial portion of the Company's cash flow from operations will be required
to pay interest with respect to such indebtedness, once the Pledged Securities
are no longer available for such purpose; (ii) the Company's flexibility may be
limited in responding to changes in the industry and economic conditions
generally; (iii) the indenture relating to the Notes (the "Indenture") will
likely contain numerous financial and other restrictive covenants, the failure
to comply with which may result in an event of default, which, if not cured or
waived, could have a material adverse effect on the Company; (iv) the ability of
the Company to satisfy its obligations pursuant to such indebtedness will be
dependent upon its future performance which, in turn, will be subject to
management, financial, business and other factors affecting the business and
operations of the Company; (v) the Company's ability to obtain any necessary
financing in the future may be limited; (vi) the Company will be more highly
leveraged than many of its competitors, which may put it at a competitive
disadvantage and (vii) the Company's leverage may make it more vulnerable in the
event of an economic downturn or if the Company's cash flow does not
significantly increase. Some of these factors are beyond the control of the
Company. See "Unaudited Pro Forma Condensed Consolidated Financial Statements,"
"Selected Historical and Pro Forma Financial Data" and "Management's Discussion
and Analysis of Financial Condition and Results of Operations." In addition,
although the Indenture will limit the ability of the Company and its
subsidiaries to incur additional indebtedness, the Indenture will permit the
Company to incur substantial additional indebtedness, which may or may not be
secured, to finance the construction of networks, the purchase of equipment and
the introduction of new services. See "Description of Notes--Certain Covenants."
Any future indebtedness may contain covenants that may limit the Company's
flexibility in responding to changes in industry and economic conditions
generally. The debt
 
                                       24
<PAGE>
service requirements of any additional indebtedness could make it more difficult
for the Company to make principal and interest payments on other indebtedness
and could exacerbate any of the foregoing consequences.
 
    There can be no assurance that the Company will be able to generate
sufficient cash flow to meet required interest and principal payments associated
with the Notes and its other indebtedness. If the Company is unable to generate
sufficient cash flow to meet its debt obligations, the Company may be required
to renegotiate the payment terms or to refinance all or a portion of its
indebtedness, to sell assets or to obtain additional financing. If the Company
is unable to refinance such indebtedness, substantially all of the Company's
long-term debt would be in default and could be declared immediately due and
payable. In the event the Company fails to comply with these various covenants,
it could be in default under the Notes. In the event of such default,
substantially all of the Company's long-term debt could be declared immediately
due and payable. See "Description of Notes--Certain Covenants."
 
ORIGINAL ISSUE DISCOUNT
 
    Because a portion of the purchase price for each Unit will be allocable to
the Warrants for federal income tax purposes, the Notes will be treated as
issued with original issue discount. Purchases of the Units therefore generally
will be required to include amounts in gross income for Federal income tax
purposes in advance of receipt of the cash interest payments on the Notes to
which the income is attributable. See "Certain Federal Income Tax
Considerations" for a more detailed discussion of the federal income tax
consequences to the purchasers of the Units resulting from the purchase,
ownership or disposition thereof.
 
    If a bankruptcy case is commenced by or against the Company under Title 11
of the United States Code, as amended (the "Bankruptcy Code") after the issuance
of the Units, the claim of a holder of the Notes with respect to the principal
amount thereof may be limited to an amount equal to the sum of (i) the initial
public offering price of the Notes and (ii) that portion of the original issue
discount that is not deemed to constitute "unmatured interest" for purposes of
the Bankruptcy Code. Any original issue discount that was not accrued as of such
bankruptcy filing may be deemed to constitute "unmatured interest." A holder of
a Note may not have any claim with respect to that portion of the issue price of
a Unit allocated to the Warrant issued as part of such Unit.
 
RISK OF INABILITY TO SATISFY CHANGE IN CONTROL OFFER
 
    Upon the occurrence of a Change in Control, the Company will be required to
make an offer to purchase all of the outstanding Notes at a purchase price in
cash equal to 101% of the principal amount thereof, together with accrued and
unpaid interest, if any, to the date of purchase. There can be no assurance that
the Company will have the funds necessary to effect such a purchase if such an
event were to occur. In the event a Change in Control occurs at a time when the
Company is unable to purchase the Notes, the Company could seek to refinance the
Notes. If the Company is unsuccessful in refinancing the Notes, the Company's
failure to purchase tendered Notes would constitute an Event of Default under
the Indenture. See "Description of Notes -- Certain Covenants -- Change in
Control."
 
                            LEGAL AND TRADING RISKS
 
ABILITY TO EXERCISE WARRANTS
 
    Holders of Warrants will be able to exercise their Warrants only if a
registration statement relating to the Warrant Shares underlying the Warrants is
then in effect or the exercise of such Warrants is exempt from the registration
requirements of the Securities Act, and such securities are qualified for sale
or exempt from qualification under the applicable securities laws of the states
in which the various holders of the Warrants reside. The Company is required
under the terms of the Warrant Agreement to use its best efforts to cause to
become effective under the Securities Act no later than August 15, 1997 the
Warrant Shelf Registration Statement covering the issuance and resale, to the
extent applicable, of the
 
                                       25
<PAGE>
Warrant Shares upon exercise of the Warrants. Subject to certain "black-out"
periods, the Company will also be required to use its best efforts to maintain
the effectiveness of the Warrant Shelf Registration Statement until the
expiration or exercise of all Warrants. See "Description of Warrants --
Registration of Warrant Shares." There can be no assurance that the Company will
be able to file, cause to be declared effective or keep a registration statement
continuously effective until all of the Warrants have been exercised or have
expired.
 
ABSENCE OF PUBLIC MARKET; POSSIBLE VOLATILITY OF STOCK PRICE
 
    There is currently no public market for the Units, the Notes or the
Warrants. The Company does not intend to apply for listing of the Units, the
Notes or the Warrants on any securities exchange or for quotation of the Units,
the Notes or the Warrants on the Nasdaq National Market. The Company has been
advised by the Underwriters that they presently intend to make a market in the
Units, the Notes and the Warrants, as permitted by applicable laws and
regulations, after the consummation of the sale of the Units; however, the
Underwriters are not obligated to do so and any such market-making activity may
be discontinued at any time without notice at the sole discretion of each
Underwriter. Accordingly, there can be no assurance as to whether an active
public market for the Units, the Notes or the Warrants will develop or, if a
public market does develop, as to the liquidity of the trading market for the
Units, the Notes or the Warrants. If an active public market does not develop,
the market price and liquidity for the Units, the Notes or the Warrants may be
adversely affected. See "Underwriting."
 
    While the Common Stock is quoted on the Nasdaq National Market, there can be
no assurance that an active public trading market will be sustained after the
Offering. The Company believes that factors such as (i) announcements of
developments related to the Company's business, (ii) announcements of new
services by the Company or its competitors, (iii) developments in the Company's
relationships with its suppliers or customers, (iv) fluctuations in the
Company's results of operations, (v) a shortfall in revenues or earnings
compared to analysts' expectations and changes in analysts' recommendations or
projections, (vi) sales of substantial amounts of securities of the Company into
the marketplace, (vii) regulatory developments affecting the telecommunications
industry or 38 GHz services or (viii) general conditions in the
telecommunications industry or the worldwide economy, could cause the price of
the Company's Common Stock to fluctuate, perhaps substantially.
 
CONTROL BY MANAGEMENT AND PRINCIPAL STOCKHOLDERS
 
    As of January 14, 1997, the Company's executive officers, directors and
their affiliates, as a group, beneficially owned approximately 20.6% (assuming
no exercise of the Warrants) of the Company's outstanding Common Stock (14.3%
upon consummation of the CommcoCCC Acquisition). In addition, upon completion of
the CommcoCCC Acquisition, Columbia Capital Corporation, as general partner of
two of the stockholders of CommcoCCC, and Commco, L.L.C., the remaining
stockholder of CommoCCC, will beneficially own approximately 16.7% and 14.5%,
respectively, of the Company's outstanding Common Stock and the Company will
elect James B. Murray, Jr. as a director of the Company after the CommcoCCC
Acquisition. As a result, these stockholders will have the ability to exercise
significant influence over the Company and the election of its directors, the
appointment of new management and the approval of any action requiring the
approval of the holders of the Company's voting stock, including adopting
certain amendments to the Company's Certificate of Incorporation and approving
mergers or sales of substantially all of the Company's assets. The directors
elected by the Company's stockholders prior to the Common Stock Offering will
have the authority to effect decisions affecting the capital structure of the
Company, including the issuance of additional capital stock, the implementation
of stock repurchase programs and the declaration of dividends. See "Principal
Stockholders."
 
ABSENCE OF DIVIDENDS ON COMMON STOCK
 
    The Company has not paid and does not anticipate paying any cash dividends
on its Common Stock in the foreseeable future. The Company intends to retain its
earnings, if any, for use in the Company's growth and ongoing operations. In
addition, the terms of the Indenture will restrict the ability of the Company to
pay dividends on the Common Stock. See "Description of Notes--Certain
Covenants."
 
                                       26
<PAGE>
ANTITAKEOVER PROVISIONS; POSSIBLE FUTURE ISSUANCES OF PREFERRED STOCK
 
    The Company's Certificate of Incorporation and Bylaws and the provisions of
the Delaware General Corporation Law (the "Delaware GCL") contain certain
provisions which may have the effect of discouraging, delaying or making more
difficult a change in control of the Company or preventing the removal of
incumbent directors. The existence of these provisions may have a negative
impact on the price of the Common Stock and may discourage third party bidders
from making a bid for the Company or may reduce any premiums paid to
stockholders for their Common Stock. Furthermore, the Company is subject to
Section 203 of the Delaware GCL, which could have the effect of delaying or
preventing a change in control of the Company. See "Description of Capital Stock
- -- Change in Control Provisions."
 
    The Company's Certificate of Incorporation also allows the Board of
Directors to issue up to 10,000,000 shares of Preferred Stock and to fix the
rights, privileges and preferences of such shares without any further vote or
action by the stockholders. The rights of the holders of Common Stock will be
subject to, and may be adversely affected by, the rights of the holders of any
Preferred Stock that may be issued in the future. While the Company has no
present intention to issue shares of Preferred Stock, any such issuance could be
used to discourage, delay or make more difficult a change in control of the
Company. See "Description of Capital Stock -- Preferred Stock."
 
                                       27
<PAGE>
                                  THE COMPANY
 
    Advanced Radio Telecom Corp. provides wireless broadband telecommunications
services using point-to-point microwave transmissions in the 38 GHz band of the
radio spectrum. The Company is seeking to address the growing demand for high
speed, high capacity digital telecommunications services on the part of business
and government end users who require cost effective, high bandwidth local access
to voice, video, data and Internet services. The Company's last mile services
are a complement and a viable alternative to fiber optic networks and offer
rapidly deployable coverage throughout the 81 markets in which the Company is
currently authorized by the FCC to provide services.
 
    The business of the Company is comprised of (i) the business of Advanced
Radio Technologies Corporation ("ART" or the "Company"), a company organized by
Vernon L. Fotheringham and W. Theodore Pierson, Jr. in 1993 for the purpose of
acquiring 38 GHz licenses, and (ii) the business of Advanced Radio Telecom Corp.
("Telecom"), a corporation organized in Delaware in March 1995 under the name
Advanced Radio Technology, Ltd. for the purposes of acquiring additional 38 GHz
licenses and developing and operating the business of ART and Telecom on a joint
basis. In April 1995, ART entered into the ART West Joint Venture Agreement (as
defined) to apply for, acquire and develop 38 GHz operations in 13 states in the
western United States. In November 1995, the Company completed the EMI
Acquisition (as defined), pursuant to which it acquired thirty-two 38 GHz
licenses and certain related assets in the northeast United States. In July
1996, the Company entered into the CommcoCCC Agreement to acquire the CommcoCCC
Assets and other agreements to acquire authorizations it currently manages. Upon
completion of these pending acquisitions, the Company will own, manage or have a
right to use on an exclusive basis a total of 233 authorizations to provide 38
GHz wireless broadband services in 169 U.S. markets. See "Risk Factors -- Risk
of Non-Consummation of CommcoCCC Acquisition and Other Acquisitions," "Business
- -- Agreements Relating to Licenses and Authorizations -- ART West Joint
Venture," "-- EMI Acquisition" and " -- CommcoCCC Acquisition."
 
    On October 28, 1996, a subsidiary of ART merged with and into Telecom
pursuant to the Merger Agreement (as defined). Upon the merger (the "Merger"),
Telecom became a wholly-owned subsidiary of ART and changed its name to "ART
Licensing Corp.," and ART changed its name to "Advanced Radio Telecom Corp." See
"Certain Transactions -- Merger." Prior to completion of the Merger, Telecom
managed the combined businesses of the Company (including all FCC licenses held
by ART and Telecom).
 
    DIGIWAVE, ART, OZ BOX and ADVANCED RADIO TELECOM are service marks of the
Company. The Company's principal executive offices are located at 500 108th
Avenue, N.E., Suite 2600, Bellevue, Washington 98004, and its telephone number
is (206) 688-8700.
 
                                       28
<PAGE>
                                USE OF PROCEEDS
 
    The net proceeds to the Company from the Offering are estimated to be
approximately $129.0 million in the aggregate after deducting estimated
underwriting discount and offering expenses.
 
    A substantial portion of the net proceeds from the Offering is expected to
be used for capital expenditures. Because the Company installs links in response
to customer orders and can redeploy links removed from service, the Company's
actual rate of capital expenditures will depend largely on levels of customer
demand. The Company currently expects to use approximately $35.0 million of the
net proceeds (including the cost to complete construction of the remaining
CommcoCCC authorizations which have not been perfected, estimated at less than
$1.5 million) for capital expenditures in 1997. An additional $3.0 million will
be used for the completion of the acquisition of certain spectrum rights, and
approximately $2.4 million of the net proceeds will be used to fund expenses
related to the CommcoCCC Acquisition, when consummated. See "Business --
Agreements Relating to Licenses and Authorizations." At the closing of the
Offering, the Company will use approximately $51.6 million of the net proceeds
to purchase the Pledged Securities. The amount of net proceeds used to purchase
the Pledged Securities may vary depending upon the then current interest rates
on U.S. government securities. See "Description of Notes -- Security."
 
    The remainder of the net proceeds will be used for general corporate
purposes, including the funding of operating cash flow shortfalls, technology
development and acquisitions of additional spectrum rights and, potentially,
related businesses. Although the Company considers potential acquisitions from
time to time, no agreement, agreement in principle, understanding or other
arrangement, other than those disclosed in this Prospectus, has been reached
with respect to any acquisition. To the extent the Company does not consummate
any of these acquisitions, or negotiates changes in such acquisitions to provide
for payment using stock or other consideration (which is not currently
contemplated), the funds reserved for such acquisitions will be available for
general corporate purposes. See "Business -- Agreements Relating to Licenses and
Authorizations." The Company anticipates that it will fund approximately an
aggregate of $1.0 million for research and development activities pursuant to a
letter of intent with Helioss Communications Corporation. Although the Company
does not have other material commitments to fund research and development and to
make investments in other companies, the Company expects to incur additional
research and development expenses and may make other investments from time to
time. Management anticipates that, based on its current plan of development and
assuming that no material new acquisitions or investments are consummated, the
remaining net proceeds of the Offering and the Common Stock Offering will be
sufficient to fund the operations of the Company at least through December 31,
1997. The Company will require substantial additional financing to fund
anticipated capital requirements and operating losses in periods after December
31, 1997. See "Description of Certain Indebtedness -- Proposed Credit Facility"
and "Risk Factors -- Significant Capital Requirements; Need for Additional
Financing."
 
                                       29
<PAGE>
                PRICE RANGE OF COMMON STOCK AND DIVIDEND POLICY
 
    The Company's Common Stock has been quoted on the Nasdaq Market since
November 5, 1996, under the symbol "ARTT." The following table sets forth, for
the fiscal periods indicated, the high and low last sale prices of the Common
Stock as reported on the Nasdaq National Market.
 
<TABLE>
<CAPTION>
                                                                           COMMON STOCK PRICE
                                                                        ------------------------
FISCAL PERIOD                                                              HIGH          LOW
- ----------------------------------------------------------------------  -----------  -----------
<S>                                                                     <C>          <C>
1996 Fourth Quarter (from November 5).................................   $   16.50    $   10.50
1997 First Quarter (through January 31)...............................   $  12.375    $  10.625
</TABLE>
 
    See the cover page of this Prospectus for a recent reported last sale price
of the Common Stock on the Nasdaq National Market. As of December 31, 1996,
there were 133 holders of record of the Common Stock.
 
    The Company has not paid and does not anticipate paying any cash dividends
on the Common Stock in the foreseeable future. The Company intends to retain its
earnings, if any, for use in the Company's growth and ongoing operations. In
addition, the terms of the Indenture will restrict the ability of the Company to
pay dividends on the Common Stock. See "Description of Notes -- Certain
Covenants."
 
                                       30
<PAGE>
                                 CAPITALIZATION
 
    The following table sets forth the capitalization of the Company as of
September 30, 1996 (i) on a historical basis, after giving effect to the Merger
of ART and Telecom, which occurred on October 28, 1996 (the Merger was accounted
for as a reorganization of entities under common control which is similar to
that of a pooling of interests), (ii) on a pro forma basis, giving effect to the
Common Stock Offering and certain other transactions occurring subsequent to
September 30, 1996 and the application of the net proceeds thereof as described
in Note 1 below and (iii) on a pro forma as adjusted basis, giving effect to, as
described in Note 2 below, (A) the pro forma adjustments in (ii), (B) the sale
by the Company of 135,000 Units in the Offering, after deducting the estimated
underwriting discount and offering expenses, the use of cash to purchase the
Pledged Securities and the value ascribed to the Warrants, (C) the receipt and
application of the aggregate net proceeds from the Offering and (D) the
consummation of the CommcoCCC Acquisition. The capitalization information set
forth in the table below is qualified by the more detailed information contained
in, and should be read in conjunction with, the audited financial statements of
the Company and the notes thereto, the unaudited condensed consolidated
financial statements of the Company and the notes thereto and the unaudited pro
forma condensed consolidated financial statements of the Company and the notes
thereto, all appearing elsewhere in this Prospectus.
 
<TABLE>
<CAPTION>
                                                                                        AS OF SEPTEMBER 30, 1996
                                                                         -------------------------------------------------------
                                                                                                                  PRO FORMA
                                                                            HISTORICAL       PRO FORMA (1)     AS ADJUSTED (2)
                                                                         ----------------  -----------------  ------------------
<S>                                                                      <C>               <C>                <C>
Cash and cash equivalents (excluding restricted cash)..................  $        752,368  $      16,208,151  $       87,633,151(3)
                                                                         ----------------  -----------------  ------------------
                                                                         ----------------  -----------------  ------------------
Short-term debt:
  March Bridge Notes...................................................  $      4,243,784  $              --  $               --
  CommcoCCC Notes......................................................         2,827,836                 --                  --
  September Bridge Notes...............................................         2,203,559                 --                  --
                                                                         ----------------  -----------------  ------------------
                                                                         $      9,275,179  $              --  $               --
                                                                         ----------------  -----------------  ------------------
                                                                         ----------------  -----------------  ------------------
Long-term debt (including current portion):
  Note payable to EMI..................................................  $      1,500,000  $       1,500,000  $        1,500,000
  Equipment Note.......................................................         1,607,422          1,607,422           1,607,422
  14% Senior Notes due 2007 (4)........................................                --                 --         105,661,273
                                                                         ----------------  -----------------  ------------------
    Total long-term debt...............................................         3,107,422          3,107,422         108,768,695
                                                                         ----------------  -----------------  ------------------
Stockholders' equity (deficit):
  Preferred stock (5)..................................................               921                 --                  --
  Common Stock (6).....................................................             6,587             13,560              19,560
  Additional paid-in capital...........................................        20,745,714         54,290,502         148,123,229
  Accumulated deficit .................................................       (23,748,434)       (31,475,840)        (31,475,840)
                                                                         ----------------  -----------------  ------------------
    Total stockholders' equity (deficit)...............................        (2,995,212)        22,828,222         116,666,949
                                                                         ----------------  -----------------  ------------------
      Total capitalization.............................................  $        112,210  $      25,935,644  $      225,435,644
                                                                         ----------------  -----------------  ------------------
                                                                         ----------------  -----------------  ------------------
</TABLE>
 
- ------------------------
(1) Reflects adjustments for the following transactions as if they had occurred
    as of September 30, 1996: (i) the sale by the Company of 2,300,500 shares of
    Common Stock offered in the Common Stock Offering in November 1996 at a
    price of $15.00 per share, after deducting the underwriting discount and
    offering expenses; (ii) the Conversion in November 1996; (iii) fees and
    expenses of approximately $6.4 million related to the CIBC Financing
    Commitment, including the issuance of the First CIBC Warrants to purchase
    300,258 shares of Common Stock, which financing commitment is assumed to be
    replaced by the issuance of the Notes in the Offering (as described in Note
    (2) below); (iv) the receipt of $1.6 million (out of a total of $4.0
    million) in cash proceeds from the September Bridge Financing in October
    1996; (v) the application of the net proceeds from the Common Stock Offering
    to repay the March Bridge Notes, the CommcoCCC Notes and the September
    Bridge Notes, which repayment occurred in November 1996, and the November
    1996 payment of $3.0 million of the total $6.0 million consideration to
    acquire the 50% ownership interest of ART West held by Extended; and (vi)
    the exercise of the Ameritech Warrant to purchase an aggregate of 318,374
    shares of Common Stock in December 1996.
(2) Reflects adjustments in (1) above and for the following transactions as if
    they had occurred as of September 30, 1996: (i) the sale by the Company of
    135,000 Units in the Offering assuming $135.0 million of gross proceeds,
    after deducting (a) the estimated underwriting discount and offering
    expenses of approximately $6.0 million, (b) the cash used to purchase the
    Pledged Securities of approximately $51.6 million and (c) the value ascribed
    to the Warrants of approximately $29.3 million (the value was based on an
    assumed value of $10.75 per share of Common Stock, an exercise price of $.01
    per share and an issuance of Warrants to purchase an aggregate of 2,731,725
    shares of Common Stock); (ii) use of $3.0 million of the net proceeds from
    the Offering to fund the remaining balance of the ART West purchase price;
    and (iii) the consummation of the CommcoCCC Acquisition in exchange for
    6,000,000 shares of Common Stock at an assumed value of $10.75 per share
    plus related estimated expenses.
(3) Cash and cash equivalents excludes restricted cash of $51.6 million used to
    purchase the Pledged Securities.
(4) The Company anticipates gross proceeds from the Offering of $135.0 million.
    The estimated value of the Warrants ($29.3 million) has been reflected as
    both a debt discount and an element of additional paid-in capital. However,
    the actual aggregate principal amount of the Notes is $135.0 million.
(5) Consists of convertible serial preferred stock, $.001 par value per share:
    10,000,000 shares authorized; historical -- 455,550 shares of Series A,
    114,679 shares of Series B, 7,363 shares of Series C, 61,640 shares of
    Series D, 232,826 shares of Series E and 48,893 shares of Series F issued
    and outstanding; pro forma and pro forma as adjusted -- no shares issued and
    outstanding.
(6) Consists of Common Stock, $.001 par value per share: 100,000,000 shares
    authorized; historical 6,586,958 shares issued and outstanding; pro forma --
    13,559,420 shares issued and outstanding; pro forma as adjusted --
    19,559,420 shares issued and outstanding.
 
                                       31
<PAGE>
                SELECTED HISTORICAL AND PRO FORMA FINANCIAL DATA
 
HISTORICAL AND PRO FORMA DATA
 
    The unaudited selected historical and pro forma financial data presented
below as of and for the nine months ended September 30, 1996 and for the year
ended December 31, 1995 were derived from the unaudited pro forma condensed
consolidated financial statements of the Company included elsewhere in this
Prospectus. For definitions of certain terms and more information about the
transactions cited in the notes thereto, see "Certain Transactions."
 
    The unaudited selected historical and pro forma financial data should be
read in conjunction with the audited financial statements of the Company, and
the notes thereto, the unaudited condensed consolidated financial statements of
the Company, and the notes thereto, and the unaudited pro forma condensed
consolidated financial statements of the Company, and the notes thereto,
included elsewhere in the Prospectus. The unaudited selected pro forma financial
data are not necessarily indicative of what the actual financial position and
results of operations of the Company would have been as of and for the nine
months ended September 30, 1996 and for the year ended December 31, 1995, nor do
they purport to represent the Company's future financial position and results of
operations.
<TABLE>
<CAPTION>
                                                                                                           NINE MONTHS
                                                                                     YEAR ENDED               ENDED
                                                                                 DECEMBER 31, 1995        SEPTEMBER 30,
                                                                            ----------------------------       1996
                                                                             HISTORICAL                   --------------
                                                                                 (1)       PRO FORMA (2)  HISTORICAL (1)
                                                                            -------------  -------------  --------------
<S>                                                                         <C>            <C>            <C>
STATEMENT OF OPERATIONS DATA:
Service revenue...........................................................   $     5,793    $     5,793    $    125,013
Non-cash compensation expense.............................................     1,089,605      1,089,605       7,504,452
Depreciation and amortization.............................................        15,684      2,408,559         504,462
Interest and financing expense............................................       131,540     32,658,543       1,396,943
Net loss..................................................................     3,234,843     34,633,966      20,378,377
Pro forma net loss per share of Common Stock (3)..........................  $       0.30   $       1.75   $        2.15
Pro forma weighted average number of shares of Common Stock outstanding
 (3)......................................................................    10,912,338     19,846,172       9,470,545
 
OTHER FINANCIAL DATA:
EBITDA (4)................................................................  $ (2,007,568 ) $ (2,007,568 ) $  (9,978,993)
Capital expenditures......................................................     3,585,144      3,585,144       7,864,110
Ratio of earnings to fixed charges (5)....................................            --             --              --
 
<CAPTION>
 
                                                                            PRO FORMA (2)
                                                                            --------------
<S>                                                                         <C>
STATEMENT OF OPERATIONS DATA:
Service revenue...........................................................  $      125,013
Non-cash compensation expense.............................................       7,504,452
Depreciation and amortization.............................................       2,299,118
Interest and financing expense............................................      26,577,589
Net loss..................................................................      44,713,113
Pro forma net loss per share of Common Stock (3)..........................  $         2.43
Pro forma weighted average number of shares of Common Stock outstanding
 (3)......................................................................      18,404,379
OTHER FINANCIAL DATA:
EBITDA (4)................................................................  $   (9,978,993)
Capital expenditures......................................................       7,864,110
Ratio of earnings to fixed charges (5)....................................              --
</TABLE>
<TABLE>
<CAPTION>
                                                                                                          AS OF
                                                                                                      SEPTEMBER 30,
                                                                                                           1996
                                                                                                      --------------
                                                                                                      HISTORICAL (1)
                                                                                                      --------------
<S>                                                                                                   <C>
BALANCE SHEET DATA:
Working capital surplus (deficit)...................................................................  $  (20,700,673)
Property and equipment, net.........................................................................      11,019,217
FCC licenses, net...................................................................................       4,276,780
Total assets........................................................................................      20,541,997
Short-term debt.....................................................................................       9,275,179
Long-term debt (including current portion)..........................................................       3,107,422
Accumulated deficit.................................................................................     (23,748,434)
Total stockholders' equity (deficit)................................................................      (2,995,212)
 
<CAPTION>
 
                                                                                                       PRO FORMA (2)
 
                                                                                                      ----------------
 
<S>                                                                                                   <C>
BALANCE SHEET DATA:
Working capital surplus (deficit)...................................................................   $   75,455,289
 
Property and equipment, net.........................................................................       11,019,217
 
FCC licenses, net...................................................................................       99,991,780
 
Total assets........................................................................................      258,520,252
 
Short-term debt.....................................................................................               --
 
Long-term debt (including current portion)..........................................................      108,768,695
 
Accumulated deficit.................................................................................      (31,475,840)
 
Total stockholders' equity (deficit)................................................................      116,666,949
 
</TABLE>
 
                                       32
<PAGE>
HISTORICAL FINANCIAL DATA
 
    The selected historical financial data of the Company below as of December
31, 1995, 1994 and 1993 and for the years ended December 31, 1995 and 1994, and
for the period from August 23, 1993 (date of inception) to December 31, 1993
were derived from and should be read in conjunction with the audited financial
statements of the Company and the related notes thereto, included elsewhere in
this Prospectus. The selected financial data of the Company below as of and for
the nine months ended September 30, 1996 and 1995 were derived from and should
be read in conjunction with the unaudited condensed consolidated financial
statements of the Company and the related notes thereto included elsewhere in
this Prospectus.
 
<TABLE>
<CAPTION>
                                                      AUGUST 23, 1993                                NINE MONTHS ENDED SEPTEMBER
                                                    (DATE OF INCEPTION)   YEAR ENDED DECEMBER 31,                30,
                                                            TO           --------------------------  ---------------------------
                                                     DECEMBER 31, 1993      1994          1995           1995          1996
                                                    -------------------  -----------  -------------  ------------  -------------
<S>                                                 <C>                  <C>          <C>            <C>           <C>
STATEMENT OF OPERATIONS DATA:
Service revenue...................................       $      --       $        --  $       5,793  $         --  $     125,013
Consulting revenue................................              --           137,489             --            --             --
Depreciation and amortization.....................             688             8,281         15,684        15,407        504,462
Interest expense..................................              --             4,375        131,540         1,539      1,396,943
Net loss..........................................           6,594           128,620      3,234,843     1,004,313     20,378,377
Pro forma net loss per share of Common Stock
 (3)..............................................              --                --  $        0.30                $        2.15
Pro forma weighted average number of shares of
 Common Stock outstanding (3).....................              --                --     10,912,338            --      9,470,545
 
OTHER FINANCIAL DATA:
EBITDA (4)........................................       $  (5,906)      $  (115,964) $  (2,007,568) $   (987,367) $  (9,978,993)
Capital Expenditures..............................              --             5,175      3,585,144        57,120      7,864,110
Ratio of earnings to fixed charges (5)............              --                --             --            --             --
</TABLE>
 
<TABLE>
<CAPTION>
                                                                  AS OF DECEMBER 31,                    AS OF SEPTEMBER 30,
                                                      -------------------------------------------  -----------------------------
                                                          1993           1994           1995           1995            1996
                                                      -------------  -------------  -------------  -------------  --------------
<S>                                                   <C>            <C>            <C>            <C>            <C>
BALANCE SHEET DATA:
Working capital surplus (deficit)...................  $      13,958  $     (76,556) $  (3,008,510) $    (168,791) $  (20,700,673)
Property and equipment, net.........................             --          3,448      3,581,561         49,488      11,019,217
FCC licenses, net...................................             --             --      4,235,734        175,000       4,276,780
Total assets........................................         74,513         42,611      9,876,559        548,203      20,541,997
Short-term debt.....................................             --             --             --             --       9,275,179
Long-term debt (including current portion)..........             --             --      6,450,000             --       3,107,422
Accumulated deficit.................................         (6,594)      (135,214)    (3,370,057)    (1,139,528)    (23,748,434)
Total stockholders' equity (deficit)................         54,542        (39,078)      (312,860)       297,900      (2,995,212)
</TABLE>
 
- ------------------------------
 
(1) The historical selected financial data of the Company reflects the Merger of
    ART and Telecom, which occurred on October 28, 1996. The Merger was
    accounted for as a reorganization of entities under common control which is
    similar to that of a pooling of interest.
 
(2) The unaudited selected financial data under the caption "Pro Forma" are
    presented as if the following transactions had occurred as of the beginning
    of the respective periods for the Statement of Operations Data and Other
    Financial Data and as of the balance sheet date for the Balance Sheet Data:
    (i) the sale by the Company of 2,300,500 shares of Common Stock offered in
    the Common Stock Offering in November 1996 at a price of $15.00 per share,
    after deducting the underwriting discount and offering expenses; (ii) the
    Conversion in November 1996; (iii) fees and expenses of approximately $6.4
    million related to the CIBC Financing Commitment, including the issuance of
    the First CIBC Warrants to purchase 300,258 shares of Common Stock, which
    financing commitment is assumed to be replaced by the issuance of the Notes
    in the Offering; (iv) the receipt of $1.6 million (out of a total of $4.0
    million) in cash proceeds from the September Bridge Financing in October
    1996; (v) the application of the net proceeds from the Common Stock Offering
    to repay the March Bridge Notes, the CommcoCCC Notes and the September
    Bridge Notes, which repayment occurred in November 1996 and the November
    1996 payment of $3.0 million of the total $6.0 million consideration to
    acquire the 50% ownership interest of ART West held by Extended; (vi) the
    exercise of the Ameritech Warrant to purchase an aggregate of 318,374 shares
    of Common Stock in December 1996; (vii) the sale by the Company of 135,000
    Units offered in the Offering assuming $135.0 million of gross proceeds,
    after deducting (a) the estimated underwriting discount and offering
    expenses (b) the cash used to purchase the Pledged Securities of
    approximately $51.6 million and (c) the value ascribed to the Warrants of
    approximately $29.3 million (the value was based on an assumed value of
    $10.75 per share of Common Stock, an exercise price of $.01 per share and an
    issuance of Warrants to purchase an aggregate of 2,731,725 shares of Common
    Stock); (viii) the use of $3.0 million of the net proceeds from the Offering
    to fund the balance of the ART West purchase price; and (ix) the
    consummation of the acquisition by the Company of the CommcoCCC Assets in
    exchange for 6,000,000 shares of Common Stock at an assumed value of $10.75
    per share plus related estimated expenses.
 
                                       33
<PAGE>
- ------------------------------
 
(3) Pro forma net loss per share is computed based on the loss for the period
    divided by the weighted average number of shares of Common Stock outstanding
    during the period including the issuance of 2,300,500 shares of Common Stock
    issued in the Common Stock Offering, the Conversion, the issuance of
    potentially dilutive instruments issued within one year prior to the Common
    Stock Offering at exercise prices below the initial public offering price of
    $15.00 per share (in measuring the dilutive effect, the treasury stock
    method was used), the issuance of the 318,374 shares of Common Stock to
    Ameritech, and the issuance of 6,000,000 shares of Common Stock in
    connection with the CommcoCCC Acquisition.
 
(4) EBITDA represents loss before interest and financing expense (net of
    interest income), income tax expense, depreciation and amortization expense,
    non-cash compensation expense and non-cash market development expense.
    EBITDA is not intended to represent cash flows from operating activities, as
    determined in accordance with generally accepted accounting principles.
    EBITDA should not be considered as an alternative to, or more meaningful
    than, operating income or loss, net income or loss or cash flow as an
    indicator of the Company's performance. EBITDA has been included because the
    Company uses it as one means of analyzing its ability to service its debt,
    because a similar measure will be used in the Indenture with respect to
    computations under certain covenants and because the Company understands
    that it is used by certain investors as one measure of a company's
    historical ability to service its debt. Not all companies calculate EBITDA
    in the same fashion and therefore EBITDA as presented may not be comparable
    to other similarly titled measures of other companies.
 
(5) For the purpose of determining earnings coverage of fixed charges, net
    losses include fixed charges representing interest expense on all
    indebtedness (including the amortization of deferred debt issuance cost and
    original issue discount). For the purpose of the pro forma information,
    fixed charges include interest expense from the Notes (including the
    amortization of deferred debt issuance costs and original issue discount for
    the value ascribed to the Warrants) at an assumed effective interest rate of
    18.92% and the financing charges from the CIBC Financing Commitment
    (including the commitment fee and the value ascribed to the First CIBC
    Warrants) offset by the reversal of interest expense from the March Bridge
    Notes, the CommcoCCC Notes and the September Bridge Notes (including
    amortization of deferred debt issuance costs and original issue discount)
    which were repaid out of the proceeds from the Common Stock Offering in
    November 1996. Earnings were deficient to cover fixed charges by the
    following amounts for the periods indicated:
 
    Pro Forma
 
<TABLE>
<S>                                                                                 <C>
Nine months ended September 30, 1996..............................................  $   44,713,113
Year ended December 31, 1995......................................................      34,633,966
</TABLE>
 
    Historical
 
<TABLE>
<S>                                                                                 <C>
Nine months ended September 30, 1996..............................................      20,378,377
Nine months ended September 30, 1995..............................................       1,004,313
Year ended December 31, 1995......................................................       3,234,843
Year ended December 31, 1994......................................................         128,620
August 23, 1993 (date of inception) to December 31, 1993..........................           6,594
</TABLE>
 
                                       34
<PAGE>
               MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
                      CONDITION AND RESULTS OF OPERATIONS
 
GENERAL
 
    The Company provides wireless broadband telecommunications services using
point-to-point microwave transmissions primarily in the 38 GHz portion of the
radio spectrum. The Company is seeking to address the growing demand for high
speed, high capacity digital telecommunications services on the part of business
and government end users who require cost effective, high bandwidth local access
to voice, video, data and Internet services.
 
    The following discussion and analysis is based upon the financial statements
of the Company, as restated to reflect the Merger effected in October 1996.
Certain statements set forth below constitute "forward-looking statements"
within the meaning of the Private Securities Litigation Reform Act of 1995. Such
forward-looking statements involve known and unknown risks, uncertainties and
other factors that may cause the actual results, performance or achievements of
the Company, or industry results, to be materially different from any future
results, performance or achievements expressed or implied by such
forward-looking statements. Given these uncertainties, prospective investors are
cautioned not to place undue reliance on such forward-looking statements. See
"Risk Factors" and "Special Note Regarding Forward-Looking Statements."
 
OVERVIEW
 
    The Company's business commenced in 1993, and the Company has generated only
nominal revenues from operations to date. The Company's primary activities have
focused on the acquisition of wireless construction permits (authorizations for
facilities that are not yet constructed) and licenses (authorizations for
facilities that are constructed), the hiring of management and other key
personnel, the raising of capital, the acquisition of equipment and the
development of its operating and support systems and infrastructure. The Company
has obtained radio spectrum rights under FCC issued licenses and construction
permits throughout the United States by applying to the FCC directly and through
the purchase or lease of such rights held by others. The Company's ability to
provide commercial services on a widespread basis and to generate positive
operating cash flow will depend on its ability, among other things, to (i)
deploy its 38 GHz technology on a market-by-market basis, (ii) attract and
retain an adequate customer base, (iii) successfully develop and deploy its
operational and support systems and (iv) acquire appropriate sites for its
operations. Proper management of the Company's anticipated growth and quality of
its service will require the Company to expand its technical, accounting and
internal management systems at a pace consistent with the Company's planned
business roll-out. This roll-out will require substantial capital expenditures.
See "Liquidity and Capital Resources" and "Risk Factors."
 
    The Company has experienced significant operating and net losses and
negative operating cash flow in connection with the development and deployment
of its wireless broadband services and systems and expects to continue to
experience operating and net losses and negative operating cash flow until such
time as it develops a revenue-generating customer base sufficient to fund
operating expenses attributable to the Company's wireless broadband operations.
See "Risk Factors." The Company expects to achieve positive operating margins
over time by (i) increasing the number of revenue generating customers and
responding to growing demand for capacity among its customers without
significantly increasing related hardware and roof rights costs and (ii)
inducing other telecommunications service providers to utilize and market the
Company's wireless broadband services as part of their own services, thereby
reducing the Company's related marketing costs. The Company expects its
operating revenues will increase in 1997; however, the Company also expects that
operating and net losses and negative operating cash flow will increase as the
Company implements its growth strategy and that, under its current business
plan, operating and net losses and negative operating cash flow will continue at
least through fiscal 1998. Accordingly, the Company will be dependent on various
financing sources to fund its growth as well as continued losses from
operations. See "--Liquidity and Capital Resources."
 
                                       35
<PAGE>
ACQUISITIONS, BUSINESS DEVELOPMENT AND CAPITAL EXPENDITURES
 
    From inception through September 30, 1996, the Company has invested an
aggregate of $4.4 million to obtain interests in FCC authorizations and
licenses, including those acquired from EMI, and invested $285,000 in the ART
West Joint Venture. From inception through September 30, 1996, expenditures for
property and equipment have totalled $11.4 million. In addition, the Company has
incurred significant other costs and expenses in the development of its business
and has recorded cumulative losses from inception through September 30, 1996 of
approximately $23.7 million, including $9.6 million of non-cash compensation and
marketing expenses, and used cash in operating activities of approximately $10.6
million. The Company has agreed to acquire, subject to FCC approval and other
conditions, additional FCC authorizations and licenses for an aggregate purchase
price (before related expenses) of $6.0 million in cash (of which $3.0 million
was paid in November 1996) and 6,000,000 shares of Common Stock. The Company
may, when and if the opportunity arises, acquire other spectrum rights and,
potentially, related businesses, incur expenses in the development of new
technologies and expand its wireless broadband services into new market areas.
 
    The recoverability of property and equipment and intangible assets
representing FCC authorizations is dependent upon the successful development of
systems in each of the respective markets, or through sale of such assets.
Management estimates that it will recover the carrying amounts of those assets
from cash flow generated by the systems once they have been developed. However,
it is possible that such estimate will change as a result of any failure by the
Company to develop its FCC authorizations on a timely basis, or technological,
regulatory or other changes. The Company anticipates that it will fund
approximately $1.0 million for research and development activities pursuant to a
letter of intent with Helioss Communications Corporation. Although the Company
does not have other material commitments to fund research and development or to
make investments in other companies, the Company expects to incur additional
research and development expenses and to make other such investments from time
to time.
 
    In October 1996, ART entered into a binding letter of intent with Advantage
Telecom, Inc. ("ATI"), a Canadian company which has applied for licenses to
provide 38 GHz service in the 66 major markets in Canada covering a population
of at least 21 million. Upon consummation of the transactions described in the
letter of intent, ART will hold a substantial direct and indirect minority
interest in ATI and will be a party to a services agreement with ATI pursuant to
which ART will construct and operate radio systems based upon any licenses that
may be granted to ATI and subject to control by ATI. The Company incurred costs
of approximately $300,000, and ATI is responsible for securing any additional
funding necessary to construct the radio systems. Due to current uncertainty in
Canada's licensing policy, there can be no assurance that ATI will be granted
these licenses or that, if granted, ATI will obtain the funding necessary to
construct the radio systems.
 
    On September 29, 1996 the Company entered into a shareholders agreement with
Trond Johannessen, pursuant to which the Company anticipates eventually
obtaining licenses and offering its wireless broadband services through separate
subsidiaries in the 17 countries comprising the European Union. The Company has
caused or will cause to be formed subsidiaries in Sweden, the United Kingdom and
Italy for this purpose. Under the shareholders agreement, in consideration for
services to be rendered and his proportionate share of the formation costs, Mr.
Johannessen is entitled to receive a 20% interest in the initial shareholdings
in certain of the subsidiaries in each country, prior to significant funding of
each subsidiary. The Company has no further commitment to fund any such
subsidiary. Mr. Johannessen is also a consultant to the Company, for which he
currently receives monthly payments of $10,000 plus expenses. The Company is
seeking but has not yet received any operating licenses, strategic alliances or
customer commitments in Europe. Although each member nation of the European
Economic Community is required pursuant to a directive of the European
Commission to open its telecommunication markets to competition over the next
several years, the timing and extent of a relaxation in entry barriers and the
degree of cooperation from the incumbent service providers in such
 
                                       36
<PAGE>
areas as interconnection to customers and the public networks is unknown. There
can be no assurance that the Company will be able to acquire the licenses
necessary in each European country, to finance and to implement its business
plan or to operate in any country on a profitable basis.
 
    The Company entered into a management consulting agreement in November 1995
with Landover Holdings Corporation ("LHC") to provide strategic planning,
corporate development and general management services. Under the agreement,
which terminated concurrently with the Common Stock Offering, the Company paid
LHC $35,000 per month for an initial one year term. In 1995 the Company paid
$140,000 to LHC for consulting services and $391,750 for expenses in connection
with the $7.0 million investment made under the LHC Purchase Agreement. In
November 1996, the Company paid LHC approximately $300,000 as a fee in
connection with various consulting services previously rendered under the
management consulting agreement. See "Certain Transactions."
 
RESULTS OF OPERATIONS
 
    From inception through September 30, 1996, the Company has generated revenue
of $130,806 from operations and has incurred aggregate expenses of approximately
$24.0 million, including $9.6 million of non-cash compensation and marketing
expenses. The remaining expenses consist of compensation and benefits, sales and
marketing expenses, consulting and legal fees, facilities expenses, systems
development costs, management consulting expenses and depreciation and
amortization related to building the Company's business infrastructure and
marketing its wireless broadband services and net interest expense. The Company
expects to generate increased revenues in 1997; however, there can be no
assurance that the Company will achieve substantially increased revenues in the
future. The Company expects that it will not achieve profitable operations at
least through fiscal 1998. See "Risk Factors -- Limited Operations; History of
Net Losses."
 
    NINE MONTHS ENDED SEPTEMBER 30, 1996 COMPARED TO SEPTEMBER 30, 1995
 
    Revenue for the nine months ended September 30, 1996 was $125,013 compared
to no revenue in 1995. Revenue in 1996 is earned from wireless broadband
telecommunications services provided by the Company. During the nine months
ended September 30, 1996, the Company operated approximately 60
revenue-generating radio links (single path point-to-point microwave
connections).
 
    Operating expenses other than interest were $19.2 million for the nine
months ended September 30, 1996 compared to $1.0 million in 1995. The increase
was primarily due to $7.5 million of non-cash compensation expense, including
$6.8 million arising from the termination of the Escrow Share Arrangement (as
defined) and subsequent release of shares to certain employees in connection
with the February 1996 Reorganization (as defined), as well as higher general
and administrative, market development and research and development expenses.
See "Certain Transactions." Excluding the non-cash compensation expense, general
and administrative expenses increased primarily due to higher payroll and
consulting costs relating to the commencement of operations of the Company.
Included in general and administrative expenses is a charge of approximately
$1.2 million associated with the Company's unsuccessful public debt offering in
July 1996. Market development expenses increased primarily due to a non-cash
marketing expense of $1.1 million related to the Ameritech Strategic
Distribution Agreement. Research and development costs were incurred as the
Company initiated its research and development of microwave radio technology.
The Company expects cash expenses for general and administrative, marketing and
research and development to increase substantially in future periods as the
development and deployment of the Company's business continues.
 
    Net interest expense was $1.3 million for the nine months ended September
30, 1996 compared to $1,539 in 1995. The increase in interest expense was
primarily due to interest on the EMI Note, the Equipment Note, the March Bridge
Notes, the CommcoCCC Notes and the September Bridge Notes. The Company expects
the issuance of the Notes and any future financings will cause interest expense
to increase substantially in future periods. The repayment in November 1996 of
the March Bridge Notes,
 
                                       37
<PAGE>
the CommcoCCC Notes and the September Bridge Notes will result in a non-cash
extraordinary loss of approximately $1.3 million in the fourth quarter of 1996
relating to the write-off of associated unamortized offering discount and
deferred financing costs.
 
    FISCAL 1995 COMPARED TO FISCAL 1994
 
    ART was formed in 1993, and, accordingly, the Company's historical financial
statements for 1994 reflect ART's activities in applying for 38 GHz licenses and
building operating systems.
 
    The Company had $137,489 in consulting services income for engineering and
management services related to filing of applications for 38 GHz licenses on
behalf of others, including Extended, in 1994 and $5,793 in service revenue in
1995 derived from customers for wireless broadband services attributable to the
markets for which licenses were acquired from EMI in November 1995. See
"Business -- Agreements Relating to Licenses and Authorizations -- EMI
Acquisition."
 
    Total expenses other than interest increased from $261,734 in 1994 to $3.1
million in 1995 due to the expansion of the business and the recognition of
non-cash compensation expenses associated with employee stock options of
$287,603 and certain Escrow Shares (as defined) of $802,002 associated with the
release to certain employees of the Company as a result of meeting certain
performance objectives for an aggregate of $1.1 million of non-cash compensation
expenses. See "Certain Transactions -- LHC Purchase Agreement -- February 1996
Reorganization." General and administrative expenses, including these non-cash
compensation expenses, increased to $2.9 million for fiscal 1995, from $253,453
for 1994. Market development expenses increased to $191,693 in 1995 from $0 in
1994. Net interest expenses increased to $121,986 in 1995 from $4,375 in 1994.
As a result, the net loss for 1995 was $3.2 million, as compared to a net loss
of $128,620 in 1994.
 
    FISCAL 1994 COMPARED TO FISCAL 1993
 
    The Company had $137,489 in consulting services income in 1994 compared to
no revenue in 1993. The increase in 1994 was primarily due to consulting
services related to 38 GHz license applications.
 
    Total expenses other than interest expense increased to $261,734 in 1994
from $6,594 in 1993. The increases were due primarily to consulting and legal
fees related to the initial operations of the Company.
 
LIQUIDITY AND CAPITAL RESOURCES
 
    The Company's operations have required substantial capital investment for
the acquisition of FCC authorizations and related assets, the purchase of
telecommunications equipment, staffing, and the development and expansion of the
Company's infrastructure to support anticipated growth. From inception through
September 30, 1996, the Company used $10.6 million of cash in its operating
activities and $9.8 million of cash in its investing activities. These cash
outflows were financed primarily through private equity and debt placements,
including the issuance of convertible notes payable to the Advent Partnerships
which were converted into equity in February 1996. At December 31, 1995 the
Company had a working capital deficit of $3.0 million and cash of $633,654, as
compared to a working capital deficit of $76,556 and cash of $5,133 at December
31, 1994. The Company had a working capital deficit of $20.7 million and cash of
$752,368 at September 30, 1996.
 
    In October 1996, the Company received the remaining $1.6 million in cash
(out of a total of $4.0 million) from the September Bridge Financing. During
November and December 1996, the Company received gross proceeds of approximately
$34.5 million from the Common Stock Offering and repaid the March Bridge Notes,
the CommcoCCC Notes and the September Bridge Notes. See "Certain Transactions."
 
    The Company's total assets increased from $42,611 as of December 31, 1994 to
$9.9 million at December 31, 1995 and $20.5 million at September 30, 1996.
Property and equipment, net of accumulated depreciation, comprised $3.6 million
of total assets at December 31, 1995 and $11.0 million at
 
                                       38
<PAGE>
September 30, 1996. FCC licenses and the investment in the ART West Joint
Venture comprised $4.5 million of total assets at December 31, 1995, compared to
$4.6 million at September 30, 1996 and $0.0 at December 31, 1994.
 
    Cash used in operating activities increased by $1.4 million to $1.5 million
in 1995 over 1994. The increase in cash used in operating activities resulted
primarily from the increase in net loss to $3.2 million, partially offset by
non-cash compensation expenses of $1.1 million and increased payables in 1995.
 
    Cash used in investing activities increased by $4.2 million in 1995 compared
to minimal amounts in 1994. The increase was primarily due to $3.0 million paid
for the EMI acquisition, and approximately $600,000 used for property and
equipment additions in 1995.
 
    Cash provided by financing activities increased by $6.2 million in 1995 over
1994. The increase was primarily due to the issuances of the Advent/ART
Securities of $5.0 million and of Telecom serial preferred stock, net of
redemptions of $2.0 million issued in 1995, partially offset by the use of cash
for stock and debt issuance costs.
 
    Capital expenditures, including deposits on equipment for fiscal 1995 and
1994, were $3.9 million and $5,175, respectively. The Company currently
purchases the majority of its wireless transmission equipment from a single
vendor, P-Com, Inc., under an equipment purchase agreement which expires at the
end of 1998. The Company is committed to purchase a total of $13.3 million of
equipment under this agreement. The Company has also entered into an equipment
purchase agreement, expiring in 1997, with Harris, providing for the purchase of
wireless transmission equipment.
 
    Cash used in operating activities increased to $9.0 million for the nine
months ended September 30, 1996 compared to $750,291 for the nine months ended
September 30, 1995. The increase was primarily due to higher operating costs.
Cash used in investing activities was approximately $5.5 million for the nine
months ended September 30, 1996 compared to $419,620 for the nine months ended
September 30, 1995. The increase was primarily due to additions to property and
equipment. Cash provided by financing activities increased to $14.6 million in
the nine months ended September 30, 1996 compared to $1.2 million for the nine
months ended September 30, 1995. The increase was primarily due to the private
equity placement with Ameritech, the issuance of the Equipment Financing, the
March Bridge Financing, the CommcoCCC Financing and the September Bridge
Financing.
 
    The Company does not currently manufacture, nor does it have or plan to
develop the capability to manufacture, any of the wireless transmission
equipment necessary to provide its services. Although there are a limited number
of manufacturers who have, or are developing, equipment that would meet the
Company's requirements, there can be no assurance that such equipment would be
available to the Company on comparable terms or on terms more favorable than
those included in its current arrangements in the event that such arrangements
are terminated. Moreover, a change in vendors could cause a delay in the
Company's ability to provide its services, which would affect future operating
results adversely.
 
    The Company has funded approximately $400,000 of research and development
costs with American Wireless Corporation ("American Wireless") related to
wireless transmission equipment. Vernon L. Fotheringham, the Chairman of the
Company, is a former director and a 3% shareholder of American Wireless. See
"Certain Transactions -- American Wireless Development Agreement." The Company
has also entered into a letter of intent with Helioss Communications Corporation
("Helioss") for the development of advanced 38 GHz radios. Under the letter of
intent, which is subject to definitive documentation, the Company will fund up
to $1.0 million of Helioss' research and development expenses. The Company will
have a right of first refusal on production capacity of the radios and will
receive a royalty on the sale of a certain number of radios to customers other
than the Company. Although the Company does not have any other material
commitments to fund research and development or to make investments in other
companies, it expects to incur additional expenses for research and development
and to make other such investments from time to time.
 
                                       39
<PAGE>
    A substantial portion of the net proceeds from the Offering is expected to
be used for capital expenditures. Because the Company installs links in response
to customer orders and can redeploy links removed from service, the Company's
actual rate of capital expenditures will depend largely on levels of customer
demand. The Company currently expects to use approximately $35.0 million of the
net proceeds for capital expenditures in 1997, consisting of approximately $29.0
million for wireless transmission equipment, approximately $3.0 million for
network design and development and related equipment and approximately $3.0
million for computer equipment and other capital requirements. Included in these
amounts are the costs of initial construction of the remaining CommcoCCC
authorizations which have not yet satisfied the FCC's construction deadline,
estimated to be less than $1.5 million, including wireless transmission
equipment. Although the Company does not anticipate substantial difficulties in
completing such initial construction on a timely basis, the failure to do so
could have a material adverse effect on the number of licenses available to the
Company to carry out its business. If the Company does not consummate the
CommcoCCC Acquisition, the impact upon capital expenditures in 1997 is not
expected to be significant, other than capital expenditures for the initial
construction of the remaining CommcoCCC authorizations. The Company expects that
capital expenditures for the installation of 38 GHz wireless transmission
equipment will increase as demand for the Company's 38 GHz services increases in
the targeted geographic markets and industry segments over the next several
years.
 
    In addition, the Company has agreed to acquire authorizations and licenses
for $6.0 million from ART West, of which $3.0 million was paid in November 1996.
The Company has entered into an agreement to acquire 129 38 GHz authorizations
from CommcoCCC in exchange for 6,000,000 shares of Common Stock. CommcoCCC has
entered into a management agreement with the Company under which the Company
will construct, manage and operate the authorizations to be acquired pending
consummation of the CommcoCCC Acquisition. See "Business -- Agreements Relating
to Licenses and Authorizations" and "Risk Factors -- Risk of Non-Consummation of
CommcoCCC Acquisition and Other Acquisitions."
 
    The Company is obliged to pay all costs and expenses of construction,
operation and management of the authorizations managed by the Company. The
Company is also obligated under the terms of the service agreements covering
such authorizations to pay fees to the current holders of those authorizations
approximating 10% to 15% of the revenue generated from such assets. See
"Business -- Agreements Relating to Licenses and Authorizations."
 
    The Company expects that it will continue to have substantial capital
requirements in connection with (i) the acquisition of appropriate sites for its
operations, (ii) deployment of its 38 GHz technology on a market-by-market
basis, (iii) capturing and retaining an adequate revenue generating customer
base and (iv) developing and deploying its operational and support systems. The
Company believes it has an opportunity to expand its wireless broadband services
business significantly and that access to capital will enable it to expand more
quickly and effectively. See "Risk Factors -- Significant Capital Requirements;
Need for Additional Financing."
 
    The Company has incurred significant operating and net losses and negative
operating cash flow attributable to the development of its wireless broadband
services and anticipates that such losses and negative operating cash flow will
increase as the Company implements its growth strategy. Accordingly, the Company
will be dependent on additional capital to fund its growth, as well as to fund
continued losses from operations.
 
    During November 1996, the Company completed the Common Stock Offering,
raising $34.5 million before expenses. An aggregate of $12.0 million from the
proceeds of the Common Stock Offering was used to repay the March Bridge Notes,
the CommcoCCC Notes and the September Bridge Notes, and $3.0 million was used to
fund a portion of the acquisition of the remaining 50% interest in ART West.
Management anticipates that, based on current plans of development, assuming
that no new material acquisitions (other than those currently under contract)
are consummated, the remaining net proceeds of the Common Stock Offering and
funds available from the Offering after the use of $3.0
 
                                       40
<PAGE>
million to complete pending acquisitions of certain spectrum rights and $2.4
million to pay expenses related to the CommcoCCC Acquisition when consummated,
will be sufficient to fund the operations of the Company at least through
December 31, 1997. Management also believes that the Company's future capital
needs will continue to be significant, and management intends to continue to
seek additional sources of financing. The Company is currently pursuing the
Credit Facility as a source of additional financing, although there can be no
assurance that the Credit Facility can be obtained. See "Description of Certain
Indebtedness--Proposed Credit Facility." In addition, if (i) the Company's plan
of development or projections change or prove to be inaccurate, (ii) the
proceeds of the Offering, together with other existing financial resources,
prove to be insufficient to fund the Company through December 31, 1997, (iii)
the Company completes any material acquisitions, other than those now under
contract, or buys spectrum at auction or (iv) the Company accelerates
implementation of its business plan, the Company may be required to obtain
additional financing earlier than December 31, 1997. There can be no assurance
that the Company will be able to obtain any additional financing, or, if such
financing is available, that the Company will be able to obtain it on acceptable
terms. In the event that the Offering is not consummated in a timely manner and
the Company is unable to obtain additional financing, the Company may be obliged
to modify, delay or abandon some or all of its development and expansion plans.
Any such modification, delay or abandonment is likely to have a material adverse
effect on the Company's business, which could adversely affect the value of the
Common Stock and may limit the Company's ability to make principal and interest
payments on its indebtedness. See "Risk Factors -- Significant Capital
Requirements; Need for Additional Financing."
 
NEW ACCOUNTING PRONOUNCEMENT
 
    In October 1995, the Financial Accounting Standards Board issued Statement
of Financial Accounting Standards No. 123, "Accounting for Stock-Based
Compensation." This Statement encourages, but does not require, accounting for
stock compensation awards granted to employees based on their fair value at the
date the awards are granted. Companies may elect to continue to apply current
accounting requirements for employee stock compensation awards, which generally
will result in no compensation cost for most fixed stock option plans, such as
the Company's Equity Incentive Plan. The expense measurement provisions of the
Statement apply to all equity instruments issued for goods and services provided
by persons other than employees. All companies are required to comply with the
disclosure requirements of the Statement. The Company expects to continue
accounting for employee stock compensation awards using current accounting
requirements.
 
INFLATION
 
    Management does not believe that its business is impacted by inflation to a
significantly different extent than is the general economy.
 
                                       41
<PAGE>
                                    BUSINESS
 
    Advanced Radio Telecom Corp. ("ART" or the "Company") provides wireless
broadband telecommunications services using point-to-point microwave
transmissions in the 38 GHz band of the radio spectrum. The Company is seeking
to address the growing demand for high speed, high capacity digital
telecommunications services on the part of business and government end users who
require cost effective, high bandwidth local access to voice, video, data and
Internet services. Upon completion of its pending acquisition of 129 38 GHz
wireless broadband authorizations (the "CommcoCCC Assets") from CommcoCCC, Inc.
("CommcoCCC") but excluding any licenses leased under the ICG Agreement, the
Company will own, manage or have a right to use on a long-term basis a total of
233 authorizations (which are also referred to herein as "licenses") granted by
the Federal Communications Commission (the "FCC") covering an aggregate
population of approximately 156 million in 169 U.S. markets. During 1996 the
Company installed over 370 radio links (single path point-to-point microwave
connections), including approximately 80 revenue-generating radio links
installed and operated by the Company and an additional 99 radio links installed
for other carriers.
 
TELECOMMUNICATIONS INDUSTRY OVERVIEW
 
    The current telecommunications landscape is being reshaped by the
convergence of three major trends: (i) the accelerating growth in demand for
high speed, high capacity digital telecommunications services, (ii) the
deregulation of telecommunications markets and (iii) the rapid advances in
wireless technologies. The growth in demand for high speed digital
telecommunications services is being driven by the revolution in microprocessor
power and advances in new multimedia and on-line applications such as the
Internet. The ability to access and distribute information quickly has become
critical to business and government users of telecommunications services. The
rapid growth of local area networks ("LANs"), Internet services, video
teleconferencing and other data intensive applications is significantly
increasing the volume of broadband telecommunications traffic. The inability of
the existing infrastructure to meet this demand is creating a "last mile"
bottleneck in the copper wire networks of the incumbent local exchange carriers
("LECs"). This increasing demand, together with changes in the regulatory
environment, is creating an opportunity to offer cost effective, high capacity
last mile access using both wireline and wireless solutions.
 
    The present structure of the U.S. telecommunications industry was shaped
principally by the 1984 court-directed divestiture of the Bell System (the
"Divestiture"). As part of the Divestiture, seven Regional Bell Operating
Companies ("RBOCs") were created and separated from the long distance service
provider, AT&T, resulting in two distinct telecommunications industries: local
exchange and inter-exchange (commonly known as long distance). Local exchange
services typically involve the carriage of telecommunications within defined
local access and transport areas ("LATAs"), and the provision of access, or
connections, between LECs and inter-exchange carriers ("IXCs") for the
completion of long distance calls.
 
    Since the Divestiture, the local exchange segment of the telecommunications
market, with total 1995 revenues estimated by the FCC at over $95.0 billion, has
remained the domain of LECs. Recently, however, regulatory policy has shifted
away from monopoly protection of the LECs. U.S. court decisions, FCC actions
and, most recently, the Telecommunications Act of 1996 (the "Telecommunications
Act") have dramatically changed the regulatory environment. These changes have
permitted increased competition in the local exchange market and created
opportunities for new companies, such as competitive access providers ("CAPs").
 
    In the late 1980s, CAPs emerged to compete with LECs by providing dedicated
private line transmission and access services. Beginning in 1994, a few states
permitted CAPs to also operate as "competitive local exchange carriers"
("CLECs"), by providing local exchange services to business customers in
addition to transmission and access services. These CAP/CLEC networks typically
consist of fiber optic facilities connecting IXC points of presence ("POPs")
with customer locations and LEC switches within a limited metropolitan area.
Initially, demand for alternative local access was driven by
 
                                       42
<PAGE>
access charges of approximately 40% to 45% of the cost of a long distance call
levied by LECs on the IXCs. In addition to providing lower access charges,
CAP/CLEC fiber optic services, where available, have generally been considered
to provide superior quality and higher capacity services than those available
from LECs' legacy copper wire networks. A leading research company estimates
that in 1994 CAPs/CLECs captured approximately $1.3 billion of the revenues
generated by the local exchange market. Such research company also projects
that, as a result of increased competition and the growth of enhanced services,
CAPs/CLECs' revenues will grow in excess of 150% per year over the next two
years. In addition to CAPs/CLECs, a wide range of alternative access providers,
including cable television operators, wireless local loop service providers and
others, are expected to emerge.
 
    Continued growth in the quality and number of competitors in the local
telecommunications market will be driven principally by (i) the growing interest
among business customers for an alternative to the LEC networks in order to
obtain higher capacity and better pricing, (ii) the increases in data
applications and capacity requirements for local and wide area network
connections, high speed Internet access and videoconferencing, (iii) the LECs'
inability to upgrade their copper networks quickly, (iv) the preference of
competing telecommunications providers to control the points of connection to
their customers and prevent LECs from obtaining confidential marketing
information and (v) new state and federal legislation mandating interconnection
and competition in the local exchange market.
 
    Wireless broadband telecommunications services are developing rapidly to
handle these growing needs for alternative access. In particular, the successful
deployment of 38 GHz links by European cellular service providers and recent
advances in 38 GHz technology, coupled with metropolitan-wide footprint
licensing, has enabled the provision of greater capacity and reliability at a
lower cost per customer than traditional copper wire networks. Furthermore, 38
GHz facilities can be installed, deinstalled and reinstalled elsewhere with
minimal time and cost compared to both fiber optic and copper wire facilities.
 
ART'S WIRELESS BROADBAND SERVICES
 
    The Company is positioned to solve the need for broadband last mile
services, linking end users to facilities of LECs, CAPs/CLECs, IXCs and Internet
Service Providers ("ISPs"). The Company is also positioned to link cell sites of
mobile communications service providers and to link metropolitan area network
sites using 38 GHz technology. The Company's wireless broadband links deliver
high quality voice and data transmissions at a level of performance which
exceeds the performance of copper based networks and is a viable alternative to
fiber optic based networks. The Company provides point-to-point wireless digital
circuits ranging in capacity from DS-1 (1.544 Megabits per second ("Mbps"),
capable of carrying 24 simultaneous voice conversations) to DS-3 (45 Mbps,
capable of carrying 672 simultaneous voice conversations). The Company believes
that it generally owns or manages sufficient 38 GHz bandwidth to satisfy the
anticipated service requirements of its target customers in each of the
Company's existing markets and the additional 80 markets to be acquired under
the CommcoCCC Agreement (as defined).
 
    The Company intends initially to market its services as a carrier's carrier
in order to leverage ART's carrier customers' sales forces, channels of
distribution and customer bases. The Company believes that its services will be
attractive to carrier customers which do not currently have broadband networks
that reach the majority of their customers. For example, the Company has entered
into a strategic distribution agreement (the "Ameritech Strategic Distribution
Agreement") with Ameritech ("Ameritech") for delivery of the Company's wireless
broadband services throughout Ameritech's midwest operating region and for
certain large customers located outside its region. Ameritech has initiated the
sale of ART's wireless broadband services on a limited basis, and the Company
expects that full-scale rollout will begin in the first quarter of 1997. See "--
Strategic Alliances -- Ameritech Strategic Distribution Agreement."
 
    Each of ART's wireless broadband links consists of paired millimeter wave
radio transceivers installed at a distance of up to five miles from one another
within a direct line of sight. The transceivers currently used by the Company
are installed primarily on rooftops. In order to deploy its links quickly,
 
                                       43
<PAGE>
the Company plans to obtain roof rights on buildings with fiber optic points of
termination for transceiver sites. To accomplish this objective, the Company is
developing proprietary site selection and network design software which will
significantly reduce the amount of time necessary to select optimal network
sites. In coordination with its marketing plans, the Company will dispatch site
acquisition specialists locations to obtain renewable site access options at
targeted locations. The Company uses a combination of its own employees and
independent contractors for site acquisition.
 
    Significant features of the Company's wireless broadband services include
(i) sufficient bandwidth and flexibility in each channel for most present day
applications, (ii) minimal channel interference from other sources, resulting
from dedicated spectrum, (iii) range of up to five miles between transmission
links (depending upon path engineering factors), (iv) performance engineered to
provide a minimum of 99.999% availability, (v) transmission accuracy engineered
to provide bit error rates of better than 10-13 (unfaded), (vi) optional forward
error correction for even higher data reliability, insuring the integrity of
transmitted data over wireless broadband paths, (vii) rapid deployment, (viii)
24-hour, seven-days-a-week network monitoring by the Company's network
management control center, (ix) available nationwide four-hour emergency
restoral time in most circumstances and (x) optional "hot" standby links that
remain powered up and switch "on line" if the primary link fails.
 
    The Company believes that a number of factors provide it with certain
significant competitive advantages in offering broadband last mile services,
including:
 
    - The characteristics of 38 GHz technology (high data transfer rates,
      significant channel capacity, rapid deployment, easy installation, very
      high transmission quality and efficient network design) are ideal for the
      provision of last mile services. See "-- 38 GHz Technology."
 
    - The Company deploys capital efficiently because of the
      installation-to-meet-demand and redeployable nature of the Company's
      wireless broadband equipment, as compared to the significant upfront cost
      for installation of fiber based networks.
 
    - As one of the first 38 GHz service providers, the Company enjoys a
      time-to-market advantage and is therefore well-positioned to capture a
      large percentage of early adopters, which are generally among the heaviest
      users. The Company believes it is one of only two 38 GHz service providers
      currently offering commercial services.
 
    - The Company is forging strategic alliances with major telecommunications
      carriers, equipment vendors and technology development companies, thus
      gaining access to important channels of distribution and early deployment
      of advanced technologies.
 
    - The broad scope of the Company's footprint enables it to offer wireless
      broadband services targeting much of the United States's addressable
      business market.
 
    - The Company's network management operational support system that provides
      24-hour, seven-days-a-week network monitoring and management. The system
      is designed to provide provisioning, link alarm monitoring, link
      performance reporting, historical link performance data, remote link
      diagnosis, remote link restoral and coordination and testing with
      associated network operating centers.
 
    - The Company is developing proprietary Geographic Information Systems
      ("GIS") that provide ART with 3-D digital modeling of all of its markets,
      including all building and landscape features, to reduce the time and
      expense of engineering its proposed radio locations. These systems will
      allow the Company to determine line of site for proposed links, produce a
      list of tenants in the buildings serviceable from such locations and
      integrate this information with its marketing databases. The GIS
      development will enable the Company remotely to determine line-of-sight
      availability and provide immediate information regarding network design
      alternatives. These systems further provide the Company with a powerful
      tool to market its services to telecommunications service providers
      seeking to offer broadband connectivity to their customers.
 
                                       44
<PAGE>
BUSINESS STRATEGY
 
    The Company is seeking to capitalize on its broad footprint of 38 GHz
authorizations to become a leading provider of wireless broadband solutions to a
diverse group of traditional and emerging telecommunications service providers
and end users. The Company has begun to implement the following strategic
initiatives to achieve this objective:
 
    - CAPITALIZE ON BROAD SPECTRUM POSITION. The Company's spectrum assets
     provide it with the foundation on which to create a large scale commercial
     network of 38 GHz wireless broadband operations. The Company plans to
     continue to build out its infrastructure and to intensify its marketing
     effort in its market areas in order to exploit the value inherent in its
     spectrum assets. See " -- Agreements Relating to Licenses and
     Authorizations."
 
    - ESTABLISH AND EXPAND KEY STRATEGIC ALLIANCES. The Company plans to utilize
     strategic alliances to bundle its services with those of its partners, to
     provide for alternative distribution channels and to gain access to
     technological advancements. The Company has established and will seek to
     continue to establish key strategic alliances with major service providers,
     equipment manufacturers and systems integrators. Under the Ameritech
     Strategic Distribution Agreement, Ameritech is targeting certain sales
     objectives and has agreed to spend internally up to $7.0 million on its
     sales and marketing of ART's services. Ameritech owns a 5.0% beneficial
     equity interest in the Company as of January 14, 1997. The Company also has
     agreements with Harris Corporation, Farinon Division ("Harris") for
     marketing ART's 38 GHz services to PCS providers and with GTE Corporation
     for installation, field servicing and network monitoring. See "-- Strategic
     Alliances."
 
    - MARKET INITIALLY AS A CARRIER'S CARRIER. The Company intends to initially
     market its services as a carrier's carrier in order to leverage ART's
     carrier customers' sales forces, channels of distribution and customer
     bases. The Company's initial target customers include LECs, CAPs/CLECs,
     IXCs, ISPs and mobile communications service providers. The Company
     believes that its services are particularly attractive to carrier customers
     who do not currently have broadband networks capable of reaching the
     majority of their customers.
 
    - PROACTIVELY IDENTIFY OFF-NET MARKET OPPORTUNITIES FOR CARRIER CUSTOMERS.
     ART utilizes its proprietary database tools, such as GIS, to analyze a
     particular carrier's network and identify high density off-net customer
     locations. The GIS database is then used to pre-clear off-net buildings for
     line-of-site, distance and network design alternatives. After a critical
     mass of sites has been pre-qualified, the Company is able to proactively
     market to the carrier access to such customer premises and pursue a "team
     selling" approach to end users. Utilizing this proactive approach with
     multiple carriers is expected to allow the Company incrementally to build a
     custom-designed wireless hub network in each of its target markets.
 
    - PURSUE OPPORTUNITIES TO PROVIDE VALUE-ADDED SERVICES. The Company will
     also market services such as data, video-conferencing, high resolution
     imaging and video on demand directly to end users in conjunction with
     system integrators, telecommunications equipment manufacturers and other
     service providers. The Company also plans to offer point-to-multipoint
     wireless broadband services and may also decide to offer switched-data
     services to end users who desire a single source telecommunications
     solution.
 
    - MAINTAIN COMPETITIVE ADVANTAGES THROUGH TECHNOLOGY ADVANCEMENTS. As 38 GHz
     microwave radios begin to be produced in large volumes with modern
     manufacturing techniques, the Company believes that the cost of such
     equipment will decline, thereby allowing the Company to meet anticipated
     price competition in its markets. In addition, through the Company's
     internal technology development efforts, as well as on-going participation
     in equipment manufacturers' research and development activities, the
     Company continuously seeks to reduce costs by designing equipment that
     allows it to more efficiently utilize its spectrum. For example, the
     Company anticipates taking delivery of 38 GHz OC-3 SONET compatible radios
     (155 Mbps) within 18-24 months.
 
                                       45
<PAGE>
MARKETING PLANS
 
    ART is addressing its initial target markets as a carrier's carrier, while
expanding its marketing efforts to include direct sales to end users of its
services. The Company is augmenting its marketing and sales channels through
resale agreements with strategic marketing partners and through alliances with
selected LECs, CAPs/CLECs, ISPs, IXCs, interconnect providers (PBX suppliers),
LAN, MAN and WAN systems integrators and other telecommunications equipment
manufacturers and service providers.
 
    To develop the market potential of its wireless broadband authorizations,
ART has organized its operations into four geographic regions: Northeastern,
Central, Southern and Western. Each region has its own General Manager in charge
of operations, field service and sales and marketing. Factors that determine the
extent of proactive sales activity in each market include (i) number of license
areas, (ii) geographic size of license areas, (iii) end user density within
license areas, (iv) radio link design variables such as precipitation patterns
and topography and (v) the strategies of the incumbent LECs and CAPs/CLECs.
Organizing its markets into regions provides ART with significant operating cost
efficiencies through the centralization of its administrative functions, and
allows ART to provide superior service to its key customers.
 
    The Company's internal salesforce is currently marketing the Company's
wireless broadband services by (i) team selling with the carriers' sales forces
(ii) performing field demonstrations of 38 GHz service, (iii) making
presentations at industry trade shows, (iv) providing an interactive Internet
home page, (v) running promotional advertisements in selected trade media and
(vi) conducting extensive one-on-one presentations and demonstrations through
its carrier sales force. The sales organization is supported by the product
marketing group which has developed programs for each of the targeted sectors.
 
    As a non-dominant carrier, ART does not have to cost-justify its rates to
regulatory bodies and therefore has a wide latitude to exercise individual case
based pricing, subject to certain policies against discriminatory treatment. As
a result, ART expects to enter into customer-specific and service-specific
arrangements, which include volume, capacity and term discounts and customized
billing and payment options. The services offered by ART are expected to be
competitively priced with those of the incumbent LECs. The Company also intends
to charge for installation and network monitoring services where appropriate.
The Company also anticipates offering metered services to various end users at
an appropriate point in the future.
 
CUSTOMERS AND APPLICATIONS
 
    The Company began deploying its links principally on a trial basis in
November 1995 and has since been hiring its staff, building its internal
infrastructure and developing its marketing plans and relationships with
potential customers. The Company has generated only nominal revenues from its
operations to date and has recently begun to finalize plans to roll out its
services on a wide-scale basis. Currently, the Company is providing or has
received orders to provide wireless broadband services to LECs, CAPs/ CLECs,
ISPs and mobile communications service providers and is in the process of
becoming a qualified vendor to all the major IXCs. The Company currently
provides services to carriers such as Ameritech, Bell Atlantic NYNEX Mobile, MFS
Communications Company, Inc./WorldCom, Inc., UUNet, DIGEX, Incorporated,
Electric Lightwave, NEXTLINK Communications LLC, American PCS, L.P., Western
Wireless, Commonwealth Telephone, Public Interest Network, Chadwick Telephone,
CGX Telecom, CAIS, Inc. and Brooks Fiber Properties, Inc., among others.
 
    The Company currently provides, or anticipates providing, wireless broadband
services to the following types of customers, among others:
 
                                       46
<PAGE>
    LOCAL EXCHANGE CARRIERS AND COMPETITIVE ACCESS PROVIDERS/COMPETITIVE LOCAL
EXCHANGE CARRIERS. Currently, CAPs/CLECs compete with LECs by installing fiber
optic cable rings in the highest density business locations to connect with long
distance carriers and for intra-ring transmissions. Due to the high cost
inherent in building fiber networks, CAPs/CLECs generally target densely
populated areas with high concentrations of large end-users. In order to reach
"off-net" customers, CAPs/CLECs must either lease or purchase facilities and
services from LECs or alternative suppliers until such time as it becomes
economical to extend the CAP/CLEC fiber networks to these customers.
 
    CAPs/CLECs face certain implementation obstacles that the Company's wireless
broadband services can assist in solving. CAPs/CLECs need to reach new customers
that are off-net quickly and inexpensively, and are expected to prefer to obtain
additional network facilities from (and share proprietary information with)
someone other than a direct competitor, such as a LEC. CAPs/CLECs can utilize
the Company's wireless broadband services as an alternative to copper,
fiber-based or other such network facilities provided to the CAPs/CLECs by LECs
(see diagram below), to extend their own networks to reach areas where such
extension is neither cost-efficient nor feasible, because of rights-of-way or
other restrictions, or to provide redundant and back-up capacity to their
existing networks.
 
    LECs are encountering many of the same obstacles CAPs/CLECs are encountering
in seeking to enhance their networks to deliver broadband services. Certain LECs
have sought to utilize 38 GHz technology to expand the range of their service
offerings to match those offered by CAPs/CLECs. Further, as LECs are permitted
to provide inter-LATA long distance services, they may seek to use 38 GHz
technology to bypass other LECs outside of their region. See "-- Strategic
Alliances -- Ameritech Strategic Distribution Agreement."
 
                                   [GRAPHIC]
 
                                       47
<PAGE>
    INTERNET SERVICE PROVIDERS.  The expanding demand for Internet access, the
growing importance of audio, video and graphic Internet applications to both
business and residents and the lack of high capacity access through local
telephone company facilities has created a growing market for wireless broadband
services similar to ART's services. The Company offers ISPs timely, reliable and
affordable access at the required high speed data rates -- both 45 Mbps and
1.544 Mbps -- allowing ISPs to keep pace with their customers' need for
increased capacity. The Company provides wireless broadband links between
customers and their ISPs and between ISP POPs and the Internet backbone. A
single 38 GHz DS-1 circuit linking a corporate user to an ISP's POP is
approximately 45 times faster than a 33.3 Kbps dial-up modem and 12 times faster
than the fastest ISDN connection. Each of the Company's 38 GHz DS-3 links can
support 28 DS-1 circuits per channel, or one DS-3 circuit per channel, which can
transfer data at a rate which is over 1,300 times the rate of the 33.3 Kbps
dial-up modem, which is the fastest dial-up modem currently in widespread
commercial use, and over 350 times the rate of the fastest ISDN lines currently
in use (128 Kbps).
 
                                [GRAPHIC]
 
                                       48
<PAGE>
    MOBILE COMMUNICATIONS SERVICE PROVIDERS.  ART's wireless broadband services
have begun to help cellular, wireless dispatch and emerging PCS carriers compete
in expanding domestic mobile communications markets by providing cost-effective
backbone network connections between cell sites, base stations and wireline
networks, regardless of location. Similar 38 GHz mobile communications
connections have been proven effective in Europe, and ART's easily installed,
economical wireless broadband links have begun to give domestic mobile carriers,
such as American PCS, L.P. and Western Wireless, a competitive edge in building
or expanding their networks through reduced construction time and installation
costs.
 
                               [GRAPHIC]
 
                                       49
<PAGE>
    INTER-EXCHANGE CARRIERS.  To minimize costly LEC access charges and to gain
more direct contact with the consumer, IXCs have begun to utilize the Company's
wireless broadband services to connect call origination or termination points
either directly to the IXCs' POPs or by way of CAP/CLEC intermediate fiber
rings. These providers have also begun to use 38 GHz services to connect two or
more of their respective POPs in a single market area. By utilizing the
Company's wireless broadband services, IXCs are able to avoid the capacity
barriers inherent in copper wire connections, which have typically prevented
them from providing their customers with the end-to-end, high bandwidth, full
digital services available from a fiber optic or wireless-based system. Wireless
broadband services also may be utilized to provide carriers with viable,
cost-efficient physical diversity routes (I.E., back-up capacity) for traffic in
situations when primary routes become incapacitated or network reliability
concerns demand alternate telecommunications paths.
 
                                 [GRAPHIC]
 
                                       50
<PAGE>
    PRIVATE USER NETWORKS.  ART's wireless broadband services enable business,
government and other heavy usage customers to create efficient, high speed, high
capacity private voice, data and video communications networks within and among
their local facilities and buildings. These customers include universities,
hospitals, hotels, shopping centers and multi-location manufacturing, business
and governmental institutions. Working directly with ART or through ART
resellers, customers will be able to access cost-effective alternatives to LEC
copper networks.
 
    Providing high speed data and video transmission and real time
communications services by linking customer computers in local, metropolitan and
wide area network configurations will be an important part of ART's private
networking business. The ability to send large amounts of data quickly and
efficiently and to interconnect personal computers both within and among
buildings in campus settings is a growing customer need. ART's wireless
broadband services are designed to serve this rapidly expanding market.
 
                               [GRAPHIC]
 
                                       51
<PAGE>
    INTERACTIVE VIDEO SERVICES USERS.  ART's wireless broadband services provide
high speed, high capacity access to communications networks for customers who
require reliable videoconferencing, video on demand, and Internet video
services. The Company believes the increasing popularity and use of these
services, particularly by large business and government customers, provide a
promising market for ART's wireless links. Videoconferencing requires high speed
communications both to and from the participants. The Company's services meet
this requirement for high bandwidth, full duplex communications.
 
                                   [GRAPHIC]
 
38 GHZ TECHNOLOGY
 
    The FCC has allocated the 37.0-40.0 GHz (the "38 GHz") band for wireless
broadband transmissions. The FCC has authorized the use of fourteen 100 MHz
channels between 38.6 GHz and 40.0 GHz, which enables licensees to provide
point-to-point wireless telecommunications services within a specified
geographic footprint usually of up to a 50-mile radius inscribed within a
rectangle.
 
    38 GHz technology was first widely deployed in Europe by cellular telephone
service providers for the interconnection of cell sites with switches. In the
early 1990s, technological advances resulted in a substantial reduction in the
cost and size of millimetric microwave components with a simultaneous increase
in reliability and quality, allowing for the provision of wireless broadband
telecommunication links at competitive prices. By 1993, advances in 38 GHz
technology, combined with its growing use in Europe and Central America, led to
increasing awareness of and interest in the potential uses of 38 GHz in the
United States.
 
    The 38 GHz band provides for the following additional advantages as compared
to other spectrum bands and wireline alternatives:
 
    - HIGH DATA TRANSFER RATES.  The total amount of bandwidth for each 38 GHz
      channel is 100 MHz, which exceeds the bandwidth of any other present
      terrestrial wireless channel allotment and supports full broadband
      capability. For example, one 38 GHz DS-3 link at 45 Mbps today can
      transfer data at a rate which is over 1,300 times the rate of the 33.3
      Kbps dial-up modem, which is the fastest dial-up modem currently in
      widespread commercial use, and over 350 times the rate of the fastest
      integrated services digital network ("ISDN") line currently in use (128
      Kbps). In addition to accommodating standard voice and data requirements,
      45 Mbps data transmission rates allow end users to receive real time, full
      motion video and 3-D graphics at their workstations and to utilize highly
      interactive applications on the Internet and other networks.
 
                                       52
<PAGE>
    - SIGNIFICANT CHANNEL CAPACITY.  Because 38 GHz radio emissions have a
      narrow beam width, a relatively short range and in most instances the
      capability to intersect without creating interference, 38 GHz service
      providers can efficiently reuse their bandwidth within a licensed area,
      thereby increasing the number of customers to which such services can be
      provided. Management believes that by using technology currently employed
      by the Company it can serve virtually all of its addressable service
      market.
 
    - RAPID DEPLOYMENT.  38 GHz technology can be deployed considerably more
      rapidly than wireline and other wireless technologies, generally within 72
      hours after obtaining access to customer premises. In contrast to the
      relative ease of installing a 38 GHz transmission link, extending fiber or
      copper-based networks to reach new customers requires significant time and
      expense. In addition, unlike providers of point-to-point microwave service
      in most other spectrum bands, a 38 GHz license holder can install and
      operate as many transmission links as it can engineer in the licensed area
      without obtaining additional approvals from the FCC. This is a substantial
      advantage over other portions of the microwave radio spectrum that must be
      licensed on a link-by-link basis and that cannot commence service until
      frequency coordination has been completed.
 
    - EASE OF INSTALLATION.  The equipment used for 38 GHz point-to-point
      applications (I.E., antennae, transceivers and digital interface units) is
      smaller, less obtrusive and less expensive than that used for microwave
      equipment applications at other frequencies, making it less susceptible to
      zoning restrictions. In addition, 38 GHz equipment can be easily
      redeployed to meet changing customer requirements.
 
    - VERY HIGH TRANSMISSION QUALITY.  The Company's wireless broadband services
      are engineered to provide 99.999% availability, with better than a 10-13
      (unfaded) bit error rate. This level of availability exceeds the
      performance of copper based networks and is a viable alternative to fiber
      based networks. When measured as the total amount of time "out of service"
      over a year, 99.999% availability equates to less than six minutes per
      year of down-time, compared to a range of four hours to 44 hours of
      historical performance of similar copper-based LEC circuits.
 
    - ADDITIONAL ADVANTAGES OVER OTHER PORTIONS OF RADIO SPECTRUM.  At
      frequencies above 38 GHz, point-to-point applications become less
      practical because attenuation increases and the maximum distance between
      transceivers accordingly decreases. Additionally, the FCC has specified
      the use of many portions of the spectrum for applications other than
      point-to-point, such as satellite and wireless cable services, and,
      accordingly, these portions of the radio spectrum often are not available
      for point-to-point applications.
 
38 GHZ WIRELESS BROADBAND LICENSES AND AUTHORIZATIONS
 
    The Company was granted the first of its authorizations to construct and
operate 38 GHz wireless broadband facilities in February 1995. Upon completion
of the CommcoCCC Acquisition, the Company will own or manage a total of 233
authorizations that will allow it to provide 38 GHz wireless broadband services
in 169 U.S. markets. The Company currently owns or manages or has the right to
use on a long-term basis 104 licenses (exclusive of the CommcoCCC Assets) that
allow it to provide 38 GHz wireless broadband services in 81 markets, 73 of
which are owned by the Company, 19 of which are managed by the Company through
the Company's interests in or arrangements with other companies and 12 of which
the Company has the right to use on a long-term basis.
 
                                       53
<PAGE>
    The table below lists the amount of bandwidth covered by authorizations
which the Company owns, manages or has a definitive agreement to acquire in the
top 100 U.S. markets, in descending order of size based on the estimated
population of the market:
 
<TABLE>
<CAPTION>
                                                     BANDWIDTH COVERED BY AUTHORIZATIONS (MHZ)
                                                    -------------------------------------------
                                                                                      UNDER
                                                                                   DEFINITIVE
                                                                                  AGREEMENT TO
                      MARKET                           OWNED       MANAGED (1)       ACQUIRE        TOTAL
- --------------------------------------------------  -----------  ---------------  -------------     -----
<S>                                                 <C>          <C>              <C>            <C>
300 MHZ OR MORE MARKETS
New York, NY                                               300         --              --               300
Washington, D.C.                                           300         --              --               300
Boston, MA                                                 200         --                 100           300
Cincinnati, OH                                             100         --                 200           300
Norfolk/Virginia Beach, VA                              --             --                 300           300
Providence, RI/Fall River, MA                              200         --                 200           400
Memphis, TN                                                100         --                 200           300
Birmingham, AL                                             100         --                 200           300
Buffalo/Niagara Falls, NY                                  300         --                 100           400
Richmond/Petersburg, VA                                    100         --                 200           300
Rochester, NY                                              300         --                 200           500
Hartford, CT                                               200         --                 200           400
Albany/Schenectady, NY                                     300         --                 200           500
Knoxville, TN                                              100         --                 200           300
New Haven/Waterbury, CT                                    200         --                 100           300
Syracuse, NY                                               200         --                 100           300
Harrisburg, PA                                             200         --                 100           300
Scranton/Wilkes-Barre, PA                                  300         --                 100           400
Springfield/Holyoke, MA                                    200         --                 200           400
Jackson, MS                                                100         --                 200           300
Shreveport, LA                                             100         --                 200           300
</TABLE>
 
                                       54
<PAGE>
<TABLE>
<CAPTION>
                                                     BANDWIDTH COVERED BY AUTHORIZATIONS (MHZ)
                                                    -------------------------------------------
                                                                                      UNDER
                                                                                   DEFINITIVE
                                                                                  AGREEMENT TO
                      MARKET                           OWNED       MANAGED (1)       ACQUIRE        TOTAL
- --------------------------------------------------  -----------  ---------------  -------------     -----
<S>                                                 <C>          <C>              <C>            <C>
200 MHZ MARKETS
Philadelphia, PA/Trenton, NJ                               200         --              --               200
Miami/Fort Lauderdale, FL                                  100         --                 100           200
Cleveland/Akron, OH                                        100         --                 100           200
St. Louis, MO                                              100         --                 100           200
Pittsburgh, PA                                             200         --              --               200
Baltimore, MD                                              200         --              --               200
Portland, OR                                            --             --                 200           200
Charlotte/Gastonia, NC                                  --             --                 200           200
Columbus, OH                                            --             --                 200           200
Nashville, TN                                              100         --                 100           200
Indianapolis, IN                                           100         --                 100           200
Louisville, KY                                             100         --                 100           200
Oklahoma City, OK                                       --             --                 200           200
Dayton/Springfield, OH                                     100         --                 100           200
Las Vegas, NV                                           --                100             100           200
Grand Rapids, MI                                        --                100             100           200
Omaha, NE                                               --             --                 200           200
Honolulu, HI                                            --                100             100           200
Albuquerque, NM                                         --                100             100           200
Des Moines, IA                                             100         --                 100           200
El Paso, TX                                             --             --                 200           200
Worcester, MA                                              200         --              --               200
Allentown/Bethlehem, PA                                    200         --              --               200
Baton Rouge, LA                                            100         --                 100           200
 
100 MHZ MARKETS
Chicago, IL                                                100         --              --               100
Los Angeles, CA                                         --                100(2)       --               100
Detroit, MI                                             --             --                 100           100
Dallas/Fort Worth, TX                                      100         --              --               100
Houston, TX                                                100         --              --               100
Atlanta, GA                                                100         --              --               100
Minneapolis, MN                                            100         --              --               100
Seattle/Tacoma, WA                                      --             --                 100           100
Phoenix, AZ                                             --                100          --               100
San Diego, CA                                           --                100          --               100
Tampa-St. Petersburg, FL                                --             --                 100           100
Denver, CO                                              --                100          --               100
Kansas City, MO                                            100         --              --               100
Milwaukee, WI                                           --             --                 100           100
San Antonio, TX                                            100         --              --               100
Salt Lake City, UT                                      --                100          --               100
Orlando, FL                                             --             --                 100           100
New Orleans, LA                                            100         --              --               100
Greensboro/Winston-Salem, NC                            --             --                 100           100
Raleigh-Durham, NC                                      --             --                 100           100
Austin, TX                                              --             --                 100           100
Little Rock, AR                                         --             --                 100           100
</TABLE>
 
                                       55
<PAGE>
<TABLE>
<CAPTION>
                                                     BANDWIDTH COVERED BY AUTHORIZATIONS (MHZ)
                                                    -------------------------------------------
                                                                                      UNDER
                                                                                   DEFINITIVE
                                                                                  AGREEMENT TO
                      MARKET                           OWNED       MANAGED (1)       ACQUIRE        TOTAL
- --------------------------------------------------  -----------  ---------------  -------------     -----
<S>                                                 <C>          <C>              <C>            <C>
Tulsa, OK                                               --             --                 100           100
Greenville/Spartanburg, SC                              --             --                 100           100
Toledo, OH                                              --             --                 100           100
Tucson, AZ                                              --             --                 100           100
Spokane, WA                                             --                100          --               100
Kingsport, TN/Bristol, VA                               --             --                 100           100
Fort Wayne, IN                                          --             --                 100           100
Charleston, SC                                             100         --              --               100
Mobile, AL                                                 100         --              --               100
Madison, WI                                                100         --              --               100
Wichita, KS                                                100         --              --               100
Springfield, MO                                         --             --                 100           100
Sarasota/Bradenton, FL                                  --             --                 100           100
Corpus Christi, TX                                      --             --                 100           100
Chattanooga, TN                                         --             --                 100           100
</TABLE>
 
- ------------------------------
 
(1) Includes authorizations (i) held by ART West, (ii) managed by ART under the
    TeleCom One services agreement pursuant to a revenue-sharing arrangement and
    (iii) those authorizations that are leased on a long-term exclusive basis.
    Does not include (i) authorizations included in the CommcoCCC Assets which
    are managed by the Company on a short-term basis, pending the CommcoCCC
    Acquisition or (ii) the DCT Systems. The Company has entered into definitive
    agreements to acquire all outstanding interests in the authorizations held
    by ART West and TeleCom One. See "--Agreements Relating to Licenses and
    Authorizations."
 
(2) Consists of authorizations in the Los Angeles market which the Company has
    the right to use on a long-term basis pursuant to the ICG Agreement. See
    "--Agreements Relating to Licenses and Authorizations--ICG Agreement."
 
    In addition to the above authorizations, the Company has 71 applications
pending before the FCC for additional authorizations. However, due to the
"freeze" imposed by the FCC and the conflicts with other applicants in same
markets, there can be no assurance that it or any other company will receive
additional authorizations with respect to any pending applications. On December
31, 1996, the FCC announced that it had adopted an order that partially lifted
the "freeze" on the processing of pending applications. Among other actions, the
order permitted applicants to modify pending applications to reduce their
coverage areas. See "Risk Factors -- Government Regulation" and "-- Government
Regulation."
 
    Excluding the CommcoCCC Assets, the Company presently owns, manages or has a
long-term right to use between 100 and 300 MHz of transmission capacity within
each of its markets. Because 38 GHz paths are very narrow and because certain
microwave paths can intersect each other without creating interference, each
market area can accommodate thousands of paths. The Company believes it
generally owns or manages sufficient 38 GHz bandwidth to satisfy the anticipated
service requirements of its target customers in each of the Company's existing
markets and the additional 80 markets to be acquired under the CommcoCCC
Agreement. Consistent with the Company's growth strategy, the Company may seek
to obtain additional spectrum by either leasing excess capacity from other 38
GHz licensees, entering into management agreements or acquiring interests in
other 38 GHz authorizations. See "Risk Factors -- Acquisition of Additional
Bandwidth in Selected Areas."
 
    Under the terms of the CommcoCCC authorizations and the Company's management
agreement with CommcoCCC, the Company must meet the FCC's construction deadline
for 53 licenses between mid-April and mid-August 1997. The Company has met the
construction deadline for 76 authorizations on a timely basis and expects it
will meet its other FCC deadlines. All of the 38 GHz licenses owned or to
 
                                       56
<PAGE>
be acquired by the Company are due to expire in February 2001. The Company
believes that, in keeping with common FCC practices, the licenses will be
renewed for successive 10-year periods upon expiration.
 
AGREEMENTS RELATING TO LICENSES AND AUTHORIZATIONS
 
    COMMCOCCC ACQUISITION.  On July 3, 1996, the Company entered into an
agreement (as amended, the "CommcoCCC Agreement") to acquire 129 38 GHz wireless
broadband authorizations (the "CommcoCCC Assets") from CommcoCCC, Inc.
("CommcoCCC") in exchange for 6,000,000 shares of Common Stock (the "CommcoCCC
Acquisition"). CommcoCCC was formed in a transaction arranged by Columbia
Capital Corporation to acquire, own and operate the 38 GHz authorizations owned
by Columbia Capital Corporation and its affiliates and those owned by Commco,
L.L.C. The CommcoCCC Acquisition is subject to various conditions including
receipt of FCC and other approvals (including approval under the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, if required), receipt by
CommcoCCC of an opinion as to the tax-free nature of the transaction,
consummation of the Offering on terms reasonably satisfactory to CommcoCCC,
minimum population coverage requirements for the authorizations of the Company
and CommcoCCC, accuracy of representations and warranties except for breaches
that do not have in the aggregate a material adverse effect, no pending or
threatened material litigation and other customary closing conditions. There can
be no assurance that all such conditions will be satisfied. On January 27, 1997,
the FCC granted its consent to the CommcoCCC Acquisition, but periods for
judicial and administrative review have not expired. In order to satisfy the
minimum population coverage requirements, the Company will be obliged to
complete the acquisitions of certain spectrum rights from ART West and TeleCom
One, or, in the event it cannot complete one or more of such acquisitions, to
acquire or lease other spectrum rights. The Company's acquisition agreements
with ART West and TeleCom One are also subject to various conditions. See
"--Additional Spectrum Rights Leases." The CommcoCCC Agreement, as amended, may
be terminated by either party if the CommcoCCC Acquisition is not consummated
before October 15, 1997. See "Risk Factors -- Risk of Non-Consummation of
CommcoCCC Acquisition and Other Acquisitions; Commco Option."
 
    In the CommcoCCC Agreement, the Company and Telecom have each agreed that,
prior to the consummation of the transaction, except in certain circumstances or
with the consent of CommcoCCC, they will not issue equity, incur debt, acquire
spectrum, make investments, consolidate, merge or sell all or substantially all
of its assets. CommcoCCC has entered into a management agreement with the
Company pursuant to which the Company bears the responsibility during the
pendency of the CommcoCCC Acquisition to construct, manage and operate the
CommcoCCC Assets, consistent with FCC rules. Under the management agreement,
CommcoCCC is obligated to reimburse ART for up to $100,000 of operating
expenses, which obligation will be cancelled if the CommcoCCC Acquisition is
consummated. In the event the management agreement is terminated other than as a
result of the consummation of the CommcoCCC Acquisition, CommcoCCC is obligated
to purchase and ART is obligated to sell at the Company's original cost the
equipment purchased by ART necessary to meet the FCC construction requirements
for the CommcoCCC authorizations.
 
    The stockholders of CommcoCCC loaned the Company $3.0 million payable
December 31, 1996 pursuant to a subordinated bridge financing facility (the
"CommcoCCC Financing") and, in connection therewith, received three-year
warrants to purchase 18,182 shares of Common Stock at a price of $24.75 per
share. In connection with an October 1996 amendment to the CommcoCCC Agreement,
the Company modified the terms of such warrants, reduced the exercise price of
such warrants to $17.1875 per share ($15.00 after giving effect to anti-dilution
adjustment) and increased the number of shares issuable upon exercise thereof to
87,273 shares (the "CommcoCCC Warrants"). The CommcoCCC Financing was repaid
with the proceeds of the Common Stock Offering.
 
    The Company has given Commco, L.L.C., a stockholder of CommcoCCC, an option
(the "Commco Option") to purchase one authorization in each of 12 specified
market areas in which the Company will have more than one authorization, which
authorizations cover in the aggregate approximately 19 million people. The
Commco Option will be exercisable only if (i) the CommcoCCC Acquisition is
 
                                       57
<PAGE>
consummated and (ii) Commco, L.L.C. obtains authorizations pursuant to certain
pending applications previously frozen under the NPRM in market areas covering
an aggregate population of at least 40 million people, and will terminate on
August 12, 1997. The purchase price for any authorizations acquired under the
Commco Option is determined by a formula based upon the fair market value at the
time the Commco Option is exercised of up to 945,455 shares of Common Stock
depending upon the number of authorizations purchased. The purchase price is
payable in cash or, if the Commco Option is exercised within the later of 120
days after the closing of the CommcoCCC Acquisition or the date of grant by the
FCC of the authorizations necessary to exercise the Commco Option, with a
two-year note secured by shares of Common Stock having a value on the date of
exercise equal to two times the principal amount of the note. In addition, if
the Commco Option becomes exercisable, an affiliate of Commco LLC will have the
right to sublease channel capacity from the Company in the New York and
Washington, D.C. markets on terms agreed to by the Company and Commco LLC. On
December 31, 1996, the FCC announced that it had adopted an order that partially
lifted the freeze on the processing of pending applications. Among other
actions, the order provides that the Commission will process certain amendments
filed before December 15, 1995 that have the effect of eliminating mutual
exclusivity among pending applications. The Company believes that the FCC order
could result in the grant to Commco L.L.C. of sufficient authorizations to
enable it to satisfy the population coverage condition of the Commco Option. See
"Risk Factors -- Risk of Non-Consummation of CommcoCCC Acquisition and Other
Acquisitions; Commco Option."
 
    As part of the CommcoCCC Acquisition, Columbia Capital Corporation and its
affiliates agreed not to compete with the Company in the provision of wireless
broadband telecommunication services in the 38 GHz band of the radio spectrum
for a five-year period commencing upon the closing of the CommcoCCC Acquisition
and have granted the Company a right of first offer to acquire any 38 GHz
authorizations that Columbia Capital Corporation or its affiliates may acquire
in the future with respect to their pending applications.
 
    As a condition to the CommcoCCC Acquisition, the Company will elect James B.
Murray, Jr. as a director of the Company promptly after the closing of the
CommcoCCC Acquisition.
 
    In late 1994 and 1995, Columbia Capital Corporation and certain of its
affiliates ("Columbia") entered into several letter agreements (the "Letter
Agreements") with Video/Phone Systems, Inc. ("Video/Phone"). In consideration
for services to be rendered under the Letter Agreements, Columbia granted or
agreed to grant to Video/Phone options to purchase minority equity interests in
entities formed or to be formed to apply for 38 GHz licenses. Columbia agreed
not to assign these licenses to any person controlling, controlled by or under
common control with Columbia unless such transferee granted to Video/Phone an
equivalent option. The CommcoCCC Assets include 67 authorizations transferred by
Columbia to CommcoCCC, subject to FCC approval. Columbia and Video/Phone are in
a dispute with respect to the performance and obligations of the parties under
the Letter Agreements. Columbia has agreed to indemnify and hold harmless the
Company with respect to any loss or damage resulting from the Letter Agreements.
 
    In connection with the CommcoCCC Acquisition, Montgomery Securities has been
retained by the Company as its financial adviser for which it will receive fees
of up to approximately $2.7 million (of which $600,000 was paid in December
1996) and the reimbursement of reasonable out-of-pocket expenses incurred in
connection therewith.
 
    EMI ACQUISITION.  On April 4, 1995, ART entered into an agreement with EMI
Communications Corporation ("EMI") to acquire EMI's thirty two 38 GHz wireless
broadband licenses and related assets in the northeastern United States (the
"EMI Assets") in exchange for $3.0 million in cash and a $1.5 million three-year
non-negotiable and non-transferable promissory note (the "EMI Note"). The EMI
Assets were acquired by the Company in November 1995. ART has also agreed to
provide wireless broadband services to EMI for a period of five years from the
date of the agreement and to certain of
 
                                       58
<PAGE>
EMI's customers on behalf of EMI for the terms provided in such EMI service
agreements, and EMI agreed to provide certain services to the Company for an
initial period of one year from the date of the agreement. See "Description of
Certain Indebtedness -- EMI Note."
 
    ART WEST JOINT VENTURE.  On April 4, 1995, ART and Extended Communications,
Inc. ("Extended") entered into a joint venture agreement (the "ART West
Agreement") resulting in the formation of ART West Joint Venture ("ART West"), a
Delaware partnership equally owned by ART and Extended. Under the terms of the
ART West Agreement, ART and Extended transferred to ART West all of their
respective interests in all of their 38 GHz authorizations (currently, 12
authorizations) in Alaska, Arizona, California, Colorado, Hawaii, Idaho,
Montana, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming (the "ART West
Markets"). Under a separate management agreement between ART and ART West, ART
is obligated to bear all costs and expenses relating to construction, operation
and management of the ART West Markets and has agreed to utilize the ART West
authorizations before other authorizations owned or managed by ART in the ART
West Markets. As compensation, ART receives 90% of the recurring revenues of ART
West, with ART West receiving the remaining 10%. To date, Extended has had no
significant responsibilities with respect to ART West, and is not expected to
invest in or contribute any services to ART West pending the proposed
acquisition of Extended's interest described below. See "Certain Transactions --
ART West Joint Venture."
 
    In June 1996, the Company entered into an agreement (the "Extended
Agreement") to acquire Extended's interest in ART West for an aggregate of $6.0
million in cash, subject to adjustment and subject to closing conditions
including final FCC approval. On January 10, 1997, the FCC granted its consent
to the Extended Agreement, but periods for judicial and administrative review
have not expired. Of the $6.0 million purchase price, $3.0 million was paid in
November 1996 as a non-refundable deposit (the "ART West Deposit") and the
balance is payable upon consummation of the acquisition. Upon payment by ART of
the ART West Deposit, Extended surrendered its rights under the ART West
Agreement (i) to participate in the acquisition of additional licenses or
authorizations in certain of the ART West Markets through ART West and (ii) to
prohibit the acquisition by ART of additional licenses or authorizations in
certain other ART West Markets.
 
    DCT SYSTEMS SERVICES AND PURCHASE AGREEMENTS.  On June 28, 1996 the Company
entered into a definitive agreement (the "DCT Agreement") with DCT to acquire
DCT's interest in sixteen 38 GHz licenses (the "DCT Systems") covering a
population of approximately 15 million in exchange for $3.6 million in cash,
subject to FCC approval, consummation of the DCT Agreement by August 28, 1997
and other customary closing conditions including accuracy of representations and
warranties, absence of litigation and receipt of opinion of counsel. ART has
entered into a services agreement with DCT pursuant to which ART bears the
responsibility for the construction, operation and management of the DCT
Systems. The agreement expires on December 31, 1998 and may be terminated
earlier by DCT if the DCT Agreement terminates. DCT has alleged that the Company
has failed to satisfy a provision of the DCT Agreement which provides that if
the Company failed to obtain debt or equity proceeds by August 31, 1996 in an
amount at least equal to $3.6 million, the DCT Agreement would terminate and DCT
could retain a $100,000 deposit paid by the Company against the purchase price.
There can be no assurance as to the outcome of such dispute and, therefore, no
assurance that the Company will be in a position to consummate the acquisition
of the DCT Systems, even if the Company wishes to do so. Although the Company
believes that it has satisfied such provision of the DCT Agreement and is
legally entitled to proceed to consummate the transactions contemplated thereby,
the Company does not currently plan to purchase the DCT Systems as contemplated
by the DCT Agreement. Accordingly, the DCT Systems are not included among the
licenses managed by the Company as disclosed in this Prospectus, and the Company
does not currently intend to use the proceeds of the Offering to consummate the
purchase thereof and would use the unpaid purchase price for general corporate
purposes. See "Use of Proceeds."
 
    Under the terms of the services agreement, ART is obligated to bear all
costs and expenses relating to construction, operation and management of the DCT
Systems. As compensation, ART was entitled to receive all of the revenues
generated by the DCT Systems until December 31, 1996. From January 1,
 
                                       59
<PAGE>
1997 until the later of January 1, 1998 and the termination of the DCT
Agreement, a license fee equal to 15% of the gross revenue generated by the DCT
Systems will be paid to DCT, and thereafter a license fee based on the number
and types of circuits operated by ART over the DCT Systems will be paid to DCT.
After December 31, 1997, DCT has the right to market to third parties utilizing
the DCT Systems. The services agreement terminates with respect to each DCT 38
GHz license upon the acquisition by ART of such license. The Company has
completed construction of all of the DCT authorizations.
 
    TELECOM ONE SERVICES AGREEMENT.  On April 24, 1996, the Company and TeleCom
One, Inc. ("TeleCom One") entered into a services agreement (the "TeleCom One
Services Agreement") pursuant to which the Company constructed, and has agreed
to operate and manage, all 38 GHz wireless broadband licenses and related
telecommunications systems owned by TeleCom One that are granted by the FCC. At
present TeleCom One has been granted two authorizations. The Company has
completed construction of the two authorizations. Under the TeleCom One Services
Agreement, the Company is obligated to pay all costs and expenses related to
construction, operation and management of the systems. As compensation, the
Company receives 90% of the net revenues generated by the systems and TeleCom
One receives the remaining 10% for ten years. On June 27, 1996, the Company and
TeleCom One entered into an agreement pursuant to which the Company will
acquire, subject to FCC approval, from TeleCom One the two currently granted
authorizations that are the subject of the TeleCom One Services Agreement for
approximately $111,000 in cash. In addition, the Company will have a right of
first refusal on all future grants of 38 GHz authorizations to TeleCom One or
its current stockholders.
 
    ICG AGREEMENT.  In October 1996, ART entered into a services agreement with
ICG Telecom Group, Inc. and Pacific & Eastern Digital Transmission Services,
Inc., pursuant to which the Company will have an exclusive right, as against
third parties, to use for a five-year term ten 38 GHz wireless broadband
authorizations covering an aggregate population of approximately 13 million in
or around the California cities of Beverly Hills, Los Angeles, Palm Springs,
Riverside, Santa Barbara, San Bernardino, Santa Monica, San Diego, Santa Anna
and Ventura. In addition, the services agreement grants to the Company a right
of first refusal with respect to the purchase of such authorizations, subject to
limited exceptions. The services agreement may be renewed for successive
one-year terms totalling five additional years upon expiration of its initial
term.
 
    MICROWAVE PARTNERS AGREEMENT.  In November 1996, ART entered into a services
agreement with Microwave Partners, pursuant to which the Company will have an
exclusive right, as against third parties, to use for a five-year term two 38
GHz wireless broadband authorizations covering an aggregate population of
approximately 755,000 in or around Palm Springs, California and Bellingham,
Washington. In addition, the services agreement grants to the Company a right of
first refusal with respect to the purchase of such authorizations, subject to
limited exceptions. The services agreement may be renewed for an additional term
of two years upon expiration of its initial term.
 
STRATEGIC ALLIANCES
 
    AMERITECH STRATEGIC DISTRIBUTION AGREEMENT.  On April 29, 1996, the Company
and Ameritech entered into a three-year strategic distribution agreement (the
"Ameritech Strategic Distribution Agreement") pursuant to which the Company
provides 38 GHz services to Ameritech, who will in turn market the Company's
services under the Ameritech name. Ameritech has agreed to be the primary
provider of the Company's services in the midwest. Ameritech has initiated on a
limited basis the sale of its "Ameritech Wireless Broadband Service," which will
be a local access component of Ameritech's GlobalDesk Managed Access Service,
allowing seamless high-speed connectivity for LAN interconnection, desktop
videoconferencing and Internet access. The Company expects that full scale
rollout of these wireless broadband services will begin in the first quarter of
1997. Under the Ameritech Strategic Distribution Agreement, Ameritech is
targeting certain sales objectives and will spend internally up to $7.0 million
on its sales and marketing of the Company's services. The Company believes that
Ameritech's sales and marketing expertise and its access to extensive
distribution channels within its region will accelerate the
 
                                       60
<PAGE>
rollout of the Company's business plan. The Ameritech Strategic Distribution
Agreement is subject to termination at any time by either party on 90 days'
notice. See "Risk Factors -- Dependence on Third Parties for Marketing and
Service."
 
    GTE SERVICES AGREEMENT.  On April 25, 1996, the Company entered into a
two-year agreement with GTE Government Systems Corporation, a subsidiary of GTE
Corporation ("GTE"). GTE will provide equipment staging and outfitting, site
preparation, equipment installation and maintenance for the Company's wireless
broadband services. Under the agreement, it is anticipated that GTE will perform
at least 75% of the Company's installations. The Company will pay a fee equal to
$1,550 for the installation of each link and a maintenance fee equal to $85 per
hour. The aggregate amount of the fee will depend on the Company's rate of
growth. The Company believes that GTE's nationwide presence and experience will
provide the Company with efficient, quality installation and maintenance for its
nationwide services. See "Risk Factors -- Dependence on Third Parties for
Marketing and Service."
 
    GTE SOFTWARE LICENSE AGREEMENT.  On March 29, 1996, the Company entered into
a software license agreement with GTE's Network Management Organization. Under
this agreement, the Company purchased software and developed its network
management and provisioning functions to produce a reliable network management
system and increase system performance. GTE's "Integrated Network Management
Products" enable the Company to quickly identify service interruptions and to
simultaneously alert the field service teams, who are able to restore services
in a timely manner. The Company will pay a license fee of approximately $1.9
million and an annual maintenance support fee of approximately $145,000. The
license fee will be paid in monthly installments commencing January 1, 1997 of
$67,000 per month, including interest. After the first year, fees are subject to
renegotiation based on market prices and conditions. See "Risk Factors --
Dependence on Third Parties for Marketing and Service."
 
    HARRIS AGREEMENTS.  On April 26, 1996, the Company and Harris Corporation,
Farinon Division ("Harris") entered into a one-year PCS marketing agreement (the
"Harris Marketing Agreement") pursuant to which the Company granted to Harris
the right to use its 38 GHz authorizations, including associated coordination
services, installation and network monitoring and field services. Pursuant to
the Harris Marketing Agreement, Harris agreed to market the Company's services
in the emerging PCS market. The Harris Marketing Agreement is automatically
renewable for successive one-year terms unless either party delivers notice of
non-renewal at least 60 days prior to the end of the initial term or any
successive term. The agreement is also subject to termination at any time by
either party on 90 days' notice.
 
    Concurrently with the Harris Marketing Agreement, the parties entered into a
one-year purchase agreement (the "Harris Purchase Agreement") pursuant to which
the Company agreed to purchase certain microwave transmission equipment,
software and services relating thereto (the "Harris Products"). The agreement
sets minimum purchase goals for the purchase by the Company of Harris Products.
If either the Harris Purchase Agreement or the Harris Marketing Agreement shall
terminate, the other shall also terminate.
 
    TECHNOLOGY DEVELOPMENT AGREEMENTS.  The Company has had discussions with
several microwave equipment or technology development companies for development
of technologies owned by such companies, for advanced 38 GHz radios highspeed
converters and other technologies. The Company will continue to monitor new
developments in technology and may elect to fund research and development
activity in such new technology.
 
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    The Company has entered into a letter of intent with Helioss Communications
Corporation ("Helioss") for the development of advanced 38 GHz radios. Under the
letter of intent, which is subject to definitive documentation, the Company will
fund up to $1.0 million of Helioss' research and development expenses. The
Company will have a right of first refusal on production capacity of the radios
for three years from delivery of the first radios produced, and will receive a
royalty on the sale of a certain number of radios to customers other than the
Company; however, the Company will have no other rights to any technology
developed.
 
    Through September 30, 1996, the Company has incurred approximately $650,000
of research and development expenses, including amounts incurred with American
Wireless (as defined) and Helioss. See "Certain Transactions -- American
Wireless Development Agreement." There can be no assurance that the Company can
complete a definitive agreement with Helioss or that Helioss can develop
technologies with commercial value for the Company. Although the Company does
not have any other material commitments to fund research and development or to
make investments in other companies, the Company expects to incur additional
research and development expenses or to make other such investments from time to
time.
 
    MASTER SERVICE AGREEMENTS.  The Company's master service agreements contain
the terms by which customers will place future orders. The terms which are
outlined in these agreements include volume discounts, approximate geographic
location of links needed and representative pricing. Although a master service
agreement is not a take or pay commitment, it lays the groundwork for future
orders by a preferred customer and is utilized to facilitate the issuance of
purchase orders by a customer without any additional negotiations between the
companies.
 
    ART has entered into master service agreements with a number of CAPs/CLECs
and ISPs, including NEXTLINK Communications LLC, DIGEX, Incorporated, CAIS,
Inc., Microwave Partners d/b/a Astrolink Communications, Inc., American PCS,
L.P., Message Center Management, Inc. ("MCM"), GST Telecom, Inc., Chadwick
Telephone and Brooks Fiber Properties, Inc.
 
    SITE ACQUISITION AGREEMENTS.  In order to reduce the lag time in the
provisioning of services and ensure that the Company can respond rapidly to
customer orders, the Company has initiated a program to obtain access to antenna
sites in advance of receiving a customer order in those situations where it can
be anticipated that there may be difficulty in obtaining such rights through the
customer's contracts and where the sites fit within the Company's marketing and
network development plans. The Company has signed an agreement with MCM which
will give the Company access to 4800 sites nationwide.
 
    TCG INSTALLATION AGREEMENT.  Under an Installation Services Agreement dated
October 2, 1996, the Company acted as a sub-contractor to Teleport to provide
transmission facilities construction services. Total gross billings to the
Company under this agreement were approximately $2.6 million. As of December 31,
1996, all such services had been substantially completed.
 
FOREIGN MARKETS
 
    Entities in which the Company has a substantial interest have applied or
intend to apply for licenses to provide wireless broadband services in Canada
and in various European countries. See "Risk Factors--Potential Rights to
Foreign Licenses."
 
    In October 1996, ART entered into a binding letter of intent with Advantage
Telecom, Inc. ("ATI"), a Canadian company which has applied for licenses to
provide 38 GHz service in the 66 major markets in Canada covering a population
of at least 21 million people. Upon consummation of the transactions described
in the letter of intent, ART will hold a substantial direct and indirect
minority interest in ATI and will be a party to a services agreement with ATI
pursuant to which ART will construct and operate radio systems based upon any
licenses that may be granted to ATI and subject to control by ATI. The Company
incurred costs of approximately $300,000, and ATI is responsible for securing
any additional
 
                                       62
<PAGE>
funding necessary to construct the radio systems. Due to current uncertainty in
Canada's licensing policy, there can be no assurance that ATI will be granted
these licenses or that, if licenses are granted, ATI will obtain the funding
necessary to construct the radio systems.
 
    On September 29, 1996 the Company entered into a shareholders agreement with
Trond Johannessen, pursuant to which the Company anticipates eventually
obtaining licenses and offering its wireless broadband services through separate
subsidiaries in the 17 countries comprising the European Union. The Company has
caused or will cause to be formed subsidiaries in Sweden, the United Kingdom and
Italy for this purpose. Under the shareholders agreement, in consideration for
services to be rendered, and his proportionate share of the formation costs, Mr.
Johannessen is entitled to receive a 20% interest in the initial shareholdings
in certain of the subsidiaries in each country, prior to significant funding of
each subsidiary. The Company has no further commitment to fund any such
subsidiary. Mr. Johannessen is also a consultant to the Company, for which he
receives monthly payments of $10,000 plus expenses. The Company is seeking but
has not yet received any operating licenses, strategic alliances or customer
commitments in Europe. Although each member nation of the European Economic
Community is required pursuant to a directive of the European Commission to open
its telecommunication markets to competition over the next several years, the
timing and extent of a relaxation in entry barriers and the degree of
cooperation from the incumbent service providers in such areas as
interconnection to customers and the public networks is unknown. There can be no
assurance that the Company, through such subsidiaries, will be able to acquire
the licenses necessary in each European country, to finance and implement its
business plan or to operate in any country on a profitable basis.
 
COMPETITION
 
    The telecommunications services industry is highly competitive. The Company
has only recently begun to market its wireless broadband services to potential
customers and is currently providing services on a limited basis. In each market
area in which the Company is authorized to provide services, the Company
competes or will compete with several other service providers and technologies.
The Company expects to compete primarily on the basis of wireless broadband
service features, quality, price, reliability, customer service and response to
customer needs. The Company faces significant competition from other 38 GHz
providers and incumbent LECs, such as the RBOCs. The Company may also compete
with CAPs/CLECs, other wireless service providers, cable television operators,
electric utilities, LECs operating outside their current local service areas and
IXCs. There can be no assurance that the Company will be able to compete
effectively in any of its market areas.
 
    COMPETITION FROM 38 GHZ SERVICE PROVIDERS.  The Company faces competition
from other 38 GHz service providers, such as WinStar and BizTel (an affiliate of
TCG), within its market areas. In many cases, one or both of these service
providers hold licenses to operate in other portions of the 38 GHz band in
geographic areas which encompass or overlap the Company's market areas. In
certain of the Company's market areas, other 38 GHz service providers may have a
longer history of operations, a larger geographic footprint or substantially
greater financial resources than the Company. WinStar commenced its 38 GHz
operations approximately one year prior to the Company, has raised significant
capital and has the competitive advantages inherent in being the first to market
38 GHz services. In addition to WinStar and BizTel several dozen smaller
entities have been granted 38 GHz authorizations in geographic regions in which
the Company plans to operate. In January 1997, WinStar acquired the 38 GHz
licenses of one such entity, Milliwave L.P. Due to the relative ease and speed
of deployment of 38 GHz technology, the Company could face intense price
competition and competition for customers from other 38 GHz service providers.
 
    The Company also faces potential competition from new entrants to the 38 GHz
market, including LECs and other leading telecommunications companies. The NPRM
contemplates an auction of certain spectrum assets, including the lower fourteen
proposed 100 MHz channels (which are similar to those used by the Company) and
four proposed 50 MHz channels in the 38 GHz spectrum band, which have not been
previously available for commercial use. See "-- Government Regulation." On
December 31,
 
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<PAGE>
1996, the FCC announced it had adopted an order that partially lifted the freeze
on the processing of new applications which would result in the grant of
additional authorizations to other 38 GHz applicants. The grant of additional
authorizations by the FCC in the 38 GHz band, or other portions of the spectrum
with similar characteristics, could result in increased competition and diminish
the value of the Company's existing 38 GHz authorizations. The Company believes
that, assuming that additional channels are made available as proposed by the
NPRM, additional entities having greater resources than the Company could
acquire authorizations to provide 38 GHz services. See "-- Government Regulation
- -- Federal Regulation -- FCC Rulemaking."
 
    OTHER WIRELESS COMPETITORS.  The Company may also face competition from
other terrestrial wireless services, including 2 GHz and 28 GHz wireless cable
systems (MMDS and LMDS), 18 GHz point-to-point microwave services (DEMS), FCC
Part 15 wireless radio devices, and other services that use existing
point-to-point microwave channels on other frequencies. Motorola Satellite
Systems, Inc. has filed an application with the FCC for a global network of
satellites in the 37.5-40.5 GHz band and the 47.2-50.2 GHz band, which is
proposed to be used for broadband voice and data services. Other companies have
filed applications for global broadband satellite systems in the 28 GHz band. If
developed, these systems could also present significant competition to the
Company.
 
    The FCC is planning to hold an auction for 28 GHz spectrum in all markets
for the provision of high capacity "wireless cable" systems. These auctions are
expected to take place in 1997. The 2 GHz wireless cable spectrum may also
provide competition for metropolitan wireless broadband services. At present,
wireless cable licenses are used primarily (if not exclusively) for the
distribution of video programming, and have only a limited capability to provide
two-way communications needed for wireless broadband telecommunications services
but there can be no assurance that this will continue to be the case.
 
    According to press reports and FCC records, Associated Communications Group,
affiliates and joint venture partners (collectively, "ACG") hold licenses in the
18 GHz band in 31 markets. Press reports indicate that ACG plans to use fixed
wireless service to provide voice, data, Internet and videoconferencing
services.
 
    The FCC has allocated a number of spectrum blocks for use by wireless
devices that do not require site or network licensing. A number of vendors have
developed such devices that may provide competition to the Company for certain
low data-rate transmission services.
 
    In January 1997, the FCC allocated 300 MHz of spectrum in the 5 GHz band for
unlicensed devices to provide short-range, high-speed wireless digital
communications. These frequencies must be shared with incumbent users without
causing interference. Although the allocation is designed to facilitate the
creation of new wireless local area networks (and thus might not be competitive
to the Company's services), it is too early to predict what kind of equipment
might ultimately be manufactured and for what purposes it might be utilized.
 
    COMPETITION FROM INCUMBENT LECS.  The Company also faces significant
competition from incumbent LECs, irrespective of whether they provide 38 GHz
services. Incumbent LECs have long-standing relationships with their customers,
generally own significant PCS or cellular assets, have the potential to
subsidize competitive services with revenues from a variety of businesses and
benefit from favorable federal and state policies and regulations. Regulatory
decisions and recent legislation, such as the Telecommunications Act, have
partially deregulated the telecommunications industry and reduced barriers to
entry into new segments of the industry. In particular, the Telecommunications
Act, among other things, (i) enhances local exchange competition by preempting
laws prohibiting competition in the local exchange market, by requiring LECs to
provide fair and equal standards for interconnection and by requiring incumbent
LECs to provide unbundling of services and (ii) permits an RBOC to compete in
the inter-LATA long distance service market once certain competitive
characteristics emerge in such RBOC's service area. The Company believes that
this trend towards greater competition will continue to provide opportunities
for broader entrance into the local exchange markets. However, as
 
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<PAGE>
LECs face increased competition, regulatory decisions are likely to provide them
with increased pricing flexibility, which in turn may result in increased price
competition. There can be no assurance that such increased price competition
will not have a material adverse effect on the Company's results of operations.
 
    A number of companies are developing enhancements to increase the
performance of LECs' legacy copper networks. These generally come under the
description of digital subscriber line products, such as ADSL (asymmetrical
digital subscriber line), HDSL (high-speed digital subscriber line), and VDSL
(video digital subscriber line). There can be no assurance that the Company will
be able to compete effectively with these enhancements.
 
    OTHER COMPETITORS.  The Company may compete with CAPs/CLECs for the
provision of last mile access and additional services in most of its market
areas. However, the Company believes that many CAPs/CLECs may utilize 38 GHz
transmission links primarily to augment their own service offerings to IXCs and
end users, and that the Company is well positioned to provide such 38 GHz
services to CAPs/ CLECs. However, there can be no assurance that CAPs/CLECs will
utilize the Company's 38 GHz services or that CAPs/CLECs will not seek to
acquire their own 38 GHz licenses or use the 38 GHz licenses of other licensees.
Furthermore, the ability of CAPs/CLECs to compete in the local exchange market
is limited by lack of parity with LECs in number portability, dialing parity and
reasonable interconnection. The Telecommunications Act requires the FCC and the
states to implement regulations that place CAPs/CLECs on a more equal
competitive footing with LECs. To the extent these changes are implemented,
CAPs/CLECs may be able to compete more effectively with LECs. However, there can
be no assurance that CAPs/CLECs or 38 GHz service providers, such as the
Company, will be able to compete effectively for the provision of last mile
access and other services.
 
    The Company may also face competition from cable television operators
deploying cable modems, which provide high speed data capability over installed
coaxial cable television networks. Although cable modems are not widely
available currently, the Company believes that the cable industry may support
the deployment of cable modems to residential cable customers through methods
such as price subsidies. Notwithstanding the cable industry's interest in rapid
deployment of cable modems, the Company believes that in order to provide
broadband capacity to a significant number of business and government users,
cable operators will be required to spend significant time and capital in order
to upgrade their existing networks to the next generation of hybrid fiber
coaxial network architecture. However, there can be no assurance that cable
television operators will not emerge as a source of competition to the Company.
 
    The Company may also face competition from electric utilities, LECs
operating outside their current local service areas, IXCs and other providers.
These entities provide transmission services using technologies which may enjoy
a greater degree of market acceptance than 38 GHz wireless broadband technology
in the provision of last mile broadband services. In addition, the Company may
face competition from new market entrants using fiber optic and enhanced copper
based networks to provide local service.
 
    Many of the Company's competitors have long-standing relationships with
customers and suppliers, greater name recognition and greater financial,
technical and marketing resources than the Company. As a result, these
competitors may be able to more quickly develop and exploit new or emerging
technologies, adapt to changes in customer requirements, or devote greater
resources to the marketing of their services than the Company. The consolidation
of telecommunications companies and the formation of strategic alliances and
cooperative relationships in the telecommunications and related industry, as
well as the development of new technologies, could give rise to significant new
competitors to the Company. In such case, there can be no assurance as to the
degree to which the Company will be able to compete effectively.
 
                                       65
<PAGE>
GOVERNMENT REGULATION
 
    The Company's wireless broadband services are subject to regulation by
federal, state and local governmental agencies. The Company believes that it is
in substantial compliance with all material laws, rules and regulations
governing its operations and has obtained, or is in the process of obtaining,
all authorizations, tariffs and approvals necessary and appropriate to conduct
its operations. Nevertheless, changes in existing laws and regulations,
including those relating to the provision of wireless local telecommunications
services via 38 GHz and/or the future granting of 38 GHz authorizations, or any
failure or significant delay in obtaining necessary regulatory approvals, could
have a material adverse effect on the Company.
 
    FEDERAL REGULATION
 
    At the federal level, the FCC has jurisdiction over the use of the
electromagnetic spectrum (I.E., wireless services) and has exclusive
jurisdiction over all interstate telecommunications services, that is, those
that originate in one state and terminate in another state. State regulatory
commissions have jurisdiction over intrastate communications, that is, those
that originate and terminate in the same state. Municipalities may regulate
limited aspects of the Company's business by, for example, imposing zoning
requirements and requiring installation permits. The Company also is subject to
taxation at the federal and state levels and may be subject to varying taxes and
fees from local jurisdictions.
 
    FCC LICENSING.  The Communications Act of 1934 (the "Communications Act")
imposes certain requirements relating to licensing, common carrier obligations,
reporting and treatment of competition. Under current FCC rules, the recipient
of an authorization for 38 GHz microwave facilities is required to construct
facilities to place the station "in operation" within 18 months of the date of
grant of the authorization. Although, under current FCC regulations, the term
"in operation" is not defined beyond the requirement that the station be capable
of providing service, the industry custom is to establish at least one link
between two transceivers in each market area for which it holds a license. In
the event that the recipient fails to comply with the construction deadline, the
license is subject to forfeiture, absent an extension of the deadline. Upon
completion of the CommcoCCC Acquisition, the Company will own or manage a total
of 233 authorizations that will allow it to provide 38 GHz wireless broadband
services in 169 U.S. markets. The Company currently owns or manages 104 licenses
(exclusive of the CommcoCCC Assets) that allow it to provide 38 GHz wireless
broadband services in 81 markets to construct and operate 38 GHz wireless
broadband facilities, 73 of which are owned by the Company, 19 of which are
managed by the Company through the Company's interests in or arrangements with
other companies and 12 of which the Company has the right to use on a long-term
basis. All of the 104 licenses (exclusive of the CommcoCCC Assets) which the
Company owns, manages or has a right to use on a long-term basis have met the
FCC's construction deadline. Under the terms of the CommcoCCC authorizations and
the Company's management agreement with CommcoCCC, the Company has met the
construction deadline for 76 licenses and must meet the construction deadline
for the remaining 53 licenses between mid-April and August 1997. The Company
believes that, in light of current FCC practice, extensions of construction
periods are highly unlikely. In addition, pursuant to rules that became
effective August 1, 1996, if a station does not transmit operational traffic
(not test or maintenance signals) for a consecutive period of twelve months at
any time after construction is complete, or if removal of equipment or
facilities renders the station incapable of providing service, the license is
subject to forfeiture, absent a waiver of the FCC's rules. Although this rule
has not been interpreted by the FCC, it is possible that it could be applied in
such a way that could cause one or more of the Company's licenses to be subject
to forfeiture. See "Risk Factors -- Risk of Forfeiture, Non-Renewal and
Fluctuation in Value of FCC Licenses."
 
    COMMON CARRIER REGULATION.  Under the terms of its licenses, the Company is
classified as a common carrier, and as such is required to offer service on a
non-discriminatory basis at just and reasonable rates to anyone reasonably
requesting such service. Although the Communications Act prohibits the Company
from discriminating among its customers, the Communications Act, as currently
interpreted by the FCC, does permit the Company substantial discretion in
classifying its customers and discriminating
 
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among such classifications. The Company generally is obligated to furnish
service to its competitors and might be obligated to allow other 38 GHz
providers to install links within one of the Company's market areas for a
non-discriminatory fee. Under the FCC's streamlined regulation of non-dominant
carriers, the Company, as a non-dominant carrier, must file tariffs with the FCC
for certain interstate services on an ongoing basis. The Company is in the
process of filing tariffs with the FCC, to the extent required, with respect to
its provision of interstate service. The FCC has recently initiated a rulemaking
proceeding to eliminate the tariff filing requirement pursuant to new
forbearance authority contained in the Telecommunications Act. The Company, as a
non-dominant carrier, is not currently subject to rate regulation.
 
    The Company manages the systems of ART West, DCT, TeleCom One and CommcoCCC
(during the pendency of certain acquisitions) pursuant to management agreements.
See "Business -- Agreements Relating to Licenses and Authorizations." In
addition, the Company recently entered into the ICG Agreement and a services
agreement with Microwave Partners. The Company believes that the provisions of
these management agreements comply with the FCC's policies concerning licensee
control of FCC-licensed facilities. Because the 38 GHz service is a new service,
however, there is no FCC precedent addressing the limits of such management
arrangements for these services. No assurance can be given that the management
arrangements or proposed acquisitions will, if challenged, be found to satisfy
the FCC's policies or what modifications, if any, may need to be made to satisfy
those policies. If the FCC were to void or require modifications of the
management arrangements, the Company's operating results would be adversely
affected.
 
    FCC REPORTING.  The Company, as an operator of millimeter wave radio
facilities, was subject to the FCC's semiannual reporting requirements with
respect to the deployment of wireless local telecommunications services in its
licensed areas. The Company believes that it fully complied with its reporting
obligation. Since August 1, 1996, the FCC rules have not required semiannual
reporting.
 
    COMPETITION.  Over the last several years, the FCC has issued a series of
decisions and Congress has recently enacted legislation making the interstate
access services market more competitive by requiring reasonable and fair
interconnection by LECs. Concomitant with its decision to require such
interconnection, the FCC has provided LECs with a greater degree of pricing
flexibility between services (such as the ability to reduce local access charges
paid by long distance carriers utilizing LECs' local networks) and between
geographic markets (such as cross-subsidizing price cuts across geographic
markets). The Company anticipates that this pricing flexibility will result in
LECs lowering their prices in high density zones. To the extent that LECs choose
to take advantage of increased pricing flexibility to lower their rates, the
ability of the Company and CAP customers of the Company to compete for certain
markets and services and the Company's operating results may be adversely
affected.
 
    THE TELECOMMUNICATIONS ACT.  The Telecommunications Act substantially
departs from prior legislation in the telecommunications industry by
establishing local exchange competition as a national policy through the removal
of state regulatory barriers to competition and the preemption of laws
restricting competition in the local exchange market. The Telecommunications
Act, among other things, mandates that LECs (i) permit resale of their services
and facilities on reasonable and nondiscriminatory terms and at wholesale rates,
(ii) allow customers to retain the same telephone number ("number portability")
when they switch carriers, (iii) permit interconnection by competitors to a
LEC's network at any technically feasible point on the same terms as LEC charges
for its own services, (iv) unbundle their network services and facilities by
permitting competitors and others to use some but not all of their facilities at
cost-based and nondiscriminatory rates and (v) ensure that the end user does not
have to dial any more digits to reach local competitors than to reach the LEC to
the extent technically feasible ("dialing parity"). The Telecommunications Act
also allows RBOCs to provide inter-LATA services once certain competitive
characteristics emerge in their local exchange markets. The provisions of the
Telecommunications Act are designed to ensure that RBOCs take affirmative steps
to level the playing field for their competitors so that CAPs and others can
compete effectively. The FCC, with advice from
 
                                       67
<PAGE>
the United States Department of Justice, and the states are given jurisdiction
to enforce these requirements. There can be no assurance, however, that the
states and the FCC will implement the Telecommunications Act in a manner
favorable to the Company and its customers.
 
    FCC RULEMAKING.  On November 13, 1995, the FCC released an order barring the
acceptance of new applications for 38 GHz authorizations. On December 15, 1995,
the FCC announced the issuance of the NPRM, pursuant to which it proposed to
amend its current rules to provide for, among other things, (i) the adoption of
an auction procedure for the issuance of authorizations in the 38 GHz band,
including a possible auction of the lower fourteen proposed 100 MHz channels
(which are similar to those used by the Company) and the lower four proposed 50
MHz channels in the 38 GHz band that have not been previously available for
commercial use and a possible auction of the unlicensed areas in the upper
fourteen 100 MHz channels, (ii) licensing frequencies using predefined
geographic service areas ("Basic Trading Areas"), (iii) the imposition of
substantially stricter construction requirements for authorizations that are not
received pursuant to auctions as a condition to the retention of such
authorizations and (iv) the implementation of certain technical rules designed
to avoid radio frequency interference among licensees. In addition, the FCC
ordered that those applications subject to mutual exclusivity with other
applicants or placed on public notice by the FCC after September 13, 1995 would
be held in abeyance pending the outcome of the NPRM and might then be dismissed
(the "freeze"). On December 31, 1996, the FCC announced that it had adopted an
order that partially lifted the freeze on the processing of pending
applications. Among other actions, the order provides that the Commission will
process certain amendments filed before December 15, 1995 that have the effect
of eliminating mutual exclusivity among pending applications, which is likely to
result in the grant of additional authorizations to 38 GHz applicants other than
the Company. Final rules issued in connection with the NPRM may require that 38
GHz service providers share the 38 GHz band with satellite services. Motorola
Satellite Systems, Inc. has filed an application with the FCC for a global
network of satellites to be used for broadband voice and data services. Motorola
proposes to use 38 GHz frequencies for transmissions from space to earth.
Satellite transmissions in the 38 GHz frequencies could adversely effect the
Company's existing operations or its future expansions by creating interference
or by inducing the FCC to impose power and other limitations upon the Company's
transmissions. However, the Motorola application would require changes in the
FCC's rules to be granted, and it would likely be a number of years before any
such system could be launched. The extent of the adverse impact upon the
Company's operations if the Motorola application were to be granted in its
current form is unknown, and there can be no assurance that the Company's
operations would not be adversely effected. The NPRM proposes substantial
strengthening of the current rules concerning the steps that a grantee of a 38
GHz authorization must take to satisfy the FCC's construction requirements. At
present, the holder of a construction permit is only required to certify that it
is operational. Although under current FCC regulations the term "operational" is
not specifically defined, the industry custom is to install one link, which may
be only temporary and may not be producing revenue for the operator. The NPRM
expresses concern that this lenient standard might allow the warehousing of 38
GHz spectrum. As a consequence, the NPRM proposes much more stringent
construction requirements for authorizations other than those received pursuant
to an auction. There can be no assurance that the final rules (if any) issued in
connection with the NPRM will resemble the rules proposed in the NPRM. There
also can be no assurance that any proposed or final rules will not have a
material adverse effect on the Company. Statutes and regulations which may
become applicable to the Company as it expands could require the Company to
alter methods of operations at costs which could be substantial or otherwise
limit the types of services offered by the Company.
 
    The NPRM also proposes that 38 GHz authorizations be awarded by auction. The
NPRM would specify the geographic areas that could be licensed instead of
continuing to allow the applicants to design the geographic circumferences of
the licenses. The Company has not determined whether to seek additional licenses
in the event of an auction. The Company believes that the FCC is likely to award
38 GHz authorizations by auction, but there can be no assurance that this will
occur. The Company does not believe that awards by auction will adversely effect
the Company and that the auction of additional spectrum could enable the Company
to broaden its geographic reach as desired.
 
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    STATE REGULATION
 
    Many of the Company's services, either now or in the future, may be
classified as intrastate and therefore may be subject to state regulation. The
Company is in the process of obtaining state authorizations deemed to be
sufficient to conduct most, if not all, of its proposed business in the
near-term, but there can be no assurance that some portion of the Company's
proposed transmissions might not be considered to be subject to state
jurisdiction in a state in which the Company does not have appropriate
authority. The Company expects that as its business and product lines expand and
the requirements of the Telecommunications Act favoring competition in the
provision of local communications services are implemented, it will offer an
increased number and type of intrastate services. The Company is implementing a
program to expand the scope of its intrastate certifications in various state
jurisdictions as its product line expands and as the Telecommunications Act is
implemented.
 
    Under current state regulatory schemes, entities can compete with LECs in
the provision of (i) local access services, (ii) dedicated access services,
(iii) private network services, including WAN services, for businesses and other
entities and (iv) long distance toll services. The remaining local
telecommunications services, including switched local exchange services
encompassing calls originating and terminating within a single LATA, are not
currently subject to competition in most states. The Telecommunication Act
requires each of these states to remove these barriers to competition. No
assurance can be given as to how quickly and how effectively each state will act
to implement the new legislation.
 
INTELLECTUAL PROPERTY RIGHTS
 
    The Company has one registered service mark, ART, and has filed for
protection for three other service marks: DigiWave (the Company's wireless
broadband trademark), OZ Box (the Company's proprietary network management
interface) and Advanced Radio Telecom. These first filings are block mark
applications, which if allowed by the Patent and Trademark Office, would protect
future variations. The Company will seek the maximum protection for its future
service marks. There can be no assurance that the service marks applied for will
be granted nor that the Company's future efforts will be successful. Although
the Company is developing various proprietary processes, software products and
databases and intends to protect its rights vigorously and to continue to
develop such proprietary systems and databases, there can be no assurance that
these measures will be successful in establishing its proprietary rights in such
assets.
 
EMPLOYEES
 
    As of December 31, 1996, the Company had a total of 121 employees, including
39 in engineering and field services, 47 in sales and marketing, 20 in
administration and finance and 15 in operations. None of the Company's employees
is represented by a collective bargaining agreement. The Company has never
experienced a work stoppage and believes that its employee relations are good.
 
PROPERTIES
 
    The Company leases approximately 22,000 square feet of office, technical
operations and engineering field services depot space in Bellevue, Washington.
The Company's corporate headquarters, network operations center and western
regional sales office occupy approximately 15,000 square feet under a sublease
expiring in January 2000. The Company's engineering department leases
approximately 5,000 square feet and 2,000 square feet for technical operations
and an engineering field services depot, respectively, pursuant to leases
expiring in May 1997 and February 1997, respectively. In addition the Company
leases 1,100 square feet of office space in Portland, Oregon for sales and
marketing personnel pursuant to a lease expiring in March 1998. The Company also
leases temporary office space in Washington, D.C. under a sub-lease from Pierson
& Burnett, L.L.P. See "Certain Transactions -- Pierson & Burnett Transactions."
 
LITIGATION
 
    The Company is not a party to any litigation.
 
                                       69
<PAGE>
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
 
    The executive officers, directors and director designate of the Company,
their ages and their positions are as follows:
 
<TABLE>
<CAPTION>
NAME                                              AGE      POSITION
- --------------------------------------------      ---      -------------------------------------------------------
<S>                                           <C>          <C>
Vernon L. Fotheringham (1)(2)(3)............          48   Chairman of the Board of Directors and Chief Executive
                                                            Officer
Steven D. Comrie............................          41   President, Chief Operating Officer and Director
Thomas A. Grina.............................          39   Executive Vice President and Chief Financial Officer
W. Theodore Pierson, Jr.....................          59   Executive Vice President and Secretary
James D. Miller.............................          54   Senior Vice President, Sales and Marketing
Richard A. Shields, Jr......................          40   Senior Vice President, Technical Operations
James C. Cook (1)(3)........................          36   Director
Mark C. Demetree (1)(2).....................          40   Director
Andrew I. Fillat (2)(3).....................          48   Director
Alan Z. Senter..............................          55   Director
James B. Murray, Jr. (4)....................          50   Director Designate
</TABLE>
 
- ------------------------------
(1)  Member of Option Committee.
 
(2)  Member of Compensation Committee.
 
(3)  Member of Audit Committee.
 
(4)  Designated for election promptly after consummation of the CommcoCCC
     Acquisition.
 
     VERNON L. FOTHERINGHAM has served as Chairman of the Board of Directors,
Chief Executive Officer of the Company and Telecom since inception. From 1993 to
1995, Mr. Fotheringham served as president and chief executive officer of Norcom
Networks Corporation, a nationwide provider of mobile satellite services. In
1992, Mr. Fotheringham co-founded Digital Satellite Broadcasting Corporation
("DSBC"), a development stage company planning to provide satellite radio
services nationwide, served as its chairman from 1992 to 1993 and currently
serves as one of its directors. From 1988 to 1994, Mr. Fotheringham served as
senior vice president of The Walter Group, Inc. ("TWG"), a wireless
telecommunications consulting and project management firm. From 1983 to 1986,
Mr. Fotheringham served as vice president of marketing of Omninet Corporation,
which was the original developer of the current Qualcomm Omni TRACS network.
Over the last ten years, Mr. Fotheringham has advised several businesses in the
telecommunications industry, including American Mobile Satellite Corporation,
ClairCom Communications ("ClairCom") and McCaw Cellular Communications, Inc.
 
    STEVEN D. COMRIE has served as President, Chief Operating Officer and a
director of the Company since July 1995. From 1992 to 1995, Mr. Comrie served as
vice president and general manager of Cypress Broadcasting Inc., a
California-based television subsidiary of Ackerley Communications Inc., a
diversified media company based in Seattle, Washington. From 1990 to 1992, Mr.
Comrie served as president of First Communication Media Inc. and as an investor,
advisor and manager of satellite, broadcast and telecommunications businesses in
the United States and Canada. In 1986, Mr. Comrie co-founded Netlink, the first
commercial direct broadcast satellite service operating in the U.S. which was
subsequently acquired by Tele-Communications Inc. ("TCI"). Previously, Mr.
Comrie served in a variety of management positions with cable and media
companies.
 
                                       70
<PAGE>
    THOMAS A. GRINA has served as Executive Vice President and Chief Financial
Officer of the Company since April 1996. From June 1989 to April 1996, Mr. Grina
was Executive Vice President, Finance and Chief Financial Officer of DialPage,
Inc. and Executive Vice President of its wholly-owned subsidiary, Dial Call
Communications, Inc., a wireless communications company operating in the
southeastern U.S.
 
    W. THEODORE PIERSON, JR. has served as Executive Vice President of the
Company and Telecom since inception. He served as a director of the Company from
its inception until July 1996 and as General Counsel of the Company from its
inception until December 31, 1996. For more than three years, Mr. Pierson has
been a partner of the firm of Pierson & Burnett, L.L.P. (and its predecessor
firms) in Washington, D.C., which specializes in telecommunications law. Prior
to becoming a partner at Pierson & Burnett, L.L.P., Mr. Pierson was a partner of
the law firm Reed, Smith Shaw & McClay. In his 32 years of practicing law, Mr.
Pierson has advised a number of start-up telecommunications companies, including
Home Box Office, Satellite Business Systems, Omninet Corporation and DSBC. Mr.
Pierson currently serves as a director of DSBC. Mr. Pierson was also counsel to
the Competitive Telecommunications Association (the largest association of long
distance carriers) from 1984 to 1988 and the Association for Local
Telecommunications Services from 1993 to 1995.
 
    JAMES D. MILLER has served as Senior Vice President, Sales and Marketing of
the Company since December 1995. From 1993 to 1995, Mr. Miller was vice
president and general manager of U.S. Intelco Wireless. Mr. Miller served as
executive vice president of Atlas Telecom from 1987 to 1993 and as national
sales manager of Sidereal Corporation from 1977 to 1987.
 
    RICHARD A. SHIELDS, JR. has served as Senior Vice President, Technical
Operations of the Company since December 1996 and served as Vice President,
Technology Development of the Company from March 1996 to December 1996. From
1992 through 1996, Mr. Shields was vice president, engineering and design for
Claircom. From 1991 to 1992, Mr. Shields served as director of product
development of TWG.
 
    JAMES C. COOK has served as a director of the Company since November 1996.
Mr. Cook is currently senior vice president of First Union Capital Partners,
Inc. ("FUCPI"), the private equity investment affiliate of First Union
Corporation, where he has been employed since 1989. Prior to joining FUCPI, Mr.
Cook served in various capacities at The Bank of New York from 1982 to 1987 and
at Kidder, Peabody & Co. Inc. in 1988.
 
    MARK C. DEMETREE has served as a director of the Company since May 1995.
Since 1993, Mr. Demetree has been president of North American Salt Company, the
second largest salt producer in North America. From 1991 through 1993, Mr.
Demetree served as president of Trona Railway Company, a shortline railroad
division of North American Chemical Company. Mr. Demetree currently is a
director of J.C. Nichols Company, a real estate company, and serves on the Board
of Governors of the Canadian Chamber of Maritime Commerce for the Great
Lakes/St. Lawrence Seaway and is the current chairman of the CEO Council of the
Salt Institute.
 
    ANDREW I. FILLAT has served as a director of the Company since November
1995. Mr. Fillat has been employed since 1989 by Advent International
Corporation ("Advent"), a global venture capital and private equity management
firm and currently serves as senior vice president. Prior to 1989, Mr. Fillat
was a partner at Fletcher and Company, a consulting firm specializing in
assisting venture-backed enterprises, and was an operating executive with
Fidelity Investments. Mr. Fillat is also a director of: Interlink Computer
Sciences, a systems management and communications software company; Lightbridge,
Inc., a company providing customer acquisition and marketing related services
for cellular and PCS carriers; Voxware, Inc., a software company providing
advanced voice compression and processing; and several private companies in the
Advent portfolio.
 
    ALAN Z. SENTER has served as a director of the Company since December 1996.
From 1994 to May 1996, Mr. Senter served as executive vice president and chief
financial officer of NYNEX Corporation. From 1993 to 1994, Mr. Senter served as
chairman of Senter Associates, a financial advisory firm. From 1992 to 1993, Mr.
Senter was executive vice president, chief financial officer and a director of
GAF/ISP
 
                                       71
<PAGE>
Corporation. From 1968 to 1992, Mr. Senter served in various capacities at Xerox
Corporation, including serving as vice president of finance from 1990 to 1992.
Mr. Senter currently serves as a director of XL Insurance Company and formerly
served as a director of NYNEX Cablecom (U.K.), Bell Atlantic NYNEX Mobile, NYNEX
Credit Co., International Specialty Products, Inc., GAF Corp., Rank Xerox Ltd.,
and Xerox Financial Services. Mr Senter has also served as a member of the
Advisory Committee of the University of Chicago Graduate School of Business.
 
    JAMES B. MURRAY, JR. will become a director of the Company promptly after
consummation of the CommcoCCC Acquisition. Since its inception in March 1989,
Mr. Murray has been a Managing Director of Columbia Capital Corporation and
since January 1995, has been a director of The Columbia Group Incorporated. From
January 1990 to January 1993, Mr. Murray was also the President of Randolph
Cellular Corp., a cellular communications company. Mr. Murray is a member of the
Board of Directors of Saville Systems, a publicly-traded entity providing
billing solutions for service providers in the telecommunications industry as
well as several privately-held telecommunications companies, including GO
Communications Corporation, Merrick Tower Corporation, Contact New Mexico, Inc.
and Columbia Spectrum Management, Inc.
 
BOARD COMPOSITION
 
    All directors hold office until their successors have been elected and
qualified. The Company's Board of Directors is divided into three classes, with
each class of directors to serve three-year staggered terms (after their initial
terms). Messrs. Comrie and Senter serve as Class I directors for an initial one-
year term expiring in 1997. Messrs. Cook and Fotheringham serve as Class II
directors for an initial two-year term expiring in 1998. Messrs. Mark C.
Demetree and Fillat serve as Class III directors for an initial three-year term
expiring in 1999.
 
    As a condition to the CommcoCCC Acquisition, the Company will elect Mr.
Murray as a Class III director of the Company.
 
PROMOTERS OF TELECOM AND THE COMPANY
 
    Landover Holdings Corporation ("LHC") and Laurence S. Zimmerman could be
deemed promoters of Telecom and the Company. See "Certain Transactions --
Organization of Telecom," "-- LHC Purchase Agreement" and "-- LHC Agreements."
Mr. Zimmerman served as a director of the Company from June to November 1996,
and as a director of Telecom from May 1995 to November 1996. Since 1985, Mr.
Zimmerman has been President, founder and beneficial owner of LHC. LHC is a
private investment firm with interests in wireless cable, wireless telephone,
cellular, managed healthcare and specialty retail companies as well as other
investments in the United States and abroad. From 1989 to 1990, Mr. Zimmerman
was a managing director of Renaissance Capital Group Inc., a leveraged buyout
firm which concentrated on emerging market and middle market telecommunications
and healthcare opportunities. In 1993, Mr. Zimmerman was a founder of, and
provided the seed capital for, National Wireless Holdings Inc., a wireless cable
company serving markets in Southern Florida. On February 1, 1995, Mr. Zimmerman
consented to the entry of an order of the Securities and Exchange Commission,
without admitting or denying the matters referred to therein, barring him from
association with any broker, dealer, municipal securities dealer, investment
company or investment adviser during the period February 1, 1995 to February 1,
1996 and requiring him not to violate certain provisions of the Federal
securities laws. The order relates to alleged violations arising out of alleged
conduct by Mr. Zimmerman in 1986 as a broker for Breuer Capital, in connection
with trading and selling shares of Balchem Corporation. Mr. Zimmerman may attend
meetings of the Board of Directors as an observer, at the invitation of the
Board of Directors. See "Principal Stockholders -- Voting Trust Agreement."
 
DIRECTOR COMPENSATION
 
    Directors who are not employees of the Company receive $4,000 per year for
services rendered as a director and $500 for attending each meeting of the Board
of Directors or one of its Committees. In
 
                                       72
<PAGE>
addition, directors may be reimbursed for certain expenses incurred in
connection with attendance at any meeting of the Board of Directors or
Committees. Other than reimbursement of expenses, directors who are employees of
the Company receive no additional compensation for service as a director.
 
    In May 1996, the Company adopted the Directors Plan (as defined) which
provides for automatic grants of options to purchase an aggregate of 75,000
shares of Common Stock to non-employee directors of the Company. See "-- Stock
Option Plans." As of January 14, 1997, options to purchase an aggregate of
19,200 shares at exercise prices ranging from $11.25 to $15.00, have been
granted to non-employee directors under the Directors Plan.
 
BOARD COMMITTEES
 
    The Company's bylaws, as amended (the "Bylaws"), provide that the Board of
Directors may establish committees to exercise certain powers delegated by the
Board of Directors. Pursuant to that authority, the Board of Directors has
established an Option Committee, Compensation Committee, Finance Committee and
Audit Committee.
 
    The Option Committee reviews, interprets and administers the Equity
Incentive Plan (as defined), prescribes rules and regulations relating thereto
and determines the stock options to be granted by the Company to its employees.
Messrs. Cook, Demetree and Fillat currently serve on the Option Committee.
 
    The Compensation Committee has responsibility for reviewing and
administering the Company's program with respect to the compensation of its
officers, employees and consultants and reviewing transactions with its
officers, directors and affiliates. As a policy, the Compensation Committee
directs the Company to pay officers, directors and affiliates of the Company for
services rendered outside the scope of their respective obligations to the
Company, in accordance with industry standards for such services, which may
include introducing major transactions or providing legal services to the
Company. Messrs. Demetree, Fillat and Fotheringham currently serve on the
Compensation Committee.
 
    The Audit Committee recommends the engagement of independent accountants to
audit the Company's financial statements and perform services related to the
audit, reviews the scope and results of the audit with the accountants, reviews
with management and the independent accountants the Company's year-end operating
results, and considers the adequacy of internal accounting procedures. Messrs.
Cook and Fillat currently serve on the Audit Committee.
 
RELATED PARTY TRANSACTIONS
 
    On February 2, 1996, the Company adopted a policy that all transactions,
including compensation, between the Company and its officers, directors and
affiliates will be on terms no less favorable to the Company than could be
obtained from unrelated third parties and shall be approved by a majority of the
disinterested members of the Compensation Committee or by a majority of the
disinterested members of the Board of Directors.
 
                                       73
<PAGE>
EXECUTIVE COMPENSATION
 
    The following table sets forth all compensation received by (i) the
Company's Chief Executive Officer and (ii) the four highest-paid executive
officers of the Company other than the Company's Chief Executive Officer
(collectively, the "Named Executive Officers"), for services rendered to the
Company in all capacities during the fiscal year ended December 31, 1996.
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                                                    LONG TERM
                                                                                   COMPENSATION
                                                                                      AWARDS
                                                                                  --------------
                                                         ANNUAL COMPENSATION        SECURITIES
                                                     ---------------------------    UNDERLYING      ALL OTHER
NAME AND PRINCIPAL POSITION                              SALARY         BONUS       OPTIONS(#)     COMPENSATION
- ---------------------------------------------------  --------------  -----------  --------------  --------------
<S>                                                  <C>             <C>          <C>             <C>
Vernon L. Fotheringham, Chief Executive Officer      $   250,000             --              --   $      9,600(1)
Steven D. Comrie, President and Chief Operating
 Officer                                                 197,500             --              --          9,600(1)
W. Theodore Pierson, Jr., Executive Vice President       186,107(2)          --              --             --
Thomas A. Grina, Executive Vice President and Chief
 Financial Officer                                       122,190(3)          --         181,818         29,800(1)(4)
James D. Miller, Senior Vice President, Sales and
 Marketing                                               135,000             --          36,364          6,200(1)
</TABLE>
 
- ------------------------------
(1)  Automobile reimbursement benefits equal to $9,600 for each of Messrs.
     Fotheringham and Comrie, $4,800 for Mr. Grina and $6,200 for Mr. Miller.
 
(2)  The Company paid Pierson & Burnett, L.L.P., of which Mr. Pierson is a
     partner, approximately $520,000 for services rendered to the Company in
     1996.
 
(3)  Reflects compensation for a partial year. See "-- Employment and Consulting
     Agreements."
 
(4)  The Company reimbursed approximately $25,000 of moving expenses.
 
                                       74
<PAGE>
    OPTION GRANTS.  The following table sets forth certain information regarding
stock option grants made to the Named Executive Officers during the fiscal year
ended December 31, 1996.
 
                       OPTION GRANTS IN LAST FISCAL YEAR
 
<TABLE>
<CAPTION>
                                               INDIVIDUAL GRANTS (2)
                               ------------------------------------------------------  POTENTIAL REALIZABLE VALUE
                                NUMBER OF      PERCENT OF                              AT ASSUMED ANNUAL RATES OF
                                SECURITIES    TOTAL OPTIONS                             STOCK PRICE APPRECIATION
                                UNDERLYING     GRANTED TO      EXERCISE                   FOR OPTION TERM (1)
                                 OPTIONS      EMPLOYEES IN     PRICE PER   EXPIRATION  --------------------------
NAME                             GRANTED       FISCAL YEAR       SHARE        DATE         5%            10%
- -----------------------------  ------------  ---------------  -----------  ----------  -----------  -------------
<S>                            <C>           <C>              <C>          <C>         <C>          <C>
Thomas A. Grina                    109,091          25.1%     $   17.1875   4/25/04    $   432,927  $   1,341,934
                                    72,727          16.7%         17.1875   10/11/01       325,270        992,323
James D. Miller                     36,364           8.4%         17.1875   10/11/01       162,635        496,161
</TABLE>
 
- ------------------------------
(1)  The potential realizable value is calculated based on the term of the
     option at its time of grant. It is calculated by assuming that the stock
     price on the date of grant appreciates at the indicated annual rate,
     compounded annually for the entire term of the option. The exercise prices
     for the options granted expiring through April 25, 2004 were determined by
     the Option Committee, which considered the fair market value of the
     Company's securities at the time of grant based upon analysis of recent
     private placements of securities. Subsequently, the Company engaged an
     independent appraisal firm who conducted a more thorough analysis of the
     value of the Company's securities and who considered such placements as
     well as comparable market transactions and other relevant factors specific
     to the placements (such as underlying security interest and liquidity). The
     exercise prices for the options granted expiring October 11, 2004, were
     determined by the Option Committee, which considered the expected price of
     the Common Stock in the Common Stock Offering. In all cases, the exercise
     price was equal to, or in excess of, the estimated fair value of the
     Company's Common Stock at the date of grant, and in the case of the options
     expiring through April 25, 2004, as determined by the independent appraisal
     firm.
 
(2)  See "-- Stock Option Plans -- Equity Incentive Plan -- Grants."
 
     AGGREGATE STOCK OPTION EXERCISES IN LAST FISCAL YEAR AND FISCAL YEAR-END
OPTION VALUES.  The following table sets forth the number and value as of
December 31, 1996 of shares underlying unexercised options held by each of the
Named Executive Officers. As of December 31, 1996, no stock options had been
exercised by any Named Executive Officers.
 
                         FISCAL YEAR-END OPTION VALUES
 
<TABLE>
<CAPTION>
                                                            NUMBER OF SHARES
                                                         UNDERLYING UNEXERCISED         VALUE OF UNEXERCISED
                                                               OPTIONS AT              IN-THE-MONEY OPTIONS AT
                                                             FISCAL YEAR END             FISCAL YEAR END (1)
                                                       ---------------------------  -----------------------------
NAME                                                   EXERCISABLE  UNEXERCISABLE    EXERCISABLE   UNEXERCISABLE
- -----------------------------------------------------  -----------  --------------  -------------  --------------
<S>                                                    <C>          <C>             <C>            <C>
Steven D. Comrie                                          172,525        102,635    $   1,660,657   $    987,923
Thomas A. Grina                                            36,364        145,454    $    --         $    --
James D. Miller                                             7,273         47,273    $      48,780   $     73,167
</TABLE>
 
- ------------------------------
(1)  Based on the last sales price of the Company's Common Stock reported on the
     Nasdaq National Market on December 31, 1996 of $11.25 per share, less the
     exercise price payable upon exercise of such options.
 
STOCK OPTION PLANS
 
    EQUITY INCENTIVE PLAN.
 
    The Equity Incentive Plan was adopted by the Company on May 30, 1996 and
amended on October 11, 1996 and approved by the stockholders on June 25, 1996
and October 14, 1996.
 
    The Equity Incentive Plan is designed to advance the Company's interests by
enhancing its ability to attract and retain employees and others in a position
to make significant contributions to the success of the Company through
ownership of shares of Common Stock. The Equity Incentive Plan provides for the
grant of incentive stock options ("ISOs"), non-statutory stock options
("NQSOs"), stock appreciation rights ("SARs"), restricted stock, unrestricted
stock, deferred stock grants, and performance awards, loans to participants in
connection with awards, supplemental grants and combinations of the above. A
total of 1,400,000 shares of common stock are reserved for issuance under the
Equity Incentive
 
                                       75
<PAGE>
Plan. The maximum number of shares as to which options or SARs may be granted to
any participant in any one calendar year is 300,000. The shares of Common Stock
issuable under the Equity Incentive Plan are subject to adjustment for stock
dividends and similar events. Awards under the Equity Incentive Plan may also
include provision for payment of dividend equivalents with respect to the shares
subject to the award.
 
    The Equity Incentive Plan is administered by the Option Committee of the
Board of Directors (the "Option Committee"). The Option Committee shall consist
of at least two directors. If the Common Stock is registered under the
Securities Exchange Act of 1934, all members of the Option Committee shall be
"outside directors" as defined. All employees of the Company and any of its
subsidiaries and other persons or entities (including non-employee directors of
the Company and its subsidiaries) who, in the opinion of the Option Committee,
are in a position to make a significant contribution to the success of the
Company or its subsidiaries are eligible to participate in the Equity Incentive
Plan.
 
    STOCK OPTIONS.  The exercise price of an ISO granted under the Equity
Incentive Plan may not be less than 100% (110% in the case of 10% shareholders)
of the fair market value of the Common Stock at the time of grant. The exercise
price of a nonstatutory option granted under the Equity Incentive Plan is
determined by the Option Committee. The term of each option may be set by the
Option Committee but cannot exceed ten years from grant (five years from grant
in the case of an incentive stock option granted to a 10% shareholder), and each
option will be exercisable at such time or times as the Option Committee
specifies. The option price may be paid in cash or check acceptable to the
Company or, if permitted by the Option Committee and subject to certain
additional limitations, by tendering shares of Common Stock, by using a
promissory note, by delivering to the Company an unconditional and irrevocable
undertaking by a broker promptly to deliver sufficient funds to pay the exercise
price, or a combination of the foregoing.
 
    STOCK APPRECIATION RIGHTS.  SARs may be granted either alone or in tandem
with stock option grants. Each SAR entitles the participant, in general, to
receive upon exercise the excess of a share's fair market value in cash or
common stock at the date of exercise over the share's fair market value on the
date the SAR was granted. The Option Committee may also grant SARs which provide
that following a change in control of the Company as determined by the Option
Committee, the holder of such right will be entitled to receive an amount
measured by specified values or averages of values prior to the change in
control. If an SAR is granted in tandem with an option, the SAR will be
exercisable only to the extent the option is exercisable. To the extent the
option is exercised, the accompanying SAR will cease to be exercisable, and vice
versa. An SAR granted in tandem with an ISO may be exercised only when the
market price of common stock subject to the option exceeds the exercise price of
such option. SARs not granted in tandem shall be exercisable at such time, and
on such conditions, as the Option Committee may specify.
 
    STOCK AWARDS.  The Equity Incentive Plan provides for awards of
nontransferable shares of restricted Common Stock subject to forfeiture as well
as of unrestricted shares of Common Stock. Awards may provide for acquisition of
restricted and unrestricted Common Stock for a purchase price specified by the
Option Committee, but in no event less than par value. Restricted Common Stock
is subject to repurchase by the Company at the original purchase price or to
forfeiture if no cash was paid by the participant if the participant ceases to
be an employee before the restrictions lapse. Other awards under the Equity
Incentive Plan may also be settled with restricted Common Stock. Restricted
securities shall become freely transferable upon the completion of the
Restricted Period including the passage of any applicable period of time and
satisfaction of any conditions to vesting. The Option Committee, in its sole
discretion, may waive all or part of the restrictions and conditions at any
time.
 
    The Equity Incentive Plan also provides for deferred grants entitling the
recipient to receive shares of Common Stock in the future at such times and on
such conditions as the Option Committee may specify, and performance awards
entitling the recipient to receive cash or Common Stock following the attainment
of performance goals determined by the Option Committee. Performance conditions
and provisions for deferred stock may also be attached to other awards under the
Equity Incentive Plan.
 
                                       76
<PAGE>
    A loan may be made under the Equity Incentive Plan either in connection with
the purchase of Common Stock under an award or with the payment of any federal,
state and local tax with respect to income recognized as a result of an award.
The Option Committee will determine the terms of any loan, including the
interest rate (which may be zero). No loan may have a term exceeding ten years
in duration. In connection with any award, the Option Committee may also provide
for and grant a cash award to offset federal, state and local income taxes or to
make a participant whole for certain taxes.
 
    Except as otherwise provided by the Option Committee, if a participant dies,
options and SARs held by such participant immediately prior to death, to the
extent then exercisable, may be exercised by the participant's executor,
administrator or transferee during a period of one year following such death (or
for the remainder of their original term, if less). Except as otherwise
determined by the Option Committee, options and SARs not exercisable at a
participant's death terminate. Outstanding awards of restricted Common Stock
must be transferred to the Company upon a participant's death and, similarly,
deferred Common Stock grants, performance awards and supplemental awards to
which a participant was not irrevocably entitled prior to death will be
forfeited, except as otherwise determined by the Option Committee.
 
    In the case of termination of a participant's association with the Company
for reasons other than death, options and SARs remain exercisable, to the extent
they were exercisable immediately prior to termination, for three months (or for
the remainder of their original term, if less), shares of restricted Common
Stock must be resold to the Company, and other awards to which the participant
was not irrevocably entitled prior to termination will be forfeited, unless
otherwise determined by the Option Committee. If any such association is
terminated due to the participant's discharge for cause which, in the opinion of
the Option Committee, casts such discredit on the participant as to justify
immediate termination of any award under the Equity Incentive Plan, such
participant's options and SARs may be terminated immediately.
 
    In the event of a consolidation or merger in which the Company is not the
surviving corporation or which results in the acquisition of substantially all
of the Company's outstanding Common Stock by a single person or entity or by a
group of persons and/or entities acting in concert or in the event of the sale
or transfer of substantially all of the Company's assets (each, a "change in
control" under the Equity Incentive Plan), the Option Committee may determine
that (i) each outstanding option and SAR will become immediately exercisable
unless otherwise provided at the time of grant, (ii) each outstanding share of
restricted Common Stock will immediately become free of all restrictions and
conditions, (iii) all conditions on deferred grants, performance awards and
supplemental grants which relate only to the passage of time and continued
employment will be removed and (iv) all loans under the Equity Incentive Plan
will be forgiven. The Committee may also arrange to have the surviving or
acquiring corporation or affiliate assume any award held by a participant or
grant a replacement award. If the optionee is terminated after such a change in
control by the Company without cause, or in the case of certain officers
designated from time to time by the Option Committee resigns under certain
circumstances, within two years following the change in control, all unvested
options will vest and all options will be exercisable for the shorter of four
years or their original duration and all other awards will vest. If the option
committee makes no such determination, outstanding awards to the extent not
fully vested will be forfeited.
 
    GRANTS.  Mr. Comrie has been granted NQSOs expiring on various dates through
June 17, 2005 to purchase 275,160 shares of Common Stock at a price of $1.6244
per share. Of the NQSOs, 172,525 are currently exercisable, and 40,724 will
become exercisable on July 17, 1997 and up to an additional 61,911 shares (the
"Additional Shares") will become exercisable on June 17, 2000. The vesting of
NQSOs to purchase 20,637 Additional Shares will be accelerated in each year
based upon the attainment of certain performance goals as determined by the
Board of Directors. In accordance with such program, the vesting of NQSOs to
purchase 20,637 Additional Shares was accelerated in December 1996. Each of Mr.
Comrie's options are exercisable for a period of five years from the date of
vesting.
 
    Mr. Grina has been granted NQSOs expiring on various dates through April 26,
2004 to purchase 109,091 shares of Common Stock at a price of $17.1875 per
share. The NQSOs are subject to vesting
 
                                       77
<PAGE>
over a three-year period, of which 36,364 are fully vested and currently
exercisable. NQSOs to purchase 72,727 shares will become exercisable on April
26, 1999; however, the vesting of 36,364 of such shares will be accelerated on
each of the first and second anniversary of the date of grant based upon
attainment of certain performance goals as determined by the Board of Directors.
Each of Mr. Grina's options are exercisable for a period of five years from the
date of vesting. All of the foregoing options will be fully vested,
notwithstanding the attainment of performance goals, on April 26, 1999. In
addition, Mr. Grina has been granted NQSOs expiring on various dates through
October 11, 2005 to purchase 72,727 shares of Common Stock at a price of
$17.1875 per share. These NQSOs vest at a rate of 25% on each anniversary of the
date of grant commencing October 14, 1997. In addition, all of his options
become immediately exercisable, without regard to the vesting period, upon a
change of control under the Equity Incentive Plan and upon other corporate
changes described in the agreement evidencing his options.
 
    Mr. Miller has been granted NQSOs expiring December 29, 2000 to purchase
18,182 shares of Common Stock at a price of $4.543 per share. The NQSOs vest at
a rate of 20% on each anniversary of the date of grant. In addition, Mr. Miller
has been granted NQSOs expiring on various dates through October 11, 2005 to
purchase 36,364 shares of Common Stock at a price of $17.1875 per share. These
NQSOs vest at a rate of 25% on each anniversary of the date of grant commencing
October 14, 1997.
 
    As of December 31, 1996, options to purchase 816,970 shares were outstanding
under the Incentive Plan.
 
    THE DIRECTORS PLAN.
 
    On May 30, 1996, the Company adopted the 1996 Non-Employee Directors
Automatic Stock Option Plan, as amended (the "Directors Plan"), which provides
for the automatic grant of stock options to non-employee directors to purchase
up to an aggregate of 75,000 shares. Under the Directors Plan, options to
acquire 2,200 shares of Common Stock are automatically granted to each
non-employee director who is a director on January 1 of each year. In addition,
each non-employee director serving on the Board of Directors immediately after
the date of the Common Stock Offering received, and in the future each newly
elected non-employee director on the date of his or her first appointment or
election to the Board of Directors will receive, an automatic grant of options
to acquire 2,600 shares of Common Stock.
 
    Although grants of the options under the Directors Plan are automatic, and
the Directors Plan is intended to be largely self-administering, the Directors
Plan will be administered by either the Board of Directors or a committee
designated by the Board of Directors, which will, to the extent necessary,
administer and interpret the Directors Plan (the "Plan Administrator"). Stock
options awarded under the Directors Plan are priced automatically at an exercise
price equal to the market price of the Common Stock on the date of grant. If at
any time no public market for the Common Stock exists, the Plan Administrator is
empowered to determine the fair market value. Under the Directors Plan, initial
option grants vest over a three-year period and are exercisable for a period of
10 years from the date of grant. Initial options to purchase an aggregate of
7,800 shares at an exercise price equal to $15.00 per share, the initial
offering price of the Common Stock in the Common Stock Offering, and initial
options to purchase 2,600 shares at an exercise price equal to $12.625 per
share, the market price of the Common Stock on December 23, 1996, have been
granted to non-employee directors under the Directors Plan. Annual options to
purchase an aggregate of 6,600 shares at an exercise price equal to $11.25 per
share, the market price of the Common Stock on December 31, 1996, have been
granted to non-employee directors under the Directors Plan.
 
EMPLOYMENT AND CONSULTING AGREEMENTS
 
    The Company has entered into a three-year employment agreement with Mr.
Fotheringham providing for full-time employment at an annualized base salary of
$250,000 for 1996, $275,000 for 1997 and $300,000 for 1998. In addition, Mr.
Fotheringham is entitled to receive an annual bonus of up to $100,000 depending
on the achievement of specified annual link installation goals. The goal for
each
 
                                       78
<PAGE>
year will be established based on the operating budget approved by the Board of
Directors. The agreement precludes Mr. Fotheringham from competing with the
Company for one year after the cessation of his employment, regardless of the
reason for such cessation.
 
    The Company has entered into a three-year employment agreement with Mr.
Comrie providing for full time employment at an annualized base salary of
$160,000 through December 31, 1995, $200,000 from January 1, 1996 to July 16,
1997 and $240,000 from July 17, 1997 to July 16, 1998. Mr. Comrie is entitled to
receive an annual bonus of up to $100,000 depending on the achievement of
specified annual link installation goals. The goal for each year will be
established based on the operating budget approved by the Board of Directors. As
part of the employment agreement, the Company provided Mr. Comrie an
interest-free loan in the amount of $30,000 and forgave payment of such loan on
January 1, 1996. The forgiveness of such loan has been accounted for as
compensation expense on the 1995 statement of operations of the Company. The
agreement also precludes Mr. Comrie from competing with the Company for one year
after the cessation of employment, regardless of the reason for such cessation.
The agreement may be terminated at any time by either party and provides that,
if the Company terminates Mr. Comrie without cause or Mr. Comrie's employment is
terminated due to his disability or death, Mr. Comrie will be entitled to
continue to receive the full amount of his base salary and any other benefits to
which he would have otherwise been entitled for a period of one year from the
date of such termination. See "-- Stock Option Plans" regarding stock options
granted to Mr. Comrie pursuant to his employment agreement.
 
    The Company has entered into an employment agreement with Mr. Grina,
providing for full time employment on an at will basis at an annualized base
salary of $190,000 through April 30, 1997. In addition, Mr. Grina is entitled to
receive an annual bonus of up to $100,000 depending upon the achievement of
specified annual link installation goals. The goal for each year will be
established based on the operating budget approved by the Board of Directors.
The agreement precludes Mr. Grina from competing with the Company for one year
after the cessation of his employment, regardless of the reason for such
cessation. The agreement may be terminated at any time by either party and
provides that, if the Company terminates Mr. Grina without cause or Mr. Grina's
employment is terminated due to his disability or death, Mr. Grina will be
entitled to continue to receive the full amount of his base salary and any other
benefits to which he would have otherwise been entitled for a period of six
months from the date of such termination. See "-- Stock Option Plans" regarding
stock options granted to Mr. Grina pursuant to his employment agreement.
 
    The Company has also entered into an employment agreement with Mr. Miller,
providing for full time employment at an annual base salary equal to $150,000.
His employment agreement provides for the payment by the Company of an annual
bonus in designated amounts based upon the achievement of specified performance
goals. The agreement has a term of three years and precludes him from competing
with the Company for one year after the cessation of employment, regardless of
the reason for such cessation. See "-- Stock Option Plans" regarding stock
options granted to Mr. Miller pursuant to his employment agreement. The
employment agreement may be terminated at any time by the Company or Mr. Miller
and provides that, if the Company terminates Mr. Miller's employment without
cause or his employment is terminated due to his disability or death, Mr. Miller
may continue to receive the full amount of his base salary and any other
benefits to which he would have otherwise been entitled for a period of six
months from the date of such termination.
 
    The Company has entered into a three-year consulting agreement with Mr.
Pierson on May 8, 1995, under which Mr. Pierson agreed to provide strategic,
business and other advisory services to the Company for base fees of $80,000 for
1995, $140,000 for 1996 and $80,000 for 1997, subject to extension at the option
of the Company. The agreement also precludes Mr. Pierson from competing with the
Company for one year after termination of the agreement, regardless of the
reason for such termination. The agreement may be terminated at any time by
either party and provides that, if the Company terminates Mr. Pierson without
cause or Mr. Pierson terminates his consulting agreement for "good reason" (as
specified in the agreement), Mr. Pierson will be entitled to continue to receive
the full amount of his base fees and any other benefits to which he would have
otherwise been entitled for a period of one year from the date of such
termination. See "Certain Transactions -- Pierson & Burnett Transactions."
 
                                       79
<PAGE>
                             PRINCIPAL STOCKHOLDERS
 
    The following table sets forth certain information, as of January 14, 1997,
regarding the beneficial ownership of the Company's Common Stock by (i) each
person known by the Company to own beneficially more than five percent of the
outstanding shares of the Company's Common Stock, (ii) the directors, director
designate and executive officers of the Company and (iii) all executive officers
and directors as a group.
 
<TABLE>
<CAPTION>
                                                                                       BENEFICIAL OWNERSHIP
                                                                                ----------------------------------
NAME                                                                                   NUMBER           PERCENT
- ------------------------------------------------------------------------------  --------------------  ------------
<S>                                                                             <C>                   <C>
Advent International Corporation (1)..........................................       1,321,511               9.7%
Ameritech Development Corp. (2)...............................................         681,323               5.0
High Sky Inc. (3).............................................................         672,219               5.0
Landover Holdings Corporation (4).............................................       2,941,165              21.7
Steven D. Comrie (5)..........................................................         172,525               1.3
James C. Cook (6).............................................................          60,168                 *
Mark C. Demetree (7)..........................................................         398,541               2.9
Andrew I. Fillat (8)..........................................................           7,327                 *
Vernon L. Fotheringham (9)....................................................       1,289,114               9.5
James B. Murray, Jr. (10).....................................................         135,000               1.4
Alan Z. Senter (11)...........................................................           4,600                 *
Thomas A. Grina (12)..........................................................          36,364                 *
James D. Miller (13)..........................................................           7,273                 *
W. Theodore Pierson, Jr. (14).................................................         856,512               6.3
Richard A. Shields, Jr. (15)..................................................           5,090                 *
All executive officers and directors as a group
 (5)(6)(7)(8)(9)(11)(12)(13)(14)(15)(16)......................................       2,837,514              20.6%
</TABLE>
 
- ------------------------
Unless otherwise indicated, the business address of each director and executive
officer named above is c/o Advanced Radio Telecom Corp., 500 108th Avenue N.E.,
Suite 2600, Bellevue, Washington 98004.
 
*   Less than 1.0%.
 
 (1) Includes 1,189,673 shares, 1,149 shares and 58,143 shares of Common Stock
    and 55,239 shares, 58 shares and 2,703 shares of Common Stock issuable upon
    exercise of March Bridge Warrants, respectively, owned by Global Private
    Equity II, L.P., Advent International Investors II, L.P. and Advent
    Partners, L.P. (collectively, the "Advent Partnerships"), each a limited
    partnership whose general partner is controlled by Advent International
    Corporation ("Advent"). Also includes 13,868 shares and 678 shares of Common
    Stock issuable upon exercise of September Bridge Warrants, respectively,
    owned by Global Private Equity II, L.P. and Advent Partners, L.P. Mr. Fillat
    is an officer of Advent. The address of Advent and each of the Advent
    Partnerships is 101 Federal Street, Boston, Massachusetts 02110.
 
 (2) Includes 60,000 shares and 21,818 shares of Common Stock issuable upon
    exercise of the March Bridge Warrants and September Bridge Warrants,
    respectively. The address of Ameritech is 30 South Wacker Drive, Chicago,
    Illinois 60601. See "Certain Transactions -- Ameritech Financing; Ameritech
    Strategic Distribution Agreement."
 
 (3) High Sky Inc. is the general partner of High Sky and High Sky II and may be
    deemed the beneficial owner of all shares held by such partnerships.
    Includes 545,048 and 127,171 shares of Common Stock owned by High Sky and
    High Sky II, respectively. Also includes 43,335 and 10,835 shares of Common
    Stock held by High Sky and High Sky II, respectively, subject to options
    owned by SERP and its designees. See "Certain Transactions -- SERP
    Agreement." High Sky Inc.'s address is c/o Frank S. Phillips Company, 6106
    MacArthur Blvd., Bethesda, Maryland 20816.
 
 (4) All of such securities are held in the LHC Voting Trust (as defined) by
    trustees who are directors of the Company and independent of LHC, Mr.
    Zimmerman and members of his family. Includes 13,636 shares and 2,036 shares
    of Common Stock issuable upon exercise of Indemnity Warrants and September
    Bridge Warrants, respectively. Does not include 36,364 shares of Common
    Stock beneficially owned by the wife and 36,364 shares of Common Stock
    beneficially owned by a family trust of Laurence S. Zimmerman, of which
    shares LHC and Mr. Zimmerman disclaim beneficial ownership. Does not reflect
    the contingent effect of the Series D Option covering 145,685 shares. LHC is
    controlled by Mr. Zimmerman. LHC's address is 667 Madison Avenue, New York,
    New York 10021. See "-- Voting Trust Agreement" and "Certain Transactions --
    Series D Preferred Stock Issuance."
 
 (5) Consists of 172,525 shares of Common Stock currently issuable upon exercise
    of options. Does not include 102,635 shares of Common Stock issuable upon
    exercise of the non-vested portion of options. See "Management -- Stock
    Option Plans."
 
 (6) Includes 8,000 shares of Common Stock issuable upon exercise of March
    Bridge Warrants and 4,800 shares of Common Stock issuable upon exercise of
    options granted under the Directors Plan.
 
                                       80
<PAGE>
 (7) Includes 4,800 shares of Common Stock beneficially issuable upon exercise
    of options granted under the Directors Plan. Does not include 56,000 shares
    and 2,909 shares of Common Stock issuable upon exercise of March Bridge
    Warrants and September Bridge Warrants, respectively, 59,090 shares of
    Common Stock issuable upon exercise of Indemnity Warrants or 1,534,964
    shares of Common Stock beneficially owned in each case by members of Mr.
    Demetree's family or a trust for their benefit, of which he disclaims
    beneficial ownership. Mr. Demetree's address is 505 Lancaster Street, #8AB,
    Jacksonville, FL 32204.
 
 (8) Includes 4,800 shares of Common Stock issuable upon exercise of options
    granted under the Directors Plan. Mr. Fillat disclaims beneficial ownership
    of the shares of Common Stock and shares of Common Stock issuable upon
    exercise of March Bridge Warrants and September Bridge Warrants held by the
    Advent Partnerships, except for 2,495 shares of Common Stock, and 3 shares
    and 29 shares issuable upon exercise of March Bridge Warrants and September
    Bridge Warrants, respectively.
 
 (9) Includes 37,917 shares of Common Stock subject to options owned by SERP and
    its designees. See "Certain Transactions -- SERP Agreement."
 
(10) Mr. Murray is expected to become a director upon consummation of the
    CommcoCCC Acquisition. He is a managing director of Columbia Capital
    Corporation, which beneficially owns 195,000 shares and, upon consummation
    of the CommcoCCC Acquisition, will beneficially own 3,462,787 shares of
    Common Stock, including 46,630 shares and 15,543 shares issuable upon
    exercise of the CommcoCCC Warrants and the September Bridge Warrants,
    respectively. Upon becoming a director, he will receive an option to
    purchase 2,600 shares of Common Stock under the Directors Plan.
 
(11) Includes 2,600 shares of Common Stock issuable upon exercise of options
    granted under the Directors Plan.
 
(12) Includes 36,364 shares of Common Stock currently issuable upon exercise of
    options.
 
(13) Includes 7,273 shares of Common Stock currently issuable upon exercise of
    an option.
 
(14) Includes 16,252 shares of Common Stock subject to options owned by SERP and
    its designees. See "Certain Transactions -- SERP Agreement." Mr. Pierson's
    address is c/o Pierson & Burnett L.L.P., 1667 K. Street, N.W., Washington,
    D.C. 20006.
 
(15) Includes 5,090 shares of Common Stock currently issuable upon exercise of
    an option.
 
(16) Does not include 2,941,165 shares of Common Stock held in the LHC Voting
    Trust by trustees, all of whom are directors of the Company of which such
    trustees disclaim beneficial ownership. See "-- Voting Trust Agreement."
 
    Upon completion of the CommcoCCC Acquisition, Columbia Capital Corporation,
as general partner of two of the stockholders of CommcoCCC, and Commco, L.L.C.,
the remaining stockholder of CommcoCCC, will beneficially own 3,462,787 and
2,878,577 shares, respectively, of Common Stock, including 46,630 and 40,643
shares, respectively, issuable upon exercise of the CommcoCCC Warrants and
15,543 and 13,548 shares, respectively, issuable upon exercise of the September
Bridge Warrants, constituting 17.7% and 14.7%, respectively, of the Company's
Common Stock. Assuming the consummation of the CommcoCCC Acquisition as of the
date of this Prospectus, the Company would have 19,559,420 shares of Common
Stock outstanding.
 
VOTING TRUST AGREEMENT
 
    Pursuant to a Voting Trust Agreement, dated November 5, 1996, LHC and the
wife and a trust for the benefit of the family of Laurence S. Zimmerman
deposited all of their shares of ART Common Stock in trust (the "LHC Voting
Trust") with Messrs. Demetree, Fillat and Fotheringham with irrevocable
instructions to vote such shares on all matters submitted to a vote of the
stockholders of the Company in proportion to, or in certain cases, consistent
with the majority of, the vote of other stockholders of the Company. The voting
trust will expire on November 5, 2006, but is subject to early termination in
the event of (i) a business combination in which ART stockholders own less than
50%, and ART directors constitute less than 50% if the board of directors, of
the combined entity and LHC owns less than 5% of the voting power of such
entity, (ii) the death of Mr. Zimmerman or (iii) the sale by LHC of such shares
to unaffiliated parties. The trustees of the trust will be indemnified by the
Company.
 
                                       81
<PAGE>
                              CERTAIN TRANSACTIONS
 
FORMATION OF ART
 
    The Company was organized in August 1993 by Vernon L. Fotheringham and W.
Theodore Pierson, Jr., for the purpose of obtaining 38 GHz licenses from the
FCC. The initial stockholders, including Messrs. Fotheringham and Pierson,
purchased for $.01 per share ART Common Stock in a private placement which, net
of certain subsequent transfers, currently constitutes an aggregate of 2,145,626
shares of Common Stock.
 
HIGH SKY PRIVATE PLACEMENTS
 
    In November 1993 and March 1994, ART raised $60,000 and $30,000 through the
sale of its common stock (which, net of sales and acquisitions of additional
shares, now constitute an aggregate of 545,048 shares and 127,171 shares of
Common Stock, respectively) to High Sky Limited Partnership and High Sky II
Limited Partnership ("High Sky II" and, collectively, the "High Sky
Partnerships"). In March 1994, ART borrowed $70,000 from High Sky II. The loan
was evidenced by a promissory note executed by ART and payable to High Sky II
(the "High Sky Note"). Pursuant to an Agreement dated March 1, 1995, High Sky II
sold the High Sky Note to Vernon L. Fotheringham and W. Theodore Pierson, Jr. in
exchange for two new promissory notes, bearing interest at 7.5% per annum,
executed by Messrs. Fotheringham and Pierson in the principal amounts of $52,675
and $22,575, respectively (the "Fotheringham/Pierson Notes"), with payment
secured by pledges of shares of Common Stock owned by them. The terms of the
notes were as favorable as could be negotiated with unrelated third parties.
After the assignment and exchange, Messrs. Fotheringham and Pierson transferred
the High Sky Note to the Company as a capital contribution. The
Fotheringham/Pierson Notes, which are due in August 1997 and which are now
unsecured, are currently held by LHC (as defined below).
 
ART WEST JOINT VENTURE
 
    The Company is party to the ART West Management Agreement, pursuant to which
it manages the business and assets of ART West, a joint venture between ART and
Extended. Mark T. Marinkovich, Vice President and General Manager, Western
Region of the Company, is also the President and a stockholder of Extended. See
"Business -- Agreements Relating to Licenses and Authorizations -- ART West
Joint Venture" and "Principal Stockholders." In connection with the ART West
Joint Venture, ART issued to Extended 133,864 shares of Common Stock. Of these
133,864 shares, 5,701 shares are subject to options owned by Southeast Research
Partners and its designees. See "-- SERP Agreement." In June 1996, the Company
agreed to acquire Extended's interest in ART West for $6,000,000 in cash,
subject to FCC approval.
 
ORGANIZATION OF TELECOM
 
    ART and Landover Holdings Corporation ("LHC") organized Advanced Radio
Telecom Corp. ("Telecom") on March 28, 1995, and purchased for $.001 per share
340,000 shares of Class A common stock and 640,000 shares of Class B common
stock of Telecom, respectively, which, after giving effect to anti-dilution
adjustments resulting from issuances of preferred stock as described in "-- LHC
Purchase Agreement," certain transfers and the transactions described in "--
February 1996 Reorganization" and "-- Merger," currently are equivalent to
3,641,111 shares and 2,650,414, shares respectively, after giving effect to the
November 1995 redemption of shares of Common Stock. In addition, Hedgerow
Corporation of Maine ("Hedgerow") and Toro Financial Corp. ("Toro") purchased
for $.001 per share 15,000 shares and 5,000 shares, respectively, of Telecom
Class A common stock which, after such anti-dilution adjustments and the Merger,
currently are equivalent to 160,637 shares and 53,546 shares of Common Stock,
respectively. LHC is controlled by Laurence S. Zimmerman, a former director of
the Company, and Hedgerow is controlled by Matthew C. Gove, also a former
director of the Company. From May 1994 until August 1996 Hedgerow and, from May
1994 until September 1996, Toro provided management and strategic consulting
services to LHC, including services relating to analysis and negotiation of
acquisitions.
 
                                       82
<PAGE>
LHC PURCHASE AGREEMENT
 
    GENERAL.  Pursuant to a Purchase Agreement, dated April 21, 1995 (the "LHC
Purchase Agreement") among ART, LHC and Telecom, LHC, on behalf of itself and
its designees, agreed to purchase additional securities of Telecom (the "LHC
Stock") for an aggregate purchase price of $7,000,000 (the "Purchase Price"),
which additional securities would dilute only LHC's interest in the Company. In
addition, ART and Telecom entered into the ART Services Agreement. Moreover, ART
and its stockholders agreed with Telecom and its stockholders to enter into a
revised stockholders agreement (the "May 1995 Stockholders Agreement"), a
registration rights agreement and a merger agreement. Messrs. Fotheringham and
Pierson deposited 733,711 and 662,495 shares of Common Stock, respectively (the
"Escrow Shares"), under such agreement to be released upon achievement by the
Company of certain performance goals (the "Escrow Arrangement"). The Escrow
Shares were released to Messrs. Fotheringham and Pierson in part on November 13,
1995 as a result of the EMI Asset Acquisition, and the balance was released on
February 2, 1996 in connection with the February 1996 Reorganization (as
defined).
 
    Upon the first closing under the LHC Purchase Agreement, on May 8, 1995,
Telecom received $700,000 from E2-2 Holdings, L.P. ("E2-2") and E2 Holdings,
L.P. ("E2"). In addition, E2-2 committed to subscribe for up to 50.0% of the
Purchase Price, matching other investors under the LHC Purchase Agreement with
protection from dilution to the extent such matching funds were not required.
The general partner of E2-2 and E2 is controlled by LHC. E2-2's limited partners
include J.C. Demetree, Jr. and Mark C. Demetree and their affiliates. In
addition, E2-2 granted to LHC an option to purchase from E2-2 35,873 shares of
Series A preferred stock (which converted into 169,581 shares of Common Stock in
November 1996). This option was exercised in November 1995. Mark C. Demetree is
a director and J.C. Demetree, Jr. was formerly a director of the Company. See
"Principal Stockholders."
 
    The additional payments on the Purchase Price were made by the Landover
Partnerships (as defined below) as follows: $700,000 on August 22, 1995 and
$600,000 on October 19, 1995. On November 13, 1995, the Advent Partnerships (as
described below) paid the $5.0 million balance of the Purchase Price and the
Company paid LHC an aggregate of $391,750 for expenses. Also, on November 13,
1995, Telecom, ART and LHC agreed that the LHC Purchase Agreement was
substantially completed.
 
    ART SERVICES AGREEMENT.  Pursuant to the LHC Purchase Agreement, ART and
Telecom entered into a Services Agreement, dated May 8, 1995 (the "ART Services
Agreement"), pursuant to which, for a 20-year term, Telecom provides management
services for, and receives 75.0% of the cash flow from, operations after
deducting certain related direct expenses under wireless licenses held by ART.
 
    LANDOVER PARTNERSHIPS.  Between May 8, 1995 and November 13, 1995, the LHC
Stock was diluted by purchases of series of Telecom preferred stock by E2-2, E2,
E1 Holdings L.P. ("E1") and E2-3 Holdings, L.P. ("E2-3" and collectively with
E1, E2 and E2-2, the "Landover Partnerships"), each a limited partnership whose
general partner is controlled by LHC, in separate private placements. E2-2,
which committed to purchase up to $3.5 million of Telecom preferred stock
matching other investors under the LHC Purchase Agreement, purchased 405,880
shares of Telecom Series A preferred stock (which converted into 1,918,705
shares of Common Stock in November 1996) for an aggregate of $946,600, and LHC
purchased 35,873 shares of such Series A preferred stock (which converted into
169,581 shares of Common Stock in November 1996) from E2-2 for $1.1 million
pursuant to an option. E2 purchased an aggregate of 105,823 shares of Telecom
Series B preferred stock (which converted into 500,254 shares of Common Stock in
November 1996) for an aggregate of $842,400. E1 purchased 13,797 shares of
Telecom Series A preferred stock (which converted into 65,222 shares of Common
Stock in November 1996) for an aggregate of $60,000 and 8,856 shares of Telecom
Series B preferred stock (which converted into 41,865 shares of Common Stock in
November 1996) for an aggregate of $38,300. E2-3 purchased an aggregate of 7,363
shares of Telecom Series C preferred stock (which converted into 34,807 shares
of Common Stock in November 1996) for an aggregate of $112,700.
 
                                       83
<PAGE>
Control of E2-2 was transferred to an affiliate of J.C. Demetree, Jr. and Mark
C. Demetree in August 1996. All of the Landover Partnerships were liquidated in
November 1996. See "Principal Stockholders."
 
    ADVENT PRIVATE PLACEMENT.  On November 13, 1995, ART sold, for an aggregate
of $5.0 million, $4.95 million principal amount of 10% notes due May 13, 1997
(the "Advent Notes") and $50,000 stated amount of ART Series A Preferred Stock
(collectively, with the Advent Notes, the "Advent/ART Securities") to Global
Private Equity II, L.P., Advent International Investors II, L.P. and Advent
Limited Partnership (collectively the "Advent Partnerships"), each a limited
partnership whose general partner is controlled by Advent International Corp.
("Advent"), pursuant to a Securities Purchase Agreement, dated November 13,
1995, among the Advent Partnerships, ART, Telecom, Vernon L. Fotheringham and W.
Theodore Pierson, Jr. (the "Advent Agreement"). The Advent Agreement provided
among other things that the Advent/ART Securities were convertible into, and in
the February 1996 Reorganization described below, were converted into, 232,826
shares of Telecom Series E preferred stock (which converted into 1,100,632
shares of Common Stock in November 1996). The Telecom Series E preferred stock
provides, among other things, that the holders thereof have a right to designate
a director of Telecom (and, after the Merger, the Company), which director's
term was extended to an initial term of three years pursuant to the Stockholders
Agreement, as described below.
 
LHC AGREEMENTS
 
    Pursuant to the LHC Purchase Agreement, LHC and Telecom entered into a
strategic and financial consulting agreement, dated May 8, 1995, under which LHC
agreed to provide financial and strategic planning and other advisory and
management services to the Company for a fee of $10,000 per month. The strategic
and financial consulting agreement was terminated on November 13, 1995, and
Telecom entered into a management consulting agreement with LHC, dated November
13, 1995, for an initial term of one year under which the Company will pay LHC
$420,000 per year and may pay a fee in the event LHC provides other services,
such as merger and acquisition advisory services, to the Company. This
management consulting agreement was terminated in November 1996. In November
1996, the Company paid LHC an aggregate of $300,000 in connection with services
previously rendered under the management consulting agreement.
 
SERP AGREEMENT
 
    Pursuant to a letter agreement, dated July 12, 1995, among Southeast
Research Partners ("SERP") ART, Vernon L. Fotheringham, W. Theodore Pierson,
Jr., High Sky Limited Partnership, High Sky II Limited Partnership and Extended
(the "SERP Agreement"), SERP agreed to procure additional capitalization or
financial assistance on behalf of ART. Under the SERP Agreement, the other
parties to such agreement agreed to grant SERP options to purchase, for an
aggregate consideration of $210,000, 114,040 shares of Common Stock and $245,000
in cash as a fee for introducing LHC to ART.
 
SERIES D PREFERRED STOCK ISSUANCE
 
    On November 9, 1995, Telecom sold 61,640 shares of Telecom Series D
preferred stock (which converted into 291,390 shares of Common Stock in November
1996) for $2.0 million in a private placement. Telecom simultaneously redeemed
293,791 shares of Telecom common stock from LHC for $2.0 million. In connection
with the February 1996 Reorganization described below, LHC granted to the
holders of such Series D preferred stock a contingent option ("Series D Option")
to purchase 145,685 shares of Telecom common stock owned by LHC at a nominal
price.
 
FEBRUARY 1996 REORGANIZATION
 
    On February 2, 1996, Telecom, ART and their respective stockholders agreed
(the "February 1996 Reorganization") to an amendment and restatement of the May
1995 Stockholders Agreement (as amended, the "Stockholders Agreement") providing
for (i) termination effective on consummation of the Common Stock Offering, (ii)
reorganization of the capital structure of Telecom, including providing for the
conversion of Telecom Class A and Class B common stock into Telecom common
stock, the revision of the terms and conversion into ART Common Stock (upon
consummation of the Common
 
                                       84
<PAGE>
Stock Offering) of the Series A, B, C, D, E and F preferred stock (originally
issued by Telecom and converted to ART preferred stock in the Merger) and a 13
for 1 stock split, (iii) the exchange of the Advent/ART Securities for Telecom
Series E preferred stock, (iv) revision of provisions for election of directors,
(v) amendment and restatement of the Company's registration rights agreement,
including waiver of registration rights relating to this offering, (vi) release
of the remaining Escrow Shares to the original owners thereof, (vii) the change
of name of Telecom to Advanced Radio Telecom Corp. and (viii) approval of a
revised merger agreement (the "Old Merger Agreement") providing for the merger
of ART into Telecom (the "Old Merger").
 
AMERITECH FINANCING; AMERITECH STRATEGIC DISTRIBUTION AGREEMENT
 
    On February 2, 1996, Ameritech Development Corp. ("Ameritech") purchased for
an aggregate of $2.5 million 48,893 shares of Telecom Series F preferred stock,
par value $0.001 per share, (the "Ameritech Financing") which converted into
231,131 shares of Common Stock in November 1996. In addition, Telecom entered
into a letter of intent with Ameritech Corp., the parent of Ameritech, to enter
into the Ameritech Strategic Distribution Agreement and in connection therewith
granted to Ameritech a ten-year warrant to purchase 318,959 shares of Common
Stock of the Company exercisable at a nominal price per share (the "Ameritech
Warrant"). On April 29, 1996, Telecom entered into the Ameritech Strategic
Distribution Agreement. See "Business -- Strategic Alliances -- Ameritech
Strategic Distribution Agreement." On December 5, 1996, Ameritech exercised the
Ameritech Warrant to purchase 318,374 shares of Common Stock.
 
MARCH BRIDGE FINANCING
 
    On March 8, 1996, Telecom entered into a financing (the "March Bridge
Financing") pursuant to which it issued $5.0 million of 10% unsecured notes due
in 1998 (the "March Bridge Notes") and five-year warrants to purchase up to an
aggregate of 400,000 shares of Telecom common stock at a price of $17.1875 per
share (the "March Bridge Warrants") to private investors including (i)
affiliates of J.C. Demetree, Jr. and Mark C. Demetree, then directors of the
Company, (ii) the Advent Partnerships and (iii) Ameritech, who invested
$700,000, $725,000 and $750,000, respectively, in the March Bridge Notes and
March Bridge Warrants. See "Principal Stockholders." The March Bridge Notes were
repaid with the proceeds of the Common Stock Offering.
 
EQUIPMENT FINANCING
 
    On April 1, 1996 CRA, Inc. ("CRA") provided the Company with $2.5 million in
equipment financing (the "Equipment Financing") for the purchase from P-Com of
38 GHz radio equipment secured by the equipment, the Company's $1.0 million
letter of credit and a $500,000 letter of credit provided by J.C. Demetree, Jr.
and Mark C. Demetree, then directors of the Company, and LHC, a principal
stockholder of the Company (the "Indemnitors"). To evidence its obligations
under the Equipment Financing the Company executed in favor of CRA its $2.5
million Promissory Note (the "Equipment Note") which note is payable in 24
monthly installments of $92,694 with a final payment of $642,305 due April 1,
1998. The Indemnitors also agreed to provide the Company with funds and support
for up to $2.0 million of its obligations in the event of default on the
Equipment Note or draw against the Company's letter of credit. Pursuant to an
arrangement approved by the Company's disinterested directors on February 16,
1996, the Company paid to the Indemnitors or their designees an aggregate of
$225,000 in cash and five-year warrants to purchase an aggregate of 118,181
shares of Common Stock (the "Indemnity Warrants") on terms substantially similar
to the March Bridge Warrants as compensation for such indemnity. LHC has
assigned Indemnity Warrants to purchase 45,455 shares of Common Stock to a
consultant to LHC. The letter of credit provided by the Indemnitors was returned
to the Indemnitors in December 1996.
 
SEPTEMBER BRIDGE FINANCING
 
    In August 1996, the Company received commitments for $3.0 million of 14.75%
unsecured notes due March 1998 (the "September Bridge Financing"). Such notes
(the "September Bridge Notes") were funded from August 1996 to October 1996. In
October 1996, the Company also received a commitment for an additional $1.0
million. The Company also issued five-year warrants to purchase up to an
aggregate of 116,363 shares of Common Stock at a price of $17.1875 per share
($15.00 after giving
 
                                       85
<PAGE>
effect to anti-dilution adjustment) (the "September Bridge Warrants") to private
investors who participated in the financing, including the Advent Partnerships,
Ameritech, affiliates of CommcoCCC, LHC and affiliates of J.C. Demetree, Jr. and
Mark C. Demetree. The September Bridge Warrants are not exercisable for a period
of one year following their date of issuance. The September Bridge Notes were
repaid with the proceeds of the Common Stock Offering.
 
PIERSON & BURNETT TRANSACTIONS
 
    W. Theodore Pierson, Jr., Executive Vice President and Secretary of the
Company is a principal in the law firm of Pierson & Burnett, L.L.P., which
regularly provides legal services to the Company. During the year ended December
31, 1996, the Company paid Pierson & Burnett, L.L.P. $520,000 for such services.
The Company believes that the terms of its relationship with Pierson & Burnett,
L.L.P. are at least as favorable to the Company as could be obtained from an
unaffiliated party. See "Management -- Executive Compensation" and "Principal
Stockholders" for a description of Mr. Pierson's consulting agreement with the
Company and for information regarding his share ownership. The Company subleases
office space for its regional office in Washington, D.C. from Pierson & Burnett,
L.L.P. The Company believes that the terms of its sublease are at least as
favorable to the Company as could be obtained from an unaffiliated party. See
"Business -- Properties."
 
AMERICAN WIRELESS DEVELOPMENT AGREEMENT
 
    In early 1996 ART entered into a memorandum of understanding with American
Wireless Corporation ("American Wireless") to jointly develop a quick-to-market
38 GHz receive only radio. Discoveries made as a result of this initial directed
work served to define ART's requirements for a series of low cost 38 GHz
transmit/receive link equipment, ranging from 4 x DS-1 to DS-3 payload capacity.
In response to this requirement American Wireless did extensive design,
performance, and cost modelling that has enabled ART to accelerate its planned
implementation of more cost effective shared network topologies. The Company has
funded approximately $400,000 of research and development costs with American
Wireless related to the development of the 38 GHz receive only radio. Vernon L.
Fotheringham, the Chairman of the Company, is a former director and a 3.0%
stockholder of American Wireless. Mr. Fotheringham has recused himself in all
negotiations regarding agreements between the Company and American Wireless.
 
COMMCOCCC ACQUISITION
 
    On July 3, 1996, the Company entered into the CommcoCCC Agreement with
CommcoCCC which provides for the acquisition of 129 38 GHz wireless broadband
authorizations in exchange for 6,000,000 shares of Common Stock, or 28.5% of the
Company on a fully diluted basis after giving effect to the Common Stock
Offering. The stockholders of CommcoCCC simultaneously loaned $3.0 million to
the Company, bearing interest at the prime rate and payable on September 30,
1996, and received three-year warrants to purchase up to an aggregate of 18,182
shares of Common Stock at a price of $24.75 per share. In connection with an
October 1996 amendment to the CommcoCCC Agreement, the Company modified the
terms of such warrants, reduced the exercise price of such warrants to $17.1875
($15.00 after giving effect to anti-dilution adjustment) per share and increased
the number of shares issuable upon exercise thereof to 87,273 shares and
increased the interest rate of the CommcoCCC Notes to 14.75% and extended the
maturity date thereof to December 31, 1996. The CommcoCCC Financing was secured
by a security interest in all of the assets of the Company, including a pledge
of the Company's stock in Telecom. The CommcoCCC Financing was repaid with the
proceeds of the Common Stock Offering. As a condition to the CommcoCCC
Acquisition, the Company will elect James B. Murray, Jr. as a Class III director
of the Company. See "Management -- Executive Officers and Directors."
 
                                       86
<PAGE>
                              DESCRIPTION OF UNITS
 
    Each Unit offered hereby consists of $1,000 principal amount at maturity of
Notes and 15 Warrants, each Warrant initially representing the right to purchase
1.349 shares of Common Stock. The Notes and the Warrants will not be separable
until the earliest to occur of (i) August 15, 1997, (ii) a Change in Control of
the Company and (iii) such earlier date as may be determined by the Underwriters
(the "Separation Date").
 
                              DESCRIPTION OF NOTES
 
    The Notes will be issued under an Indenture (the "Indenture") between the
Company and The Bank of New York, as trustee (the "Trustee"). The Notes will be
secured by a portion of the proceeds of the Unit Offering pursuant to the pledge
and escrow agreement, dated as of the Issue Date (the "Pledge Agreement"),
between the Company and The Bank of New York, as collateral agent (the
"Collateral Agent"). Copies of the form of the Indenture and the Pledge
Agreement have been filed as exhibits to the Registration Statement of which
this Prospectus is a part. The following summary of the material provisions of
the Indenture and the Pledge Agreement does not purport to be complete and is
subject to, and is qualified in its entirety by reference to, the Trust
Indenture Act of 1939, as amended (the "Trust Indenture Act"), and to all of the
provisions of the Indenture and the Pledge Agreement, including the definitions
of certain terms therein and those terms made a part of the Indenture by
reference to the Trust Indenture Act, as in effect on the date of the Indenture.
The definitions of certain terms used in the following summary are set forth
below under "-- Certain Definitions."
 
    As of the date of the Indenture, all of the Company's Subsidiaries will be
Restricted Subsidiaries, other than foreign Subsidiaries that the Company may
establish prior to such date. However, under certain circumstances, the Company
will be able to designate future Subsidiaries as Unrestricted Subsidiaries.
Unrestricted Subsidiaries will not be subject to many of the restrictive
covenants set forth in the Indenture.
 
GENERAL
 
    The Notes will be unsecured senior obligations of the Company, will be
limited to $135.0 million aggregate principal amount and will mature on February
15, 2007. Cash interest on the Notes will be payable, at a rate of 14% per
annum, semi-annually in arrears on February 15 and August 15 of each year (each,
an "Interest Payment Date"), commencing August 15, 1997, to the holders of
record of Notes at the close of business on the February 1 and August 1
immediately preceding such Interest Payment Date. Interest on the Notes will
accrue from the most recent Interest Payment Date to which interest has been
paid or, if no interest has been paid, from the Issue Date. Interest will be
computed on the basis of a 360-day year of twelve 30-day months. Interest on
overdue principal and, to the extent permitted by law, on overdue installments
of interest will accrue at the rate of interest borne by the Notes.
 
    Principal of, premium, if any, and interest on the Notes will be payable,
and the Notes will be exchangeable and transferable, at the office or agency of
the Company in the City of New York maintained for such purposes (which
initially will be the office of the Trustee); PROVIDED, HOWEVER, the payment of
interest may be made by check mailed to the address of the Person entitled
thereto as shown on the security register. The Notes will be issued only in
fully registered form without coupons and only in denominations of $1,000 and
any integral multiple thereof. No service charge will be made for any
registration of transfer, exchange or redemption of Notes, but the Company may
require payment in certain circumstances of a sum sufficient to cover any tax or
other governmental charge that may be imposed in connection therewith.
 
SECURITY
 
    The Indenture will provide that upon the closing of the Offering, the
Company will be required to purchase, and pledge to the Collateral Agent for the
benefit of the Collateral Agent and the holders of
 
                                       87
<PAGE>
the Notes, the Pledged Securities in such amount as will be sufficient upon
receipt of scheduled interest and principal payments of such securities, in the
opinion of a nationally recognized firm of independent public accountants
selected by the Company, to provide for payment in full of the first six
scheduled interest payments on the Notes when and as due. The Company expects to
use approximately $51.6 million of the net proceeds of the Offering to acquire
the Pledged Securities; however, the precise amount of securities to be acquired
will depend upon the interest rates on government securities prevailing at the
time of the closing of the Offering. The Pledged Securities will be pledged by
the Company to the Collateral Agent for the benefit of the Collateral Agent and
the holders of Notes pursuant to the Pledge Agreement and will be held by the
Collateral Agent in the Pledge Account. Pursuant to the Pledge Agreement,
immediately prior to an Interest Payment Date on the Notes, the Company may
either deposit with the Collateral Agent from funds otherwise available to the
Company cash sufficient to pay the interest scheduled to be paid on such date or
the Company may direct the Collateral Agent to release from the Pledge Account
proceeds sufficient to pay interest then due. In the event that the Company
exercises the former option, the Pledge Agreement provides that the Company may
thereafter direct the Collateral Agent to release to the Company proceeds or the
Pledged Securities from the Pledge Account in like amount.
 
    Interest earned on the Pledged Securities will be added to the Pledge
Account. In the event that the funds or Pledged Securities held in the Pledge
Account exceed (giving no effect to any excess created by the substitution of
Temporary Cash Investments for the Government Securities originally pledged as
collateral) the amount sufficient, in the opinion of a nationally recognized
firm of independent public accountants selected by the Company, to provide for
payment in full of the first six scheduled interest payments due on the Notes
(or, in the event an interest payment or payments have been made, an amount
sufficient to provide for payment in full of any interest payment remaining, up
to and including the sixth scheduled interest payment), the Collateral Agent
will be permitted to release to the Company at the Company's request any such
excess amount. The Notes will be secured by a first priority security interest
in the Pledged Securities and in the Pledge Account and, accordingly, the
Pledged Securities and the Pledge Account will also secure repayment of the
principal amount of the Notes to the extent of such security. At any time while
the Pledge Agreement is in force, the Pledge Agreement allows the Company to
substitute Temporary Cash Investments of the types described in clauses (i)
through (v) in the definition thereof for the Government Securities originally
pledged as Collateral; PROVIDED, HOWEVER, Temporary Cash Investments so
substituted must, upon receipt of scheduled interest and principal payments
thereon, in the opinion of a nationally recognized firm of independent public
accountants selected by the Company, provide funds at least equal to 125.0% (or
100.0%, in the case of substituted Government Securities) of the amount of any
of the first six scheduled interest payments on the Notes that are unpaid (or
the portion of such interest payments to be funded by such Temporary Cash
Investments) as of the date such Temporary Cash Investments are proposed to be
substituted as security for the Company's obligation under the Pledge Agreement.
 
    Under the Pledge Agreement, assuming that the Company makes the first six
scheduled interest payments on the Notes in a timely manner, all of the Pledged
Securities will have been released from the Pledge Account and thereafter the
Notes will be unsecured.
 
REDEMPTION
 
    OPTIONAL REDEMPTION
 
    The Notes will be redeemable at the option of the Company, in whole or in
part, at any time on or after February 15, 2002, upon not less than 30 nor more
than 60 days' notice, at the redemption prices
 
                                       88
<PAGE>
(expressed as percentages of principal amount) set forth below, plus accrued and
unpaid interest, if any, to the date of redemption, if redeemed during the
12-month period beginning on February 15 of the years indicated below:
 
<TABLE>
<CAPTION>
                                                             REDEMPTION
                           YEAR                                PRICE
                --------------------------                  ------------
<S>                                                         <C>
2002......................................................      107.00%
2003......................................................      104.67%
2004......................................................      102.33%
2005 and thereafter.......................................      100.00%
</TABLE>
 
    Notwithstanding the foregoing, in the event of a sale by the Company of its
Common Stock in one or more Equity Offerings or Investments by one or more
Strategic Equity Investors on or prior to February 15, 2000 (other than in
connection with a Change in Control of the Company), the Company may, at its
option, use all or a portion of the net proceeds thereof to redeem up to a
maximum of 25% of the initially outstanding aggregate principal amount of the
Notes at a redemption price equal to 114% of the principal amount thereof, plus
accrued and unpaid interest thereon, if any, to the redemption date; PROVIDED
that not less than 75% of the initially outstanding aggregate principal amount
of the Notes remains outstanding following such redemption. Any such redemption
must be effected upon not less than 30 nor more than 60 days' notice given
within 30 days after any such Equity Offering or sale to a Strategic Equity
Investor.
 
    MANDATORY REDEMPTION
 
    The Company is not required to make any mandatory sinking fund payments in
respect of the Notes. However, (i) upon the occurrence of a Change in Control,
the Company is obligated to make an offer to purchase all outstanding Notes at a
price of 101% of the principal amount thereof, plus accrued and unpaid interest
thereon, if any, to the date of purchase, and (ii) the Company may be obligated
to make an offer to purchase Notes with the Net Cash Proceeds of certain Asset
Sales at a price of 100% of the principal amount thereof, plus accrued and
unpaid interest, if any, to the date of purchase. See "-- Certain Covenants --
Change in Control" and "-- Disposition of Proceeds of Asset Sales."
 
    SELECTION; EFFECT OF REDEMPTION NOTICE
 
    In the case of a partial redemption, selection of the Notes for redemption
will be made PRO RATA, by lot or by such other method as the Trustee in its sole
discretion deems fair and appropriate or in such manner as complies with the
applicable requirements of the principal national securities exchange, if any,
on which the Notes being redeemed are listed. Upon giving of a redemption
notice, interest on the Notes called for redemption will cease to accrue from
and after the date fixed for redemption (unless the Company defaults in
providing the funds for such redemption) and, upon redemption on such redemption
date, such Notes will cease to be outstanding.
 
RANKING
 
    The Notes will represent senior obligations of the Company and will be
unsecured, except for the pledge by the Company of the Pledged Securities. The
Notes will rank PARI PASSU in right of payment with any future unsecured, senior
Indebtedness of the Company and will rank senior in right of payment to all
existing and future subordinated indebtedness of the Company. At September 30,
1996, on a pro forma basis after giving effect to the Common Stock Offering, the
Offering and the application of the net proceeds therefrom, the aggregate
principal amount of indebtedness of the Company (excluding the Notes) was
approximately $3.1 million, which consisted of the EMI Note and the Equipment
Note, all of which ranked PARI PASSU with the Notes. However, $1.6 million of
such indebtedness constituted secured indebtedness which will effectively rank
senior to the Notes with respect to the assets securing such indebtedness.
Although the Indenture will limit the ability of the Company and its
subsidiaries to incur additional indebtedness, including senior indebtedness,
the Indenture will permit the Company to incur a substantial amount of secured
indebtedness, including vendor indebtedness and indebtedness under the Credit
Facility, which, if incurred, will effectively rank senior to the Notes
 
                                       89
<PAGE>
with respect to the assets securing such indebtedness. In addition, the
Indenture will permit the subsidiaries of the Company (including any subsidiary
holding all or any part of the Company's FCC licenses and authorizations) to
guarantee the indebtedness of the Company under the Credit Facility on a secured
basis (consistent with applicable FCC rules), which guarantees and security
interests would effectively rank senior in right of payment to the Notes. See
"-- Certain Covenants," "Risk Factors -- Possible Incurrence of Substantial
Secured Indebtedness" and "Description of Certain Indebtedness."
 
CERTAIN COVENANTS
 
    LIMITATION ON INDEBTEDNESS
 
    The Indenture will provide that the Company will not, and will not permit
any of its Subsidiaries to, Incur any Indebtedness (including Acquired Debt);
PROVIDED that the Company may Incur Indebtedness (including Acquired Debt) if,
after giving effect to the Incurrence of such Indebtedness and the receipt and
application of the proceeds therefrom, the Indebtedness to EBITDA Ratio would be
greater than zero and less than 5 to 1.
 
    The foregoing provisions will not apply to:
 
      (i)
       Indebtedness of the Company outstanding at any time in an aggregate
       principal amount not to exceed $100.0 million, less any amount of
Indebtedness permanently repaid as provided under the "Disposition of Proceeds
of Asset Sales" covenant described below (other than any such permanent
reduction of the Indebtedness under clause (xiii) hereof; PROVIDED, HOWEVER,
that the aggregate principal amount of Indebtedness outstanding pursuant to
clauses (i) and (xiii) hereof shall not exceed $125.0 million at any time;
 
     (ii)
       Indebtedness of any of the Company's Restricted Subsidiaries owing to the
       Company or another Restricted Subsidiary; PROVIDED, HOWEVER, that (A) any
subsequent issuance or transfer of Capital Stock that results in any such
Indebtedness being held by a Person other than the Company or a Restricted
Subsidiary and (B) any sale or other transfer of any such Indebtedness to a
Person that is not the Company or a Restricted Subsidiary shall be deemed, in
each case, to constitute an Incurrence of such Indebtedness by the Company;
 
    (iii)
       Indebtedness issued in exchange for, or the net proceeds of which are
       used to refinance or refund, then outstanding Indebtedness, other than
Indebtedness Incurred under clause (i), (ii), (v), (vi) or (viii) of this
paragraph, and any refinancings thereof in an amount not to exceed the amount so
refinanced or refunded (plus premiums, accrued interest, fees and expenses);
PROVIDED that Indebtedness the proceeds of which are used to refinance or refund
the Notes or Indebtedness that is PARI PASSU with, or subordinated in right of
payment to, the Notes shall only be permitted under this clause (iii) if (A) in
case the Notes are refinanced in part or the Indebtedness to be refinanced is
PARI PASSU with the Notes, such new Indebtedness (by its terms or by the terms
of any agreement or instrument pursuant to which such new Indebtedness is
outstanding) is PARI PASSU with, or is expressly made subordinate in right of
payment to, the remaining Notes, (B) in case the Indebtedness to be refinanced
is subordinated in right of payment to the Notes, such new Indebtedness, by its
terms or by the terms of any agreement or instrument pursuant to which such new
Indebtedness is outstanding, is expressly made subordinate in right of payment
to the Notes at least to the extent that the Indebtedness to be refinanced is
subordinated to the Notes, and (C) such new Indebtedness, determined as of the
date of Incurrence of such new Indebtedness, does not have a Stated Maturity
prior to the Stated Maturity of the Indebtedness to be refinanced or refunded,
and the Average Life of such new Indebtedness is at least equal to the remaining
Average Life of the Indebtedness to be refinanced or refunded; and PROVIDED
FURTHER that in no event may Indebtedness of the Company be refinanced by means
of any Indebtedness of any Restricted Subsidiary of the Company pursuant to this
clause (iii);
 
     (iv)
       Indebtedness (A) in respect of performance, surety or appeal bonds
       provided in the ordinary course of business; and (B) arising from
agreements providing for indemnification, adjustment of
 
                                       90
<PAGE>
purchase price or similar obligations, or from Guarantees or letters of credit,
surety bonds or performance bonds securing any obligations of the Company or any
of the Restricted Subsidiaries pursuant to such agreements, in any case Incurred
in connection with the disposition of any business, assets or Restricted
Subsidiary of the Company (other than Guarantees of Indebtedness Incurred by any
Person acquiring all or any portion of such business, assets or Restricted
Subsidiary of the Company for the purpose of financing such acquisition), in a
principal amount not to exceed the gross proceeds actually received by the
Company or any Restricted Subsidiary in connection with such disposition;
 
      (v)
       without duplication of clause (viii) hereof, Indebtedness of the Company
       not to exceed, at any one time outstanding, two TIMES an amount equal to
(A) the aggregate proceeds (less appropriate fees and expenses) (which proceeds
may consist of cash, Capital Stock of an entity that as a result of such
transaction becomes a Restricted Subsidiary of the Company, or
Telecommunications Assets which in connection with such transaction become held
by the Company or a Restricted Subsidiary of the Company, and the value of which
proceeds shall be the fair market value thereof as determined in good faith by
the Board, which in all events shall make any appropriate adjustments on account
of any Indebtedness associated with such Capital Stock or Telecommunications
Assets in making such determination) received by the Company from the issuance
and sale of its Capital Stock (other than Redeemable Stock and Preferred Stock
that provides for the payment of dividends in cash) after the Issue Date MINUS
(B) the fair market value of any Directed Investments made with the proceeds of
such issuances or sales; PROVIDED that such Indebtedness (x) does not have a
Stated Maturity prior to the Stated Maturity of the Notes and has an Average
Life longer than the Notes and (y) is unsecured and is expressly subordinated in
right of payment to the Notes;
 
     (vi)
       Indebtedness to the extent such Indebtedness is secured by Liens
       permitted under clause (xxiv) of the definition of "Permitted Liens;"
 
    (vii)
       Indebtedness of the Company, to the extent the proceeds thereof are
       immediately used to purchase Notes tendered in an Offer to Purchase made
as a result of a Change in Control;
 
   (viii)
       without duplication of clause (v) hereof, Indebtedness of the Company
       Incurred in connection with the acquisition of (A) 38 GHz licenses or
authorizations through auctions conducted by the FCC or (B) other licenses or
authorizations through other spectrum auctions conducted by the FCC with respect
to other frequencies approved for microwave point-to-point transmissions, in an
amount not to exceed, at any one time outstanding, the greater of (1) $10.0
million and (2) an amount equal to the aggregate proceeds (less appropriate fees
and expenses) (which proceeds may consist of cash, Capital Stock of an entity
that as a result of such transaction becomes a Restricted Subsidiary of the
Company, or Telecommunications Assets which in connection with such transaction
become held by the Company or a Restricted Subsidiary of the Company, and the
value of which proceeds shall be the fair market value thereof as determined in
good faith by the Board, which in all events shall make any appropriate
adjustments on account of any Indebtedness associated with such Capital Stock or
Telecommunications Assets in making such determination) received by the Company
from the issuance and sale of its Capital Stock (other than Redeemable Stock and
Preferred Stock that provides for the payment of dividends in cash) after the
Issue Date MINUS the fair market value of any Directed Investments made with the
proceeds of such issuances or sales; PROVIDED that such Indebtedness (x) does
not have a Stated Maturity prior to the Stated Maturity of the Notes and has an
Average Life longer than the Notes and (y) is unsecured and is PARI PASSU or
subordinated in right of payment with the Notes;
 
     (ix)
       revolving credit Indebtedness of any Restricted Subsidiary Incurred
       pursuant to a credit facility in an aggregate amount not to exceed, at
any one time outstanding, the greater of 62.5% and such greater percentage
permitted pursuant to such credit facility of the accounts receivable net of
reserves and allowances for doubtful accounts, determined in accordance with
GAAP, of such Restricted Subsidiary and its Restricted Subsidiaries (without
duplication); PROVIDED that such Indebtedness is not Guaranteed by the Company
or any of its other Restricted Subsidiaries;
 
                                       91
<PAGE>
      (x)
       the Incurrence by the Company or any of its Restricted Subsidiaries of
       Hedging Obligations that are Incurred for the purpose of fixing or
hedging interest rate risk with respect to any floating rate Indebtedness of the
Company or any Restricted Subsidiary, as the case may be, that is permitted by
the terms of the Indenture to be outstanding;
 
     (xi)
       the Incurrence by the Company's Unrestricted Subsidiaries of Non-Recourse
       Debt, PROVIDED, HOWEVER, that if any such Indebtedness ceases to be
Non-Recourse Debt of an Unrestricted Subsidiary, such event shall be deemed to
constitute an incurrence of Indebtedness by a Restricted Subsidiary of the
Company;
 
    (xii)
       the Incurrence by Unrestricted Subsidiaries of Indebtedness to the
       Company or any Restricted Subsidiary of the Company to the extent
permitted by the "Limitation on Restricted Payments" covenant;
 
   (xiii)
       Indebtedness of the Company outstanding at any time in an aggregate
       principal amount not to exceed $100.0 million Incurred pursuant to the
Credit Facility less any amount of Indebtedness under the Credit Facility
permanently repaid as provided under the "Disposition of Proceeds of Asset
Sales" covenant described below; PROVIDED, HOWEVER, that the aggregate principal
amount of Indebtedness outstanding pursuant to clauses (i) and (xiii) hereof
shall not exceed $125.0 million at any time;
 
    (xiv)
       Guarantees by the Company's Restricted Subsidiaries of the Indebtedness
       referred to in clause (xiii) above;
 
     (xv)
       Indebtedness of the Company existing on the Issue Date; and
 
    (xvi)
       Indebtedness of the Company represented by the Notes and the Indenture.
 
    For purposes of determining compliance with this "Limitation on
Indebtedness" covenant, in the event that an item of Indebtedness meets the
criteria of more than one of the types of Indebtedness described in the above
clauses, the Company, in its sole discretion, shall classify such item of
Indebtedness and only be required to include the amount and type of such
Indebtedness in one of such clauses.
 
    The Company will not, and will not permit any Restricted Subsidiary to,
Incur any Guarantee of Indebtedness of any Unrestricted Subsidiary.
 
    The Indenture will provide that, notwithstanding the foregoing, ART
Licensing shall not Incur any Indebtedness or issue any Preferred Stock;
PROVIDED that ART Licensing may Incur Indebtedness of the type and in the amount
set forth in clause (xiv) of the second paragraph of this "Limitation on
Indebtedness" covenant.
 
    LIMITATION ON RESTRICTED PAYMENTS
 
    The Indenture will provide that the Company will not, and will not permit
any Restricted Subsidiary to, directly or indirectly, (i) declare or pay any
dividend or make any distribution on its or such Restricted Subsidiary's Capital
Stock (other than dividends or distributions payable solely in shares of its or
such Restricted Subsidiary's Capital Stock (other than Redeemable Stock) or in
options, warrants or other rights to acquire such shares of Capital Stock) other
than such Capital Stock held by the Company or any of its Restricted
Subsidiaries (and other than pro rata dividends or distributions on Common Stock
of Restricted Subsidiaries), (ii) repurchase, redeem, retire or otherwise
acquire for value any shares of Capital Stock (including options, warrants or
other rights to acquire such shares of Capital Stock) of the Company (other than
any such Capital Stock held by the Company or any Wholly Owned Restricted
Subsidiary of the Company), (iii) make any voluntary or optional principal
payment, or voluntary or optional redemption, repurchase, defeasance, or other
acquisition or retirement for value, of Indebtedness of the Company that is
subordinated in right of payment to the Notes or (iv) make any Investment, other
than a Permitted Investment, in any Person (such payments or any other actions
described in clauses (i) through (iv) being collectively "Restricted Payments")
if, at the time of, and after giving effect to, the proposed Restricted Payment:
 
       (A) a Default or Event of Default shall have occurred and be continuing;
 
       (B) except with respect to any Investment (other than an Investment
           consisting of the designation of a Restricted Subsidiary as an
    Unrestricted Subsidiary), the Company could not Incur at least $1.00 of
    Indebtedness under the first paragraph of the "Limitation on Indebtedness"
    covenant; and
 
                                       92
<PAGE>
       (C) the aggregate amount expended for all Restricted Payments (the amount
           so expended, if other than in cash, to be determined in good faith by
    the Board, whose determination shall be conclusive and evidenced by a
    resolution of the Board) after the Issue Date shall exceed the sum of (1)
    50% of the aggregate amount of the Adjusted Consolidated Net Income (or, if
    the Adjusted Consolidated Net Income is a loss, MINUS 100% of such amount)
    (determined by excluding income resulting from transfers of assets by the
    Company or a Restricted Subsidiary to an Unrestricted Subsidiary) accrued on
    a cumulative basis during the period (taken as one accounting period)
    beginning on the first day of the fiscal quarter immediately following the
    Issue Date and ending on the last day of the last fiscal quarter preceding
    the date for which reports have been filed pursuant to the "Reports"
    covenant, PLUS (2) the aggregate Net Cash Proceeds received by the Company
    after the Issue Date from the issuance and sale permitted by the Indenture
    of its Capital Stock (other than Redeemable Stock) to a Person who is not a
    Subsidiary of the Company, or from the issuance to a Person who is not a
    Subsidiary of the Company of any options, warrants or other rights to
    acquire Capital Stock of the Company (in each case, exclusive of any
    convertible Indebtedness, Redeemable Stock or any options, warrants or other
    rights that are redeemable at the option of the holder, or are required to
    be redeemed, prior to the Stated Maturity of the Notes), MINUS the actual
    amount of Net Cash Proceeds used to make Directed Investments, PLUS (3) an
    amount equal to the net reduction in Investments (other than reductions in
    Permitted Investments) in any Person resulting from payments of interest on
    Indebtedness, dividends, repayments of loans or advances, or other transfers
    of assets, in each case to the Company or any Restricted Subsidiary (except
    to the extent any such payment is included in the calculation of Adjusted
    Consolidated Net Income), or from the redesignation of Unrestricted
    Subsidiaries as Restricted Subsidiaries (valued in each case as provided in
    the definition of "Investments"), not to exceed the amount of Investments
    previously made by the Company and its Restricted Subsidiaries in such
    Person.
 
    The foregoing provision shall not be violated by reason of:
 
      (i)
       the payment of any dividend within 60 days after the date of declaration
       thereof if, at said date of declaration, such payment would comply with
the foregoing paragraph;
 
     (ii)
       the redemption, repurchase, defeasance or other acquisition or retirement
       for value of Indebtedness that is subordinated in right of payment to the
Notes, including premium, if any, and accrued and unpaid interest, with the
proceeds of, or in exchange for, Indebtedness Incurred under clause (iii) of the
second paragraph of the "Limitation on Indebtedness" covenant;
 
    (iii)
       the repurchase, redemption or other acquisition of Capital Stock of the
       Company (or options, warrants or other rights to acquire such Capital
Stock) in exchange for, or out of the proceeds of a substantially concurrent
offering of, shares of Capital Stock or options, warrants or other rights to
acquire such Capital Stock (in each case, other than Redeemable Stock) of the
Company;
 
     (iv)
       the making of any principal payment or repurchase, redemption,
       retirement, defeasance or other acquisition for value of Indebtedness of
the Company which is subordinated in right of payment to the Notes in exchange
for, or out of the proceeds of a substantially concurrent offering of, shares of
the Capital Stock of the Company (other than Redeemable Stock);
 
      (v)
       payments or distributions, in the nature of satisfaction of dissenters'
       rights, pursuant to or in connection with a consolidation, merger or
transfer of assets that complies with the provisions of the Indenture applicable
to mergers, consolidations and transfers of all or substantially all of the
property and assets of the Company;
 
     (vi)
       any purchase or acquisition from, or withholding on issuances to, any
       employee of the Company's Capital Stock in order to satisfy any
applicable federal, state or local tax payments in respect of the receipt of
shares of the Company's Capital Stock;
 
    (vii)
       any purchase or acquisition from, or withholding on issuances to, any
       employee of the Company's Capital Stock in order to pay the purchase
price of such Capital Stock or similar instrument pursuant to a stock option,
equity incentive or other employee benefit plan or agreement of the Company or
any of its Restricted Subsidiaries;
 
   (viii)
       the repurchase of shares of, or options to purchase shares of, the
       Company's Capital Stock from employees of the Company in connection with
the termination of their employment; PROVIDED that (A) the aggregate price paid
for all such repurchased shares of Capital Stock made in any twelve-month period
shall not exceed $250,000 PLUS the aggregate cash proceeds received by the
Company during
 
                                       93
<PAGE>
such twelve-month period from any reissuance of such Capital Stock by the
Company to employees of the Company and its Restricted Subsidiaries and (B) no
Default shall have occurred and be continuing immediately after such
transaction;
 
     (ix)
       payments and distributions pursuant to any tax sharing agreement between
       the Company and any other Person with which the Company files a
consolidated tax return or with which the Company is part of a consolidated
group, in each case, for federal income tax purposes;
 
      (x)
       cash payments in lieu of the issuance of fractional shares of Common
       Stock of the Company upon conversion of any class of Preferred Stock of
the Company; and
 
     (xi)
       the issuance of shares of Common Stock upon exercise of warrants to
       purchase shares of common stock of ART Licensing existing on the Issue
Date, including any contribution of such shares of Common Stock to ART
Licensing, any payment by ART Licensing to the Company in consideration thereof
and any contribution by the Company to ART Licensing in respect thereof;
 
PROVIDED that, except in the case of clauses (i) and (ii), no Default or Event
of Default shall have occurred and be continuing or occur as a consequence of
the actions or payments set forth herein. Any Investments made other than in
cash shall be valued, in good faith, by the Board.
 
    Each Restricted Payment permitted pursuant to the preceding paragraph (other
than Restricted Payments referred to in clause (ii) thereof) and the Net Cash
Proceeds from any issuance of Capital Stock referred to in clause (iii) or (iv)
shall be included in calculating whether the conditions of clause (C) of the
first paragraph of this "Limitation on Restricted Payments" covenant have been
met with respect to any subsequent Restricted Payments. In the event the
proceeds of an issuance of Capital Stock of the Company are used for the
redemption, repurchase or other acquisition of the Notes or Indebtedness that is
PARI PASSU with the Notes, then the Net Cash Proceeds of such issuance shall be
included in clause (C) of the first paragraph of this "Limitation on Restricted
Payments" covenant only to the extent such proceeds are not used for such
redemption, repurchase or other acquisition of Indebtedness.
 
    The Board may designate any Restricted Subsidiary to be an Unrestricted
Subsidiary if such designation would not cause a Default. For purposes of making
such determination, all outstanding Investments by the Company and its
Restricted Subsidiaries (except to the extent repaid in cash) in the Subsidiary
so designated will be deemed to be Restricted Payments at the time of such
designation and will reduce the amount available for Restricted Payments under
the first paragraph of this covenant. All such outstanding Investments will be
deemed to constitute Investments in an amount valued in accordance with the
definition of "Investment." Such designation will only be permitted if such
Restricted Payment would be permitted at such time and if such Restricted
Subsidiary otherwise meets the definition of an Unrestricted Subsidiary.
 
    LIMITATION ON LIENS SECURING CERTAIN INDEBTEDNESS
 
    The Indenture will provide that the Company will not, and will not permit
any Subsidiary to, create, Incur, assume or suffer to exist any Lien, other than
Permitted Liens, on any of its assets or properties of any character, or any
shares of Capital Stock or Indebtedness of any Subsidiary, without making
effective provision for all of the Notes and all other amounts due under the
Indenture to be directly secured equally and ratably with (or, if the obligation
or liability to be secured by such Lien is subordinated in right of payment to
the Notes, prior to) the obligation or liability secured by such Lien.
 
    LIMITATION ON DIVIDEND AND OTHER PAYMENT RESTRICTIONS AFFECTING RESTRICTED
SUBSIDIARIES
 
    The Indenture will provide that the Company will not, and will not permit
any Restricted Subsidiary to, create or otherwise cause or suffer to exist or
become effective any consensual encumbrance or restriction of any kind on the
ability of any Restricted Subsidiary to (i) pay dividends or make other
distributions permitted by applicable law on any Capital Stock of such
Restricted Subsidiary owned by the Company or any other Restricted Subsidiary,
(ii) pay any Indebtedness owed to the Company or any other Restricted Subsidiary
that owns, directly or indirectly, any Capital Stock of such Restricted
Subsidiary, (iii) make loans or advances to the Company or any other Restricted
Subsidiary that owns, directly or indirectly, any Capital Stock of such
Restricted Subsidiary or (iv) transfer any of its property or assets to the
Company or any other Restricted Subsidiary that owns, directly or indirectly,
any Capital Stock of such Restricted Subsidiary.
 
    The foregoing provisions shall not prohibit any encumbrances or
restrictions:
 
      (i)
       existing on the Issue Date in the Indenture or any other agreement in
       effect on the Issue Date, and any extension, refinancing, renewal or
replacement of any such agreement; PROVIDED that the
 
                                       94
<PAGE>
encumbrances and restrictions in any such extension, refinancing, renewal or
replacement are no less favorable in any material respect to the holders than
those encumbrances or restrictions that are then in effect and that are being
extended, refinanced, renewed or replaced;
 
     (ii)
       existing under or by reason of applicable law;
 
    (iii)
       existing with respect to any Person or the property or assets of such
       Person acquired by the Company or any Restricted Subsidiary, at the time
of such acquisition and not Incurred in contemplation thereof, which
encumbrances or restrictions are not applicable to any Person or the property or
assets of any Person other than such Person or the property or assets of such
Person so acquired;
 
     (iv)
       in the case of clause (iv) of the first paragraph of this "Limitation on
       Dividend and Other Payment Restrictions Affecting Restricted
Subsidiaries" covenant, (A) that restrict in a customary manner the subletting,
assignment or transfer of any property or asset that is a lease, license,
conveyance or contract or similar property or asset, (B) existing by virtue of
any transfer of, agreement to transfer, option or right with respect to, or Lien
on, any property or assets of the Company or any Restricted Subsidiary, not
otherwise prohibited by the Indenture or (C) arising or agreed to in the
ordinary course of business, not relating to any Indebtedness, and that do not,
individually or in the aggregate, detract from the value of property or assets
of the Company or any Restricted Subsidiary in any manner material to the
Company or any Restricted Subsidiary;
 
      (v)
       imposed pursuant to an agreement that has been entered into for the sale
       or disposition of Capital Stock of, or property or assets of, the Company
or a Restricted Subsidiary; PROVIDED that such encumbrance or restriction shall
only remain in force during the pendency of such acquisition or disposition; or
 
     (vi)
       imposed pursuant to agreements governing Indebtedness permitted to be
       Incurred under clauses (xiii) and (xiv) of the second paragraph of the
"Limitation of Indebtedness" covenant.
 
    Nothing contained in this "Limitation on Dividend and Other Payment
Restrictions Affecting Restricted Subsidiaries" covenant shall prevent the
Company or any Restricted Subsidiary from (a) creating, Incurring, assuming or
suffering to exist any Liens otherwise permitted in the "Limitation on Liens
Securing Certain Indebtedness" covenant or (b) restricting the sale or other
disposition of property or assets of the Company or any of its Restricted
Subsidiaries that secure Indebtedness of the Company or any of its Restricted
Subsidiaries.
 
    LIMITATION ON TRANSACTIONS WITH AFFILIATES
 
    The Indenture will provide that the Company will not, and will not permit
any of its Restricted Subsidiaries to, sell, lease, transfer or otherwise
dispose of any of its properties or assets to, or purchase any property or
assets from, or enter into or make any contract, agreement, loan, advance or
Guarantee with, or any contract, agreement, loan, advance or Guarantee for the
specific benefit of, any Affiliate (each of the foregoing, an "Affiliate
Transaction"), unless (i) such Affiliate Transaction is on terms that are no
less favorable to the Company or the relevant Restricted Subsidiary than those
that would have been obtained in a comparable transaction by the Company or such
Restricted Subsidiary with an unrelated Person and (ii) the Company delivers to
the Trustee (A) with respect to any Affiliate Transaction involving aggregate
consideration in excess of $1.0 million, a resolution of the Board of Directors
set forth in an Officers' Certificate certifying that such Affiliate Transaction
complies with clause (A) above and that such Affiliate Transaction has been
approved by a majority of the disinterested members of the Board of Directors
and (B) with respect to any Affiliate Transaction involving aggregate
consideration in excess of $5.0 million, a written opinion, appraisal or
certification from a nationally recognized professional experienced in
evaluating similar types of transactions stating that the terms of such
transaction are fair to the Company or such Restricted Subsidiary, as the case
may be, from a financial point of view; PROVIDED that the following shall not be
deemed to constitute Affiliate Transactions:
 
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<PAGE>
    (i)  the payment of reasonable fees to directors of the Company who are not
employees of the Company;
 
    (ii) agreements and arrangements existing on the date hereof;
 
    (iii) any employment agreement entered into by the Company or any of its
Restricted Subsidiaries in the ordinary course of business of the Company or
such Restricted Subsidiary;
 
    (iv) the adoption of employee benefit plans in the ordinary course of
business and payments and other transactions thereunder; PROVIDED that any such
adoption, payment or other transaction shall have been approved by a majority of
the disinterested members of the Board;
 
    (v) transactions between or among the Company and/or its Wholly Owned
Restricted Subsidiaries;
 
    (vi) any contract, agreement, loan, advance or Guarantee for the general
benefit of the Company and its stockholders, including stockholders that are
Affiliates of the Company; and
 
    (vii) any Affiliate Transactions permitted by the provisions of the
Indenture described above under the caption "-- Limitation on Restricted
Payments."
 
    LIMITATION ON ISSUANCES AND SALES OF CAPITAL STOCK OF RESTRICTED
SUBSIDIARIES
 
    The Indenture will provide that the Company will not sell, and will not
permit any Restricted Subsidiary, directly or indirectly, to issue or sell any
shares of Capital Stock of a Restricted Subsidiary (including options, warrants
or other rights to purchase shares of such Capital Stock), except (i) to the
Company or a Wholly Owned Restricted Subsidiary, (ii) issuances or sales to
foreign nationals of shares of Capital Stock of foreign Restricted Subsidiaries,
to the extent required by applicable law, (iii) if, immediately after giving
effect to such issuance or sale, such Restricted Subsidiary would no longer
constitute a Restricted Subsidiary or (iv) issuances or sales of Common Stock of
Restricted Subsidiaries, if within six months of each such issuance or sale, the
Company or such Restricted Subsidiary applies an amount not less than the Net
Cash Proceeds thereof (if any) in accordance with clause (A) or (B) of the first
paragraph of the "Disposition of Proceeds of Asset Sales" covenant.
 
    BUSINESS ACTIVITIES OF THE COMPANY AND RESTRICTED SUBSIDIARIES
 
    The Company will not, and will not permit any Restricted Subsidiary to,
engage in (i) any business other than the Telecommunications Business and such
business activities as are incidental or related thereto and (ii) any business,
activities or services in which the Company and its Restricted Subsidiaries were
engaged on the Issue Date. In addition, the Company will (i) at such time and to
the extent permitted by the FCC, transfer, or cause to be transferred, all FCC
licenses and authorizations owned or acquired by the Company or any Restricted
Subsidiary to ART Licensing (except that the Company may directly own or acquire
and retain such FCC licenses and authorizations) and (ii) cause ART Licensing to
remain a Wholly Owned Restricted Subsidiary of the Company.
 
    Notwithstanding the foregoing, (i) to the extent permitted by the FCC, the
Company will not permit ART Licensing to engage in any business or activity,
other than the application for, acquisition of or ownership of FCC licenses and
authorizations; PROVIDED, HOWEVER, that ART Licensing shall be permitted to own
and operate any equipment or assets that were owned by ART Licensing on or prior
to the Issue Date and (ii) nothing herein shall prohibit any action permitted
under the covenant described under "--Limitation on Restricted Payments" or any
action permitted under the covenant described under "--Disposition of Proceeds
of Asset Sales," other than sales of less than all of the Capital Stock of a
Wholly Owned Restricted Subsidiary.
 
    CHANGE IN CONTROL
 
    In the event of a Change in Control, the Company must commence and
consummate an Offer to Purchase for all the Notes then outstanding, at a
purchase price equal to 101% of the principal amount thereof, together with
accrued and unpaid interest, if any, to the date of purchase. Not later than 20
days
 
                                       96
<PAGE>
following any Change in Control, the Company will mail a notice to each holder
describing the transaction or transactions that constitute the Change in Control
and offering to repurchase Notes pursuant to the procedures required by the
Indenture and described in such notice.
 
    The Indenture does not contain provisions that permit the holders of the
Notes to require that the Company repurchase or redeem the Notes in the event of
a highly leveraged transaction, including a takeover, recapitalization or
similar restructuring, that may adversely effect the holders of the Notes if
such transaction does not otherwise constitute a Change in Control. See "--
Certain Definitions." In addition, with the consent of at least 66 2/3% in
principal amount of the Notes then outstanding, the Company may amend, and the
holders of Notes may waive any Default in the performance of, the provisions
described in this "Change in Control" covenant. See "-- Amendments and Waivers."
There can be no assurance that the Company will have sufficient funds available
at the time of any Change in Control to make any debt payment (including
repurchases of Notes) required by the foregoing covenant (as well as may be
contained in other securities of the Company which might be outstanding at the
time).
 
    DISPOSITION OF PROCEEDS OF ASSET SALES
 
    The Indenture will provide that the Company will not, and will not permit
any Restricted Subsidiary to, consummate any Asset Sale, unless (a) the
consideration received by the Company or such Restricted Subsidiary is at least
equal to the fair market value of the assets sold or disposed of and (b) at
least 85% of the consideration received consists of cash or Temporary Cash
Investments, PROVIDED that any notes or other obligations received by the
Company or any such Restricted Subsidiary as consideration that are converted by
the Company or such Restricted Subsidiary into cash within 30 days of their
receipt (to the extent of the cash received), shall be deemed to be cash for
purposes of this provision. In the event and to the extent that the Net Cash
Proceeds received by the Company or its Restricted Subsidiaries from one or more
Asset Sales occurring on or after the Issue Date in any period of 12 consecutive
months exceed 10% of Adjusted Consolidated Net Tangible Assets (determined as of
the date closest to the commencement of such 12-month period for which a
consolidated balance sheet of the Company and its Restricted Subsidiaries has
been prepared), then the Company shall or shall cause the relevant Restricted
Subsidiary to (i) within six months after the date Net Cash Proceeds so received
exceed 10% of Adjusted Consolidated Net Tangible Assets (A) apply an amount
equal to such excess Net Cash Proceeds to permanently repay unsubordinated
Indebtedness of the Company or any of its Restricted Subsidiaries owing to a
Person other than the Company or any of its Restricted Subsidiaries or (B)
invest an equal amount, or the amount not so applied pursuant to clause (A) (or
enter into a definitive agreement committing to so invest within six months
after the date of such agreement), in property or assets of a nature or type or
that are used in a business (or in a company having property and assets of a
nature or type, or engaged in a business) similar or related to the nature or
type of the property and assets of, or the business of, the Company and its
Restricted Subsidiaries existing on the date of such Investment (as determined
in good faith by the Board, whose determination shall be conclusive and
evidenced by a resolution of the Board and (ii) apply (no later than the end of
the six-month period referred to in clause (i)) such excess Net Cash Proceeds
(to the extent not applied pursuant to clause (i)) as provided in the following
paragraph of this "Disposition of Proceeds of Asset Sales" covenant. The amount
of such excess Net Cash Proceeds required to be applied (or to be committed to
be applied) during such six-month period as set forth in clause (i) of the
preceding sentence and not applied as so required by the end of such period
shall constitute "Excess Proceeds."
 
    If, as of the first day of any calendar month, the aggregate amount of
Excess Proceeds not theretofore subject to an Offer to Purchase pursuant to this
"Limitation on Asset Sales" covenant totals at least $5.0 million, the Company
must commence, not later than the fifteenth business day of the succeeding
month, and consummate an Offer to Purchase from the holders on a pro rata basis
an aggregate principal amount of Notes equal to the Excess Proceeds on such
date, at a purchase price equal to 100% of the principal amount thereof, plus
accrued and unpaid interest, if any, to the date of purchase.
 
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<PAGE>
    NO AMENDMENT TO VOTING TRUST AGREEMENTS
 
    The Indenture will provide that the Company will not amend, modify or alter
any Voting Trust Agreement without having obtained the consent of the holders of
not less than a majority in principal amount of the Notes then outstanding;
PROVIDED, HOWEVER, that the Company may amend, modify or alter any Voting Trust
Agreement, if, in the opinion of Delaware counsel, such amendment, modification
or alteration is necessary to cause such Voting Trust Agreement to comply with
Delaware law or any change thereto.
 
    REPORTS
 
    The Indenture will provide that, whether or not required by the rules and
regulations of the Securities and Exchange Commission (the "Commission"), so
long as any Notes are outstanding, the Company will furnish to the Holders of
Notes (i) all quarterly and annual financial information that would be required
to be contained in a filing with the Commission on Forms 10-Q and 10-K if the
Company were required to file such Forms, including a "Management's Discussion
and Analysis of Financial Condition and Results of Operations" and, with respect
to the annual information only, a report thereon by the Company's certified
independent accountants and (ii) all current reports that would be required to
be filed with the Commission on Form 8-K if the Company were required to file
such reports. In addition, whether or not required by the rules and regulations
of the Commission, the Company will file a copy of all such information and
reports with the Commission for public availability (unless the Commission will
not accept such a filing) and make such information available to securities
analysts and prospective investors upon request.
 
CONSOLIDATION, MERGER, SALE OF ASSETS, ETC.
 
    The Indenture will provide that the Company shall not consolidate with,
merge with or into, or sell, convey, transfer, lease or otherwise dispose of all
or substantially all of its property and assets (as an entirety or substantially
an entirety in one transaction or a series of related transactions) to, any
Person (other than a consolidation or merger with or into a Wholly Owned
Restricted Subsidiary with a positive net worth; PROVIDED that, in connection
with any such merger or consolidation, no consideration (other than Capital
Stock in the surviving Person or the Company) shall be issued or distributed to
the stockholders of the Company) or permit any Person to merge with or into the
Company unless: (i) the Company shall be the continuing Person, or the Person
(if other than the Company) formed by such consolidation or into which the
Company is merged or that acquired or leased such property and assets of the
Company shall be a corporation organized and validly existing under the laws of
the United States of America or any jurisdiction thereof and shall expressly
assume, by a supplemental indenture, executed and delivered to the Trustee, all
of the obligations of the Company on all of the Notes and under the Indenture;
(ii) immediately after giving effect to such transaction, no Default or Event of
Default shall have occurred and be continuing; (iii) immediately after giving
effect to such transaction on a pro forma basis, the Indebtedness to Total
Market Capitalization Ratio (determined as of a date no earlier than 10 days
prior to such transaction) of the Company, or any person becoming the successor
obligor of the Notes, would be no greater than 130% of the Indebtedness to Total
Market Capitalization Ratio of the Company immediately prior to giving effect to
such transaction; PROVIDED that this clause (iii) shall not apply to any
transaction or series of transactions effected solely for the purpose of
creating a parent corporation of which the Company shall be a Wholly Owned
Subsidiary and whose stockholders shall be identical (without regard to the
exercise of options or warrants, or securities convertible or exchangeable into
shares of Common Stock) to those of the Company immediately prior thereto; and
(iv) the Company delivers to the Trustee an Officers' Certificate (attaching the
arithmetic computations to demonstrate compliance with clause (iii)) and an
Opinion of Counsel, in each case, stating that such consolidation, merger or
transfer and such supplemental indenture complies with this provision and that
all conditions precedent provided for herein relating to such transaction have
been complied with; PROVIDED, HOWEVER, that clause (iii) above does not apply
if, in the good faith determination of the Board,
 
                                       98
<PAGE>
whose determination shall be evidenced by a resolution of the Board, the
principal purpose of such transaction is to change the state of incorporation of
the Company; and PROVIDED FURTHER that any such transaction shall not have as
one of its purposes the evasion of the foregoing limitations.
 
EVENTS OF DEFAULT AND REMEDIES
 
    The following events are "Events of Default" under the Indenture:
 
      (i)
       default in the payment of interest on the Notes when it becomes due and
       payable as to any interest payment date on or prior to February 15, 2000,
and continuance of such default for a period of five (5) days or more; or
default in the payment of interest on the Notes when it becomes due and payable
as to any interest payment date after February 15, 2000, and continuance of such
default for a period of thirty (30) days or more; or
 
     (ii)
       default in the payment of principal of, or premium, if any, on the Notes
       when due; or
 
    (iii)
       default in the performance, or breach, of any covenant described under
       "Certain Covenants -- Limitation on Restricted Payments," "-- Limitation
on Indebtedness," "-- Change in Control," "-- Disposition of Proceeds of Asset
Sales," the first sentence of "Security" and "Consolidation, Merger, Sale of
Assets, Etc."; or
 
     (iv)
       default in the performance, or breach, of any covenant in the Indenture
       (other than defaults specified in clause (i), (ii) or (iii) above), and
the continuance of such default or breach for a period of 30 days or more after
written notice to the Company by the Trustee or to the Company and the Trustee
by the holders of at least 25% in aggregate principal amount at maturity of the
outstanding Notes (in each case, when such notice is deemed received in
accordance with the Indenture); or
 
      (v)
       default under any mortgage, indenture or instrument under which there may
       be issued or by which there may be secured or evidenced any Indebtedness
for money borrowed by the Company or any of its Restricted Subsidiaries (or the
payment of which is Guaranteed by the Company or any of its Restricted
Subsidiaries) whether such Indebtedness or Guarantee now exists, or is created
after the Issue Date, which default (A) is caused by a failure to pay principal
of or premium, if any, or interest on such Indebtedness prior to the expiration
of the grace period provided in such Indebtedness on the date of such default (a
"Payment Default") or (B) results in the acceleration of such Indebtedness prior
to its express maturity and, in each case, the principal amount of any such
Indebtedness, together with the principal amount of any other such Indebtedness
under which there has been a Payment Default, or the maturity of which has been
so accelerated, aggregates $5.0 million or more; or
 
     (vi)
       any final judgment or order (not covered by insurance) for the payment of
       money in excess of $5.0 million in the aggregate for all such final
judgments or orders against all such Persons (treating any deductibles,
self-insurance or retention as not so covered) shall be rendered against the
Company or any Significant Subsidiary and shall not be paid or discharged, and
there shall be any period of 60 consecutive days following entry of the final
judgment or order that causes the aggregate amount for all such final judgments
or orders outstanding and not paid or discharged against all such Persons to
exceed $5.0 million during which a stay of enforcement of such final judgment or
order, by reason of a pending appeal or otherwise, shall not be in effect; or
 
    (vii)
       a court having jurisdiction in the premises enters a decree or order for
       (A) relief in respect of the Company or any Significant Subsidiary in an
involuntary case under any applicable bankruptcy, insolvency or other similar
law now or hereafter in effect, (B) the appointment of a receiver, liquidator,
assignee, custodian, trustee, sequestrator or similar official of the Company or
any Significant Subsidiary or for all or substantially all of the property and
assets of the Company or any Significant Subsidiary or (C) the winding up or
liquidation of the affairs of the Company or any Significant Subsidiary and, in
each case, such decree or order shall remain unstayed and in effect for a period
of 60 consecutive days; or
 
   (viii)
       the Company or any Significant Subsidiary (A) commences a voluntary case
       under any applicable bankruptcy, insolvency or other similar law now or
hereafter in effect, or consents to the entry of an
 
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order for relief in an involuntary case under any such law, (B) consents to the
appointment of or taking possession by a receiver, liquidator, assignee,
custodian, trustee, sequestrator or similar official of the Company or any
Significant Subsidiary or for all or substantially all of the property and
assets of the Company or any Significant Subsidiary or (C) effects any general
assignment for the benefit of creditors.
 
    If any Event of Default (other than an Event of Default specified in clause
(vii) or (viii) above with respect to the Company) occurs and is continuing,
then the Trustee or the holders of at least 25% in principal amount of
outstanding Notes may, by written notice, and the Trustee upon the request of
the holders of not less than 25% in principal amount of the outstanding Notes
shall, declare the Default Amount of, and any accrued and unpaid interest on,
all outstanding Notes to be immediately due and payable and upon any such
declaration such amounts shall become immediately due and payable. If an Event
of Default specified in clause (vii) or (viii) above with respect to the Company
occurs and is continuing, then all outstanding Notes shall IPSO FACTO become and
be immediately due and payable without any declaration or other act on the part
of the Trustee or any holder.
 
    After a declaration of acceleration, the holders of a majority in aggregate
principal amount of outstanding Notes may, by notice to the Trustee, rescind
such declaration of acceleration if all existing Events of Default, other than
nonpayment of the principal of, and any accrued and unpaid interest on, the
Notes that has become due solely as a result of such acceleration, have been
cured or waived and if the rescission of acceleration would not conflict with
any judgment or decree. The holders of a majority in principal amount of the
outstanding Notes also have the right to waive past defaults under the
Indenture, except a default in the payment of the principal of, or any interest
on, any outstanding Note, or in respect of a covenant or a provision that cannot
be modified or amended without the consent of all holders of Notes.
 
    No holder of any of the Notes has any right to institute any proceeding with
respect to the Indenture or any remedy thereunder, unless such holder gives the
Trustee written notice of a continuing Event of Default, the holders of at least
25% in principal amount of the outstanding Notes have made written request, and
offered reasonable security or indemnity, to the Trustee to institute such
proceeding as Trustee, the Trustee has failed to institute such proceeding
within 60 days after receipt of such notice and the Trustee has not within such
60-day period received directions inconsistent with such written request by
holders of a majority in principal amount of the outstanding Notes. Such
limitations do not apply, however, to a suit instituted by a holder of a Note
for the enforcement of the payment of the principal of, or any accrued and
unpaid interest on, such Note on or after the respective due dates expressed in
such Note.
 
    During the existence of an Event of Default, the Trustee is required to
exercise such rights and powers vested in it under the Indenture and use the
same degree of care and skill in its exercise thereof as a prudent Person would
exercise under the circumstances in the conduct of such Person's own affairs.
Subject to the provisions of the Indenture relating to the duties of the
Trustee, if an Event of Default shall occur and be continuing, the Trustee is
not under any obligation to exercise any of its rights or powers under the
Indenture at the request or direction of any of the holders unless such holders
shall have offered to such Trustee reasonable security or indemnity. Subject to
certain provisions concerning the rights of the Trustee, the holders of a
majority in principal amount at maturity of the outstanding Notes have the right
to direct the time, method and place of conducting any proceeding for any remedy
available to the Trustee or exercising any trust or power conferred on the
Trustee.
 
    The Indenture provides that the Trustee will, within 45 days after the
occurrence of any Default, give to the holders of the Notes notice of such
Default known to it, unless such Default shall have been cured or waived;
PROVIDED that the Trustee shall be protected in withholding such notice if it
determines in good faith that the withholding of such notice is in the interest
of such holders.
 
    The Company is required to furnish to the Trustee annually a statement as to
its compliance with all conditions and covenants under the Indenture.
 
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DEFEASANCE
 
    The Company may at any time terminate all of its obligations with respect to
the Notes ("defeasance"), except for certain obligations, including those
regarding any trust established for a defeasance and obligations to register the
transfer or exchange of the Notes, to replace mutilated, destroyed, lost or
stolen Notes as required by the Indenture and to maintain agencies in respect of
the Notes. The Company may at any time terminate its obligations under certain
covenants set forth in the Indenture, some of which are described under "Certain
Covenants" above, and any omission to comply with such obligations shall not
constitute a Default with respect to the Notes ("covenant defeasance"). To
exercise either defeasance or covenant defeasance, the Company must irrevocably
deposit in trust with the Trustee, for the benefit of the holders of the Notes,
money (in United States dollars) or U.S. government obligations (denominated in
United States dollars), or a combination thereof, in such amounts as will be
sufficient to pay the principal of, premium, if any, and interest on the
outstanding Notes to redemption or maturity and comply with certain other
conditions, including the delivery of a legal opinion as to certain tax matters.
 
SATISFACTION AND DISCHARGE
 
    The Indenture will be discharged and will cease to be of further effect
(except as to surviving rights or registration of transfer or exchange of Notes)
as to all outstanding Notes when either (a) all such Notes theretofore
authenticated and delivered (except lost, stolen or destroyed Notes that have
been replaced or paid and Notes for whose payment money has theretofore been
deposited in trust or segregated and held in trust by the Company and thereafter
repaid to the Company or discharged from such trust) have been delivered to the
Trustee for cancellation or (b)(i) all such Notes not theretofore delivered to
the Trustee for cancellation have become due and payable by their terms or shall
have been called for redemption and the Company has irrevocably deposited or
caused to be deposited with the Trustee as trust funds in trust for the purpose
an amount of money sufficient to pay and discharge the entire Indebtedness on
the Notes not theretofore delivered to the Trustee for cancellation or
redemption, for the principal amount, premium, if any, and accrued interest to
the date of such deposit; (ii) the Company has paid all other sums payable by it
under the Indenture; and (iii) the Company has delivered irrevocable
instructions to the Trustee to apply the deposited money toward the payment of
the Notes at maturity or on the redemption date, as the case may be. In
addition, the Company must deliver an Officers' Certificate and an Opinion of
Counsel stating that all conditions precedent to satisfaction and discharge have
been complied with.
 
AMENDMENTS AND WAIVERS
 
    From time to time the Company, when authorized by resolutions of its Board,
and the Trustee, without the consent of the holders of the Notes, may amend,
waive or supplement the Indenture, the Pledge Agreement or the Notes for certain
specified purposes, including, among other things, curing ambiguities, defects
or inconsistencies, maintaining the qualification of the Indenture under the
Trust Indenture Act or making any change that does not adversely affect the
rights of any holder. Other amendments and modifications of the Indenture, the
Pledge Agreement and the Notes may be made by the Company and the Trustee with
the consent of the holders of not less than a majority of the aggregate
principal amount of the outstanding Notes (including consents obtained in
connection with a tender offer or exchange offer for Notes); PROVIDED that no
such modification or amendment may, without the consent of the holder of each
outstanding Note affected thereby, (i) reduce the principal amount of, extend
the fixed maturity of, or alter the redemption provisions of, the Notes, (ii)
change the currency in which any Notes or any premium or the accrued interest
thereon is payable, (iii) reduce the percentage in principal amount outstanding
of Notes who must consent to an amendment, supplement or waiver or consent to
take any action under the Indenture or the Notes, (iv) impair the right to
institute suit for the enforcement of any payment on or with respect to the
Notes, (v) waive a default in payment with respect to the Notes, (vi) reduce the
rate or extend the time for payment of interest on the
 
                                      101
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Notes, (vii) adversely affect the ranking of the Notes in a manner adverse to
the holder of the Notes or (viii) release any Collateral from the Lien created
by the Pledge Agreement, except in accordance with the terms thereof.
 
    In addition, without the consent of at least 66 2/3% in principal amount of
the Notes then outstanding (including consents obtained in connection with a
tender offer or exchange offer for Notes), no amendment to the Indenture may
make any change in, and no waiver may be made with respect to any Default in the
performance of, the provisions described above under the captions "Change in
Control" and "Disposition of Proceeds of Asset Sales."
 
CONCERNING THE TRUSTEE
 
    The Indenture provides that, except during the continuance of an Event of
Default, the Trustee will perform only such duties as are specifically set forth
in the Indenture. If an Event of Default has occurred and is continuing, the
Trustee will exercise such rights and powers vested in it under the Indenture
and use the same degree of care and skill in its exercise as a prudent Person
would exercise under the circumstances in the conduct of such Person's own
affairs.
 
    The Indenture and the provisions of the Trust Indenture Act incorporated by
reference therein contain certain limitations on the rights of the Trustee
thereunder, should it become a creditor of the Company, to obtain payment of
claims in certain cases, or to realize on certain property received by it in
respect of any such claims, as security or otherwise. The Trustee is permitted
to engage in other transactions; PROVIDED, HOWEVER, that if it acquires any
conflicting interest, it must eliminate such conflict or resign.
 
GOVERNING LAW
 
    The Indenture and the Notes will be governed by, and construed in accordance
with, the laws of the State of New York without giving effect to the principles
of conflicts of law thereof.
 
CERTAIN DEFINITIONS
 
    Set forth below are certain defined terms used in the Indenture. Reference
is made to the Indenture for any other capitalized terms used herein for which
no definition is provided.
 
    "ACQUIRED DEBT" means, with respect to any specified Person, (i)
Indebtedness of any other Person existing at the time such other Person is
merged with or into or became a Subsidiary of such specified Person, including,
without limitation, Indebtedness incurred in connection with, or in
contemplation of, such other Person merging with or into or becoming a
Subsidiary of such specified Person, and (ii) Indebtedness secured by a Lien
encumbering any asset acquired by such specified Person.
 
    "ADJUSTED CONSOLIDATED NET INCOME" means, for any period, the aggregate net
income (or loss) of the Company and its Restricted Subsidiaries for such period
determined in conformity with GAAP; PROVIDED that the following items shall be
excluded in computing Adjusted Consolidated Net Income (without duplication):
(i) the net income of any Person (other than net income attributable to a
Restricted Subsidiary) in which any Person (other than the Company or any of its
Restricted Subsidiaries) has a joint interest and the net income of any
Unrestricted Subsidiary, except to the extent of the amount of dividends or
other distributions actually paid to the Company or any of its Restricted
Subsidiaries by such other Person (including, without limitation, an
Unrestricted Subsidiary) during such period; (ii) solely for the purposes of
calculating the amount of Restricted Payments that may be made pursuant to
clause (C) of the first paragraph of the "Limitation on Restricted Payments"
covenant described above (and in such case, except to the extent includable
pursuant to clause (i) above), the net income (or loss) of any Person accrued
prior to the date it becomes a Restricted Subsidiary or is merged into or
consolidated with the Company or any of its Restricted Subsidiaries or all or
substantially all of the property and assets of such Person are acquired by the
Company or any of its Restricted Subsidiaries; (iii) the net income of any
Restricted Subsidiary to the extent that the declaration or payment of dividends
or similar distributions by such Restricted Subsidiary of such net income is not
at the time permitted by the operation of
 
                                      102
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the terms of its charter or any agreement, instrument, judgment, decree, order,
statute, rule or governmental regulation applicable to such Restricted
Subsidiary; (iv) any gains or losses (on an after-tax basis) attributable to
Asset Sales; (v) except for purposes of calculating the amount of Restricted
Payments that may be made pursuant to clause (C) of the first paragraph of the
"Limitation on Restricted Payments" covenant described above, any amount paid
as, or accrued for, cash dividends on Preferred Stock of the Company or any
Restricted Subsidiary owned by Persons other than the Company and any of its
Restricted Subsidiaries; and (vi) all extraordinary or nonrecurring gains and
losses; and (vii) the net income of the Company in respect of the Pledged
Securities.
 
    "ADJUSTED CONSOLIDATED NET TANGIBLE ASSETS" means the total amount of assets
of the Company and its Restricted Subsidiaries (less applicable depreciation,
amortization and other valuation reserves), except to the extent resulting from
write-ups of capital assets (excluding write-ups in connection with accounting
for acquisitions in conformity with GAAP), after deducting therefrom (i) all
current liabilities of the Company and its Restricted Subsidiaries (excluding
intercompany items) and (ii) all goodwill, trade names, trademarks, patents,
unamortized debt discount and expense and other like intangibles (other than
licenses issued by the FCC), all as set forth on the quarterly or annual
consolidated balance sheet of the Company and its Restricted Subsidiaries,
prepared in conformity with GAAP and most recently filed with the Commission
pursuant to the "Reports" covenant; PROVIDED that the value of any licenses
issued by the FCC shall, in the event of an auction for similar licenses, be
equal to the fair market value ascribed thereto in good faith by the Board and
evidenced by a resolution of the Board. As used in the Indenture, references to
financial statements of the Company and its Restricted Subsidiaries shall be
adjusted to exclude Unrestricted Subsidiaries if the context requires.
 
    "AFFILIATE" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person. For purposes of this definition, "control"
(including, with correlative meanings, the terms "controlling," "controlled by"
and "under common control with"), as used with respect to any Person, shall mean
the possession, directly or indirectly, of the power to direct or cause the
direction of the management or policies of such Person, whether through the
ownership of voting securities, by agreement or otherwise; PROVIDED that
beneficial ownership of 10% or more of the voting securities of a Person shall
be deemed to be control. For purposes of the Indenture, the term "Affiliate"
shall at all times include Laurence S. Zimmerman, Landover Holdings Corporation
and their respective Affiliates.
 
    "ART LICENSING" means ART Licensing Corp., a Delaware corporation and a
wholly owned subsidiary of the Company, or any successor thereto, or such other
Restricted Subsidiary or Restricted Subsidiaries of the Company formed for the
purpose of the application for, acquisition of or ownership of FCC licenses and
authorizations.
 
    "ART WEST" means ART West Joint Venture, a Delaware partnership owned by the
Company and Extended Communications, Inc.
 
    "ASSET ACQUISITION" means (i) an Investment by the Company or any of its
Restricted Subsidiaries in any other Person pursuant to which such Person shall
become a Restricted Subsidiary of the Company or shall be merged into or
consolidated with the Company or any of its Restricted Subsidiaries or (ii) an
acquisition by the Company or any of its Restricted Subsidiaries of the property
and assets of any Person other than the Company or any of its Restricted
Subsidiaries that constitute substantially all of a division or line of business
of such Person.
 
    "ASSET SALE" means any sale, transfer or other disposition (including by way
of merger, consolidation or sale-leaseback transaction) in one transaction or a
series of related transactions by the Company or any of its Restricted
Subsidiaries to any Person other than the Company or any of its Restricted
Subsidiaries of (i) all or any of the Capital Stock of any Restricted
Subsidiary, (ii) all or substantially all of the property and assets of an
operating unit or business of the Company or any of its Restricted Subsidiaries
or (iii) any other property or assets of the Company or any of its Restricted
Subsidiaries outside the ordinary course of business of the Company or such
Restricted Subsidiary; PROVIDED that the following shall not be included within
the meaning of "Asset Sale": (A) sales or other dispositions of
 
                                      103
<PAGE>
inventory, receivables and other current assets; (B) sales or other dispositions
of equipment that has become worn out, obsolete, damaged or otherwise unsuitable
or undesirable for use in connection with the business of the Company or its
Restricted Subsidiaries; (C) Permitted Asset Swaps; (D) sales, transfers or
other dispositions otherwise constituting Asset Sales in an aggregate amount not
to exceed $500,000 during the relevant twelve-month period referred to in the
"Disposition of Proceeds of Asset Sales" covenant; (E) any Restricted Payment
permitted by the "Limitation on Restricted Payments" covenant; (F) any Lien
permitted to be Incurred by the "Limitation on Liens Securing Certain
Indebtedness" covenant; (G) any transaction that is governed by the provisions
of the "Consolidation, Merger, Sale of Assets, Etc." covenant; (H) any sale,
transfer or other disposition of the Capital Stock of an Unrestricted
Subsidiary; and (I) any disposition pursuant to the Option Agreement, dated as
of July 3, 1996, between the Company and Commco, L.L.C.
 
    "AVERAGE LIFE" means, at any date of determination with respect to any debt
security, the quotient obtained by dividing (i) the sum of the products of (A)
the number of years from such date of determination to the dates of each
successive scheduled principal payment of such debt security and (B) the amount
such principal payment by (ii) the sum of all such principal payments.
 
    "BOARD" means the Board of Directors of the Company.
 
    "CAPITAL STOCK" means (i) in the case of a corporation, corporate stock,
(ii) in the case of an association or business entity, any and all shares,
interests, participations, rights or other equivalents (however designated) of
corporate stock, (iii) in the case of a partnership, partnership interests
(whether general or limited) and (iv) any other interest or participation that
confers on a Person the right to receive a share of the profits and losses of,
or distributions of assets of, the issuing Person.
 
    "CAPITALIZED LEASE" means, as applied to any Person, any lease of any
property (whether real, personal or mixed) of which the discounted present value
of the rental obligations of such Person as lessee, in conformity with GAAP, is
required to be capitalized on the balance sheet of such Person; and "Capitalized
Lease Obligations" means the discounted present value of the rental obligations
under such lease.
 
    "CHANGE IN CONTROL" means such time as (i) a "person" or "group" (within the
meaning of Sections 13(d) and 14(d)(2) of the Exchange Act) becomes the ultimate
"beneficial owner" (as defined in Rule 13d-3 under the Exchange Act) of Voting
Stock representing more than 50% of the total voting power of the Voting Stock
of the Company on a fully diluted basis, (ii) individuals who on the Issue Date
constitute the Board (together with any new directors whose election by the
Board or whose nomination for election by the Company's stockholders was
approved by a vote of at least two-thirds of the members of the Board then in
office who either were members of the Board on the Issue Date or whose election
or nomination for election was previously so approved) cease for any reason to
constitute a majority of the members of the Board then in office or (iii) the
merger or consolidation of the Company with or into another corporation, or the
merger or consolidation of another corporation with and into the Company, with
the effect that, immediately after such transaction, the stockholders of the
Company immediately prior to such transaction hold less than 50% of the Voting
Stock of the Person surviving such merger or consolidation.
 
    "COLLATERAL" means, for so long as held pursuant to the Pledge Agreement,
(a) all of Company's now owned and existing and hereafter arising or acquired
right, title and interest in and to the Pledged Securities and the Pledge
Account, (b) the certificates or other evidences of ownership representing any
Pledged Securities or the Pledge Account and (c) all proceeds of any of the
Pledged Securities, including, without limitation, all dividends, interest,
principal payments, cash, options, warrants, rights, instruments, investment
property, subscriptions and other property or proceeds from time to time
received, receivable or otherwise distributed or distributable in respect of or
in exchange for any or all of the Pledged Securities.
 
                                      104
<PAGE>
    "COMMON STOCK" of any Person means Capital Stock of such Person that does
not rank prior to, as to the payment of dividends or as to the distribution of
assets upon any voluntary or involuntary liquidation, dissolution or winding up
to such Person, to shares of Capital stock of any other class of such Person.
 
    "CONSOLIDATED EBITDA" means, for any period, the sum of the amounts for such
period of (i) Adjusted Consolidated Net Income, (ii) Consolidated Interest
Expense, to the extent such amount was deducted in calculating Adjusted
Consolidated Net Income, (iii) income taxes, to the extent such amount was
deducted in calculating Adjusted Consolidated Net Income (other than income
taxes (either positive or negative) attributable to extraordinary and
non-recurring gains or losses or sales of assets), (iv) depreciation expense, to
the extent such amount was deducted in calculating Adjusted Consolidated Net
Income, (v) amortization expense, to the extent such amount was deducted in
calculating Adjusted Consolidated Net Income and (vi) all other non-cash items
reducing Adjusted Consolidated Net Income (other than items that will require
cash payments and for which an accrual or reserve is, or is required by GAAP to
be, made), less all non-cash items increasing Adjusted Consolidated Net Income,
all as determined on a consolidated basis for the Company and its Restricted
Subsidiaries in conformity with GAAP; PROVIDED that, if any Restricted
Subsidiary is not a Wholly Owned Restricted Subsidiary, Consolidated EBITDA
shall be reduced (to the extent not otherwise reduced in accordance with GAAP)
by an amount equal to (A) the amount of the Adjusted Consolidated Net Income
attributable to such Restricted Subsidiary MULTIPLIED BY (B) the quotient of (1)
the number of shares of outstanding Common Stock of such Restricted Subsidiary
not owned on the last day of such period by the Company or any of its Restricted
Subsidiaries DIVIDED BY (2) the total number of shares of outstanding Common
Stock of such Restricted Subsidiary on the last day of such period.
Notwithstanding the foregoing, the provision for taxes based on the income or
profits of, and the depreciation and amortization and other non-cash charges of,
a Restricted Subsidiary of a Person shall be added to Adjusted Consolidated Net
Income to compute Consolidated EBITDA only to the extent (and in the same
proportion) that the net income of such Restricted Subsidiary was included in
calculating the Adjusted Consolidated Net Income of such Person and only if a
corresponding amount would be permitted at the date of determination to be
dividended to the Company by such Restricted Subsidiary without prior approval
(that has not been obtained), pursuant to the terms of its charter and all
agreements, instruments, judgments, decrees, orders, statutes, rules and
governmental regulations applicable to that Restricted Subsidiary or its
stockholders.
 
    "CONSOLIDATED INTEREST EXPENSE" means, for any period, the aggregate amount
of interest in respect of Indebtedness (including amortization of original issue
discount on any Indebtedness and the interest portion of any deferred payment
obligation, calculated in accordance with the effective interest method of
accounting; all commissions, discounts and other fees and charges owed with
respect to letters of credit and bankers' acceptance financing and net payments
(if any) pursuant to Hedging Obligations; and Indebtedness that is Guaranteed or
secured by the Company or any of its Restricted Subsidiaries) and all but the
principal component of rentals in respect of Capitalized Lease Obligations paid,
accrued or scheduled to be paid or to be accrued by the Company and its
Restricted Subsidiaries during such period; EXCLUDING, HOWEVER, (i) any amount
of such interest of any Restricted Subsidiary if the net income of such
Restricted Subsidiary is excluded from the calculation of Adjusted Consolidated
Net Income pursuant to clause (iii) of the definition thereof (but only in the
same proportion as the net income of such Restricted Subsidiary is excluded from
the calculation of Adjusted Consolidated Net Income pursuant to clause (iii) of
the definition thereof) and (ii) any premiums, fees and expenses (and any
amortization thereof) payable in connection with the offering of the Notes, all
as determined on a consolidated basis (without taking into account Unrestricted
Subsidiaries) in conformity with GAAP.
 
                                      105
<PAGE>
    "CREDIT FACILITY" means a bank credit facility, to be entered into among the
Company, Canadian Imperial Bank of Commerce, Inc., as agent (the "Agent"), and
certain lenders to be party thereto, on substantially the terms set forth in the
Summary of Terms and Conditions of the Agent, dated as of December 19, 1996, and
any amendment, extension, restatement, refinancing or refunding thereof;
PROVIDED that the Company and the Agent shall have (A) executed a commitment
letter with respect to such facility not later than June 30, 1997 and (B)
entered into such facility not later than December 31, 1997; PROVIDED FURTHER
that, in the event that the Company and the Agent shall have failed to execute a
commitment letter or enter into such facility within the time periods specified
in the first and the second provision of this definition, respectively, clauses
(xiii) and (xiv) of the second paragraph of the "Limitation on Indebtedness"
covenant shall be of no further force and effect.
 
    "DEFAULT" means any event that is, or with the passage of time or the giving
of notice or both would be, an Event of Default.
 
    "DIRECTED INVESTMENT" means any Investment in a Telecommunications Business
that is made by investing the net proceeds of the issuance of Capital Stock
(other than Redeemable Stock) by the Company (or options, warrants or other
rights to purchase such Capital Stock) after the Issue Date; PROVIDED that such
Investment shall be made with such net proceeds in the form received by the
Company and shall be limited to an amount equal to (A) 50% of such net proceeds
to the extent that such net proceeds consist of cash, and (B) 100% of such net
proceeds to the extent such net proceeds consist of Capital Stock or
Telecommunications Assets; PROVIDED FURTHER that such Investment is made within
180 days of such issuance of Capital Stock.
 
    "EQUITY OFFERING" means an underwritten public offering or flotation of
Common Stock of the Company which has been registered under the Securities Act
and/or admitted to listing on a national securities exchange.
 
    "FAIR MARKET VALUE" means the price that would be paid in an arm's length
transaction between an informed and willing seller under no compulsion to sell
and an informed and willing buyer under no compulsion to buy, as determined in
good faith by the Board (whose determination shall be conclusive) and evidenced
by a resolution of the Board; PROVIDED that, with respect to the Pledged
Securities, the fair market value thereof shall be net of the accrued and unpaid
interest, if any, on the Notes.
 
    "FCC" means the United States Federal Communications Commission and any
state or local telecommunications authority, department, commission or agency
(and any successors thereto).
 
    "GAAP" means generally accepted accounting principles in the United States
of America as in effect from time to time, including, without limitation, those
set forth in the opinions and pronouncements of the Accounting Principles Board
of the American Institute of Certified Public Accountants and statements and
pronouncements of the Financial Accounting Standards Board or in such other
statements by such other entity as approved by a significant segment of the
accounting profession. All ratios and computations contained in the Indenture
shall be computed in conformity with GAAP applied on a consistent basis, except
that calculations made for purposes of determining compliance with the terms of
the covenants and with other provisions of the Indenture shall be made without
giving effect to (i) the amortization of any expenses incurred in connection
with the offering of the Notes and (ii) except as otherwise provided, the
amortization of any amounts required or permitted by Accounting Principles Board
Opinion Nos. 16 and 17.
 
    "GOVERNMENT SECURITIES" means direct obligations of, or obligations
guaranteed by, the United States of America for the payment of which guarantee
or obligations the full faith and credit of the United States is pledged.
 
    "GUARANTEE" means any obligation, contingent or otherwise, of any Person
directly or indirectly guaranteeing any Indebtedness or other obligation of any
other Person and, without limiting the generality of the foregoing, any
obligation, direct or indirect, contingent or otherwise, of such Person (i) to
purchase or pay (or advance or supply funds for the purchase or payment of) such
Indebtedness or other obligation of such other Person (whether arising by virtue
of partnership arrangements, or by
 
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agreements to keep-well, to purchase assets, goods, securities or services, to
take-or-pay, or to maintain financial statement conditions or otherwise) or (ii)
entered into for purposes of assuring in any other manner the obligee of such
Indebtedness or other obligation of the payment thereof or to protect such
obligee against loss in respect thereof (in whole or in part); PROVIDED that the
term "Guarantee" shall not include endorsements for collection or deposit in the
ordinary course of business. The term "Guarantee" used as a verb has a
corresponding meaning.
 
    "HEDGING OBLIGATIONS" means, with respect to any Person, the obligations of
such Person under (i) interest rate swap agreements, interest rate cap
agreements and interest rate collar agreements and (ii) other agreements or
arrangements designed to protect such Person against fluctuations in interest
rates.
 
    "INCUR" means, with respect to any Indebtedness, to incur, create, issue,
assume, Guarantee or otherwise become liable for or with respect to, or become
responsible for, the payment of, contingently or otherwise, such Indebtedness,
including, with respect to the Company and its Restricted Subsidiaries, an
"incurrence" of Indebtedness by reason of a Person becoming a Restricted
Subsidiary of the Company; PROVIDED that neither the accrual of interest nor the
accretion of original issue discount shall be considered an Incurrence of
Indebtedness.
 
    "INDEBTEDNESS" means, with respect to any Person at any date of
determination (without duplication), (i) all indebtedness of such person for
borrowed money, (ii) all obligations of such Person evidenced by bonds,
debentures, notes or other similar instruments (whether negotiable or
non-negotiable), (iii) all obligations of such Person in respect of letters of
credit or other similar instruments (including reimbursement obligations with
respect thereto), (iv) all obligations of such Person to pay the deferred and
unpaid purchase price of property or services, which purchase price is due more
than six months after the date of placing such property in service or taking
delivery and title thereto or the completion of such services, except trade
payables and escrows, holdbacks and comparable arrangements to secure
indemnification obligations under acquisition agreements, (v) all obligations of
such Person as lessee under Capitalized Leases, (vi) all indebtedness of other
Persons secured by a Lien on any asset of such Person, whether or not such
indebtedness is assumed by such Person, PROVIDED that the amount of such
indebtedness shall be the lesser of (A) the fair market value of such asset at
such date of determination and (B) the amount of such indebtedness, (vii) the
balance deferred and unpaid of the purchase price of any property or
representing any Hedging Obligations, except any such balance that constitutes
an accrued expense or trade payable and (viii) all indebtedness of other Persons
Guaranteed by such Person to the extent such indebtedness is Guaranteed by such
Person. The amount of Indebtedness of any Person at any date shall be the
outstanding balance at such date of all unconditional obligations as described
above and, with respect to contingent obligations that are included in any of
clauses (i) through (viii) above, the maximum liability upon the occurrence of
the contingency giving rise to the obligation, PROVIDED (A) that the amount
outstanding at any time of any Indebtedness issued with original issue discount
is the face amount of such Indebtedness, less the remaining unamortized portion
of the original issue discount (other than original issue discount attributable
to the issuance of warrants or other equity securities in connection with the
Incurrence of such Indebtedness) of such Indebtedness on such date, (B) that
Indebtedness shall not include any liability for federal, state, local or other
taxes and (C) that Indebtedness shall not include 100% of the fair market value
of the Pledged Securities that are Government Securities and 80% of the fair
market value of other Temporary Cash Investments, in each case then held by the
Collateral Agent, as determined in good faith by an officer of the Company.
 
    "INDEBTEDNESS TO EBITDA RATIO" means, as at any date of determination, the
ratio of (i) the aggregate amount of Indebtedness of the Company and its
Restricted Subsidiaries on a consolidated basis ("Consolidated Indebtedness") as
at the date of determination (the "Transaction Date") to (ii) the Consolidated
EBITDA of the Company for the then most recent four full fiscal quarters for
which reports have been filed pursuant to the "Reports" covenant described above
(such four full fiscal quarter period being referred to herein as the "Four
Quarter Period"); PROVIDED that (x) pro forma effect shall be given to any
Indebtedness Incurred from the beginning of the Four Quarter Period through the
Transaction Date (including any Indebtedness Incurred on the Transaction Date),
to the extent outstanding on the
 
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Transaction Date, (y) if during the period commencing on the first day of such
Four Quarter Period through the Transaction Date (the "Reference Period"), the
Company or any of the Restricted Subsidiaries shall have engaged in any Asset
Sale, Consolidated EBITDA for such period shall be reduced by an amount equal to
the EBITDA (if positive), or increased by an amount equal to the EBITDA (if
negative), directly attributable to the assets which are the subject of such
Asset Sale and any related retirement of Indebtedness as if such Asset Sale and
related retirement of Indebtedness had occurred on the first day of such
Reference Period or (z) if during such Reference Period the Company or any of
the Restricted Subsidiaries shall have made any Asset Acquisition, Consolidated
EBITDA of the Company shall be calculated on a pro forma basis as if such Asset
Acquisition and any Incurrence of Indebtedness to finance such Asset Acquisition
had taken place on the first day of such Reference Period.
 
    "INDEBTEDNESS TO TOTAL MARKET CAPITALIZATION RATIO" means, at any date of
determination, the ratio of (i) the aggregate amount of Indebtedness of the
Person and Restricted Subsidiaries on a consolidated basis outstanding to (ii)
the Total Market Capitalization of the Person.
 
    "INVESTMENT" in any Person means any direct or indirect advance, loan or
extension of credit (including, without limitation, by way of Guarantee or
similar arrangement, but excluding advances to customers in the ordinary course
of business that are, in conformity with GAAP, recorded as accounts receivable
on the balance sheet of the Company or its Restricted Subsidiaries) or capital
contribution to (by means of any transfer of cash or other property to others or
any payment for property or services for the account or use of others), or any
purchase or acquisition of Capital Stock, bonds, notes, debentures or other
similar instruments issued by, such Person and shall include (i) the designation
of a Restricted Subsidiary as an Unrestricted Subsidiary and (ii) the fair
market value of the Capital Stock held by the Company and the Restricted
Subsidiaries of any Person that has ceased to be a Restricted Subsidiary by
reason of any transaction permitted by clause (iii) of the "Limitation on the
Issuance and Sale of Capital Stock of Restricted Subsidiaries" covenant. For
purposes of the definition of "Unrestricted Subsidiary" and the "Limitation on
Restricted Payments" covenant, (i) "Investment" shall include the fair market
value of the assets (net of liabilities) of any Restricted Subsidiary of the
Company at the time that such Restricted Subsidiary is designated an
Unrestricted Subsidiary and shall exclude the fair market value of the assets
(net of liabilities) of any Unrestricted Subsidiary at the time that such
Unrestricted Subsidiary is designated a Restricted Subsidiary of the Company and
(ii) any property transferred to or from an Unrestricted Subsidiary shall be
valued at its fair market value at the time of such transfer, in each case as
determined by the Board in good faith.
 
    "ISSUE DATE" means the date of original issuance of the Notes.
 
    "LIEN" means, with respect to any asset, any mortgage, lien, pledge, charge,
security interest or encumbrance of any kind in respect of such asset, whether
or not filed, recorded or otherwise perfected under applicable law (including
any conditional sale or other title retention agreement, any lease in the nature
thereof, any option or other agreement to sell or give a security interest in
and any filing of or agreement to give any financing statement under the Uniform
Commercial Code (or equivalent statutes) of any jurisdiction).
 
    "NET CASH PROCEEDS" means (a) with respect to any Asset Sale, the proceeds
of such Asset Sale in the form of cash or cash equivalents, including payments
in respect of deferred payment obligations (to the extent corresponding to the
principal, but not interest, component thereof) when received in the form of
cash or cash equivalents (except to the extent such obligations are financed or
sold with recourse to the Company or any Restricted Subsidiary of the Company)
and proceeds from the conversion of other property received when converted to
cash or cash equivalents, net of (i) brokerage commissions and other fees and
expenses (including fees and expenses of counsel and investment bankers) related
to such Asset Sale, (ii) provisions for all taxes (whether or not such taxes
will actually be paid or are payable) as a result of such Asset Sale without
regard to the consolidated results of operations of the Company and its
Restricted Subsidiaries, taken as a whole, (iii) payments made to repay
Indebtedness or any other obligation outstanding at the time of such Asset Sale
that either (A) is secured by a Lien on the property or assets sold or (B) is
required to be paid as a result of such sale and (iv) appropriate amounts to be
provided by the Company or any Restricted Subsidiary of the Company as a reserve
against any
 
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liabilities associated with such Asset Sale, including, without limitation,
pension and other post-employment benefit liabilities, liabilities related to
environmental matters and liabilities under any indemnification obligations
associated with such Asset Sale, all as determined in conformity with GAAP and
(b) with respect to any issuance or sale of Capital Stock, the proceeds of such
issuance or sale in the form of cash or cash equivalents, including payments in
respect of deferred payment obligations (to the extent corresponding to the
principal, but not interest, component thereof) when received in the form of
cash or cash equivalents (except to the extent such obligations are financed or
sold with recourse to the Company or any Restricted Subsidiary of the Company)
and proceeds from the conversion of other property received when converted to
cash or cash equivalents, net of attorney's fees, underwriters' or placement
agents' fees, discounts or commissions and brokerage, consultant and other fees
incurred in connection with such issuance or sale and net of taxes paid or
payable as a result thereof.
 
    "NON-RECOURSE DEBT" means Indebtedness (a) as to which neither the Company
nor any of its Restricted Subsidiaries (i) provides credit support of any kind
(including any undertaking, agreement or instrument that would constitute
Indebtedness) or (ii) is directly or indirectly liable (as a guarantor or
otherwise); (b) no default with respect to which (including any rights that the
holders thereof may have to take enforcement action against an Unrestricted
Subsidiary) would permit (upon notice, lapse of time or both) any holder of any
other Indebtedness (other than the Notes) of the Company or any of its
Restricted Subsidiaries to declare a default on such other Indebtedness or cause
the payment thereof to be accelerated or payable prior to its stated maturity;
and (c) as to which the lender of any indebtedness for borrowed money in an
aggregate amount in excess of $5.0 million has been notified in writing that
such lender will not have any recourse to the stock or assets of the Company or
any of its Restricted Subsidiaries.
 
    "OFFER TO PURCHASE" means an offer to purchase Notes by the Company from the
holders that is required by the "Disposition of Proceeds of Asset Sales" or
"Change in Control" covenants of the Indenture and which is commenced by mailing
a notice to the Trustee and each holder stating: (i) the covenant pursuant to
which the offer is being made and that all Notes validly tendered will be
accepted for payment on a pro rata basis; (ii) the purchase price and the date
of purchase (which shall be a business day no earlier than 30 days nor later
than 60 days from the date such notice is mailed) (the "Payment Date"); (iii)
that any Note not tendered will continue to accrue interest pursuant to its
terms; (iv) that, unless the Company defaults in the payment of the purchase
price, any Note accepted for payment pursuant to the Offer to Purchase shall
cease to accrue interest on and after the Payment Date; (v) that holders
electing to have a Note purchased pursuant to the Offer to Purchase will be
required to surrender the Note together with the form entitled "Option of the
Holder to Elect Purchase" on the reverse side thereof completed, to the Paying
Agent at the address specified in the notice prior to the close of business on
the business day immediately preceding the Payment Date; (vi) that holders will
be entitled to withdraw their election if the Payment Agent receives, not later
than the close of business on the third business day immediately preceding the
Payment Date, a telegram, facsimile transmission or letter setting forth the
name of such holder, the principal amount of Notes delivered for purchase and a
statement that such holder is withdrawing his election to have such Notes
purchased; and (vii) that holders whose Notes are being purchased only in part
will be issued new Notes equal in principal amount to the unpurchased portion
thereof; PROVIDED that each Note purchased and each new Note issued shall be in
a principal amount of $1,000 or integral multiples thereof. On the Payment Date,
the Company shall (i) accept for payment on a pro rata basis Notes or portions
thereof tendered pursuant to an Offer to Purchase, (ii) deposit with the Paying
Agent money sufficient to pay the purchase price of all Notes or portions
thereof so accepted and (iii) deliver, or cause to be delivered, to the Trustee
all Notes or portions thereof so accepted together with an Officers' Certificate
specifying the Notes or portions thereof so accepted for payment by the Company.
The Paying Agent shall promptly mail to the holders of Notes so accepted for
payment in an amount equal to the purchase price, and the Trustee shall promptly
authenticate and mail to such holders a new Note equal in principal amount to
any unpurchased portion of the Note surrendered; PROVIDED that each Note
purchased and each new Note issued shall be in a principal amount of $1,000 or
integral multiples thereof. The Company will publicly announce the results of an
Offer to Purchase as soon as practicable after the Payment Date. The Trustee
 
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shall act as the Paying Agent for an Offer to Purchase. The Company will comply
with Rule 14e-1 under the Exchange Act and any other securities laws and
regulations thereunder to the extent such laws and regulations are applicable,
in the event that the Company is required to repurchase Notes pursuant to an
Offer to Purchase.
 
    "PERMITTED ASSET SWAP" means any disposition by the Company or any of its
Restricted Subsidiaries of Telecommunications Assets or a majority of the Voting
Stock of a Restricted Subsidiary in exchange for comparable Telecommunications
Assets or a majority of the Voting Stock of a comparable Restricted Subsidiary;
PROVIDED that the Board shall have approved such disposition and exchange and
determined the fair market value of the assets subject to such transaction as
evidenced by a resolution of the Board or such fair market value has been
determined by a written opinion of an investment banking firm of national
standing or other recognized independent expert with experience appraising the
terms and conditions of the type of transaction contemplated thereby.
 
    "PERMITTED INVESTMENTS" MEANS:
 
         (i) an Investment in a Restricted Subsidiary or a Person which will,
    upon the making of such Investment, become a Restricted Subsidiary or be
    merged or consolidated with or into or transfer or convey all or
    substantially all its assets to, the Company or a Restricted Subsidiary;
 
        (ii) Temporary Cash Investments;
 
        (iii) payroll, travel and similar advances to cover matters that are
    expected at the time of such advances ultimately to be treated as expenses
    in accordance with GAAP;
 
        (iv) loans or advances to employees (other than executive officers of
    the Company) in an aggregate principal amount not to exceed $1.0 million at
    any one time outstanding;
 
        (v) stock, obligations or securities received in satisfaction of
    judgments;
 
        (vi) Investments, to the extent that the consideration provided by the
    Company or any of its Restricted Subsidiaries consists solely of Capital
    Stock (other than Redeemable Stock) of the Company;
 
       (vii) notes payable to the Company that are received by the Company as
    payment of the purchase price for Capital Stock (other than Redeemable
    Stock) of the Company;
 
       (viii) Investments in an aggregate amount not to exceed $20.0 million at
    any one time outstanding;
 
        (ix) Investments in an aggregate amount not to exceed $1.0 million at
    any time outstanding in Unrestricted Subsidiaries engaged in the
    Telecommunications Business outside of the United States;
 
        (x) Investments in entities (other than ART West) that own licenses
    granted by the FCC; PROVIDED that (A) such Investments are made pursuant to
    a senior promissory note, in an amount equal to such Investment, that by its
    terms is payable in full at or before any required repayment of principal on
    the Notes, (B) such promissory note is secured equally and ratably with (or
    prior to) any other secured Indebtedness of such entity, (C) such Investment
    is made and used for the purpose of effecting, and does not exceed the
    amount reasonably required to effect, the minimum build-out with respect to
    such licenses that is required by the FCC as a prerequisite to the transfer
    of a majority equity interest in such entity to the Company or one of its
    Restricted Subsidiaries, as determined in good faith by the Board and (D)
    the Company, at the time such Investment is made, had a contractual right
    to, and intends (subject in all cases to compliance with applicable FCC
    rules and regulations) to, acquire such majority equity interest;
 
        (xi) Investments existing on the Issue Date;
 
       (xii) the acquisition of all equity interests of ART West not otherwise
    owned by the Company;
 
      (xiii) Directed Investments; and
 
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       (xiv) promissory notes from Commco, L.L.C. in payment of the exercise
    price of the option granted by the Company to Commco, L.L.C. in accordance
    with the terms of the Option Agreement, dated as of July 3, 1996, between
    the Company and Commco, L.L.C.
 
        "PERMITTED LIENS" MEANS:
 
         (i) Liens for taxes, assessments, governmental charges or claims that
    are being contested in good faith by appropriate legal proceedings timely
    instituted and diligently conducted and for which a reserve or other
    appropriate provision, if any, as shall be required in conformity with GAAP
    shall have been made;
 
        (ii) statutory or common law Liens of landlords and carriers,
    warehousemen, mechanics, suppliers, materialmen, repairmen or other similar
    Liens arising in the ordinary course of business and with respect to amounts
    not yet delinquent or being contested in good faith by appropriate legal
    proceedings timely instituted and diligently conducted and for which a
    reserve or other appropriate provision, if any, as shall be required in
    conformity with GAAP shall have been made;
 
        (iii) Liens incurred or deposits made in the ordinary course of business
    in connection with workers' compensation, unemployment insurance and other
    types of social security;
 
        (iv) Liens incurred or deposits made to secure the performance of
    tenders, bids, leases, statutory or regulatory obligations, bankers'
    acceptances, surety and appeal bonds, government contracts, performance and
    return-of-money bonds and other obligations of a similar nature incurred in
    the ordinary course of business (exclusive of obligations for the payment of
    borrowed money) and a bank's unexercised right of set-off with respect to
    deposits made in the ordinary course;
 
        (v) easements, rights-of-way, municipal and zoning ordinances and
    similar charges, encumbrances, title defects or other irregularities that do
    not materially interfere with the ordinary course of business of the Company
    or any of its Subsidiaries or other irregularities that do not materially
    interfere with the ordinary course of business of the Company or any of its
    Subsidiaries;
 
        (vi) Liens (including extensions and renewals thereof) upon real or
    personal property acquired after the Issue Date; PROVIDED that (A) such Lien
    is created solely for the purpose of securing Indebtedness Incurred in
    accordance with the "Limitation on Indebtedness" covenant, (1) to finance
    the cost (including the cost of improvement or construction) of the item of
    property or assets subject thereto and such Lien is created prior to, at the
    time of or within six months after the later of the acquisition, the
    completion of construction or the commencement of full operation of such
    property or (2) to refinance any Indebtedness previously so secured, (B) the
    principal amount of the Indebtedness secured by such Lien does not exceed
    100% of such cost and (C) any such Lien shall not extend to or cover any
    property or assets other than such item of property or assets and any
    improvements on such item;
 
       (vii) leases or subleases granted to others that do not materially
    interfere with the ordinary course of business of the Company and its
    Subsidiaries, taken as a whole;
 
       (viii) Liens encumbering property or assets under construction arising
    from progress or partial payments by a customer of the Company or its
    Subsidiaries relating to such property or assets;
 
        (ix) any interest or title of a lessor in the property subject to any
    Capitalized Lease or operating lease;
 
        (x) Liens arising from filing Uniform Commercial Code financing
    statements regarding leases;
 
        (xi) Liens on property of, or on shares of stock or Indebtedness of, any
    corporation existing at the time such corporation becomes, or becomes a part
    of, any Subsidiary; PROVIDED that such Liens do not extend to or cover any
    property or assets of the Company or any Subsidiary other than the property
    or assets acquired;
 
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       (xii) Liens in favor of the Company or any Subsidiary;
 
      (xiii) Liens arising from the rendering of a final judgment or order
    against the Company or any Subsidiary of the Company that does not give rise
    to an Event of Default;
 
       (xiv) Liens securing reimbursement obligations with respect to letters of
    credit that encumber documents and the property relating to such letters of
    credit and the products and proceeds thereof;
 
       (xv) Liens in favor of customs and revenue authorities arising as a
    matter of law to secure payment of customs duties in connection with the
    importation of goods;
 
       (xvi) Liens arising out of conditional sale, title retention, consignment
    or similar arrangements for the sale of goods entered into by the Company or
    any of its Subsidiaries in the ordinary course of business in accordance
    with the past practices of the Company and its Subsidiaries prior to the
    Issue Date;
 
      (xvii) Liens on or sales of receivables;
 
     (xviii) Liens securing other Indebtedness in an aggregate amount not to
    exceed $250,000 at any one time;
 
      (xix) Liens on assets of Unrestricted Subsidiaries that secure
    Non-Recourse Debt of Unrestricted Subsidiaries;
 
       (xx) Liens existing on the Issue Date and any extension, renewal or
    replacement of any Liens existing on Issue Date, PROVIDED that the Liens in
    any such extension, renewal or replacement are no less favorable in any
    material respect to the holders of the Notes than those Liens that are being
    extended, renewed or replaced;
 
      (xxi) Liens granted after the Issue Date on any assets or Capital Stock of
    the Company or its Subsidiaries created in favor of the holders of the
    Notes;
 
      (xxii) Liens with respect to the assets of a Subsidiary granted by such
    Subsidiary to the Company or a Wholly Owned Restricted Subsidiary to secure
    Indebtedness owing to the Company or such other Wholly Owned Restricted
    Subsidiary;
 
     (xxiii) Liens securing Indebtedness which is Incurred to refinance secured
    Indebtedness which is permitted to be Incurred under clause (iii) of the
    second paragraph of the "Limitation on Indebtedness" covenant; PROVIDED that
    such Liens do not extend to or cover any property or assets of the Company
    or any Restricted Subsidiary other than the property or assets securing the
    Indebtedness being refinanced;
 
     (xxiv) purchase money Liens upon equipment, software or systems acquired or
    held by the Company or any of its Subsidiaries taken or retained by the
    seller (or a financing institution acting on behalf of the seller) of such
    equipment, software or systems to secure all or a part of the purchase price
    therefor; PROVIDED that such Liens do not extend to or cover any property or
    assets of the Company or any Subsidiary other than the equipment so
    acquired;
 
      (xxv) Liens securing Indebtedness which is permitted to be Incurred under
    clause (xiii) or (xiv) of the second paragraph of the "Limitation on
    Indebtedness" covenant; and
 
     (xxvi) Liens on the Pledged Securities in favor of the holders of the
    Notes.
 
    "PERSON" means any individual, corporation, limited liability company,
partnership, joint venture, association, joint-stock company, trust,
unincorporated organization or government or any agency or political subdivision
thereof.
 
    "PLEDGE ACCOUNT" means an account established with the Trustee pursuant to
the terms of the Pledge Agreement for the deposit of the Pledged Securities
purchased by the Company with a portion of the net proceeds from the Unit
Offering.
 
                                      112
<PAGE>
    "PLEDGE AGREEMENT" means the Collateral Pledge and Security Agreement, dated
as of the date of the Indenture, by and between The Bank of New York and the
Company, among other things, governing the disbursement of funds from the Pledge
Account.
 
    "PLEDGED SECURITIES" means the Government Securities purchased by the
Company with a portion of the net proceeds from the sale of the Notes and
deposited in the Pledge Account and any securities substituted therefor pursuant
to the Pledge Agreement.
 
    "PREFERRED STOCK" means, with respect to any Person, any and all shares,
interests, participations or other equivalents (however designated) of such
Person's preferred or preference stock, whether now outstanding or issued after
the Issue Date, and including, without limitation, all classes and series of
preferred or preference stock of such Person.
 
    "REDEEMABLE STOCK" means any class or series of Capital Stock of any Person
that by its terms or otherwise is (i) required to be redeemed prior to the
Stated Maturity of the Notes, (ii) redeemable at the option of the holder of
such class or series of Capital Stock at any time prior to the Stated Maturity
of the Notes (unless the redemption price is, at the Company's option, without
conditions precedent, payable solely is Common Stock (other than Redeemable
Stock) of the Company) or (iii) convertible into or exchangeable for Capital
Stock referred to in clause (i) or (ii) above or Indebtedness having a scheduled
maturity prior to the Stated Maturity of the Notes; PROVIDED that any Capital
Stock that would not constitute Redeemable Stock but for provisions thereof
giving holders thereof the right to require such Person to repurchase or redeem
such Capital Stock upon the occurrence of an "asset sale" or "change of control"
occurring prior to the Stated Maturity of the Notes shall not constitute
Redeemable Stock if the "asset sale" or "change of control" provisions
applicable to such Capital Stock are no more favorable to the holders of such
Capital Stock than the provisions contained in "Disposition of Proceeds of Asset
Sales" and "Change in Control" covenants described above and such Capital Stock
specifically provides that such Person will not repurchase or redeem any such
stock pursuant to such provision prior to the Company's repurchase of such Notes
as are required to be repurchased pursuant to the "Disposition of Proceeds of
Asset Sales" and "Change in Control" covenants described above.
 
    "RESTRICTED SUBSIDIARY" of a Person means any Subsidiary of the referent
Person that is not an Unrestricted Subsidiary.
 
    "SIGNIFICANT SUBSIDIARY" means, at any date of determination, any Restricted
Subsidiary of the Company that, together with its Subsidiaries, (i) for the most
recent fiscal year of the Company, accounted for more than 10% of the
consolidated revenues of the Company and its Restricted Subsidiaries or (ii) as
of the end of such fiscal year, had assets accounting for more than 10% of the
consolidated assets of the Company and its Restricted Subsidiaries, all as set
forth on the most recently available consolidated financial statements of the
Company for such fiscal year.
 
    "SPECIFIED DATE" means any redemption date, any date of purchase of Notes
pursuant to the "Disposition of Proceeds of Asset Sales" or "Change in Control"
covenants described above, or any date on which the Notes are due and payable
after an Event of Default.
 
    "STATED MATURITY" means, (i) with respect to any debt security, the date
specified in such debt security as the fixed date on which the final installment
of principal of such debt security is due and payable and (ii) with respect to
any scheduled installment of principal of or interest on any debt security, the
date specified in such debt security as the fixed date on which such installment
is due and payable.
 
    "STRATEGIC EQUITY INVESTOR" means any Person which is (or a controlled
Affiliate of any Person which is or a controlled Affiliate of which is) engaged
principally in the Telecommunications Business and which has a Total Market
Capitalization of at least $1.0 billion.
 
    "SUBSIDIARY" means, with respect to any Person, (i) any corporation,
association or other business entity of which more than 50% of the total voting
power of shares of Capital Stock entitled (without regard to the occurrence of
any contingency) to vote in the election of directors, managers or trustees
thereof is at the time owned or controlled, directly or indirectly, by such
Person or one or more of the
 
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other Subsidiaries of that Person (or a combination thereof) and (ii) any
partnership (a) the sole general partner or the managing general partner of
which is such Person or a Subsidiary of such Person or (b) the only general
partners of which are such Person or of one or more Subsidiaries of such Person
(or any combination thereof).
 
    "TELECOMMUNICATIONS ASSETS" means all assets (including, without limitation,
assets consisting of subscribers), rights (contractual or otherwise) and
properties, whether tangible or intangible, used in connection with a
Telecommunications Business.
 
    "TELECOMMUNICATIONS BUSINESS" means, when used in reference to any Person,
that such Person is engaged primarily in the business of (i) providing voice,
video or data communications services, (ii) creating, developing, marketing or
selling communications related equipment, software and other devices or (iii)
evaluating, participating in or pursuing any other activity or opportunity that
is related or incidental to those identified in clauses (i) or (ii) above.
 
    "TEMPORARY CASH INVESTMENT" means any of the following: (i) direct
obligations of the United States or any agency thereof or obligations fully and
unconditionally guaranteed by the United States or any agency thereof; (ii) time
deposit accounts, certificates of deposit and money market deposits maturing
within six months of the date of acquisition thereof issued by a bank or trust
company which is organized under the laws of the United States, any state
thereof or any foreign country recognized by the United States, and which bank
or trust company has capital, surplus and undivided profits aggregating in
excess of $500.0 million (or the foreign currency equivalent thereof) and has
outstanding debt which is rated "A" (or such similar equivalent rating) or
higher by at least one nationally recognized statistical rating organization (as
defined in Rule 436 under the Securities Act) or any money-market fund sponsored
by a registered broker dealer or mutual fund distributor; (iii) repurchase
obligations with a term of not more than 30 days for underlying securities of
the types described in clause (i) above entered into with a bank meeting the
qualifications described in clause (ii) above; (iv) commercial paper, maturing
not more than six months after the date of acquisition, issued by a corporation
(other than an Affiliate of the Company) organized and in existence under the
laws of the United States, any state thereof or any foreign country recognized
by the United States with rating at the time as of which any investment therein
is made of "P-1" (or higher) according to Moody's Investors Service, Inc. or
"A-1" (or higher) according to Standard & Poor's Ratings Group; and (v)
securities with maturities of six months or less from the date of acquisition
issued or fully and unconditionally guaranteed by any state, commonwealth or
territory of the United States, or by any political subdivision or taxing
authority thereof, and rated at least "A" by Standard & Poor's Ratings Group or
Moody's Investors Service, Inc.
 
    "TOTAL MARKET CAPITALIZATION" of any Person means, as of any day of
determination, the sum of (a) the consolidated Indebtedness of such Person and
its Restricted Subsidiaries on such day, PLUS (b) the product of (i) the
aggregate number of outstanding shares of Common Stock of such Person on such
day (which shall not include any options or warrants on, or securities
convertible or exchangeable into, shares of Common Stock of such Person) and
(ii) the average Closing Price of such Common Stock over the 10 consecutive
Trading Days ending not earlier than 10 Trading Days immediately prior to such
date of determination, PLUS (c) the liquidation value of any outstanding shares
of Preferred Stock of such Person on such day. If no such Closing Price exists
with respect to shares of any such class, the value of such shares for purposes
of clause (b) of the preceding sentence shall be determined by the Board in good
faith and evidenced by a resolution of the Board filed with the Trustee.
Notwithstanding the foregoing, unless the Company's Common Stock is listed on
any national securities exchange or on the Nasdaq National Market, the "Total
Market Capitalization" of the Company shall mean, as of any day of
determination, the enterprise value (without duplication) of the Company and its
Restricted Subsidiaries (including the fair market value of their debt and
equity, but excluding the enterprise value of the Company's Unrestricted
Subsidiaries), as determined by an independent banking firm of national standing
with experience in such valuations and evidenced by a written opinion in
customary form filed with the Trustee; PROVIDED that for purposes of any such
determination, the enterprise value of the Company shall be calculated as if the
Company were a publicly held corporation without a controlling
 
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stockholder. For purposes of any such determination, such banking firm's written
opinion may state that such fair market value is no less than a specified amount
and such opinion may be as of a date no earlier than 90 days prior to the date
of such determination.
 
    "TRADING DAY" with respect to a securities exchange or automated quotation
system means a day on which such exchange or system is open for a full day of
trading.
 
    "UNRESTRICTED SUBSIDIARY" means any Subsidiary that is designated by the
Board as an Unrestricted Subsidiary pursuant to a resolution of the Board; but
only to the extent that such Subsidiary (i) has no Indebtedness other than
Non-Recourse Debt; (ii) is not party to any agreement, contract, arrangement or
understanding with the Company or any Restricted Subsidiary of the Company
unless the terms of any such agreement, contract, arrangement or understanding
are no less favorable to the Company or such Restricted Subsidiary than those
that might be obtained at the time from Persons who are not Affiliates of the
Company; (iii) is a Person with respect to which neither the Company nor any of
its Restricted Subsidiaries has any direct or indirect obligation (A) to
subscribe for additional equity interests, except to the extent that such
obligation complies with the "Limitation on Restricted Payments" covenant, or
(B) to maintain or preserve such Person's financial condition or to cause such
Person to achieve any specified levels of operating results; (iv) is not a
guarantor of or otherwise directly or indirectly provides credit support for any
Indebtedness of the Company or any of its Restricted Subsidiaries; and (v) has,
immediately prior to the commencement of material business operations, at least
one director on its board of directors that is not a director or executive
officer of the Company or any of its Restricted Subsidiaries and has at least
one executive officer that is not a director or executive officer of the Company
or any of its Restricted Subsidiaries. Any such designation by the Board shall
be evidenced to the Trustee by filing with the Trustee a certified copy of the
resolution of the Board giving effect to such designation and an Officers'
Certificate certifying that such designation complied with the foregoing
conditions and was permitted by the covenant described above under the caption
"Limitation on Restricted Payments." If, at any time, any Unrestricted
Subsidiary would fail to meet the foregoing requirements as an Unrestricted
Subsidiary, it shall thereafter cease to be an Unrestricted Subsidiary for
purposes of the Indenture and any Indebtedness of such Subsidiary shall be
deemed to be Incurred by a Restricted Subsidiary of the Company as of such date
(and, if such Indebtedness is not permitted to be Incurred as of such date under
the covenant described under the caption "Limitation on Indebtedness," the
Company shall be in default of such covenant). The Board may at any time
designate any Unrestricted Subsidiary to be a Restricted Subsidiary; PROVIDED
that such designation shall be deemed to be an Incurrence of Indebtedness by a
Restricted Subsidiary of the Company of any outstanding Indebtedness of such
Unrestricted Subsidiary and such designation shall only be permitted if (i) such
Indebtedness is permitted under the covenant described under the caption
"Limitation on Indebtedness" and (ii) no Default or Event of Default would be in
existence following such designation.
 
    "VOTING STOCK" means, with respect to any Person, Capital Stock of any class
or kind ordinarily having the power to vote for the election of directors,
managers or other voting members of the governing body of such Person.
 
    "VOTING TRUST AGREEMENTS" means (i) that certain Voting Trust Agreement,
(ii) that certain Cooperation Agreement and (iii) Section 7 of that certain
Confidentiality Agreement, each dated as of November 5, 1996.
 
    "WHOLLY OWNED" means, with respect to any Subsidiary of any Person, such
Subsidiary if all of the outstanding Capital Stock in such Subsidiary (other
than any director's qualifying shares or Investments by foreign nationals
mandated by applicable law) is owned by such Person or one or more Wholly Owned
Subsidiaries of such Person.
 
                                      115
<PAGE>
                            DESCRIPTION OF WARRANTS
 
    The Warrants will be issued pursuant to a warrant agreement (the "Warrant
Agreement") by and between the Company and Continental Stock Transfer and Trust
Company, as warrant agent (the "Warrant Agent"). The following summary of
certain provisions of the Warrant Agreement and the Warrants does not purport to
be complete and is qualified in its entirety by reference to the Warrant
Agreement and the Warrants, including the definitions therein of certain terms.
The Warrant Agreement will be substantially in the form of the Warrant Agreement
filed as an exhibit to the Registration Statement of which this Prospectus is a
part.
 
GENERAL
 
    Each Warrant, when exercised, will entitle the holder thereof to receive
1.349 shares of Common Stock (such shares, the "Warrant Shares") at an exercise
price of $.01 per share (the "Exercise Price"). The Exercise Price and the
number of Warrant Shares issuable on exercise of a Warrant are both subject to
adjustment in certain cases referred to below. The Warrants are exercisable at
any time on or after August 15, 1997. Unless exercised, the Warrants will
automatically expire on February 15, 2007 (the "Expiration Date"). Upon
exercise, the holders of Warrants would be entitled, in the aggregate, to
purchase 2,731,725 shares of Common Stock, representing 12.0% of the outstanding
Common Stock on a fully diluted basis on the date hereof, after giving effect to
the CommcoCCC Acquisition.
 
    The Warrants may be exercised at any time on or after August 15, 1997 by
surrendering to the Company at the office of the Warrant Agent the Warrant
certificates evidencing such Warrants with the accompanying form of election to
purchase properly completed and executed, together with payment of the Exercise
Price. Payment of the Exercise Price may be made in the form of cash or a
certified or official bank check payable to the order of the Company or upon the
surrender of additional Warrants. Upon surrender of the Warrant certificate and
payment of the Exercise Price, the Warrant Agent will deliver or cause to be
delivered, to or upon the written order of such holder, a stock certificate
representing the number of whole Warrant Shares or other securities or property
to which such holder is entitled under the Warrant Agreement and the Warrants,
including, without limitation, any cash payment to adjust for fractional
interests in Warrant Shares issuable upon such exercise. If less than all of the
Warrants evidenced by a Warrant certificate are to be exercised, a new Warrant
certificate will be issued for the remaining number of Warrants. The Warrant
Shares to be issued upon the exercise of the Warrants will be registered under
the Securities Act.
 
    No fractional Warrant Share will be issued upon exercise of the Warrants. If
any fraction of a Warrant Share would, except for the foregoing provision, be
issuable on the exercise of any Warrants (or a specified portion thereof), the
Company shall pay an amount in cash equal to the current market price per
Warrant Share, as determined on the day immediately preceding the date the
Warrant is presented for exercise, multiplied by such fraction, computed to the
nearest whole U.S. cent.
 
    Certificates for Warrants will be issued in registered form only, and no
service charge will be made for registration of transfer or exchange upon
surrender of any Warrant certificate at the office of the Warrant Agent
maintained for that purpose. The Company may require payment of a sum sufficient
to cover any tax or other governmental charge that may be imposed in connection
with any registration, transfer or exchange of Warrant certificates.
 
    The holders of the Warrants have no right to vote on matters submitted to
the stockholders of the Company and have no right to receive dividends. The
holders of the Warrants are not be entitled to share in the assets of the
Company in the event of liquidation, dissolution or winding up of the Company's
affairs.
 
    In the event of taxable distribution to holders of Common Stock which
results in an adjustment to the number of Warrant Shares or other consideration
for which a Warrant may be exercised, the holders of the Warrants may, in
certain circumstances, be deemed to have received a distribution subject to
United States federal income tax as a dividend. See "Certain Federal Income Tax
Considerations."
 
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<PAGE>
REGISTRATION OF WARRANT SHARES
 
    Holders of Warrants will be able to exercise their Warrants only if a
registration statement relating to the Warrant Shares is then in effect, or the
exercise of such Warrants is exempt from the registration requirements of the
Securities Act, and such securities are qualified for sale or exempt from
qualification under the applicable securities laws of the states in which the
various holders of the Warrants or other persons to whom it is proposed that the
Warrant Shares be issued on exercise of the Warrants reside. The Company is
required under the terms of the Warrant Agreement to file and use its best
efforts to cause to become effective no later than August 15, 1997 a shelf
registration statement (the "Warrant Shelf Registration Statement") on an
appropriate form under the Securities Act covering the issuance and resale, to
the extent applicable, of the Warrant Shares upon the exercise of the Warrants.
Subject to "black-out" periods not to exceed 90 days in the aggregate in any
calendar year, the Company will also be required to use its best efforts to
maintain the effectiveness of the Warrant Shelf Registration Statement until the
expiration or exercise of all Warrants. There can be no assurance that the
Company will be able to file, cause to be declared effective or keep a
registration statement continuously effective until all of the Warrants have
been exercised or have expired.
 
ADJUSTMENTS
 
    The number of shares of Common Stock purchasable upon the exercise of the
Warrants and the Exercise Price both will be subject to adjustment in certain
events (subject to certain exceptions) including (i) the payment by the Company
of dividends (and other distributions) on Common Stock payable in Common Stock
or other shares of the Company's capital stock, (ii) subdivisions, combinations
and reclassifications of Common Stock, (iii) the issuance to all holders of
Common Stock of rights, options or warrants entitling them to subscribe for
Common Stock or of securities convertible into or exchangeable for Common Stock,
for a consideration per share of Common Stock which is less than the current
market price per share of Common Stock and (iv) the distribution to all holders
of Common Stock of any of the Company's assets, debt securities or any rights or
warrants to purchase securities (excluding those rights and warrants referred to
in clause (iii) above and excluding cash dividends less than a specified
amount). In addition, the Exercise Price may be reduced in the event of
purchases of Common Stock pursuant to a tender or exchange offer made by the
Company or any subsidiary thereof at a price greater than the sale price of the
Common Stock at the time such tender or exchange offer expires.
 
    No adjustment in the Exercise Price will be required unless such adjustment
would require an increase or decrease of at least one percent (1%) in the
Exercise Price; PROVIDED, HOWEVER, that any adjustment which is not made will be
carried forward and taken into account in any subsequent adjustment.
 
    In the case of certain consolidations or mergers of the Company, or the sale
of all or substantially all of the assets of the Company to another corporation,
each Warrant shall thereafter be exercisable for the right to receive the kind
and amount of shares of stock or other securities or property to which such
holder would have been entitled as a result of such consolidation, merger or
sale had the Warrants been exercised immediately prior thereto.
 
AUTHORIZED SHARES
 
    The Company has authorized for issuance such number of shares of Common
Stock as shall be issuable upon the due exercise of all outstanding Warrants.
Such shares of Common Stock, when paid for and issued, will be duly and validly
issued, fully paid and non-assessable, free of preemptive rights and free from
all taxes, liens, charges and security interests with respect to the issue
thereof (other than any such tax, lien, charge or security interest imposed upon
or granted by the holder of the Common Stock).
 
AMENDMENT
 
    From time to time, the Company and the Warrant Agent, without the consent of
the holders of the Warrants, may amend or supplement the Warrant Agreement for
certain purposes, including curing
 
                                      117
<PAGE>
defects or inconsistencies or making changes that do not materially adversely
affect the rights of any holder. Any amendment or supplement to the Warrant
Agreement that has a material adverse effect on the interests of the holders of
the Warrants shall require the written consent of the holders of a majority of
the then outstanding Warrants (excluding Warrants held by the Company or any of
its Affiliates). The consent of each holder of the Warrants affected shall be
required for any amendment pursuant to which the Exercise Price would be
increased or the number of Warrant Shares purchasable upon exercise of Warrants
would be decreased (other than pursuant to adjustments provided in the Warrant
Agreement).
 
GOVERNING LAW
 
    The Warrant Agreement and the Warrants will be governed by, and construed in
accordance with, the laws of the State of New York without regard to the
principles of conflicts of law thereof.
 
REPORTS
 
    Whether or not the Company is subject to the reporting requirements of the
Exchange Act, the Company shall cause copies of the reports described under
"Description of Notes -- Certain Covenants -- Reports" to be filed with the
Commission (to the extent permitted) and the Warrant Agent and mailed to the
holders at their addresses appearing in the register of Warrants maintained by
the Warrant Agent to the same extent as such reports are furnished to the
holders of Notes in accordance with the Indenture.
 
                          DESCRIPTION OF CAPITAL STOCK
 
    The authorized capital stock of the Company consists of 100,000,000 shares
of Common Stock, $.001 par value, and 10,000,000 shares of Serial Preferred
Stock, $.001 par value (the "Preferred Stock").
 
COMMON STOCK
 
    As of December 31, 1996, there were 13,559,420 shares of Common Stock
outstanding held of record by 133 stockholders (without giving effect to any
exercise of outstanding warrants or options). The holders of Common Stock are
entitled to one vote per share on all matters to be voted on by the
stockholders. Subject to preferences that may be applicable to the outstanding
shares of Preferred Stock, if any, the holders of Common Stock are entitled to
receive ratably such dividends as may be declared from time to time by the Board
of Directors out of funds legally available therefor. In the event of the
liquidation, dissolution or winding up of the Company, the holders of Common
Stock are entitled to share ratably in all assets remaining after payment of
liabilities, subject to prior liquidation rights of the Preferred Stock then
outstanding. The Common Stock has no preemptive conversion rights or other
subscription rights. There are no redemption or sinking fund provisions
applicable to the Common Stock. All outstanding shares of Common Stock are fully
paid and non-assessable, and the shares of Common Stock issuable upon exercise
of the Warrants will be fully paid and non-assessable.
 
PREFERRED STOCK
 
    As of December 31, 1996, there were no shares of Preferred Stock
outstanding. The Board of Directors has the authority to issue Preferred Stock
in one or more series and to fix the rights, preferences, privileges and
restrictions granted to or imposed upon any wholly unissued shares of Preferred
Stock and to fix the number of shares constituting any series in the
designations of such series, without any further vote or action by the
stockholders. The Board of Directors, without stockholder approval, can issue
Preferred Stock with voting and conversion rights which could adversely affect
the voting power of the holders of Common Stock. The issuance of Preferred Stock
may have the effect of delaying, deferring or preventing a change in control of
the Company. The Company does not presently intend to issue Preferred Stock.
 
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<PAGE>
CHANGE IN CONTROL PROVISIONS
 
    Certain provisions of the Company's Certificate of Incorporation and Bylaws
may have the effect of preventing, discouraging or delaying any change in the
control of the Company any may maintain the incumbency of the Board of Directors
and management. The authorization of Preferred Stock makes it possible for the
Board of Directors to issue Preferred Stock with voting or other rights or
preferences that could impede the success of any attempt to effect a change in
control of the Company. Certain provisions of the Certificate of Incorporation
create three classes of directors serving for staggered three-year terms and
prevent any amendment to such provisions without the consent of holders of at
least 75% of the then outstanding shares of Common Stock. These provisions could
also impede the success of any attempt to effect a change in control of the
Company.
 
    The Company is subject to Section 203 ("Section 203") of the Delaware
General Corporation Law (the "Delaware GCL"). Section 203 prohibits a
publicly-held Delaware corporation from engaging in a "business combination"
with an "interested stockholder" for a period of three years after the date of
the transaction in which the person became an interested stockholder, unless (i)
prior to such date, the board of directors of the corporation approves either
the business combination or the transaction which resulted in the stockholder
becoming an interested stockholder, (ii) upon consummation of the transaction
which resulted in the stockholder becoming an interested stockholder, the
interested stockholder owns at least 85% of the outstanding voting stock
(excluding certain shares held by persons who are both directors and officers of
the corporation and certain employee stock plans), or (iii) on or after the
consummation date, the business combination is approved by the board of
directors and by the affirmative vote of at least 66 2/3% of the outstanding
voting stock that is not owned by the interested stockholder. For purposes of
Section 203, a "business combination" includes, among other things, a merger,
asset sale or other transaction resulting in a financial benefit to the
interested stockholder, and an "interested stockholder" is generally a person
who, together with affiliates and associates, owns (or within three years,
owned) 15% or more of the corporation's voting stock.
 
INDEMNIFICATION OF DIRECTORS AND OFFICERS AND LIMITATION OF DIRECTOR LIABILITY
 
    The Company's Certificate of Incorporation contains provisions that
eliminate the personal liability of its directors to the fullest extent
permitted by the Delaware GCL for monetary damages resulting from breaches of
their fiduciary duty. The Certificate of Incorporation also contains provisions
requiring the indemnification of the Company's directors and officers to the
fullest extent permitted by the Delaware GCL against all losses or liabilities
which he or she may sustain or incur on or about the execution of the duties of
his or her office or otherwise in relation thereto. The Company believes that
these provisions are necessary to attract and retain qualified persons as
directors and officers.
 
TRANSFER AGENT AND REGISTRAR
 
    The Transfer Agent and Registrar for the Common Stock is Continental Stock
Transfer & Trust Company.
 
LISTING
 
    The Common Stock is quoted on the Nasdaq Stock Market under the symbol
"ARTT."
 
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                      DESCRIPTION OF CERTAIN INDEBTEDNESS
 
CIBC FINANCING COMMITMENT
 
    The Company has entered into agreements with the CIBC Investors which
provide that the Company may draw down $50.0 million of 12.5% Senior Secured
Notes, due in two years (the "CIBC Financing Commitment"). The Company has the
option of drawing down the Senior Secured Notes until February 10, 1997. Upon
completion of the Offering, the CIBC Financing Commitment will terminate, and,
accordingly, the Company will not issue the Senior Secured Notes in such event.
The interest rate on the Senior Secured Notes increases by 0.50% per annum on
February 12, 1997 and by an additional 0.50% per annum for each three-month
period thereafter.
 
    The Senior Secured Notes, if issued, will be secured by a first priority
security interest in substantially all the assets of the Company, including a
pledge of the Company's stock in its subsidiaries. The Senior Secured Notes, if
issued, will be guaranteed by the Company's domestic subsidiaries. The Senior
Secured Notes, if issued, will contain covenants that restrict the ability of
the Company to pay dividends and make other restricted payments, to incur
additional debt, guarantees and liens, to sell its assets, to enter into mergers
and consolidations, to conduct sale and leaseback transactions and to enter into
affiliate transactions, among other restrictions.
 
    The Company must apply the net proceeds received by it or any of its
subsidiaries from the net cash proceeds of any bank financing, sale of senior or
subordinated debt securities (excluding vendor financing and indebtedness
assumed in acquisitions and including the Offering) or any sale of equity
securities (other than equity issuances in permitted acquisitions) to prepay the
Senior Secured Notes. Upon a change of control (as defined in the CIBC Financing
Commitment agreements), the Company must make an offer to repurchase the Senior
Secured Notes at 101% of principal plus accrued and unpaid interest. The Company
may prepay the Senior Secured Notes at any time at par plus accrued interest.
 
    In November 1996, the Company delivered to the CIBC Investors ten-year
warrants to purchase 300,258 shares of Common Stock (1.5% of the fully diluted
Common Stock of the Company after giving effect to the CommcoCCC Acquisition) at
an exercise price of $.01 per share (the "First CIBC Warrants"). The Company is
obligated to deliver to the CIBC Investors additional warrants to purchase 1.5%
of the fully diluted Common Stock upon first drawing down of the Senior Secured
Notes (the "Second CIBC Warrants" and, collectively with the First CIBC
Warrants, the "Initial CIBC Warrants"). If the Senior Secured Notes are
outstanding on May 12, 1997, the Company shall issue to the CIBC Investors
additional such warrants to purchase 3% of the fully diluted Common Stock (the
"Third CIBC Warrants"), and if the Senior Secured Notes are outstanding after
such initial six month period, the Company will issue to the CIBC Investors
additional such warrants (the "Fourth CIBC Warrants", and collectively with the
Third CIBC Warrants, the "Additional CIBC Warrants") until the repayment date of
the Senior Secured Notes on the basis of 3% of the fully diluted Common Stock
for every six month period, pro-rated for any partial periods. The Initial CIBC
Warrants and Additional CIBC Warrants are referred to collectively as the "CIBC
Warrants." The CIBC Warrants have anti-dilution protection and demand and
piggyback registration rights under the Company's Registration Rights Agreement.
See "Shares Eligible for Future Sale--Registration Rights."
 
    The commitment for sale of the Senior Secured Notes and the CIBC Warrants
(the "CIBC Financing Commitment") was arranged by CIBC Wood Gundy (as defined).
One of the CIBC Investors, CIBC WG Argosy Merchant Fund 2, L.L.C., is affiliated
with CIBC Wood Gundy. See "Underwriting." In connection with the CIBC Financing
Commitment, the Company is obligated to pay to CIBC Wood Gundy a
structuring/placement fee and is obligated to pay to the CIBC Investors a
commitment fee, of which 50% was paid in November 1996 and 50% is payable upon
the earlier of draw down or March 31, 1997 if the Senior Secured Notes are
issued. Under an exclusive placement agent agreement, the Company has agreed to
indemnify CIBC Wood Gundy and its affiliates for liabilities resulting from the
CIBC Financing Commitment and certain future financings.
 
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<PAGE>
EMI NOTE
 
    In connection with the acquisition of the EMI Assets, the Company issued to
EMI a $1.5 million principal amount non-negotiable and non-transferable,
unsecured promissory note (the "EMI Note"). Interest on the EMI Note accrues at
a rate equal to the prime rate plus 2%. The Company is obligated to make
quarterly principal repayments of $187,500, commencing January 1, 1997. The EMI
Note matures on November 14, 1998. See "Business -- Agreements Relating to
Licenses and Acquisitions -- EMI Acquisition."
 
EQUIPMENT FINANCING
 
    On April 1, 1996, CRA, Inc. ("CRA") entered into a secured Equipment
Financing with the Company for the purchase from P-Com of 38 GHz radio
equipment. To evidence its obligations under the Equipment Financing, the
Company issued in favor of CRA a $2,445,000 Equipment Note, payable in twenty
four monthly installments of $92,694 with a final payment equal to $642,305 due
April 1, 1998. See "Certain Transactions -- Equipment Financing."
 
PROPOSED CREDIT FACILITY
 
    Canadian Imperial Bank of Commerce has provided the Company a Summary of
Terms and Conditions on which it and other banks might extend credit pursuant to
a Senior Secured Revolving Credit Facility converting to an Amortizing Term Loan
(the "Credit Facility"). Under the Credit Facility, up to $100,000,000 in
revolving loans would be available based on incurrence provisions which have not
been determined as of the date hereof but would include measures of total debt
to operating cash flows, numbers of links, numbers of links per population unit
or market and amount of revenue per link. The proceeds could be used to finance
the construction of the Company' systems, capital expenditures, permitted
acquisitions, operating losses and working capital. The Credit Facility would be
secured by all of the assets of the Company and its subsidiaries including a
pledge of stock and assets of all subsidiaries, subject to certain exceptions to
be determined, and would be guaranteed by all subsidiaries. The interest rate
would initially be at 2.50% over the bank's base rate or 3.50% over LIBOR
subject to reduction. Mandatory prepayment will be required with respect to a
percentage of excess cash flow and proceeds of equity offerings and asset sales.
The revolving credit facility will convert to a term loan after a period, for a
term and with an amortization to be determined.
 
    In addition, the Credit Facility would include financial covenants to be
determined relating to ratios of total debt to annualized operating cash flow,
operating cash flow to cash interest expense, cash flow available for debt
service to pro forma fixed charges and total debt per total links as well as to
minimum revenues, minimum operating cash flow (or maximum loss), minimum revenue
per link and minimum number of links. The Credit Facility would prohibit the
Company from making restricted payments and acquisitions other than permitted
acquisitions, from incurring indebtedness, except with certain limitations, or
liens, or merging, and would limit investments and asset sales. The Credit
Facility would contain a provision relating to change of control of the Company.
The Credit Facility would also contain customary events of default, including
but not limited to nonpayment of principal and interest when due, violations of
covenants, falsity of representations and warranties in any material respect,
actual or asserted invalidity of security documents and security interests and
the occurrence of certain events with respect to the Company or any subsidiary
including cross-default and cross-acceleration, bankruptcy, material judgments,
ERISA violations, change in control and loss or material impairment of FCC
licenses.
 
    The Company would be required to pay a structuring fee which has not yet
been determined, a facility fee of 3.5% payable at closing and a commitment fee
of 0.5% per annum on the unused portion of the facility. Execution of the Credit
Facility will be dependent upon, among other things, satisfactory due diligence
review by the banks, consummation of the Offering on terms satisfactory to the
banks and negotiation and execution of mutually satisfactory documentation.
There is no assurance that the Credit Facility will be executed, what the terms
of the Credit Facility will be, or if executed, that the Company will be able to
borrow under the Credit Facility.
 
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<PAGE>
                   CERTAIN FEDERAL INCOME TAX CONSIDERATIONS
 
    The following discussion is a summary of the material United States federal
income tax considerations relevant to the purchase, ownership and disposition of
the Units, Notes and Warrants by holders acquiring Units on original issue for
cash, but does not purport to be a complete analysis of all potential tax
effects. The discussion is based upon the Internal Revenue Code of 1986, as
amended (the "Code"), Treasury regulations, Internal Revenue Service ("IRS")
rulings and pronouncements and judicial decisions all in effect as of the date
hereof, all of which are subject to change at any time, and any such change may
be applied retroactively in a manner that could adversely affect a holder of the
Units, Notes or Warrants. The discussion does not address all of the federal
income tax consequences that may be relevant to a holder in light of such
holder's particular circumstances or to holders subject to special rules, such
as certain financial institutions, insurance companies, dealers in securities,
foreign corporations, nonresident alien individuals and persons holding the
Units, Notes or Warrants as part of a "straddle," "hedge" or "conversion
transaction." Moreover, the effect of any applicable state, local or foreign tax
laws is not discussed. The discussion deals only with Units, Notes and Warrants
held as "capital assets" within the meaning of section 1221 of the Code.
 
    The Company has not sought and will not seek any rulings from the IRS with
respect to the position of the Company discussed below. There can be no
assurance that the IRS will not take a different position concerning the tax
consequences of the purchase, ownership or disposition of the Units, Notes or
Warrants or that any such position would not be sustained.
 
    PROSPECTIVE INVESTORS SHOULD CONSULT THEIR OWN TAX ADVISORS WITH REGARD TO
THE APPLICATION OF THE TAX CONSIDERATIONS DISCUSSED BELOW TO THEIR PARTICULAR
SITUATIONS AS WELL AS THE APPLICATION OF ANY STATE, LOCAL, FOREIGN OR OTHER TAX
LAWS.
 
THE UNITS
 
    Because the original purchasers of the Notes also will acquire Warrants,
each Note will be treated for federal income tax purposes as having been issued
as part of an "investment unit" consisting of the Note and associated Warrants.
The issue price of an investment unit consisting of the Note and associated
Warrants will be the first price at which a substantial amount of Units are sold
to the public for money (excluding sales to bond houses, brokers, or similar
persons or organizations acting in the capacity of underwriters, placement
agents or wholesalers). The "issue price" of an investment unit is allocated
between its component parts based on their relative fair market values. The
Company will allocate the issue price of a Unit between the Note and the
associated Warrants in accordance with the Company's determination of their
relative fair market values on the issue date. The Company will use that
allocation to determine the issue price of the Notes and the holder's tax basis
in the Warrants. Although the Company's allocation is not binding on the IRS, a
holder of a Unit must use the Company's allocation unless the holder discloses
on its federal income tax return for the year in which the Unit was acquired
that it plans to use an allocation that is inconsistent with the Company's
allocation.
 
THE NOTES
 
    Holders of the Notes will be required to include payments of "qualified
stated interest" (as defined below) received thereon in taxable income in
accordance with their respective methods of accounting for federal income tax
purposes. In addition, the Notes will be issued with "original issue discount"
for federal income tax purposes. A holder generally is required to include
original issue discount in gross income as it accrues, regardless of the
holder's method of accounting for federal income tax purposes. Accordingly, each
holder will be required to include amounts in gross income without regard to
when the cash or other payments to which such income is attributable are
received.
 
    The amount of original issue discount with respect to each Note is an amount
equal to the excess of the "stated redemption price at maturity" of such Note
over its issue price. The stated redemption price at maturity of each Note will
include all cash payments other than "qualified stated interest" payments,
 
                                      122
<PAGE>
including principal and interest, required to be made thereunder until maturity.
Stated interest on the Notes will be treated as qualified stated interest. The
issue price of a Note will be equal to that portion of the issue price of the
Unit allocable to the Note as described above. It is expected that each Note
will be issued with a substantial amount of original issue discount.
 
    TAXATION OF ORIGINAL ISSUE DISCOUNT.  Each holder of a Note will be required
to include in gross income for federal income tax purposes an amount equal to
the sum of the "daily portions" of the original issue discount of the Note for
all days during each taxable year in which the holder holds the Note. The daily
portions of original issue discount will be determined on a constant interest
rate basis by allocating to each day in an accrual period a pro rata portion of
the original issue discount thereon that is attributable to the accrual period
in which such day is included. The amount of the original issue discount
attributable to each full accrual period will be the product of the "adjusted
issue price" of the Note at the beginning of such accrual period and the "yield
to maturity" of the Note (adjusted to reflect the length of the accrual period).
The adjusted issue price of a Note at the beginning of an accrual period is the
original issue price of the Note plus the aggregate amount of original issue
discount that has accrued in all prior accrual periods, less any cash payments
on the Note other than qualified stated interest on or before the first day of
such accrual period. The yield to maturity is the discount rate that, when used
in computing the present value of all principal and interest payments to be made
on the Note, produces an amount equal to the issue price. Under these rules,
holders will have to include increasingly greater amounts of original issue
discount in each successive accrual period. Each payment made under a Note
(except for payments of qualified stated interest) will be treated first as a
payment of original issue discount (which was previously includable in income)
to the extent of original issue discount that has accrued as of the date of
payment and has not been allocated to prior payments and second as a payment of
principal (which is not includable in income).
 
    The accrual period generally is the six-month period ending on the day in
each calendar year corresponding to the day before the maturity date of the Note
or the date six months before such date. The initial accrual period of a note is
the short period beginning on the issue date and ending on the day before the
first day of the first full accrual period. The amount of original issue
discount attributable to an initial short accrual period may be computed under
any reasonable method.
 
    The Company is required to furnish certain information to the IRS, and will
furnish annually to record holders of a Note, information with respect to
original issue discount accruing during the calendar year. That information will
be based upon the adjusted issue price of the Note as if the holder were the
original holder of the Note.
 
    A holder who purchases a Note for an amount other than the adjusted issue
price and/or on a date other than the end of an accrual period will be required
to determine for himself the amount of original issue discount, if any, he is
required to include in gross income for federal income tax purposes.
 
    OPTIONAL REDEMPTION.  Under the original issue discount Regulations, the
Company will be presumed to exercise its option to redeem the Notes if, by
utilizing the date of exercise of the call option as the maturity date and the
Redemption Price as the stated redemption price at maturity, the yield on the
Notes would be lower than such yield would be if the option were not exercised.
See "Description of Notes--Optional Redemption."
 
    If the Company's option to redeem the Notes were presumed exercised on a
given date (the "Presumed Exercise Date"), the Notes would bear original issue
discount in an amount equal to the amount for which the Notes could be redeemed
(the "Redemption Amount") over their issue price. For purposes of calculating
the current inclusion of such discount, the yield on the Notes would be computed
on their issue date by treating the Presumed Exercise Date as the maturity date
of the Notes and the Redemption Amount as their stated redemption price at
maturity. If the Company's option to redeem the Notes were presumed exercised
but were not exercised in fact on the Presumed Exercise Date, the Notes would be
treated, for certain purposes, as if the option were exercised and new debt
instruments were issued on the Presumed Exercise Date for an amount of cash
equal to the Redemption
 
                                      123
<PAGE>
Amount. In such case, it appears that any payment of stated interest due under
the Notes after the Presumed Exercise Date would constitute qualified stated
interest (rather than original issue discount) and would be taxable as ordinary
interest income at the time such interest was accrued or was received, in
accordance with such holder's regular method of accounting for tax purposes.
 
    SALE OR RETIREMENT OF A NOTE.  In general, a holder of a Note will recognize
gain or loss upon the sale, retirement, redemption or other taxable disposition
of such Note in an amount equal to the difference between (a) the amount of cash
and the fair market value of other property received in exchange therefor (other
than amounts attributable to accrued but unpaid stated interest) and (b) the
holder's adjusted tax basis in such Note.
 
    A holder's tax basis in a Note generally will be equal to the price paid for
such Note, increased by the amount of original issue discount, if any,
includable in gross income prior to the date of disposition, and decreased by
the amount of any payment on such Note other than qualified stated interest
prior to disposition.
 
    Any gain or loss recognized on the sale, retirement, redemption or other
taxable disposition of a Note generally will be capital gain or loss. Such
capital gain or loss generally will be long-term capital gain or loss if the
Note has been held by the holder for more than one year and otherwise will be a
short term capital gain or loss.
 
    Holders should be aware that the resale of the Note may be effected by the
"Market Discount" rules of the Code under which a subsequent Purchaser of a Note
acquiring the Note at a market discount generally would be required to include
as ordinary income a portion of the gain realized upon the disposition or
retirement of such Note, to the extent of the market discount that has accrued
while the debt instrument was held by such holder.
 
THE WARRANTS
 
    Upon the sale, exchange or other taxable disposition of a Warrant (including
the receipt of cash in lieu of a fractional interest in a Warrant Share upon
exercise of a Warrant), a holder will recognize gain or loss for federal income
tax purposes in an amount equal to the difference between the amount of cash
plus the fair market value of property received therefor and the holder's
adjusted tax basis in the Warrant. A holder's initial tax basis in a Warrant
acquired in the Unit Offering will be that portion of the issue price of the
Units allocable to the Warrant, as described above, subject to adjustment in the
events described below. Such gain or loss will be capital gain or loss if the
Warrant Shares to which the Warrants relate would be a capital asset in the
hands of the Warrant holder. Any such capital gain or loss will be long-term
capital gain or loss if the Warrant was held for more than one year at the time
of the sale or exchange and otherwise will be a short term capital gain or loss.
 
    Notwithstanding the above, it is possible that a redemption of a Warrant by
the Company would not be treated as a sale or exchange of a capital asset. In
that event, the holder of a Warrant could recognize ordinary income or loss on
such redemption.
 
    The exercise of a Warrant for cash will not result in a taxable event to the
holder of the Warrant (except to the extent of cash, if any, received in lieu of
fractional interest in a Warrant Share). Upon such exercise, the holder's
adjusted tax basis in the Warrant Shares obtained will be equal to the sum of
such holder's adjusted tax basis in the Warrant (described above) and the
exercise price of the Warrant; the holder's holding period with respect to such
Warrant Shares will commence on the day after the date of exercise. The holder
will generally realize capital gain or loss on the sale or exchange of a Warrant
Share if the Warrant Share is a capital asset in the hands of the holder, and
such capital gain or loss will be long-term if the Warrant Share was held for
more than one year. If a Warrant expires without being exercised, the holder
will recognize a loss in an amount equal to its tax basis in the Warrant. Such
loss will be a capital loss if the Warrant Shares to which the Warrants relate
would have been a capital asset in the hands of the Warrant holder, and such
capital loss will be a long-term capital loss is the Warrant was held for more
than one year at the time of the lapse.
 
                                      124
<PAGE>
    It is possible that the Warrants may be deemed to have been exercised for
tax purposes on the date on which they first become exercisable or possibly on
the date issued, regardless of whether they are actually exercised on the date
on which they are first exercisable. As a result, it is possible that the
holding period of a Warrant Share may be deemed to have begun on the date on
which the Warrants first become exercisable or possibly on the date issued, and
that a holder may have a long-term capital gain or loss upon a sale or exchange
of a Warrant Share more than one year after that date.
 
    Adjustments to the conversion ratio of the Warrants, or the failure to make
adjustments, may in certain circumstances result in the receipt of taxable
constructive dividends by the holder resulting in ordinary income (subject to
possible dividends received deduction in the case of corporate holders) to the
extent of the Company's current and accumulated earnings and profits. In such
event the holder's tax basis in the Warrants would be increased by an amount
equal to the constructive dividend.
 
BACKUP WITHHOLDING
 
    A holder of a Note may be subject to backup withholding at a rate of 31%
with respect to interest and original issue discount on, and gross proceeds upon
sale or retirement of, a Note unless such holder (i) is a corporation or other
exempt recipient and, when required, demonstrates that fact, or (ii) provides a
correct taxpayer identification number, certifies under penalty of perjury, when
required, that the taxpayer identification number provided is the holder's
correct number and that such holder is not subject to backup withholding, and
otherwise complies with applicable requirements of the backup withholding rules.
Backup withholding is not an additional tax; any amounts so withheld are
creditable against the holder's federal income tax, provided the required
information is provided to the IRS. Holders of the Notes should consult their
tax advisors as to their qualification for exemption from backup withholding and
the procedure for obtaining such an exemption.
 
APPLICABLE HIGH-YIELD DISCOUNT OBLIGATIONS
 
    It is expected that the Notes will be considered to have "significant
original issue discount" and that the yield of the Notes will be at least five
percentage points above the applicable federal rate. As a result, it is expected
that the Company will not be able to deduct for tax purposes any original issue
discount accruing with respect thereto. A corporate holder may be entitled to
treat the original issue discount that is not deductible as a dividend to the
extent of the earnings and profits of the Company, which may then qualify for
the dividends received deduction. If the disqualified portion exceeds the
Company's current and accumulated earnings and profits, the excess will continue
to be taxed as ordinary original issue discount income in accordance with the
rules described above. Corporate holders should consult their tax advisers
concerning the availability of the dividends received deduction.
 
                                      125
<PAGE>
                                  UNDERWRITING
 
    Subject to the terms and conditions set forth in a purchase agreement (the
"Purchase Agreement"), among the Company and Merrill Lynch, Pierce, Fenner &
Smith Incorporated ("Merrill Lynch") and CIBC Wood Gundy Securities Corp. ("CIBC
Wood Gundy" and, collectively with Merrill Lynch, the "Underwriters"), the
Company has agreed to sell to the Underwriters, and each Underwriter has agreed
to purchase from the Company, severally but not jointly, the number of Units set
forth opposite its name below. The Purchase Agreement provides that, subject to
the terms and conditions set forth therein, the Underwriters will be obligated
to purchase all of the Units if any such Units are purchased.
 
<TABLE>
<CAPTION>
                                                                    NUMBER
              UNDERWRITER                                          OF UNITS
                                                                   ---------
<S>                                                                <C>
Merrill Lynch, Pierce, Fenner & Smith
           Incorporated..........................................     74,250
CIBC Wood Gundy Securities Corp..................................     60,750
                                                                   ---------
           Total.................................................    135,000
                                                                   ---------
                                                                   ---------
</TABLE>
 
    The several Underwriters propose to offer the Units directly to the public
at the offering price set forth on the cover page of this Prospectus, and in
part to certain selected dealers at such price less a concession not in excess
of .25% per Unit. The several Underwriters may allow, and such dealers may
reallow, a discount not in excess of .125% per Unit to certain other dealers.
After the Offering, the public offering price, concession and discount may be
changed.
 
    Merrill Lynch acted as an underwriter in the Common Stock Offering for which
Merrill Lynch received customary compensation. The Company has granted to
Merrill Lynch a right of first refusal with respect to the performance of
certain investment banking services for which Merrill Lynch will receive
customary compensation. The Company also has engaged CIBC Wood Gundy to provide
certain investment banking services for which CIBC Wood Gundy will receive
customary compensation. In addition, in connection with the CIBC Financing
Commitment, (i) CIBC Wood Gundy received a $1.25 million structuring/placement
fee and (ii) CIBC WG Argosy Merchant Fund 2, LLC, an affiliate of CIBC Wood
Gundy (the "Merchant Fund"), committed to purchase $20.0 million of Senior
Secured Notes, if issued, and consequently received warrants to purchase 120,104
shares of Common Stock and a commitment fee of $200,000 in connection therewith.
If the Senior Secured Notes are issued, (i) CIBC Wood Gundy will receive an
additional $1.25 million installment of its structuring/placement fee and (ii)
the Merchant Fund will receive an additional $200,000 installment of its
commitment fee. In the event that the Senior Secured Notes are issued, the
Merchant Fund would, under certain circumstances, be entitled to receive
additional warrants to purchase Common Stock. See "Description of Certain
Indebtedness -- CIBC Financing Commitment." On February 3, 1997, the Merchant
Fund agreed to shorten the term of the CIBC Warrants held by it to five years.
 
    The Merchant Fund has agreed not to sell, transfer, assign, pledge or
hypothecate any of the CIBC Warrants held by it or the Common Stock for which
such CIBC Warrants may be exercised for a period of one year following the date
hereof, other than by operation of law or by reason of reorganization of the
Company. Notwithstanding the foregoing, (i) the Merchant Fund may transfer any
CIBC Warrants held by it to any NASD member participating in the Offering (and
the bona fide officers or partners thereof) and (ii) the Merchant Fund may
exercise such CIBC Warrants so long as the shares of Common Stock received upon
such exercise remain subject to the foregoing restrictions for the remainder of
the initially applicable time period.
 
    There is currently no public market for the Units, the Notes or the
Warrants, and the Company does not intend to apply for listing of the Units, the
Notes or the Warrants on any securities exchange or on any inter-dealer
quotation system. The Common Stock has been approved for quotation on the Nasdaq
National Market. The Company has been advised by the Underwriters that,
following the completion of the initial public offering of the Notes, the
Underwriters presently intend to make a market in the Units, the Notes and the
Warrants as permitted by applicable laws and regulations; however, they are not
obligated to do so and any such market-making may be discontinued at any time
without notice at the sole discretion of each Underwriter. Accordingly, there
can be no assurance as to
 
                                      126
<PAGE>
whether an active public market for the Units, the Notes or the Warrants will
develop or, if a public market does develop, as to the liquidity of the trading
market for the Units, the Notes or the Warrants. If an active public market does
not develop, the market price and liquidity for the Units, the Notes or the
Warrants may be adversely affected. See "Risk Factors -- Absence of Public
Market; Possible Volatility of Stock Price."
 
    The Company has agreed to indemnify the Underwriters against certain
liabilities, including liabilities under the Securities Act of 1933, as amended
(the "Securities Act"), and, under certain circumstances, to contribute to
payments the Underwriters may be required to make in respect thereof.
 
    The Company has agreed that it will not, for a period of 180 days from the
date of this Prospectus, without the prior written consent of the Underwriters,
directly or indirectly, offer, sell, grant any option to purchase or otherwise
dispose of, any debt security of the Company which is publicly offered or sold
pursuant to Rule 144A under the Securities Act.
 
                                 LEGAL MATTERS
 
    The validity of the Units, the Notes and the Warrants offered hereby will be
passed upon for the Company by Hahn & Hessen LLP, New York, New York. Certain
legal matters in connection with the Offering will be passed upon for the
Underwriters by Latham & Watkins, Washington, D.C. As of the date of this
Prospectus, a member of Hahn & Hessen LLP beneficially owns 8,618 shares of
Common Stock (including 2,000 shares issuable upon exercise of March Bridge
Warrants). Latham & Watkins, Washington, D.C., currently represents the Company
with respect to certain FCC matters.
 
                                    EXPERTS
 
    The balance sheets as of December 31, 1995 and 1994 and the statements of
operations, stockholders' equity (deficit) and cash flows for the years ended
December 31, 1995 and 1994 and for the period from August 23, 1993 (date of
inception) to December 31, 1993 included in this Prospectus, have been included
herein in reliance on the report of Coopers & Lybrand L.L.P., independent
accountants, given on the authority of that firm as experts in accounting and
auditing.
 
                             AVAILABLE INFORMATION
 
    The Company has filed with the Commission a registration statement on Form
S-1 (together with all amendments, exhibits, schedules and supplements thereto,
the "Registration Statement") under the Securities Act with respect to the
securities offered hereby. This Prospectus, which forms a part of the
Registration Statement, does not contain all of the information set forth in the
Registration Statement, certain parts of which have been omitted in accordance
with the rules and regulations of the Commission. For further information with
respect to the Company and the securities offered hereby, reference is made to
the Registration Statement and to the schedules and exhibits filed therewith.
Statements contained in this Prospectus as to the contents of certain documents
are not necessarily complete, and, in each instance, reference is made to the
copy of the document filed as an exhibit to the Registration Statement. The
Registration Statement, including the exhibits and schedules thereto, can be
inspected and copied at the public reference facilities maintained by the
Commission at Room 1024, Judiciary Plaza, 450 Fifth Street, N.W., Washington,
D.C. 20549, and at the following regional offices of the Commission: New York
Regional Office, 7 World Trade Center, New York, New York 10007; and Chicago
Regional Office, Suite 1400, Northwestern Atrium Center, 500 West Madison
Street, Chicago, Illinois 60661. Copies of such material can also be obtained
from the Commission at prescribed rates through its Public Reference Section at
450 Fifth Street, N.W., Washington, D.C. 20549. The Commission also maintains a
site on the World Wide Web at http://www.sec.gov that contains reports, proxy
and information statements and other information that registrants file with the
Commission.
 
                                      127
<PAGE>
    The Company is subject to the informational requirements of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and in accordance
therewith is required to file reports and other information with the Commission.
Such reports may be inspected and copied at the public reference facilities at
the addresses set forth above and at the Public Reference Section of the
Commission at the address set forth above. In addition, the Indenture and the
Warrant Agreement provide that the Company, to the extent that it is not
required to file such information pursuant to the Exchange Act, shall provide
the Trustee and holders of the Notes and Warrants with audited year-end
financial statements of the Company prepared in accordance with GAAP and
unaudited quarterly financial statements of the Company prepared in accordance
with GAAP.
 
               SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
 
    Certain statements contained in this Prospectus, including, without
limitation, statements containing the words "believes," "anticipates," "expects"
and words of similar import, constitute "forward-looking statements" within the
meaning of the Private Securities Litigation Reform Act of 1995. Such
forward-looking statements involve known and unknown risks, uncertainties and
other factors that may cause the actual results, performance or achievements of
the Company, or industry results, to be materially different from any future
results, performance or achievements expressed or implied by such
forward-looking statements. Such factors include, among others, the following:
the limited nature of the Company's operations and its history of net losses;
the uncertain acceptance of 38 GHz services; competition; the risk of the
Company's failure to consummate the CommcoCCC Acquisition; existing government
regulations and changes in, or the failure to comply with, government
regulations; the risk of loss, non-renewal or fluctuation in value of the
Company's FCC licenses; the ability of the Company to sustain, manage or
forecast its growth; technological limitations with respect to 38 GHz
technology; dependence on significant suppliers and marketers and the potential
loss thereof; the availability of additional 38 GHz bandwidth; the changing
nature of wireless broadband services and the telecommunications industry; the
ability to attract and retain qualified personnel; the Company's significant
capital requirements and need for additional financing; the Company's leverage
and ability to service its indebtedness; ownership of Common Stock; the use of
proceeds of the Offering; retention of earnings (if any); and other factors
referenced in this Prospectus. Certain of these factors are discussed in more
detail elsewhere in this Prospectus, including, without limitation, under the
captions "Risk Factors," "Use of Proceeds," "Price Range of Common Stock and
Dividend Policy," "Capitalization," "Selected Historical and Pro Forma Financial
Data," "Management's Discussion and Analysis of Financial Condition and Results
of Operations," "Business" and "Principal Stockholders." GIVEN THESE
UNCERTAINTIES, PROSPECTIVE INVESTORS ARE CAUTIONED NOT TO PLACE UNDUE RELIANCE
ON SUCH FORWARD-LOOKING STATEMENTS. The Company disclaims any obligation to
update any such factors or to publicly announce the result of any revisions to
any of the forward-looking statements contained or incorporated by reference
herein to reflect future events or developments.
 
                                      128
<PAGE>
                                    GLOSSARY
 
    38 GHZ -- The fourteen 100 MHz channels between 38.6 GHz and 40.0 GHz and
the frequency between 37.0 and 38.5 GHz allocated by the FCC for wireless
broadband transmissions.
 
    10-13 BIT ERROR RATE -- The measurement of a transmission path's ability to
pass data in an uncorrupted format. Bit error rate ("BER") is defined as the
number of erroneous bits ("errors"), divided by the number of bits over a
stipulated period of time. In the example of a BER of 10-13, a BER tester (a
test and measurement instrument), placed in line to measure the transmission
path (in real time) would have to measure, and analyze, ten trillion bits of
data before it detected one bit of erroneous data.
 
    ACCESS CHARGES -- The fees paid by long distance carriers to LECs for
originating and terminating long distance calls on their local networks.
 
    BANDWIDTH -- At any given level of compression, the amount of information
transportable over a link per unit of time. A DS-1, or Digital Service 1,
circuit will carry up to 1,544,000 bits (or 1.544 megabits) per second.
 
    BIT -- A bit is the basic unit of information, yes-or-no, on-or-off, 1-or-0
in the binary (base 2) system which is the basis of digital computing. In
contrast, a voice telephone signal over a copper wire is analog, reflecting a
continuous range of vocal tone (frequency) and volume (amplitude).
 
    BROADBAND -- Data streams of at least 1.544 megabits per second. Broadband
communications systems can transmit large quantities of voice, data and video by
way of digital or analog signals. Examples of broadband communication systems
include DS-3 systems, which can transmit 672 simultaneous voice conversations,
or a broadcast television station signal that transmits high resolution audio
and video signals into the home. Broadband connectivity is an essential element
for interactive multimedia applications.
 
    BTA (BASIC TRADING AREA) -- An area erected by Rand McNally based upon
various business demographics to establish a contiguous urban area, without
reference to political or similar boundaries. The FCC has proposed to use BTAs
to auction 38 GHz authorizations.
 
    CAP (COMPETITIVE ACCESS PROVIDER) -- A company that provides its customers
with an alternative to the local telephone company for local and interstate
transport of private line, special access and switched access telecommunications
services. CAPs are also referred to in the industry as competitive local
exchange carriers (CLECs), alternative local telecommunications service
providers (ALTs) and metropolitan area network providers (MANs) and were
formerly referred to as alternative access vendors (AAVs).
 
    CELLULAR -- Characterized by "cells," the area accessible by transceiver(s)
typically located at one site. A cellular phone connects to the transceiver in
its current cell, then the connection is handed-off as and when the user moves
to any other cell.
 
    COMPRESSION -- Any process that transforms a signal to a more compact form
(fewer bits) for easier transfer, and then restores the signal after transfer.
 
    CLEC (COMPETITIVE LOCAL EXCHANGE CARRIER) -- A company that provides local
exchange services in competition with the incumbent local exchange carrier.
 
    COPPER WIRE -- A shorthand reference to traditional telephone lines using
electric current to carry signals over copper wire.
 
    DIGITAL -- A method of storing, processing and transmitting information
through the use of distinct electronic or optical pulses that represent the
binary code digits 0 and 1. Digital transmission and switching technologies
employ a sequence of these pulses to represent information as opposed to the
 
                                      129
<PAGE>
continuously variable analog signal. Digital transmission and switching
technologies offer a threefold improvement in speed and capacity over analog
techniques, allowing much more efficient and cost-effective transmission of
voice, video, and data.
 
    DIALING PARITY -- Dialing parity is one of the changes, intended to level
the competitive playing field, that is required by the Telecommunication Act.
Dialing parity when implemented will enable customers to dial only 1+ or 0+ for
service no matter which local or long distance carrier they choose.
 
    DS-0, DS-1, DS-3 -- Standard telecommunications industry digital signal
formats, which are distinguishable by bit rate (the number of binary digits (0
and 1) transmitted per second). DS-0 service has a bit rate of 64 kilobits per
second. DS-1 service has a bit rate of 1.544 megabits per second and DS-3
service has a bit rate of 45 megabits per second.
 
    FCC -- Federal Communications Commission.
 
    FIBER OPTICS -- Fiber optic cable largely immune to electrical interference
and environmental factors that affect copper wiring and satellite transmission.
Fiber optic technology involves sending laser light pulses across glass strands
in order to transmit digital information.
 
    GHZ (GIGAHERTZ) -- Billions of cycles or hertz per second.
 
    HERTZ -- Cycles per second. A Hertz is one full cycle (an s-shaped sine
curve with one peak and one valley).
 
    INTER-LATA LONG DISTANCE -- Inter-LATA long distance calls are calls that
pass from one LATA to another. Typically, these calls are simply referred to as
"long distance" calls although intra-LATA calls can also be long distance calls.
 
    INTERNET -- An array of interconnected networks using a common set of
protocols defining the information coding and processing requirements that can
communicate across hardware platforms and over many links now operated by a
consortium of telecommunications service providers and others.
 
    ISP -- Internet service provider.
 
    IXC (INTER-EXCHANGE CARRIERS) -- Usually referred to as long distance
providers. There are many facilities-based IXCs, including AT&T, MCI, WorldCom,
Sprint and Frontier.
 
    KILOBIT -- One thousand bits of information. The information-carrying
capacity (i.e., bandwidth) of a circuit may be measured in "kilobits per
second."
 
    KBPS -- Kilobits per second.
 
    LANS (LOCAL AREA NETWORKS) -- The interconnection of computers for the
purpose of sharing files, programs and various devices such as work stations,
printers and high-speed modems. LANs may include dedicated computers or file
servers that provide a centralized source of shared files and programs. Most
office computer networks use a LAN to share files, printers, modems and other
items. Where computers are separated by greater distances, a Metropolitan Area
Net (MAN) or other Wide Area Net (WAN) may be used.
 
    LAST MILE -- A shorthand reference to the last section of a
telecommunications path to the ultimate end user which may be less than or
greater than a mile.
 
    LATAS (LOCAL ACCESS AND TRANSPORT AREAS) -- The geographically defined areas
in which RBOCs were authorized by the MFJ to provide local exchange services.
These LATAs roughly reflect the population density of their respective states
(California has 11 LATAs while Wyoming has only one). There are 164 LATAs in the
United States. LATAs have one or more area codes and may cross state lines.
 
    LEC (LOCAL EXCHANGE CARRIER) -- A company providing local exchange services.
The traditional local telephone companies (also known as incumbent local
exchange carriers), such as the RBOCs, which until recently were monopolies.
 
                                      130
<PAGE>
    LINE OF SIGHT -- An unobstructed view between two transceivers.
 
    LINK -- A transmission link between two transceivers.
 
    MAN -- Metropolitan Area Network.
 
    MARKET -- The potential and actual customers within the boundaries of a
wireless license. For simplicity, the definition of the market in this
Prospectus has been based on Basic Trading Areas, though each application as
granted defines its own actual boundaries.
 
    MEGABIT -- One million bits of information. The information-carrying
capacity (i.e., bandwidth) of a circuit may be measured in "megabits per
second."
 
    MFJ (MODIFIED FINAL JUDGMENT) -- The MFJ was a settlement of an antitrust
suit reached made in 1982 between AT&T and the Department of Justice which
forced the breakup of the old Bell System. This judgment, also known as the
Divestiture of AT&T, established seven separate RBOCs and enhanced the
establishment of two distinct segments of telecommunications service: local and
long distance. This laid the groundwork for intense competition in the long
distance industry. The MFJ has been superseded by the Telecommunications Act of
1996.
 
    MICROWAVE -- A portion of the radio spectrum having radio waves that are
physically very short, ranging in length between about 30 cm and 0.3 cm and
generally used to refer to frequencies above 2 GHz.
 
    MILLIMETRIC MICROWAVE OR MILLIMETER WAVE -- Those portions of the microwave
radio spectrum having wave lengths measured in millimeter lengths and generally
used to refer to frequencies above 20 GHz.  A shorter wave length means a higher
frequency and vice versa.
 
    MHZ (MEGAHERTZ) -- Millions of cycles or hertz per second.
 
    MBPS -- Megabits per second.
 
    NPRM (NOTICE OF PROPOSED RULEMAKING) -- A term used in governmental,
principally FCC, rulemaking proceedings to refer to initiation of the process.
 
    NUMBER PORTABILITY -- The ability of an end user to change local exchange or
long distance carriers while retaining the same telephone number. If number
portability does not exist, customers will have to change phone numbers when
they change carriers.
 
    OC-3 RADIOS -- A transmission protocol most often deployed on fiber optic
SONET networks that operates at 155 megabits per second when provisioned using
electronic rather than optical media referred to as STS-3.
 
    PCS (PERSONAL COMMUNICATIONS SERVICES) -- Cellular-like services provided at
the 2 GHz band of the radio spectrum rather than 800 MHz. A type of wireless
telephone system that uses light, inexpensive handheld sets and communicates via
low power antennas.
 
    POPS (POINTS OF PRESENCE) -- Locations where a carrier has installed
transmission equipment in a service area that serves as, or relays calls to, a
network switching center of that carrier.
 
    RBOCS (REGIONAL BELL OPERATING COMPANIES) -- The holding companies owning
LEC affiliates of the old AT&T or Bell system.
 
    REPEATER -- An intermediate transceiver between two transceivers each of
which is connected to end users and established to circumvent obstacles in the
line of sight between communication ports, such as buildings in urban areas and
hills in rural areas.
 
    RESELLERS -- Companies which purchase telecommunications services wholesale
from underlying carriers and resell them to end users at retail rates.
 
    ROOF RIGHTS -- The legal right to locate, maintain and operate equipment
(most commonly antennas and transceivers) on the roofs of buildings, on special
towers or even on utility poles or pylons.
 
                                      131
<PAGE>
    SONET (SYNCHRONOUS OPTICAL NETWORK) -- A set of standards for optical
communications transmission systems that define the optical rates and formats,
signal characteristics, performance, management and maintenance information to
be embedded within the signals and the multiplexing techniques to be employed in
optical communications transmission systems. SONET facilitates the
interoperability of dissimilar vendors equipment. SONET benefits business
customers by minimizing the equipment necessary for various telecommunications
applications and supports networking diagnostic and maintenance features.
 
                                      132
<PAGE>
                          ADVANCED RADIO TELCOM CORP.
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                                                              PAGE
                                                                                                            ---------
 
<S>                                                                                                         <C>
 Unaudited Pro Forma:
    Unaudited Pro Forma Condensed Consolidated Balance Sheet as of September 30, 1996.....................        F-3
    Unaudited Pro Forma Condensed Consolidated Statements of Operations for the nine months ended
     September 30, 1996 and for the year ended December 31, 1995..........................................        F-4
    Notes to Unaudited Pro Forma Condensed Consolidated Financial Statements..............................        F-5
 
  Historical:
    Report of Independent Accountants.....................................................................        F-8
    Balance Sheets as of December 31, 1995 and 1994.......................................................        F-9
    Statements of Operations for the years ended December 31, 1995 and 1994 and for the period from August
     23, 1993 (date of inception) to December 31, 1993....................................................       F-10
    Statements of Stockholders' Equity (Deficit) for the years ended December 31, 1995 and 1994 and for
     the period from August 23, 1993 (date of inception) to December 31, 1993.............................       F-11
    Statements of Cash Flows for the years ended December 31, 1995 and 1994 and for the period from August
     23, 1993 (date of inception) to December 31, 1993....................................................       F-13
    Notes to the Financial Statements.....................................................................       F-14
    Unaudited Condensed Consolidated Balance Sheets as of September 30, 1996 and 1995.....................       F-28
    Unaudited Condensed Consolidated Statements of Operations for the nine months ended September 30, 1996
     and 1995 and for the three months ended September 30, 1996 and 1995..................................       F-29
    Unaudited Condensed Consolidated Statements of Stockholders' Deficit for the nine months ended
     September 30, 1996...................................................................................       F-30
    Unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 1996
     and 1995.............................................................................................       F-31
    Notes to Unaudited Condensed Consolidated Financial Statements........................................       F-32
</TABLE>
 
                                      F-1
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
        UNAUDITED PRO FORMA CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
 
    The following unaudited pro forma condensed consolidated financial
statements are presented for the following transactions: (i) the sale by the
Company of an aggregate of 2,300,500 shares of Common Stock offered in the
November 1996 Common Stock Offering at a price of $15.00 per share, after
deducting underwriting discount and expenses of approximately $5,600,000; (ii)
the conversion of the serial preferred stock into shares of Common Stock in
November 1996; (iii) fees and expenses of approximately $6,400,000 related to
the receipt of the CIBC Financing Commitment of $50 million, including the
issuance of CIBC Warrants to purchase 300,257 shares of Common Stock in November
1996, which financing commitment is assumed to be replaced by the issuance of
the Notes in the Offering; (iv) the October 1996 receipt of the remaining
$1,550,000 (out of a total of $4,000,000) in cash proceeds from the September
Bridge Financing; (v) the application of the net proceeds from the Common Stock
Offering to repay the March Bridge Notes, the CommcoCCC Notes and the September
Bridge Notes and to pay an initial $3,000,000 (out of a total of $6,000,000) to
acquire the 50% ownership interest of ART West held by Extended; (vi) the
exercise of the Ameritech Warrant to purchase an aggregate of 318,374 shares of
Common Stock in December 1996; (vii) the sale by the Company of 135,000 Units
(consisting of Notes and Warrants) offered in the Offering assuming $135,000,000
in gross proceeds, after deducting the estimated underwriting discount and
offering expenses and the cash used for the purchase of Pledged Securities;
(viii) the payment of the remaining $3,000,000 in the acquisition of the 50%
ownership interest of ART West held by Extended and (ix) the consummation of the
acquisition by the Company of the CommcoCCC Assets in exchange for 6,000,000
shares of Common Stock at an assumed value of $10.75 per share.
 
    All such transactions are reflected as if they had occurred as of the
beginning of the respective periods for the unaudited pro forma condensed
consolidated statements of operations and at the balance sheet date for the
unaudited pro forma condensed consolidated balance sheet.
 
    These unaudited pro forma condensed consolidated financial statements were
derived from and should be read in conjunction with the audited financial
statements and the related notes thereto, and the unaudited condensed
consolidated financial statements of the Company and the related notes thereto,
included elsewhere herein. In management's opinion, all adjustments necessary to
reflect the foregoing and related transactions have been made.
 
    The unaudited pro forma condensed consolidated financial statements are not
necessarily indicative of what the actual financial position or results of
operations would have been assuming that the transactions described in the
preceding paragraphs had occurred on the dates indicated, nor does it purport to
represent the future financial position or results of operations of the Company.
 
                                      F-2
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
            UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET
 
<TABLE>
<CAPTION>
                                                                         AS OF SEPTEMBER 30, 1996
                                                            ---------------------------------------------------
<S>                                                         <C>              <C>               <C>
                                                                                PRO FORMA
                                                            HISTORICAL (A)   ADJUSTMENTS (B)      PRO FORMA
                                                            ---------------  ----------------  ----------------
                                                    ASSETS
Current assets:
  Cash and cash equivalents...............................  $       752,368  $     30,789,438(1) $
                                                                                    1,550,000(3)       87,633,151
                                                                                  (12,000,000 (4)
                                                                                   (6,000,000 (5)
                                                                                   (3,000,000 (7)
                                                                                   (1,883,655 (8)
                                                                                   77,425,000(9)
  Accounts receivable.....................................           78,645
                                                                                                         78,645
  Other current assets....................................          140,227
                                                                                                        140,227
                                                            ---------------  ----------------  ----------------
    Total current assets..................................          971,240        86,880,783        87,852,023
Restricted cash...........................................        1,000,000        51,600,000(9)       52,600,000
Property and equipment, net...............................       11,019,217
                                                                                                     11,019,217
Equity investment.........................................          285,000          (285,000 (5)        --
FCC licenses, net.........................................        4,276,780         6,285,000(5)       99,991,780
                                                                                   89,430,000(7)
Deferred financing costs, net.............................        2,343,087        (1,907,528 (1)
                                                                                    5,975,000(9)        6,410,559
Deposits..................................................          463,036
                                                                                                        463,036
Other assets..............................................          183,637
                                                                                                        183,637
                                                            ---------------  ----------------  ----------------
                                                            $    20,541,997  $    237,978,255  $    258,520,252
                                                            ---------------  ----------------  ----------------
                                                            ---------------  ----------------  ----------------
                                LIABILITIES AND STOCKHOLDERS' EQUITY (DEFICIT)
Current liabilities:
  Accounts payable and accrued liabilities................  $    11,154,608  $                 $     11,154,608
  March Bridge Notes......................................        4,243,784        (4,243,784 (4)        --
  CommcoCCC Notes.........................................        2,827,836        (2,827,836 (4)        --
  September Bridge Notes..................................        2,203,559         1,384,918(3)
                                                                                   (3,588,477 (4)        --
  Current portion of long-term debt.......................        1,242,126
                                                                                                      1,242,126
                                                            ---------------  ----------------  ----------------
    Total current liabilities.............................       21,671,913        (9,275,179)       12,396,734
Note payable to EMI, net of current portion...............          937,500
                                                                                                        937,500
Equipment financing note payable, net of current
 portion..................................................          927,796
                                                                                                        927,796
Senior Notes, net of discount.............................        --              105,661,273(9)      105,661,273
Deferred tax liability....................................        --               21,930,000(7)       21,930,000
                                                            ---------------  ----------------  ----------------
    Total liabilities.....................................       23,537,209       118,316,094       141,853,303
                                                            ---------------  ----------------  ----------------
Stockholders' equity (deficit):
  Serial preferred stock, $.001 par.......................              921              (921 (2)        --
  Common Stock, $.001 par.................................            6,587             2,301(1)           19,560
                                                                                        4,354(2)
                                                                                          318(6)
                                                                                        6,000(7)
  Additional paid-in capital..............................       20,745,714        28,879,609(1)      148,123,229
                                                                                       (3,433 (2)
                                                                                      165,082(3)
                                                                                         (318 (6)
                                                                                   64,494,000(7)
                                                                                    4,503,848(8)
                                                                                   29,338,727(9)
  Accumulated deficit.....................................      (23,748,434)       (1,339,903 (4)      (31,475,840)
                                                                                   (6,387,503 (8)
                                                            ---------------  ----------------  ----------------
    Total stockholders' equity (deficit)..................       (2,995,212)      119,662,161       116,666,949
                                                            ---------------  ----------------  ----------------
                                                            $    20,541,997  $    237,978,255  $    258,520,252
                                                            ---------------  ----------------  ----------------
                                                            ---------------  ----------------  ----------------
</TABLE>
 
    See the accompanying notes to unaudited pro forma condensed consolidated
                             financial statements.
 
                                      F-3
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
      UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
<TABLE>
<CAPTION>
                                                                 NINE MONTHS ENDED SEPTEMBER 30, 1996
                                                           -------------------------------------------------
                                                                               PRO FORMA
                                                           HISTORICAL (A)   ADJUSTMENTS (B)     PRO FORMA
                                                           ---------------  ---------------  ---------------
<S>                                                        <C>              <C>              <C>
 
Service revenue..........................................  $       125,013   $               $       125,013
                                                           ---------------  ---------------  ---------------
Operating expenses:
  Selling, general and administrative (D)................       16,942,052                        16,942,052
  Market development (E).................................        1,053,000                         1,053,000
  Research and development...............................          666,406                           666,406
  Depreciation and amortization..........................          504,462       1,794,656 (11       2,299,118
                                                           ---------------  ---------------  ---------------
                                                                19,165,920       1,794,656        20,960,576
                                                           ---------------  ---------------  ---------------
Other:
  Interest expense.......................................        1,396,943        (811,483)(4)
                                                                                19,604,626 (10      20,190,086
  Financing expense......................................        --              6,387,503(8)       6,387,503
  Interest income........................................          (59,473)     (2,070,450) 10)      (2,129,923)
                                                           ---------------  ---------------  ---------------
                                                                 1,337,470      23,110,196        24,447,666
                                                           ---------------  ---------------  ---------------
      Pretax loss........................................       20,378,377      24,904,852        45,283,229
Deferred tax benefit.....................................        --               (570,116) 11)        (570,116)
                                                           ---------------  ---------------  ---------------
      Net loss...........................................  $    20,378,377   $  24,334,736   $    44,713,113
                                                           ---------------  ---------------  ---------------
                                                           ---------------  ---------------  ---------------
Pro forma net loss per share of Common Stock (C).........  $          2.15                   $          2.43
                                                           ---------------                   ---------------
                                                           ---------------                   ---------------
Pro forma weighted average number of shares of Common
 Stock outstanding (C)                                           9,470,545                        18,404,379
                                                           ---------------                   ---------------
                                                           ---------------                   ---------------
 
<CAPTION>
 
                                                                     YEAR ENDED DECEMBER 31, 1995
                                                           -------------------------------------------------
                                                                               PRO FORMA
                                                           HISTORICAL (A)   ADJUSTMENTS (B)     PRO FORMA
                                                           ---------------  ---------------  ---------------
<S>                                                        <C>              <C>              <C>
Service revenue..........................................  $         5,793   $               $         5,793
                                                           ---------------  ---------------  ---------------
Operating expenses:
  Selling, general and administrative (D)................        2,911,273                         2,911,273
  Market development.....................................          191,693                           191,693
  Depreciation and amortization..........................           15,684       2,392,875 (11       2,408,559
                                                           ---------------  ---------------  ---------------
                                                                 3,118,650       2,392,875         5,511,525
                                                           ---------------  ---------------  ---------------
Other:
  Interest expense.......................................          131,540      26,139,500 (10      26,271,040
  Financing expense......................................        --              6,387,503(8)       6,387,503
  Interest income........................................           (9,554)     (2,760,600) 10)      (2,770,154)
                                                           ---------------  ---------------  ---------------
                                                                   121,986      29,766,403        29,888,389
                                                           ---------------  ---------------  ---------------
      Pretax loss........................................        3,234,843      32,159,278        35,394,121
Deferred tax benefit.....................................        --               (760,155) 11)        (760,155)
                                                           ---------------  ---------------  ---------------
      Net loss...........................................  $     3,234,843   $  31,399,123   $    34,633,966
                                                           ---------------  ---------------  ---------------
                                                           ---------------  ---------------  ---------------
Pro forma net loss per share
 of Common Stock (C).....................................  $          0.30                   $          1.75
                                                           ---------------                   ---------------
                                                           ---------------                   ---------------
Pro forma weighted average number of shares of Common
 Stock outstanding (C)...................................       10,912,338                        19,846,172
                                                           ---------------                   ---------------
                                                           ---------------                   ---------------
</TABLE>
 
    See the accompanying notes to unaudited pro forma condensed consolidated
                             financial statements.
 
                                      F-4
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
              NOTES TO UNAUDITED PRO FORMA CONDENSED CONSOLIDATED
                              FINANCIAL STATEMENTS
 
(A) Represents the historical consolidated balance sheet of the Company as of
    September 30, 1996 and the consolidated statements of operations of the
    Company for the year ended December 31, 1995 and the nine months ended
    September 30, 1996.
 
(B) Pro forma adjustments:
 
    (1)Issuance of 2,300,500 shares of Common Stock offered in the November 1996
       Common Stock Offering based on the initial public offering price of
       $15.00 per share, after deducting the estimated Underwriting discount and
       related expenses of approximately $5,600,000.
 
    (2)The November 1996 conversion of the serial preferred stock into shares of
       Common Stock in connection with the Common Stock Offering.
 
    (3)The receipt of the remaining $1,550,000 in October 1996 (out of a total
       of $4,000,000) in cash from the September Bridge Financing in exchange
       for the September Bridge Notes and September Bridge Warrants. The value
       ascribed to the September Bridge Warrants issued after September 30, 1996
       was $165,082 (out of a total of $426,019).
 
    (4)Repayment in November 1996 of the March Bridge Notes, the CommcoCCC Notes
       and the September Bridge Notes out of the net proceeds from the Common
       Stock Offering and the reversal of the related interest expense. The
       unamortized offering discount and deferred financing costs associated
       with the March Bridge Financing, the CommcoCCC Financing and the
       September Bridge Financing will result in an extraordinary loss of
       approximately $1,340,000, which has been excluded from the pro forma
       condensed consolidated statements of operations.
 
    (5)The acquisition of the 50% ownership interest of ART West held by
       Extended for $6,000,000 in cash of which $3,000,000 has been paid in
       November 1996.
 
    (6)The exercise by Ameritech of its Warrant to purchase 318,374 shares of
       Common Stock.
 
    (7)The acquisition of the CommcoCCC Assets, accounted for as a business
       combination, in exchange for 6,000,000 shares of Common Stock based on an
       assumed value of $10.75 per share, the recognition of the related
       deferred tax liabilities and the estimated payment of related expenses of
       $3,000,000 of which $600,000 was paid in December 1996.
 
    (8)The fees and expenses related to the receipt of a commitment from certain
       investors to borrow up to $50,000,000 of 12.5% Senior Secured Notes due
       1998 (the "Senior Secured Notes") pursuant to financing arranged by CIBC
       Wood Gundy Securities Corp. (the "CIBC Financing Commitment") which is
       assumed to be replaced by the issuance of the Notes in the Offering. The
       Company incurred approximately $1,900,000 in fees and issued warrants to
       purchase 300,258 shares of Common Stock (representing 1.5% of the
       outstanding shares of Common Stock of the Company on a fully diluted
       basis after giving effect to the Common Stock Offering and the CommcoCCC
       Acquisition) for a nominal amount. The value ascribed to the Initial CIBC
       Warrants was $4,503,848. Assumes no draw down under the CIBC Financing
       Commitment.
 
    (9)Assumed gross proceeds of $135,000,000 from the issuance of the 135,000
       Units (consisting of Notes and Warrants) in the Offering, the related
       estimated underwriting discount and related expenses of approximately
       $5,975,000 and the cash used for the purchase of Pledged Securities of
       approximately $51,600,000. The value ascribed to the Unit Warrants
       totaled approximately $29,300,000 based on an assumed issuance of
       Warrants to purchase an aggregate of
 
                                      F-5
<PAGE>
       2,731,725 shares of Common Stock of the Company (representing
       approximately 12.0% of the Common Stock outstanding on a fully diluted
       basis after giving effect to the Common Stock Offering, the Offering and
       the CommcoCCC Acquisition).
 
    (10)
       Interest expense on the Notes, at an assumed coupon rate of 14.0%
       (resulting in an effective interest rate of 18.92% on the Notes,
       including the amortization of debt issuance costs and original issue
       discount representing the value ascribed to the Warrants) as if the Notes
       were issued as of the beginning of the respective periods. If the
       interest rate on the Notes changed by 0.5%, interest expense would change
       by approximately $675,000 and $506,250 for the year ended December 31,
       1995 and for the nine months ended September 30, 1996, respectively.
       Interest income of $2,070,450 for the nine months ended September 30,
       1996 and $2,760,600 for the year ended December 31, 1995 on the Pledged
       Securities at an assumed rate of 5.35%.
 
    (11)
       Depreciation and amortization expense related to the acquisition of the
       CommcoCCC Assets and the 50% ownership interest in ART West and the
       related deferred taxes.
 
(C) Pro forma net loss per share and the weighted average number of shares of
    Common Stock reflect (i) the conversion of the serial preferred stock to
    Common Stock; (ii) the issuance of potentially dilutive instruments issued
    within one year prior to the Common Stock Offering at exercise prices below
    the initial public offering price of $15.00 per share; (iii) the issuance of
    2,300,500 shares of Common Stock in the Common Stock Offering; (iv) the
    exercise of the Ameritech Warrant to purchase 318,374 shares of Common
    Stock; and (v) the issuance of shares of Common Stock in connection with the
    acquisition of the CommcoCCC Assets.
 
<TABLE>
<CAPTION>
                                                 As of            As of
                                             December 31,     September 30,
                                                 1995             1996
                                            ---------------  ---------------
 
<S>                                         <C>              <C>
  Weighted average number of shares of
   Common Stock outstanding for primary
   computation............................      5,946,338(1)     6,580,627(1)
  Issuances of shares of serial preferred
   stock assumed converted into shares of
   Common Stock...........................      3,720,253(2)     2,480,169(2)
  Options and warrants issued and
   outstanding............................        605,195(2)       403,463(2)
  Issuance of Common Stock ...............        640,552(3)         6,286(3)
                                            ---------------  ---------------
  Historical pro forma weighted average
   number of shares of Common Stock.......     10,912,338(2)     9,470,545(2)
  Common Stock issued in the Common Stock
   Offering...............................      2,300,500        2,300,500
  Common Stock issued in connection with
   the conversion of the serial preferred
   stock and the exercise of the Ameritech
   Warrant................................        633,334(4)       633,334(4)
  Common Stock issued in connection with
   the acquisition of the CommcoCCC
   Assets.................................      6,000,000        6,000,000
                                            ---------------  ---------------
  Pro Forma weighted average number of
   shares of Common Stock.................     19,846,172       18,404,379
                                            ---------------  ---------------
                                            ---------------  ---------------
</TABLE>
 
                                      F-6
<PAGE>
 
<TABLE>
<S>        <C>
           ------------------------
           (1) The weighted average number of shares of Common Stock for primary computation
           exclude all common stock equivalents, which are anti-dilutive.
           (2) The Securities and Exchange Commission requires that potentially dilutive
           instruments issued within one year prior to the Common Stock Offering at exercise
               prices below the initial public offering price be treated as outstanding for the
               entire periods presented in the Common Stock Offering prospectus. The pro forma
               weighted average number of shares of Common Stock on a historical basis reflects
               those potentially dilutive instruments based on the initial public offering price
               of $15 per share in the Common Stock Offering. In measuring the dilutive effect,
               the treasury stock method was used.
           (3) Represents the issuance of Common Stock at prices below the initial public
           offering price of $15 per share in the Common Stock Offering, presented as if such
               shares were outstanding for the entire periods presented in the Common Stock
               Offering prospectus to reflect potentially dilutive instruments.
           (4) Included as potentially dilutive instruments in item (2) are the shares of Common
           Stock issued in connection with the conversion of the preferred stock and the exercise
               of the Ameritech Warrant. The additional shares of Common Stock are an adjustment
               to the weighted average number of shares to eliminate the effect of the treasury
               stock method for the conversion of the serial preferred stock and the exercise of
               the Ameritech Warrant.
</TABLE>
 
(D) General and administrative expense includes non-recurring, non-cash
    compensation expense of $802,002 and $6,795,514 for the year ended December
    31, 1995 and for the nine months ended September 30, 1996, respectively,
    associated with the release of Escrow Shares in 1995 and the termination of
    the Escrow Shares arrangement in 1996.
 
(E) Market development expense for the nine months ended September 30, 1996
    represents the value ascribed to the Ameritech Strategic Distribution
    Agreement in connection with the February 1996 investment in the Company by
    Ameritech.
 
                                      F-7
<PAGE>
                       REPORT OF INDEPENDENT ACCOUNTANTS
 
To the Board of Directors and Stockholders of
Advanced Radio Telecom Corp.:
 
    We have audited the accompanying balance sheets of Advanced Radio Telecom
Corp. as of December 31, 1995 and 1994, and the related statements of
operations, stockholders' equity (deficit) and cash flows for the years ended
December 31, 1995 and 1994 and for the period from August 23, 1993 (date of
inception) to December 31, 1993. These financial statements are the
responsibility of the Company's management. Our responsibility is to express an
opinion on these financial statements based on our audits.
 
    We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
    In our opinion, the financial statements referred to above present fairly,
in all material respects, the financial position of Advanced Radio Telecom Corp.
as of December 31, 1995 and 1994, and the results of its operations and its cash
flows for the years ended December 31, 1995 and 1994 and for the period from
August 23, 1993 (date of inception) to December 31, 1993, in conformity with
generally accepted accounting principles.
                                          COOPERS & LYBRAND L.L.P.
 
New York, New York
April 26, 1996, except for Note 5B as to which the date is
  June 26, 1996, except for the second paragraph of Note 2A,
  Note 2C and the second paragraph of Note 11A as to which the date is
  October 11, 1996 and except for the fourth paragraph of Note 1A and Note 1C
  as to which the date is November 12, 1996.
 
                                      F-8
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                            BALANCE SHEETS (NOTE 1A)
                           DECEMBER 31, 1995 AND 1994
 
<TABLE>
<CAPTION>
                                                                                           1995           1994
                                                                                      --------------  ------------
<S>                                                                                   <C>             <C>
                                               ASSETS
 
Current assets:
  Cash and cash equivalents.........................................................  $      633,654  $      5,133
  Other current assets..............................................................          52,325
                                                                                      --------------  ------------
      Total current assets..........................................................         685,979         5,133
Property and equipment, net.........................................................       3,581,561         3,448
Equity investment...................................................................         285,000
FCC licenses........................................................................       4,235,734
Deferred financing costs, net.......................................................         778,897
Deposits............................................................................         284,012
Other assets........................................................................          25,376        34,030
                                                                                      --------------  ------------
      Total assets..................................................................  $    9,876,559  $     42,611
                                                                                      --------------  ------------
                                                                                      --------------  ------------
 
                                      LIABILITIES AND STOCKHOLDERS' DEFICIT
Current liabilities:
  Accounts payable and accrued liabilities..........................................  $    3,694,489  $     11,689
  Note payable to related party.....................................................                        70,000
                                                                                      --------------  ------------
      Total current liabilities.....................................................       3,694,489        81,689
Convertible notes payable...........................................................       4,950,000
Note payable to EMI.................................................................       1,500,000
                                                                                      --------------  ------------
      Total liabilities.............................................................      10,144,489        81,689
                                                                                      --------------  ------------
Redeemable preferred stock, $.01 par value, 1 share issued and outstanding at
 December 31, 1995..................................................................          44,930
                                                                                      --------------  ------------
Commitments and contingencies
Stockholders' deficit:
  Serial preferred stock, $.001 par value, 488,492 shares issued and outstanding at
   December 31, 1995................................................................             488
  Common Stock, $.001 par value, 6,529,975 and 2,141,830 shares issued and
   outstanding......................................................................           6,530         2,142
  Additional paid-in capital........................................................       3,050,179        93,994
  Accumulated deficit...............................................................      (3,370,057)     (135,214)
                                                                                      --------------  ------------
      Total stockholders' deficit...................................................        (312,860)      (39,078)
                                                                                      --------------  ------------
        Total liabilities and stockholders' deficit.................................  $    9,876,559  $     42,611
                                                                                      --------------  ------------
                                                                                      --------------  ------------
</TABLE>
 
    The accompanying notes are an integral part of the financial statements.
 
                                      F-9
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                       STATEMENTS OF OPERATIONS (NOTE 1A)
                 FOR THE YEARS ENDED DECEMBER 31, 1995 AND 1994
          AND FOR THE PERIOD FROM AUGUST 23, 1993 (DATE OF INCEPTION)
                              TO DECEMBER 31, 1993
 
<TABLE>
<CAPTION>
                                                                                                     PERIOD FROM
                                                                                                     AUGUST 23,
                                                                               YEARS ENDED            (DATE OF
                                                                               DECEMBER 31,         INCEPTION) TO
                                                                        --------------------------  DECEMBER 31,
                                                                            1995          1994          1993
                                                                        -------------  -----------  -------------
<S>                                                                     <C>            <C>          <C>
Service revenue.......................................................  $       5,793  $              $
Consulting revenue....................................................                     137,489
                                                                        -------------  -----------  -------------
      Total revenue...................................................          5,793      137,489
                                                                        -------------  -----------  -------------
General and administrative expenses...................................      2,911,273      253,453        5,906
Market development expenses...........................................        191,693
Depreciation and amortization.........................................         15,684        8,281          688
                                                                        -------------  -----------  -------------
      Total operating expenses........................................      3,118,650      261,734        6,594
                                                                        -------------  -----------  -------------
Interest income.......................................................          9,554
Interest expense......................................................        131,540        4,375
                                                                        -------------  -----------  -------------
      Interest expense, net...........................................        121,986        4,375
                                                                        -------------  -----------  -------------
      Net loss........................................................  $   3,234,843  $   128,620    $   6,594
                                                                        -------------  -----------  -------------
                                                                        -------------  -----------  -------------
Pro forma net loss per share of Common Stock..........................  $        0.30
                                                                        -------------
                                                                        -------------
Pro forma weighted average number of shares of Common Stock
 outstanding..........................................................     10,912,338
                                                                        -------------
                                                                        -------------
</TABLE>
 
    The accompanying notes are an integral part of the financial statements.
 
                                      F-10
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
             STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) (NOTE 1A)
                 FOR THE YEARS ENDED DECEMBER 31, 1995 AND 1994
          AND FOR THE PERIOD FROM AUGUST 23, 1993 (DATE OF INCEPTION)
                              TO DECEMBER 31, 1993
 
<TABLE>
<CAPTION>
                                                                                           PREFERRED STOCK
                                                          COMMON     -----------------------------------------------------------
                                                           STOCK     SERIES A    SERIES B     SERIES C     SERIES D      TOTAL
                                                        -----------  ---------  -----------  -----------  -----------  ---------
 
<S>                                                     <C>          <C>        <C>          <C>          <C>          <C>
SHARES
Net issuance of Common Stock for cash.................    1,070,915
                                                        -----------
Balance, December 31, 1993............................    1,070,915
Issuance of Common Stock for cash.....................    1,070,915
                                                        -----------
Balance, December 31, 1994............................    2,141,830
Issuance of Common Stock to ART West..................       26,773
Issuance of Common Stock to existing shareholders.....    1,472,508
Issuance of Common Stock to Landover and affiliates
 for cash.............................................    3,120,000
Issuance of preferred stock to limited partnerships
 affiliated with Landover for cash:
  Series A............................................                 332,091                                           332,091
  Series B............................................                              82,318                                82,318
  Series C............................................                                            5,402                    5,402
Issuance of Series D preferred stock for cash.........                                                        61,640      61,640
Shares issued to reflect anti-dilution................       62,655      2,852       4,189                                 7,041
Redemption of Common Stock from Landover..............     (293,791)
                                                        -----------  ---------  -----------       -----   -----------  ---------
Balance, December 31, 1995............................    6,529,975    334,943      86,507        5,402       61,640     488,492
                                                        -----------  ---------  -----------       -----   -----------  ---------
                                                        -----------  ---------  -----------       -----   -----------  ---------
</TABLE>
 
                                   Continued
 
                                      F-11
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
       STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) (NOTE 1A), CONTINUED
                 FOR THE YEARS ENDED DECEMBER 31, 1995 AND 1994
          AND FOR THE PERIOD FROM AUGUST 23, 1993 (DATE OF INCEPTION)
                              TO DECEMBER 31, 1993
<TABLE>
<CAPTION>
                                                                     PAR VALUE
                                 ----------------------------------------------------------------------------------
                                                                         PREFERRED STOCK                             ADDITIONAL
                                   COMMON     ---------------------------------------------------------------------    PAID-IN
                                    STOCK      SERIES A      SERIES B       SERIES C       SERIES D        TOTAL       CAPITAL
                                 -----------  -----------  -------------  -------------  -------------     -----     -----------
<S>                              <C>          <C>          <C>            <C>            <C>            <C>          <C>
 
AMOUNTS
Net issuance of Common Stock
 for cash......................   $   1,071                                                                          $    60,065
Net loss.......................
                                 -----------                                                                         -----------
Balance, December 31, 1993.....       1,071                                                                               60,065
Issuance of Common Stock for
 cash..........................       1,071                                                                               33,929
Net loss.......................
                                 -----------                                                                         -----------
Balance, December 31, 1994.....       2,142                                                                               93,994
Issuance of Common Stock to ART
 West..........................          27                                                                               24,973
Issuance of Common Stock to
 existing shareholders.........       1,472                                                                               (1,472)
Conversion of note payable and
 interest to paid-in capital...                                                                                           75,250
Issuance of Common Stock to
 Landover and affiliates for
 cash..........................       3,120                                                                               (2,100)
Issuance of preferred stock to
 limited partnerships
 affiliated with Landover for
 cash:
  Series A.....................                $     332                                                 $     332     1,006,268
  Series B.....................                              $      82                                          82       880,618
  Series C.....................                                             $       5                            5       112,695
Issuance of Series D preferred
 stock for cash................                                                            $      62            62     1,999,938
Shares issued to reflect anti-
 dilution......................          63            3             4                                           7           (70)
Serial preferred stock issuance
 costs.........................                                                                                         (229,814)
Redemption of Common Stock from
 Landover......................        (294)                                                                          (1,999,706)
Increase in additional paid-in
 capital as a result of the
 release of escrow shares......                                                                                          802,002
Accrued stock option
 compensation..................                                                                                          287,603
Net loss.......................
                                                                                   --
                                 -----------       -----           ---                           ---         -----   -----------
Balance, December 31, 1995.....   $   6,530    $     335     $      86      $       5      $      62     $     488   $ 3,050,179
                                                                                   --
                                                                                   --
                                 -----------       -----           ---                           ---         -----   -----------
                                 -----------       -----           ---                           ---         -----   -----------
 
<CAPTION>
 
                                  ACCUMULATED
                                    DEFICIT        TOTAL
                                 -------------  -----------
<S>                              <C>            <C>
AMOUNTS
Net issuance of Common Stock
 for cash......................   $             $    61,136
Net loss.......................        (6,594)       (6,594)
                                 -------------  -----------
Balance, December 31, 1993.....        (6,594)       54,542
Issuance of Common Stock for
 cash..........................                      35,000
Net loss.......................      (128,620)     (128,620)
                                 -------------  -----------
Balance, December 31, 1994.....      (135,214)      (39,078)
Issuance of Common Stock to ART
 West..........................                      25,000
Issuance of Common Stock to
 existing shareholders.........
Conversion of note payable and
 interest to paid-in capital...                      75,250
Issuance of Common Stock to
 Landover and affiliates for
 cash..........................                       1,020
Issuance of preferred stock to
 limited partnerships
 affiliated with Landover for
 cash:
  Series A.....................                   1,006,600
  Series B.....................                     880,700
  Series C.....................                     112,700
Issuance of Series D preferred
 stock for cash................                   2,000,000
Shares issued to reflect anti-
 dilution......................
Serial preferred stock issuance
 costs.........................                    (229,814)
Redemption of Common Stock from
 Landover......................                  (2,000,000)
Increase in additional paid-in
 capital as a result of the
 release of escrow shares......                     802,002
Accrued stock option
 compensation..................                     287,603
Net loss.......................    (3,234,843)   (3,234,843)
 
                                 -------------  -----------
Balance, December 31, 1995.....   $(3,370,057)  $  (312,860)
 
                                 -------------  -----------
                                 -------------  -----------
</TABLE>
 
    The accompanying notes are an integral part of the financial statements.
 
                                      F-12
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                       STATEMENTS OF CASH FLOWS (NOTE 1A)
                 FOR THE YEARS ENDED DECEMBER 31, 1995 AND 1994
          AND FOR THE PERIOD FROM AUGUST 23, 1993 (DATE OF INCEPTION)
                              TO DECEMBER 31, 1993
 
<TABLE>
<CAPTION>
                                                                                                   PERIOD FROM
                                                                                                 AUGUST 23, 1993
                                                                          YEARS ENDED                (DATE OF
                                                                          DECEMBER 31,              INCEPTION)
                                                                  ----------------------------   TO DECEMBER 31,
                                                                       1995           1994             1993
                                                                  --------------  ------------  ------------------
<S>                                                               <C>             <C>           <C>
Cash flows from operating activities:
  Net loss......................................................  $   (3,234,843) $   (128,620)    $     (6,594)
  Adjustments to reconcile net loss to net cash provided by
    (used in) operating activities:
  Noncash interest expense......................................         110,828
  Depreciation and amortization.................................          15,684         8,281              688
  Non-cash compensation expense.................................       1,089,605
  Changes in operating assets and liabilities:
    Accounts payable and accrued liabilities....................         563,351        (8,282)          19,971
    Other current assets........................................         (52,325)
    Deposits....................................................          (4,012)
                                                                  --------------  ------------         --------
        Net cash provided by (used in) operating activities.....      (1,511,712)     (128,621)          14,065
                                                                  --------------  ------------         --------
Cash flows from investing activities:
  Additions to property and equipment...........................        (621,364)       (5,175)
  Investment in ART West........................................        (255,000)
  Acquisition of EMI licenses and property and equipment........      (3,023,971)
  Acquisition of FCC licenses...................................         (13,912)
  Deposits on equipment.........................................        (280,000)
  Increase in other assets......................................                                        (41,272)
                                                                  --------------  ------------         --------
        Net cash used in investing activities...................      (4,194,247)       (5,175)         (41,272)
                                                                  --------------  ------------         --------
Cash flows from financing activities:
  Proceeds from issuance of Common Stock........................           1,020        35,000           61,136
  Proceeds from loan and note payable...........................           8,500        70,000
  Proceeds from issuance of preferred stock.....................       4,050,000
  Advances from Landover and affiliates.........................         175,000
  Proceeds from convertible notes payable.......................       4,950,000
  Redemption of Common Stock....................................      (2,000,000)
  Stock issuance costs..........................................        (213,884)
  Repayment on loan.............................................          (8,500)
  Additions to deferred financing costs.........................        (452,656)
  Payments on advances from Landover and affiliates.............        (175,000)
                                                                  --------------  ------------         --------
        Net cash provided by financing activities...............       6,334,480       105,000           61,136
                                                                  --------------  ------------         --------
        Net increase (decrease) in cash.........................         628,521       (28,796)          33,929
Cash, beginning of period.......................................           5,133        33,929
                                                                  --------------  ------------         --------
Cash, end of period.............................................  $      633,654  $      5,133     $     33,929
                                                                  --------------  ------------         --------
                                                                  --------------  ------------         --------
Supplemental cash flow information:
  Non-cash financing and investing activities:
    Additions to property and equipment.........................  $    2,666,630
    Issuance of promissory note payable to EMI..................  $    1,500,000
    Additional paid-in capital as a result of the release of
      escrow shares.............................................  $      802,002
    Accrued stock issuance costs................................  $       21,000
    Accrued deferred financing costs............................  $      370,617
    Issuance of stock and contribution of licenses to ART
      West......................................................  $       30,000
    Conversion of note payable and interest to Common Stock.....  $       75,250
</TABLE>
 
    The accompanying notes are an integral part of the financial statements.
 
                                      F-13
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                         NOTES TO FINANCIAL STATEMENTS
 
1.  FORMATION OF THE COMPANY AND BASIS OF PRESENTATION:
 
A -- THE COMPANY
 
    Advanced Radio Telecom Corp. ("ART" and, collectively with ART Licensing
Corp., the "Company"), formerly named Advanced Radio Technologies Corporation,
was organized as a Delaware corporation on August 23, 1993 to develop, market
and provide broadband wireless digital telecommunication and information
services throughout the United States. The Company's business objective is to
organize and finance local operating facilities, establish strategic alliances
with other businesses, acquire new wireless telecommunications technologies, and
market broadband wireless services to telecommunications service providers and
end users.
 
    During 1995 the Company established a strategic alliance with Extended
Communications, Inc. ("Extended") to form the ART West joint venture. ART West
was formed on April 4, 1995 to develop and expand the Company's wireless digital
telecommunications services in various markets throughout the western United
States (see Note 5).
 
    ART Licensing Corp. ("Telecom"), formerly named Advanced Radio Telecom Corp.
and Advanced Radio Technology Ltd., was organized by ART and Landover Holdings
Corporation ("Landover") on March 28, 1995, with one of its initial objectives
to acquire certain 38 GHz licenses in the northeastern United States from EMI
Communications, Corp. ("EMI") (see Note 6). Under the terms of a purchase
agreement between ART, Landover, and Telecom dated April 21, 1995, (the
"Purchase Agreement") Landover was obligated to purchase $7,000,000 of
securities of Telecom. Pursuant to the Purchase Agreement and a stockholders'
agreement between ART, Telecom and their respective shareholders dated May 8,
1995 (the "Stockholders' Agreement"), ART and Telecom were to merge once
approval from the Federal Communications Commission ("FCC") had been granted
(see Note 2).
 
    On October 11, 1996, ART, Telecom and a wholly owned subsidiary of ART
("Merger Sub") entered into a revised merger agreement (see Note 2), which
provided for the merger of Merger Sub into Telecom (the "Merger"). The Merger
was completed on October 28, 1996 and Telecom, through the Merger, became a
wholly owned subsidiary of ART. The Merger was accounted for in a manner
consistent with a reorganization of entities under common control which is
similar to that of a pooling of interests and the financial statements of prior
periods have been restated. All transactions and balances between ART and
Telecom have been eliminated.
 
B -- INITIAL CAPITALIZATION
 
    ART was formed on August 23, 1993 by two of its executives (the "Founding
Stockholders") by issuing 1,070,915 shares of Common Stock in exchange for
$1,136. During November 1993, ART redeemed 428,366 shares of Common Stock from
the Founding Stockholders and through a private placement issued 428,366 shares
of Common Stock to High Sky Limited Partnership ("High Sky") in exchange for
$60,000. During March 1994, High Sky II Limited Partnership ("High Sky II"), an
affiliate of High Sky (collectively referred to as the "High Sky Partnerships")
contributed $100,000 to ART in exchange for 214,183 shares of Common Stock and a
$70,000 Promissory Note. In connection with the High Sky II financing, ART
issued an additional aggregate of 856,732 shares to the Founding Stockholders
and High Sky whereby the Founding Stockholders and the High Sky Partnerships
would each own a 50% interest in ART. Additionally, during 1994, one of the
Founding Stockholders contributed an additional $5,000 for which contribution
there were no shares issued.
 
    Pursuant to an agreement dated March 1, 1995, High Sky II agreed to assign
the $70,000 Promissory Note, plus accrued interest, to the Founding Stockholders
in exchange for two new Promissory Notes executed by the Founding Stockholders.
Concurrent with the exchange of the promissory notes, the Founding Stockholders
contributed the $70,000 Promissory Note plus accrued interest of $5,250 to ART,
for which contribution there were no additional shares issued.
 
                                      F-14
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
1.  FORMATION OF THE COMPANY AND BASIS OF PRESENTATION, CONTINUED:
C -- BASIS OF PRESENTATION
 
    The financial statements have been prepared on the going concern basis of
accounting, which contemplates realization of assets and liquidation of
liabilities in the ordinary course of business. The Company has a substantial
working capital deficit, has incurred operating losses since inception and does
not expect to recognize material operating revenues until the further
development of its commercial services, which commenced in fiscal 1996. The
Company estimates that revenues in 1996 and 1997 will not be sufficient to fund
its operating expenses, capital expenditures and other working capital needs,
including consulting, service and purchase commitments set forth in Notes 5, 9,
10, 14 and 16. The Company's continued funding of its operating expenses,
capital expenditures, working capital needs and contractual commitments is
dependent upon its ability to raise financing. During November 1996, the Company
completed an initial public offering of equity securities, raising $34,500,000
before expenses. In connection with the initial public offering, the Company
obtained a commitment from certain investors to borrow up to $50,000,000 (the
"CIBC Financing Commitment"). The proceeds from the initial public offering were
used to repay certain indebtedness and partially fund the acquisition of the
remaining 50% interest in ART West. Management believes that, based upon its
current business plans, the funds received from the initial public offering and
available under the CIBC Financing Commitment are sufficient to enable the
Company to fund its operations at least through December 31, 1997. As a result,
the previous reference to the existence of substantial doubt regarding the
Company's ability to continue as a going concern is no longer required.
 
2.  PURCHASE AGREEMENT:
 
A -- INITIAL CAPITALIZATION OF TELECOM
 
    Pursuant to the Purchase Agreement, as its initial capitalization, an
aggregate of 3,120,000 shares of Class B and Class A common stock were issued by
Telecom to Landover and consultants to Landover, respectively, for an aggregate
cash consideration of $1,020. Such shares of Class B and Class A common stock
represented 64% and 2%, respectively, of the total number of shares of capital
stock of Telecom then outstanding. Concurrently, ART received 1,607,273 shares
of Class A common stock, representing 34% of the total number of shares of
capital stock of Telecom then outstanding in exchange for $340.
 
    On February 2, 1996 and October 11, 1996, the Board of Directors of Telecom
authorized a 13 for 1 stock split and a 1 for 2.75 reverse stock split,
respectively. All of the references to shares of common stock of Telecom have
been adjusted to reflect the 13 for 1 stock split and the 1 for 2.75 reverse
stock split but are prior to the issuance of anti-dilutive shares described
below.
 
    Under the Purchase Agreement, Landover agreed to invest or cause to be
invested $7,000,000 in ART, Telecom and their affiliates (the "Landover Funding
Commitment"). In consideration for this $7,000,000 investment, Telecom agreed to
issue preferred stock, the number of shares of which would be designated by
Landover. Under the anti-dilution provisions of the Class A common stock, in
respect of each such preferred stock issuance, Telecom agreed to issue, for no
consideration, additional shares of Class A common stock in number necessary to
maintain the 36% ownership interest in Telecom of the holders of Class A common
stock.
 
    Under the Purchase Agreement, the individual shareholders of ART were
required to place 1,874,101 shares of Common Stock in escrow (the "Escrow
Shares") to be released upon the completion of the then pending EMI Asset
acquisition (see Note 6), Telecom's attainment of specific operating income
levels for the years 1997 through 1999 and the acquisition of interests in a
specified number of FCC license authorizations by April 30, 2000. As a result of
the consummation of the EMI Asset acquisition, in November 1995, 681,102 of the
Escrow Shares were released. The fair value of the Escrow Shares released in
1995, amounting to $802,002, has been recognized as additional paid-in
 
                                      F-15
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
2.  PURCHASE AGREEMENT, CONTINUED:
capital. Pursuant to the February 2, 1996 reorganization, the Escrow Shares
arrangement was terminated and all of the remaining Escrow Shares were released
to the stockholders of ART. The fair value of the remaining Escrow Shares
released, in the amount of approximately $6.8 million, will be accounted for in
the same manner during 1996.
 
B -- MERGER
 
    Under the terms of the Purchase Agreement, ART and Telecom agreed to operate
both companies as a single enterprise and were committed to merge if and when
permitted by the FCC. Concurrent with the Purchase Agreement, ART and Telecom
entered into an exclusive 20-year services agreement (the "Services Agreement")
for the construction, development and operation of systems in the Company's
markets.
 
    On February 2, 1996, ART, Telecom and their respective shareholders agreed
to an amendment and restatement of the Stockholders' Agreement providing for (i)
termination effective on the closing of a public share offering, (ii) amendment
and restatement of the Certificate of Incorporation and reorganization of the
capital structure of Telecom; (iii) the exchange of the convertible notes
payable and one share of redeemable preferred stock for shares of serial
preferred stock of Telecom; (iv) revision of provisions for election of
directors; (v) amendment and restatement of ART's registration rights
agreements; (vi) release of shares escrowed in connection with the original
Stockholders' Agreement; and (vii) approval of a definitive merger agreement.
 
C -- AMENDED MERGER
 
    The definitive merger agreement, as entered into on February 2, 1996 and
subsequently restated and amended on June 26, 1996 and October 11, 1996, (the
"Merger Agreement") provided for the merger of Merger Sub into Telecom subject
to certain conditions, including the receipt of FCC approval. Prior to the
Merger, each outstanding share of each series of Telecom's serial preferred
stock was converted into a share of a similar series of the Company's preferred
stock. Upon completion of the initial public offering, all shares of all series
of the Company's preferred stock (920,951) automatically convert into 4,353,587
shares of the Company's common stock. In the Merger, each outstanding share of
common stock of Telecom was exchanged for an equal number of shares of Common
Stock of ART. As a result, Telecom became a wholly owned subsidiary of ART. The
Merger Agreement also provided for the assignment of Telecom's interests in all
of its agreements, including the various services agreements, employment
agreements, equipment purchase agreements and purchase option agreements, to
ART. Further, the holders of warrants to purchase an aggregate of 924,413 shares
of Telecom common stock are entitled to purchase an equivalent number of shares
of ART's Common Stock. Employee stock options to purchase 816,970 shares of
Telecom's common stock were replaced by stock options to purchase an equal
number of shares of Common Stock of ART. The terms of the warrants and stock
options are similar except that the exercise price of the warrants and options,
and the number of shares subject thereto, have been adjusted on a proportional
basis to reflect the 1 for 2.75 reverse stock split.
 
3.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES:
 
A -- DEVELOPMENT STAGE ENTERPRISE
 
    Prior to July 1, 1996, the Company was considered a development stage
enterprise as defined in Statement of Financial Accounting Standards No. 7,
"Accounting and Reporting by Development Stage Enterprises." During the three
months ended September 30, 1996, the Company perfected substantially all of its
licenses and commenced commercial operations. Accordingly, the Company is no
longer considered to be in the development stage. Such change in classification
of the Company had no impact on the net loss or stockholders' equity (deficit)
for any periods presented.
 
                                      F-16
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
3.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, CONTINUED:
B -- CASH AND CASH EQUIVALENTS
 
    The Company considers all highly liquid investments purchased with remaining
maturities of three months or less to be cash equivalents.
 
C -- PROPERTY AND EQUIPMENT
 
    Property and equipment is stated at cost. Depreciation and amortization are
computed using the straight-line method over the estimated useful lives of the
related assets as follows: wireless transmission equipment -- 5 years; office
furniture equipment -- 3 years.
 
D -- EQUITY INVESTMENT
 
    The Company accounts for its 50% interest in the ART West joint venture
under the equity method.
 
E -- FCC LICENSES
 
    The Company has obtained radio spectrum rights under FCC issued
authorizations and licenses throughout the United States by petitioning the FCC
directly and through the purchase of such rights held by others. Such licenses
are issued for an initial term of six years and are renewable subject to review
by the FCC. The costs associated with the acquisition of such licenses are
capitalized and amortized on a straight-line basis over a 40-year period
beginning upon commencement of operations in the related market. The 40-year
period is based upon management's license renewal expectations.
 
F -- RECOVERABILITY OF LONG-LIVED ASSETS
 
    The recoverability of property and equipment and capitalized FCC
authorizations and licenses is dependent upon the successful development of
systems in each of the respective markets, or through sale of such assets.
Management estimates that it will recover the carrying amount of those costs
from cash flow generated by the systems once they have been developed. However,
it is reasonably possible that such estimate will change in the near term as a
result of the failure to develop the FCC authorizations on a timely basis, or
technological, regulatory or other changes.
 
    The Company's policy is to assess annually any impairment in value based
upon a comparison of projected operating cash flows from each market over its
expected period of operation, on an undiscounted basis, to the carrying amount
of the property and equipment, licenses and other capitalized costs related to
the market.
 
G -- FINANCING COSTS
 
    Direct costs associated with obtaining debt financing are deferred and
charged to interest expense using the effective interest rate method over the
term of the debt. Direct costs associated with obtaining equity financing are
deferred and charged to additional paid-in capital as the related funds are
raised. Deferred costs associated with unsuccessful financings are charged to
expense.
 
    Accumulated amortization of deferred financing costs totaled $44,376 at
December 31, 1995.
 
H -- REVENUE RECOGNITION
 
    Revenue from telecommunications services are recognized ratably over the
period such services are provided.
 
    During 1994, the Company recognized income from consulting fees associated
with the application of FCC licenses on behalf of third parties, including
consulting fees of approximately $80,000 from Extended.
 
                                      F-17
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
3.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, CONTINUED:
I -- INCOME TAXES
 
    The Company accounts for income taxes under the liability method of
accounting. Under the liability method, deferred taxes are determined based on
the differences between the financial statement and tax bases of assets and
liabilities at enacted tax rates in effect in the year in which the differences
are expected to reverse. Valuation allowances are established, when necessary,
to reduce deferred tax assets to the amounts expected to be realized.
 
K -- NET LOSS PER SHARE
 
    Historical net loss per share is computed based on the loss for the period
divided by the weighted average number of shares of Common Stock outstanding
during each period. Historical net loss per share and the weighted average
number of shares of Common Stock outstanding are as follows:
 
<TABLE>
<CAPTION>
                                                       FOR THE YEARS ENDED DECEMBER 31,
                                                  -------------------------------------------
<S>                                               <C>            <C>            <C>
                                                      1995           1994           1993
                                                  -------------  -------------  -------------
 
Net loss per share..............................  $        0.54  $        0.04  $    --
                                                  -------------  -------------  -------------
                                                  -------------  -------------  -------------
Weighted average number of shares of Common
 Stock outstanding..............................      5,946,338      3,337,685      1,820,555
                                                  -------------  -------------  -------------
                                                  -------------  -------------  -------------
</TABLE>
 
    The Securities and Exchange Commission requires that potentially dilutive
instruments issued within one year prior to a proposed initial public offering
at exercise prices below the expected initial public offering price be treated
as outstanding for all periods presented. Accordingly, an additional 4,966,000
shares are reflected in the weighted average number of shares of Common Stock
outstanding in computing the unaudited pro forma net loss per share for the year
ended December 31, 1995.
 
L -- USE OF ESTIMATES
 
    The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities as of the date of the financial
statements and the reported amounts of expenses during the reporting period.
Actual results could differ from those estimates.
 
M -- CONCENTRATIONS OF CREDIT RISK
 
    The Company places its temporary cash investments with major financial
institutions. At December 31, 1995, the Company's temporary cash investments are
principally placed in one entity. Deposits on equipment are financial
instruments which expose the Company to potential credit risk.
 
4.  CONVERTIBLE NOTES PAYABLE:
    The Company and several entities affiliated with Advent International Corp.
(collectively, the "Advent Group"), entered into a securities purchase agreement
(the "Advent Purchase Agreement") dated November 13, 1995 under which the Advent
Group agreed to acquire a 10% interest in the Company and certain specified
affiliates. The Company issued promissory notes (the "Advent Notes") with an
aggregate principal amount of $4,950,000 and one share of redeemable preferred
stock in exchange for $5,000,000 in cash.
 
    The Advent Notes carried interest at a rate of 10% per annum and were
payable on demand at any time on or after May 13, 1997. The Advent Notes were
collateralized by certain assets of the Company. The Advent Notes were
convertible into that number of shares of preferred stock which represented in
the aggregate at least 10% of the fully diluted capital stock of the combined
entities described above, as
 
                                      F-18
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
4.  CONVERTIBLE NOTES PAYABLE, CONTINUED:
defined in the Advent Purchase Agreement. The Advent Notes were convertible
either (i) immediately prior to an initial public offering with aggregate gross
proceeds of at least $10,000,000 or (ii) at the Advent Group's election.
 
    At December 31, 1995, the Company accrued interest expense of $66,542 on the
Advent Notes, which has been included in accounts payable and accrued
liabilities.
 
    On February 2, 1996, the Company and several entities affiliated with the
Advent Group entered into an exchange agreement under which the convertible
notes payable to the Advent Group, including accrued interest, and the one share
of redeemable preferred stock held by the Advent Group were exchanged for
232,826 shares of Series E preferred stock of Telecom and the notes payable to
the Advent Group were canceled.
 
5.  EQUITY INVESTMENT:
 
A -- INVESTMENT IN ART WEST JOINT VENTURE
 
    On April 4, 1995, ART entered into an agreement with Extended to form ART
West, a jointly controlled general partnership established to acquire, develop,
and operate radio systems using 38 GHz licenses in certain western states of the
U.S. The ART West joint venture will continue until December 31, 2055, unless
terminated earlier. The Company's initial capital contribution consisted of
$255,000 in cash, FCC licenses and related assets with a carrying value of
approximately $5,000, and 26,773 shares of Common Stock. Extended's initial
capital contribution consisted of $5,000 in cash and FCC licenses. The combined
systems are collectively referred to as the ART West Systems. Additionally,
Extended received distributions of $250,000 in cash and the 26,773 shares of
Common Stock contributed by the Company to ART West. As a result of these
contributions and distributions, the Company and Extended share equally in the
partnership interests of ART West. The Company recorded its investment in ART
West in the amount of $285,000. The excess of the Company's share of the
underlying net assets of ART West over the Company's recorded investment will be
amortized over the life of the ART West Systems.
 
    On October 1, 1994, the Company entered into an exclusive services agreement
with Extended, whereby the Company is responsible for the construction,
operation and management of Extended's telecommunications systems. The term of
the services agreement is for five years. In connection with the formation of
ART West, Extended assigned its interest in the services agreement to ART West.
Under the terms of the services agreement, the Company will incur all costs and
expenses related to construction, operation and management of the systems. As
compensation, the Company will receive all revenues generated by the systems
after deducting certain related direct expenses, less 45% which is to be paid to
ART West. Under the services agreement, title to the system assets purchased by
the Company and used to provide services in ART West's markets remains with the
Company upon termination of the services agreement. There have been no services
provided through December 31, 1995 under the services agreement. An officer of
the Company is also the President and a shareholder of Extended.
 
B -- ART WEST JOINT VENTURE ACQUISITION AND MANAGEMENT AGREEMENTS
 
    In June 1996, the Company agreed to acquire Extended's 50% ownership
interest in ART West for $6,000,000 in cash upon consummation of public equity
and debt offerings with aggregate net proceeds of $125.0 million to the Company
and receipt of FCC approval. In addition, the Company entered into a ten-year
management agreement which, effective June 1, 1996, replaces the services
agreement referred to above with an arrangement whereby the Company agrees to
construct, operate and manage the ART West Systems in exchange for a license fee
equal to 10% of recurring operating revenues.
 
                                      F-19
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
6.  ACQUISITION OF ASSETS OF EMI:
 
    On April 4, 1995, the Company entered into a purchase option agreement with
EMI to acquire EMI's interest in certain 38 GHz radio spectrum licenses and
related assets in the Northeastern United States (the "EMI Assets") in exchange
for $3,000,000 in cash and a three year non-negotiable promissory note in the
amount of $1,500,000. The FCC approved the transfer of the EMI licenses and the
Company acquired the EMI Assets in November 1995. The total purchase price,
including expenses, was allocated to the acquired assets as follows:
 
<TABLE>
<S>                                                              <C>
Property and equipment.........................................  $  297,150
FCC licenses...................................................   4,226,821
                                                                 ----------
                                                                 $4,523,971
                                                                 ----------
                                                                 ----------
</TABLE>
 
    The promissory note issued is payable in quarterly installments of principal
of $187,500 beginning January 1, 1997. Interest is payable quarterly at a major
commercial bank's prime rate plus 2%, or 10.5% as of December 31, 1995.
 
    On November 8, 1995, Landover advanced $175,000 to the Company to fund a
portion of the initial payment to EMI. The Company repaid such amount later in
the same month.
 
7.  PROPERTY AND EQUIPMENT:
 
    At December 31, 1995, property and equipment comprises:
 
<TABLE>
<S>                                                              <C>
Wireless transmission equipment................................  $3,496,905
Office furniture and equipment.................................      93,414
                                                                 ----------
                                                                  3,590,319
Accumulated depreciation.......................................      (8,758)
                                                                 ----------
                                                                 $3,581,561
                                                                 ----------
                                                                 ----------
</TABLE>
 
    As of December 31, 1995, excluding the property and equipment acquired from
EMI (Note 6), the wireless transmission equipment acquired to date has not been
placed into service.
 
8.  ACCOUNTS PAYABLE AND ACCRUED LIABILITIES
 
    At December 31, 1995, accounts payable and accrued liabilities comprise:
 
<TABLE>
<S>                                                              <C>
Accrued interest payable.......................................  $   87,254
Salaries and other employee related costs......................     267,091
Trade accounts payable.........................................     673,514
Wireless transmission equipment payable........................   2,666,630
                                                                 ----------
                                                                 $3,694,489
                                                                 ----------
                                                                 ----------
</TABLE>
 
9.  DCT AGREEMENTS:
 
SYSTEM PURCHASE AGREEMENT
 
    On September 1, 1994, the Company entered into an agreement with DCT
Communications, Inc. ("DCT"), in which the Company obtained the option to
purchase certain FCC licenses (the "Systems") from DCT for $500,000 and shares
of Common Stock that represent 5% of its fully diluted equity as of the date of
transfer. The option is exercisable at any time after December 31, 1995 and up
to the date
 
                                      F-20
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
9.  DCT AGREEMENTS, CONTINUED:
that is three years after the FCC issues DCT's first license. At any time after
December 31, 1995, DCT may require that the Company purchase the Systems for
$50,000, plus reimbursement of certain costs defined in the agreement.
 
SERVICES AGREEMENT
 
    On September 1, 1994, the Company entered into an exclusive services
agreement with DCT whereby the Company is responsible for the construction,
operation and management of DCT's Systems. The term of the Agreement is for five
years. Under the terms of the services agreement, the Company will incur all
costs and expenses related to construction, operation and management of the
systems. As compensation, the Company will receive all revenues generated by the
systems after deducting certain related direct expenses, less 45% which is to be
paid to DCT. Under the services agreement, title to the system assets purchased
by the Company and used to provide services in DCT's markets remains with the
Company upon termination of the services agreement. There have been no services
provided through December 31, 1995 under the services agreement.
 
CONSULTING AND LOAN AGREEMENT
 
    On March 13, 1995, the Company entered into a consulting and loan agreement
(the "Consulting and Loan Agreement"). Under the terms of the Consulting and
Loan Agreement, DCT agreed to loan the Company $8,500, bearing interest at 9%
per annum. The loan, including interest of $431, was due and paid on August 31,
1995.
 
DCT PRELIMINARY AGREEMENT
 
    On April 25, 1996, the Company entered into a preliminary agreement with DCT
to acquire DCT's interest in certain FCC authorizations and licenses in exchange
for $3.6 million in cash, subject to the completion of a definitive purchase
agreement and services agreement. The definitive purchase agreement will
supersede and replace all other existing agreements between DCT and the Company.
The definitive purchase agreement must be signed by June 28, 1996 and the
closing of the transaction is subject to FCC approval.
 
10. COMMITMENTS:
 
EQUIPMENT PURCHASE AGREEMENT
 
    On August 11, 1995, the Company entered into an agreement to purchase
wireless transmission equipment from a vendor. Under the terms of the agreement,
the Company is obligated to purchase a specified number of wireless transmission
units between August 11, 1995 and December 31, 1998, subject to termination upon
90 days advance notice by either party. The initial non-cancelable equipment
purchase order amounts to $13,260,000. The Company has purchased and paid for
$522,812 of equipment under this contract through December 31, 1995. In
addition, a $280,000 deposit has been made under this agreement which is to be
applied against future purchases after the Company has purchased a specified
amount of equipment, which is expected to occur in 1996.
 
    The Company currently purchases the majority of its wireless transmission
equipment from this vendor. Any reduction or interruption in supply from this
vendor could have a material adverse effect on the Company until alternative
supply sources are established. The Company does not manufacture, nor does it
have the capability to manufacture, any of the wireless transmission equipment
necessary to provide its services. Although there are a limited number of other
manufacturers who have, or are developing, equipment that would meet the
Company's requirements, there can be no assurance that such equipment would be
available to the Company on comparable terms or on terms more favorable to those
included in its current arrangements. Moreover, a change in vendors could cause
a delay in the Company's ability to provide its services, which would affect
future operating results adversely.
 
                                      F-21
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
10. COMMITMENTS, CONTINUED:
TELECOM ONE OPTION
 
    On May 25, 1995, the Company entered into an agreement with TeleCom One
Incorporated ("TeleCom One") whereby the Company agreed to assist TeleCom One in
its applications for certain FCC licenses (the "TeleCom One Agreement"). Under
the terms of the TeleCom One Agreement, in exchange for its services, the
Company acquired options to purchase a 49% interest in each of the FCC licenses
obtained by TeleCom One at a price of $.0133 per person covered by the
geographical license area. The term of the TeleCom One Agreement is for five
years. The Company has not exercised any of its options.
 
    On April 24, 1996, the Company entered into a services agreement to
construct, operate and manage the FCC licenses and related telecommunications
systems of TeleCom One in exchange for all revenues generated by the systems,
after deducting certain expenses, less 10% which is paid to TeleCom One. Under
the services agreement, title to the system assets purchased by the Company and
used to provide services in TeleCom One's markets remains with the Company upon
termination of the services agreements.
 
EMPLOYMENT AND CONSULTING AGREEMENTS
 
    On May 8, 1995, the Company entered into consulting agreements with two
executive officers of the Company, effective as of January 1, 1995 and
continuing for a term of three years, with minimum payments aggregating
approximately $170,000 annually. The aggregate expense incurred by the Company
under these consulting agreements through December 31, 1995 amounted to
$166,750.
 
    On December 16, 1995, one of the executive officers of the Company,
previously a party to one of the consulting agreements described above, entered
into a full-time employment agreement. The employment agreement is for a
three-year term with an annual salary of $250,000 in the first year, $275,000 in
the second year and $300,000 in the third year. In addition, the agreement
provides for a cash bonus of up to $100,000 for each year based upon achievement
of specific performance objectives.
 
    On July 11, 1995, the Company entered into an employment agreement, as
amended January 8, 1996, with an officer of the Company. The term of the
agreement is three years at an annual salary of $160,000 in the first year,
$200,000 in the second year and $240,000 in the third year. Options to purchase
shares of the Common Stock were awarded to this officer equivalent to 2.5% of
the outstanding capital stock of the Company (see Note 12). The agreement also
provides for an engagement bonus of $17,000 upon execution of the agreement and
a cash bonus of up to $100,000 for each year based upon achievement of specific
performance objectives.
 
    The Company has also entered into employment agreements with other
executives that provide for annual base salaries and cash bonuses based on
achievement of specific performance goals. These contracts may be terminated at
any time by management.
 
FINANCING AGREEMENT
 
    During 1994, the Company entered into an agreement with Southeast Research
Partners ("SERP"), a subsidiary of Josephthal, Lyons & Ross, a Florida broker
dealer, to procure additional financing for the Company in exchange for cash and
options to purchase capital stock of the Company. Pursuant to a letter agreement
dated July 12, 1995, the Company paid SERP $245,000 and the shareholders of ART
granted SERP options to purchase 114,041 shares of Common Stock directly from
the Founding Stockholders for an aggregate consideration of $210,000.
 
    As of December 31, 1995, the Company have accounted for the fee of $245,000
as part of the financing provided by Landover and, accordingly, $175,000 has
been recorded as deferred financing
 
                                      F-22
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
10. COMMITMENTS, CONTINUED:
costs related to the issuance of the Advent Notes (see Note 4) and the balance
of $70,000 has been recognized as an offset against the proceeds from the
issuance of the serial preferred stock of Telecom (see Note 11).
 
LEASES
 
    The Company has entered into operating leases for office space and antenna
sites which expire between 1997 and 2001. Lease expense amounted to $16,044 for
1995. Future annual minimum lease payments as of December 31, 1995 are as
follows:
 
<TABLE>
<S>                                                                  <C>
1996...............................................................   $ 363,079
1997...............................................................     352,480
1998...............................................................     302,727
1999...............................................................     297,417
2000 and thereafter................................................      25,825
                                                                     ----------
                                                                     $1,341,528
                                                                     ----------
                                                                     ----------
</TABLE>
 
11. STOCKHOLDERS' DEFICIT:
 
A--ART
 
    On April 5, 1994, the Board of Directors authorized a 5 for 1 stock split.
Subsequently, on April 5, 1995, the Board of Directors authorized a 1 for 5
reverse stock split and simultaneously issued an additional 1,472,508 shares of
Common Stock.
 
    On May 30, 1996, the Board of Directors authorized a 29,450.16 for 1 stock
split, increased the number of authorized shares of preferred stock and Common
Stock to 10,000,000 and 100,000,000, respectively, and changed the par value per
share from $.01 to $.001. On October 11, 1996, the Board of Directors authorized
a 1 for 2.75 reverse stock split of shares of common stock issued and
outstanding. All references to the number of shares and per share amounts of
Common Stock in the accompanying financial statements have been restated to
reflect the 5 for 1 stock split, the 1 for 5 reverse stock split, the 29,450.16
for 1 stock split and the 1 for 2.75 reverse stock split, unless otherwise
indicated. All par value amounts have been restated to reflect the change in par
value to $.001 per share.
 
B--TELECOM
 
    At December 31, 1995, Telecom's Certificate of Incorporation authorized the
issuance of 20,000,000 shares of stock of all classes, divided into (i)
10,000,000 shares of common stock, $0.001 par value per share, of which
7,000,000 shares are designated as Class A common stock and 3,000,000 shares are
designated as Class B common stock and (ii) 10,000,000 shares of preferred
stock, $0.001 par value per share of which 451,513 shares are designated as
Series A preferred stock, 113,663 shares are designated as Series B preferred
stock, 7,297 shares are designated as Series C preferred stock and 61,640 shares
are designated as Series D preferred stock, before giving effect to the 13 for 1
stock split discussed below. Pursuant to the reorganization (see Note 2), the
Certificate of Incorporation of Telecom was amended and restated on February 2,
1996 to (i) convert each share of Class A common stock and Class B common stock
into one share of common stock, par value $0.001 per share, (ii) change the
authorized capital stock of Telecom to 70,000,000 shares of stock of all
classes, (iii) change the authorized common stock to 60,000,000 shares, (iv)
amend the terms of the preferred stock and each series thereof, (v) provide for
two new series of preferred stock designated as "Series E preferred stock" and
"Series F preferred stock," and (vi) effect a 13 for 1 stock split of each share
of Telecom common stock issued and outstanding.
 
                                      F-23
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
11. STOCKHOLDERS' DEFICIT, CONTINUED:
    The holders of Telecom Class A common stock had anti-dilution protection,
but in all other respects such shares were identical to the Telecom Class B
common stock. Under the anti-dilution provisions, additional shares of Class A
common stock were issued, for no consideration, to the holders of the Class A
common stock upon the issuance of serial preferred stock, so that the holders of
Class A common stock maintained their 36% ownership interest through the $7.0
million Landover Funding Commitment as set forth in the Purchase Agreement.
 
    Each issuance of serial preferred stock pursuant to the Landover Funding
Commitment is a separate class and, as a class, has a liquidation preference
equal to the aggregate price paid for such class and an ownership interest
designated by Landover at issuance. The ownership interest of each outstanding
class of serial preferred stock was not to be diluted by subsequent issuances of
shares of other classes of serial preferred stock through the satisfaction of
the Landover Funding Commitment. As a result, additional shares of serial
preferred stock were issued to the existing holders upon the issuance of such
other shares so that each outstanding class maintained its designated aggregate
liquidation preference and aggregate ownership interest.
 
    Each share of serial preferred stock outstanding at December 31, 1995 is
convertible into 4.7273 shares of Telecom common stock, subject to certain
anti-dilution adjustments. The holders of serial preferred stock have a vote,
and receive dividends or distributions, equivalent to the votes and amounts
which would be obtainable by them upon conversion of their shares into Telecom
common stock.
 
    In partial satisfaction of the Landover Funding Commitment, during 1995,
Telecom issued 332,091 shares of Series A preferred stock, 82,318 shares of
Series B preferred stock and 5,402 shares of Series C preferred stock to three
separate limited partnerships of which an affiliate of Landover is the general
partner, for aggregate cash consideration of $2.0 million.
 
    On November 9, 1995, Telecom issued 61,640 shares of Series D preferred
stock for cash of $2.0 million. The Series D preferred stock purchase agreement
provided that in the event that Telecom and ART on a combined basis did not
achieve an equity valuation of $225.0 million, as defined, on or before November
1, 1997, the holders of the Series D preferred stock had the option to purchase
additional shares of serial preferred stock for $0.001 per share up to a maximum
of 1.33% of the then outstanding capital stock of Telecom. The Series D
preferred stock purchase agreement was amended February 2, 1996 whereby the
option to purchase additional serial preferred stock was replaced with an option
to purchase 145,685 shares of Telecom common stock directly from Landover for
$0.001 per share in the event ART and Telecom on a combined basis does not
attain certain equity valuation objectives.
 
    On November 13, 1995, the Advent Group executed a securities purchase
agreement with ART and Telecom. As a result of the exchange agreement dated
February 2, 1996, the Advent Group received 232,826 shares of Series E preferred
stock of Telecom (see Note 4).
 
    The serial preferred stock transactions described above satisfied the
Landover Funding Commitment. As a result, the anti-dilution protection for the
Class A common stock and serial preferred stock terminated. As the actual cash
proceeds received were in excess of Landover's $7.0 million commitment, on
November 13, 1995, Telecom used the proceeds from the sale of Series D preferred
stock to redeem 293,791 shares of Class B common stock held by Landover.
 
    The Series E and F preferred stock (see Note 16) are senior in liquidation
preference to the Series A, B, C and D preferred stock. The Series D preferred
stock is senior in liquidation preference to the Series A, B and C preferred
stock. At any time on or after November 13, 2000, the Series E and F preferred
stock may be redeemed at the option of the holders of such stock at a price
equal to the liquidation amount plus all accrued and unpaid dividends.
 
                                      F-24
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
12. STOCK OPTION PLANS:
 
    On July 22, 1995, the Company adopted the 1995 Stock Option Plan (the
"Plan") that provides for option grants to employees, directors and independent
consultants of the Company. The Company has reserved 909,091 shares of Common
Stock for issuance under the Plan. Options granted to employees may be
designated as incentive stock options ("ISO's") or non-qualified stock options
("NQSO's"), as defined by the Internal Revenue Service. Options granted to
independent consultants and other non-employees may only be designated NQSO's.
 
    The exercise price of options granted under the Plan may not be less than
100% of the fair market value of the Common Stock on the grant date. Generally,
options will be exercisable for a term that will not exceed ten years from the
date of grant.
 
    Under the Plan, options to purchase an aggregate of 297,175 and 85,455
shares of Common Stock were granted to employees of the Company on July 22, 1995
and December 29, 1995, respectively, at an option price of $1.6244 and $4.5430
per share, respectively. The difference between the exercise price of the
options issued at $1.6244 and the deemed fair value of Common Stock of $3.30 per
share as determined on the measurement date, is recognized as compensation
expense over the respective vesting period. The options vest at various dates
during a 5-year period. At December 31, 1995, 131,558 options were vested and
compensation expense recognized amounted to $210,339. There were no options
exercised or canceled during 1995.
 
    On February 15, 1996, options to purchase an aggregate of 52,727 shares of
Common Stock were granted to employees of the Company under the Plan at an
option price of $10.8350 per share.
 
    On April 24, 1996, the Company adopted the 1996 Non-Employee Directors
Automatic Stock Option Plan (the "Directors Plan"), subject to shareholder
approval, which provides for the automatic grant of stock options to
non-employee directors to purchase up to an aggregate of 72,727 shares. Under
the Directors Plan, options to acquire approximately 2,200 shares of common
stock are automatically granted to each non-employee director who is a director
on January 1 of each year. In addition, each non-employee director serving on
the Board of Directors effective on the date of an initial public offering, and
in the future each newly elected non-employee director on the date of his or her
first appointment or election to the Board of Directors will receive an
automatic grant of options to acquire approximately 2,600 shares of Common
Stock.
 
    In October 1995, the Financial Accounting Standards Board issued Statement
of Financial Accounting Standards No. 123, "Accounting for Stock-Based
Compensation." This statement encourages, but does not require, accounting for
stock compensation awards granted to employees based on their fair value at the
date the awards are granted. Companies may elect to continue to apply current
accounting requirements for employee stock compensation awards, which generally
will result in no compensation cost for most fixed stock option plans, such as
the Plan. The expense measurement provisions of the Statement apply to all
equity instruments issued for goods and services provided by persons other than
employees. All companies are required to comply with the disclosure requirements
of the statement. The Company expects to continue accounting for employee stock
compensation awards using current accounting requirements.
 
13. INCOME TAXES:
 
    As of December 31, 1995 and 1994, the Company has net operating loss
carry-forwards for income tax purposes of approximately $2.4 million and
$134,000, respectively, which will expire between 2008 and 2010. Deferred tax
assets of approximately $870,000 and $46,000 at December 31, 1995 and 1994,
 
                                      F-25
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
13. INCOME TAXES, CONTINUED:
respectively, principally comprised of such net operating tax loss
carry-forwards and temporary differences arising from compensation expense
related to stock option plans, have been offset in full by a valuation
allowance.
 
14. RELATED PARTY TRANSACTIONS:
 
    On May 8, 1995, the Company entered into a consulting agreement with
Landover as a strategic and financial consultant. The Company paid Landover
$70,000 for services under this agreement during 1995. The consulting agreement
was terminated on November 13, 1995.
 
    On November 13, 1995, the Company entered into a management consulting
agreement with Landover to provide strategic planning, corporate development and
general management. Under the agreement, the Company will pay Landover $35,000
per month for an initial one year term, renewable by the Company for two
additional one year terms. The aggregate expense recognized by the Company under
this agreement during 1995 amounted to $70,000. The agreement also provides that
in the event Landover arranges financing, acquisitions or certain other
transactions for the Company and Landover will be paid a fee in accordance with
industry standards.
 
    Pursuant to the Purchase Agreement, the Company paid Landover $391,750 for
expenses in connection with the Landover Funding Commitment, of which $250,000
has been capitalized as deferred financing costs and the balance of $141,750 has
been charged to paid-in capital.
 
    In 1994, the Company shared office space with a law firm in which a
principal of the law firm was also one of the Founding Stockholders. The Company
paid rent in the amount of $6,353 to the law firm for the use of their office
space. The law firm also regularly provides legal services to the Company.
During 1995 and 1994, the Company incurred fees of $34,770 and $74,550,
respectively, for such services.
 
15. FAIR VALUES OF FINANCIAL INSTRUMENTS:
 
    The carrying amounts and fair values of the Company's financial instruments
at December 31 were as follows:
 
<TABLE>
<CAPTION>
                                                      1995                      1994
                                          ----------------------------  --------------------
<S>                                       <C>            <C>            <C>        <C>
                                            CARRYING         FAIR       CARRYING     FAIR
                                             AMOUNT          VALUE       AMOUNT      VALUE
                                          -------------  -------------  ---------  ---------
 
Cash and cash equivalents...............  $     633,654  $     633,654  $   5,133  $   5,133
Notes payable...........................  $   4,950,000  $   4,950,000  $  70,000  $  70,000
</TABLE>
 
    Cash and cash equivalents: The carrying amount reported in the balance sheet
approximates fair value.
 
    Notes Payable: The carrying amounts reported in the balance sheet
approximate fair values based upon interest rates that are currently available
to the Company for issuance of similar debt with similar terms and maturities.
 
16. SUBSEQUENT EVENTS:
 
AMERITECH FINANCING
 
    On February 2, 1996, Telecom sold 48,893 shares of Series F preferred stock
for an aggregate purchase price of $2.5 million to Ameritech Development
Corporation ("Ameritech"). In addition, the Company entered into a strategic
distribution agreement with Ameritech Corp., the parent of Ameritech, and, as
partial consideration, granted warrants to Ameritech to purchase up to 318,959
shares of
 
                                      F-26
<PAGE>
                          ADVANCED RADIO TELECOM CORP.
                    NOTES TO FINANCIAL STATEMENTS, CONTINUED
 
16. SUBSEQUENT EVENTS, CONTINUED:
common stock at a nominal price per share, exercisable on February 2, 1996
through February 2, 2006. The Series F preferred stock and warrants are
collectively referred to as the Ameritech Securities. The strategic distribution
agreement provides for Ameritech to be the principal distributor of the
Company's services within five midwestern states. The Company incurred fees of
$150,000 in connection with this transaction.
 
    Under the terms of the securities purchase agreement with Ameritech,
Ameritech is entitled to a put option to require the Company to repurchase the
Ameritech Securities if the Department of Justice finds that this investment is
in violation of restrictions under the Modification of Final Judgment in the
United States vs. AT&T Civil Action 82-0192 ("MFJ"). Telecom would be required
to repurchase the Ameritech Securities at a purchase price equal to the fair
market value on the date it is determined that the investment is in violation of
the MFJ.
 
BRIDGE FINANCING
 
    On March 8, 1996, the Company issued a private placement of $5.0 million,
two year, 10% notes (the "Bridge Notes") and five year warrants to purchase up
to an aggregate of 400,000 shares of common stock at a price of $17.1875 per
share (the "Bridge Warrants") to certain holders of serial preferred stock. The
Bridge Warrants are exercisable on March 8, 1996 through March 8, 2001. In the
event of nonpayment of interest or default, the Company is required to issue
additional warrants to purchase shares of Common Stock.
 
EQUIPMENT FINANCING
 
    On April 24, 1996, the Board of Directors approved the adoption of
resolutions necessary to complete a $2,445,000 equipment financing for the
purchase of wireless transmission equipment.
 
RESEARCH AND DEVELOPMENT ARRANGEMENTS
 
    On January 26, 1996, the Company entered into a preliminary agreement to
invest from $700,000 to $1.0 million in an entity in which an executive of the
Company is a director and a shareholder. The preliminary agreement provides for
the entity to perform research and development of wireless transmission
equipment in which the Company will receive a right of first refusal on
production capacity and a license fee in exchange for its investment.
 
    On March 13, 1996, the Company issued a letter of intent to a third party to
provide the Company with specific technology consulting in connection with the
development of wireless transmission equipment. The aggregate amount to be paid
pursuant to the letter of intent totals $90,000. The letter of intent was
executed in connection with an agreement currently under negotiations for the
development and manufacture of wireless transmission equipment.
 
SOFTWARE LICENSE AGREEMENT
 
    On March 29, 1996, the Company entered into a software license agreement
(the "Software License Agreement"). The terms of the Software License Agreement
provide for licensed software and hardware for the Company's network management
and maintenance support services. The Software License Agreement provides for an
initial software license fee of approximately $2,000,000 and an annual
maintenance support fee of approximately $300,000 per year. An initial payment
of $250,000 for the software license fee was payable upon execution of the
agreement with the balance payable in monthly installments of principal and
interest commencing January 1, 1997.
 
                                      F-27
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
            UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (NOTE 1)
                          SEPTEMBER 30, 1996 AND 1995
 
<TABLE>
<CAPTION>
                                                                                            SEPTEMBER 30,
                                                                                   -------------------------------
                                                                                        1996             1995
                                                                                   ---------------  --------------
<S>                                                                                <C>              <C>
                                                      ASSETS
 
Current assets:
  Cash and cash equivalents......................................................  $       752,368  $       81,512
  Accounts receivable............................................................           78,645
  Other current assets...........................................................          140,227
                                                                                   ---------------  --------------
      Total current assets.......................................................          971,240          81,512
Restricted cash..................................................................        1,000,000
Property and equipment, net......................................................       11,019,217          49,488
Equity investment................................................................          285,000         212,500
FCC licenses, net................................................................        4,276,780         175,000
Deferred financing costs, net....................................................        2,343,087
Deposits.........................................................................          463,036
Other assets.....................................................................          183,637          29,703
                                                                                   ---------------  --------------
      Total assets...............................................................  $    20,541,997  $      548,203
                                                                                   ---------------  --------------
                                                                                   ---------------  --------------
                                  LIABILITIES AND STOCKHOLDERS' EQUITY (DEFICIT)
Current liabilities:
  Accounts payable and accrued liabilities.......................................  $    11,154,608  $      250,303
  March Bridge Notes.............................................................        4,243,784
  CommcoCCC Notes................................................................        2,827,836
  September Bridge Notes.........................................................        2,203,559
  Current portion of long-term debt..............................................        1,242,126
                                                                                   ---------------  --------------
      Total current liabilities..................................................       21,671,913         250,303
Equipment financing note payable (net of current portion)........................          927,796
Note payable to EMI (net of current portion).....................................          937,500
                                                                                   ---------------  --------------
      Total liabilities..........................................................       23,537,209         250,303
                                                                                   ---------------  --------------
Stockholders' equity (deficit):
  Serial preferred stock, $.001 par value, 920,951 and 123,545 shares issued and
    outstanding, respectively....................................................              921             124
  Common Stock, $.001 par value, 6,586,958 and 6,761,111 shares issued and
    outstanding, respectively....................................................            6,587           6,761
  Additional paid-in capital.....................................................       20,745,714       1,430,543
  Accumulated deficit............................................................      (23,748,434)     (1,139,528)
                                                                                   ---------------  --------------
      Total stockholders' equity (deficit).......................................       (2,995,212)        297,900
                                                                                   ---------------  --------------
        Total liabilities and stockholders' equity (deficit).....................  $    20,541,997  $      548,203
                                                                                   ---------------  --------------
                                                                                   ---------------  --------------
</TABLE>
 
   The accompanying notes are an integral part of the consolidated financial
                                  statements.
 
                                      F-28
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
       UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (NOTE 1)
           FOR THE NINE MONTHS ENDED SEPTEMBER 30, 1996 AND 1995 AND
             FOR THE THREE MONTHS ENDED SEPTEMBER 30, 1996 AND 1995
 
<TABLE>
<CAPTION>
                                                           NINE MONTHS ENDED              THREE MONTHS ENDED
                                                             SEPTEMBER 30,                  SEPTEMBER 30,
                                                    -------------------------------  ----------------------------
<S>                                                 <C>              <C>             <C>             <C>
                                                         1996             1995            1996           1995
                                                    ---------------  --------------  --------------  ------------
Service revenue...................................  $       125,013  $     --        $       63,493  $    --
                                                    ---------------  --------------  --------------  ------------
Selling, general and administrative expenses......       16,942,052         987,367       3,640,254       622,611
Market development expense........................        1,053,000        --              --             --
Research and development expense..................          666,406        --               145,000       --
Depreciation and amortization.....................          504,462          15,407         226,087         9,353
                                                    ---------------  --------------  --------------  ------------
      Total operating expenses....................       19,165,920       1,002,774       4,011,341       631,964
                                                    ---------------  --------------  --------------  ------------
Interest income...................................          (59,473)       --               (19,584)      --
Interest expense..................................        1,396,943           1,539         778,249           664
                                                    ---------------  --------------  --------------  ------------
      Interest expense, net.......................        1,337,470           1,539         758,665           664
                                                    ---------------  --------------  --------------  ------------
      Net loss....................................  $   (20,378,377) $   (1,004,313) $   (4,706,513) $   (632,628)
                                                    ---------------  --------------  --------------  ------------
                                                    ---------------  --------------  --------------  ------------
Pro forma net loss per share of Common Stock......  $         (2.15)
                                                    ---------------
                                                    ---------------
Pro forma weighted average number of shares of
 Common Stock outstanding.........................        9,470,545
                                                    ---------------
                                                    ---------------
</TABLE>
 
   The accompanying notes are an integral part of the consolidated financial
                                  statements.
 
                                      F-29
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
  UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' DEFICIT (NOTE 1)
                  FOR THE NINE MONTHS ENDED SEPTEMBER 30, 1996
 
<TABLE>
<CAPTION>
                                                                                                         SERIAL
                                                                                             COMMON     PREFERRED
SHARES                                                                                        STOCK       STOCK
- -----------------------------------------------------------------------------------------  -----------  ---------
<S>                                                                                        <C>          <C>
Balance at December 31, 1995.............................................................    6,529,975    488,492
Issuance of Series E preferred stock.....................................................                 232,826
Shares issued to reflect anti-dilution adjustments.......................................       56,983    150,740
Issuance of Series F preferred stock.....................................................                  48,893
                                                                                           -----------  ---------
Balance at September 30, 1996............................................................    6,586,958    920,951
                                                                                           -----------  ---------
                                                                                           -----------  ---------
</TABLE>
 
<TABLE>
<CAPTION>
                                                        SERIAL       ADDITIONAL
                                           COMMON      PREFERRED      PAID-IN        ACCUMULATED
AMOUNTS                                     STOCK        STOCK        CAPITAL          DEFICIT           TOTAL
- ---------------------------------------  -----------  -----------  --------------  ---------------  ---------------
<S>                                      <C>          <C>          <C>             <C>              <C>
Balance at December 31, 1995...........   $   6,530    $     488   $    3,050,179  $    (3,370,057) $      (312,860)
Issuance of Series E preferred stock...                      233        4,672,953                         4,673,186
Shares issued to reflect anti-dilution
 adjustments...........................          57          151             (208)
Issuance of Series F preferred stock
 and warrants in exchange for cash and
 the Ameritech Strategic Distribution
 Agreement, net of expenses of
 $150,000..............................                       49        3,402,951                         3,403,000
Increase in additional paid-in capital
 as a result of the release of escrow
 shares................................                                 6,795,514                         6,795,514
Value ascribed to the March Bridge
 Warrants..............................                                 1,050,000                         1,050,000
Value ascribed to the equipment
 financing warrants....................                                   484,937                           484,937
Value ascribed to the CommcoCCC
 Warrants..............................                                   319,514                           319,514
Value ascribed to the September Bridge
 Warrants..............................                                   260,937                           260,937
Accrued stock option compensation......                                   708,937                           708,937
Net loss...............................                                                (20,378,377)     (20,378,377)
                                         -----------       -----   --------------  ---------------  ---------------
Balance at September 30, 1996..........   $   6,587    $     921   $   20,745,714  $   (23,748,434) $    (2,995,212)
                                         -----------       -----   --------------  ---------------  ---------------
                                         -----------       -----   --------------  ---------------  ---------------
</TABLE>
 
   The accompanying notes are an integral part of the consolidated financial
                                  statements.
 
                                      F-30
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
       UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (NOTE 1)
             FOR THE NINE MONTHS ENDED SEPTEMBER 30, 1996 AND 1995
 
<TABLE>
<CAPTION>
                                                                                        1996             1995
                                                                                   ---------------  --------------
 
<S>                                                                                <C>              <C>
Cash flows from operating activities:
  Net loss.......................................................................  $   (20,378,377) $   (1,004,313)
                                                                                   ---------------  --------------
  Adjustments to reconcile net loss to net cash used in operating activities:
    Depreciation and amortization................................................          504,462          15,407
    Noncash interest expense.....................................................          632,994
    Noncash compensation expense.................................................        7,504,452
    Noncash market development expense...........................................        1,053,000
    Writeoff of deferred financing costs.........................................        1,248,000
    Changes in operating assets and liabilities:
      Other current assets.......................................................          (87,902)
      Accounts receivable........................................................          (78,645)
      Accounts payable and accrued liabilities...................................          805,179         238,615
      Deposits...................................................................         (179,024)
                                                                                   ---------------  --------------
        Net cash used in operating activities....................................       (8,975,861)       (750,291)
                                                                                   ---------------  --------------
Cash flows from investing activities:
  Additions to property and equipment............................................       (4,241,470)        (57,120)
  Restricted cash................................................................       (1,000,000)
  Additions to FCC licenses......................................................         (112,131)       (175,000)
  Additions to other assets......................................................         (165,185)
  Investment in ART West.........................................................                         (187,500)
                                                                                   ---------------  --------------
        Net cash used in investing activities....................................       (5,518,786)       (419,620)
                                                                                   ---------------  --------------
Cash flows from financing activities:
  Proceeds from issuance of Common Stock.........................................                            1,040
  Proceeds from issuance of serial preferred stock...............................        2,500,000       1,311,616
  Proceeds from issuance of March Bridge Notes...................................        5,000,000
  Proceeds from issuance of the equipment financing note payable.................        2,445,000
  Proceeds from issuance of CommcoCCC Notes......................................        3,000,000
  Proceeds from issuance of September Bridge Notes...............................        2,450,000
  Principal payments made on the equipment financing note payable................         (437,407)
  Stock issuance costs...........................................................         (150,000)        (66,366)
  Additions to deferred financing costs..........................................         (194,232)
                                                                                   ---------------  --------------
        Net cash provided by financing activities................................       14,613,361       1,246,290
                                                                                   ---------------  --------------
Net increase in cash and cash equivalents........................................          118,714          76,379
Cash and cash equivalents at beginning of period.................................          633,654           5,133
                                                                                   ---------------  --------------
Cash and cash equivalents at end of period.......................................  $       752,368  $       81,512
                                                                                   ---------------  --------------
                                                                                   ---------------  --------------
- ------------------------------------------------------------------------------------------------------------------
Supplemental cash flow information:
  Interest paid..................................................................  $       281,062
  Noncash financing and investing activities:
    Additions to property and equipment..........................................        6,260,000
    Exchange of Advent Notes for Series E preferred stock, net of deferred
      financing costs............................................................        4,673,186
    Value ascribed to warrants reflected as paid-in capital......................        2,115,388
    Accrued deferred financing costs.............................................        1,784,300
    Conversion of note payable and interest to Common Stock......................                   $       75,250
    Investment in ART West.......................................................                           25,000
</TABLE>
 
   The accompanying notes are an integral part of the consolidated financial
                                  statements.
 
                                      F-31
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
 
         Notes to Unaudited Condensed Consolidated Financial Statements
 
1.  THE COMPANY AND BASIS OF PRESENTATION:
 
THE COMPANY
 
    Advanced Radio Telecom Corp. ("ART" and, collectively with its subsidiaries,
the "Company"), formerly named Advanced Radio Technologies Corporation, was
organized as a Delaware corporation on August 23, 1993 to develop, market and
provide broadband wireless digital telecommunication and information services
throughout the United States. The Company's business objective is to organize
and finance local operating facilities, establish strategic alliances with other
businesses, acquire new wireless telecommunications technologies, and market
broadband wireless services to telecommunications service providers and end
users.
 
    ART Licensing Corp. ("Telecom"), formerly named Advanced Radio Telecom Corp.
and Advanced Radio Technology Ltd., was incorporated in Delaware on March 28,
1995, with one of its initial objectives to acquire certain 38 GHz licenses.
 
    On October 11, 1996, ART, Telecom and a wholly owned subsidiary of ART
("Merger Sub") entered into a revised merger agreement, which provided for the
merger of Merger Sub into Telecom (the "Merger"). The Merger was completed on
October 28, 1996 and Telecom, through the Merger, became a wholly owned
subsidiary of ART (see Note 2). The Merger was accounted for as a reorganization
of entities under common control which is similar to that of a pooling of
interests, and the financial statements of prior periods have been restated. All
transactions and balances between ART and Telecom have been eliminated.
 
BASIS OF PRESENTATION
 
    The unaudited condensed consolidated financial statements included herein
have been prepared by the Company. The foregoing statements contain all
adjustments, consisting only of normal recurring adjustments which are, in the
opinion of the Company's management, necessary to present fairly the
consolidated financial position of the Company as of September 30, 1996 and the
consolidated results of its operations and its consolidated cash flows for the
nine and three months ended September 30, 1996 and 1995.
 
    Certain information and footnote disclosures normally included in financial
statements have been condensed or omitted pursuant to the rules and regulations
of the Securities and Exchange Commission. These unaudited condensed
consolidated financial statements should be read in conjunction with the
December 31, 1995 audited financial statements of the Company and notes thereto.
 
    The financial statements have been prepared on the going concern basis of
accounting, which contemplates realization of assets and liquidation of
liabilities in the ordinary course of business. The Company has limited
financial resources, incurred operating losses since inception and does not
expect to recognize material operating revenues until the further deployment of
its commercial services, which commenced in fiscal 1996. The Company estimates
that revenues in 1996 and 1997 will not be sufficient to fund its operating
expenses, capital expenditures and other working capital needs. The Company's
continued funding of its operating expenses, working capital needs and
contractual commitments is dependent upon its ability to raise financing. During
November 1996, the Company completed an initial public offering of equity
securities, raising $34,500,000 before expenses. In connection with the initial
public offering, the Company obtained a commitment to borrow up to $50,000,000
through the issuance of Senior Secured Notes (the "CIBC Financing Commitment")
(see Note 8). The proceeds from the initial public offering were used to repay
the March Bridge Notes, the CommcoCCC Notes and the September Bridge Notes and
partially fund the acquisition of the remaining 50% interest in ART West.
Management believes that, based upon its current business plans, the funds
received from the initial public equity offering and available under the CIBC
Financing Commitment are sufficient to enable the Company to continue as a going
concern at least through December 31, 1997.
 
                                      F-32
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
 
   NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS, CONTINUED
 
2.  MERGER AND PUBLIC OFFERING:
 
    In connection with the formation of Telecom, the stockholders of ART and
Telecom entered into a stockholders' agreement dated May 8, 1995 (the
"Stockholders' Agreement"), which provided for the merger of ART and Telecom
once approval from the Federal Communications Commission ("FCC") was granted. On
February 2, 1996, ART, Telecom and their respective stockholders agreed to an
amendment and restatement of the Stockholders' Agreement providing for (i)
termination effective on the closing of a public share offering, (ii) amendment
and restatement of the Certificate of Incorporation and reorganization of the
capital structure of Telecom; (iii) the exchange of the convertible notes
payable and one share of redeemable preferred stock for shares of serial
preferred stock of Telecom; (iv) revision of provisions for election of
directors; (v) amendment and restatement of ART's registration rights
agreements; (vi) release of shares escrowed in connection with the original
Stockholders' Agreement; and (vii) approval of the definitive merger agreement.
 
    The definitive merger agreement, as entered into February 2, 1996, and
subsequently restated and amended on June 26, 1996 and October 11, 1996 (the
"Merger Agreement") provided for the merger of Merger Sub into Telecom subject
to certain conditions, including the receipt of FCC approval. FCC approval was
received and, on October 28, 1996, the Merger was completed. As a result,
Telecom became a wholly owned subsidiary of the Company. In connection with the
Merger, each outstanding share of each series of Telecom's serial preferred
stock was converted into a share of a similar series of the Company's preferred
stock. Upon completion of the initial public offering in November 1996, all
shares of all series of the Company's preferred stock (920,951) automatically
converted into 4,353,587 shares of the Company's common stock. The Merger
Agreement also provided for the assignment of Telecom's interests in all of its
agreements, including the various services agreements, employment agreements,
equipment purchase agreements and purchase option agreements, to the Company.
Further, the holders of warrants to purchase an aggregate of 924,413 shares of
Telecom common stock are entitled to purchase an equal number of shares of the
Company's common stock. Employee stock options to purchase 816,970 shares of
Telecom's common stock were replaced by stock options to purchase an equal
number of shares of common stock of the Company. The terms of the warrants and
stock options are similar except that the exercise price of the warrants and
stock options and the number of shares subject thereto, have been adjusted on a
proportional basis to reflect the 1 for 2.75 reverse stock split (see Note 9).
 
3.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES:
CONSOLIDATION
 
    The consolidated financial statements include all majority owned
subsidiaries in which the Company has the ability to exercise control. All
intercompany transactions have been eliminated in consolidation. During 1996,
the Company incorporated two wholly owned subsidiaries, Advanced Radio Telecom
AB and Advanced Radio Telecom Ltd. for its planned European operations in the
future. There have been no operations by these two subsidiaries to date.
 
FINANCING COSTS
 
    Direct costs associated with obtaining financing are deferred and charged to
interest expense using the effective interest rate method over the term of the
debt or, in the case of equity, charged to additional paid-in capital. Deferred
costs associated with unsuccessful financings are charged to expense. The
Company charged approximately $1,248,000 to expense during the nine months ended
September 30, 1996 associated with its unsuccessful public debt offering.
 
FCC LICENSES
 
    The Company has obtained radio spectrum rights under FCC issued licenses
throughout the United States through the purchase of such rights held by others
and by petitioning the FCC directly.
 
                                      F-33
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
 
   NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS, CONTINUED
 
3.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, CONTINUED:
The costs associated with the acquisition of such licenses, including the cost
of perfecting such licenses pursuant to FCC requirements, are capitalized and
amortized on a straight-line basis over a 40 year period upon commencement of
operations in the related market.
 
PROPERTY AND EQUIPMENT
 
    Property and equipment is stated at cost. Depreciation and amortization are
computed using the straight-line method over the estimated useful lives. As of
September 30, 1996, approximately $1.4 million out of a total of $9.7 million of
wireless transmission equipment has been placed into service.
 
DEVELOPMENT STAGE ENTERPRISE
 
    During the three months ended September 30, 1996, the Company perfected
substantially all of its licenses and commenced commercial operations.
Accordingly, the Company is no longer considered to be in the development stage.
Prior to July 1, 1996, the Company was considered to be in the development
stage. Such change in classification of the Company had no impact on net loss or
stockholders' deficit for any periods presented.
 
4.  NET LOSS PER SHARE:
 
    Historical net loss per share is computed based on the loss for the period
divided by the weighted average number of shares of Common Stock outstanding
during the period. Historical net loss per share and the weighted average number
of shares of Common Stock outstanding are as follows:
 
<TABLE>
<CAPTION>
                                                               FOR THE NINE MONTHS       FOR THE THREE MONTHS
                                                               ENDED SEPTEMBER 30,       ENDED SEPTEMBER 30,
                                                             ------------------------  ------------------------
<S>                                                          <C>          <C>          <C>          <C>
                                                                1996         1995         1996         1995
                                                             -----------  -----------  -----------  -----------
 
Net loss per share.........................................  $      3.10  $      0.18  $      0.71  $      0.09
                                                             -----------  -----------  -----------  -----------
                                                             -----------  -----------  -----------  -----------
Weighted average number of shares of common stock
  outstanding..............................................    6,580,627    5,721,111    6,586,958    6,761,111
                                                             -----------  -----------  -----------  -----------
                                                             -----------  -----------  -----------  -----------
</TABLE>
 
    The Securities and Exchange Commission requires that potentially dilutive
instruments issued within one year prior to an initial public offering at
exercise prices below the initial public offering price be treated as
outstanding for all periods presented in the public offering prospectus.
Accordingly, an additional 2,889,918 shares are reflected in the weighted
average number of shares of Common Stock outstanding in computing the unaudited
pro forma net loss per share for the nine months ended September 30, 1996.
 
5.  CONVERTIBLE NOTES PAYABLE:
 
    On February 2, 1996, the Company and several entities affiliated with Advent
International Corp. (collectively, the "Advent Group") entered into an exchange
agreement under which the convertible notes payable to the Advent Group,
including accrued interest, and the one share of ART's redeemable preferred
stock held by the Advent Group were exchanged for 232,826 shares of serial
preferred stock of Telecom (converted into 1,100,632 shares of Common Stock
concurrent with the initial public equity offering). As a result, the notes
payable by the Company to the Advent Group were canceled and the related
interest forgiven.
 
6.  EQUITY INVESTMENT:
 
    The Company accounts for its 50% interest in the ART West joint venture
under the equity method. In June 1996, the Company agreed to acquire the
remaining 50% ownership interest in ART West held
 
                                      F-34
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
 
   NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS, CONTINUED
 
6.  EQUITY INVESTMENT, CONTINUED:
by Extended Communications Inc. ("Extended") for $6,000,000 in cash upon
consummation of public equity and debt offerings with aggregate net proceeds of
$125,000,000 and receipt of FCC approval. In addition, the Company entered into
a ten-year management agreement which, effective June 1, 1996, replaced the
services agreement with ART West with an arrangement whereby the Company agreed
to construct, operate, and manage the ART West systems in exchange for a license
fee equal to 10% of recurring operating revenues. During November 1996, upon
completion of its initial public offering, the Company made a $3,000,000
nonrefundable payment to Extended pursuant to the acquisition agreement.
 
7.  COMMCOCCC ASSET ACQUISITION:
 
    During July 1996, the Company entered into an agreement with CommcoCCC, Inc.
("CommcoCCC") to acquire CommcoCCC's interests in certain 38 GHz FCC
authorizations (the "CommcoCCC Assets") in exchange for 6,000,000 shares of
Common Stock of the Company. The acquisition of the CommcoCCC Assets is subject
to various conditions including (i) minimum population coverage of the
authorizations of the Company and CommcoCCC, (ii) receipt of final FCC and other
approvals, (iii) receipt by CommcoCCC of an opinion as to the tax-free nature of
the transaction, (iv) the accuracy of representations and warranties except for
breaches that do not have in the aggregate a material adverse effect, (v) no
pending or threatened material litigation, (vi) consummation of a public equity
offering and a debt offering on terms reasonably satisfactory to CommcoCCC, and
(vii) other customary closing conditions. Pending the completion of the
acquisition, the Company has agreed to construct, manage and operate the
CommcoCCC Assets. Under the management agreement, CommcoCCC is obligated to
reimburse the Company up to $100,000 of operating expenses, which obligation is
canceled upon consummation of the acquisition.
 
    The Company has given a stockholder ("Commco LLC") of CommcoCCC an option
(the "Option") to purchase FCC authorizations in specified market areas in which
the Company will have more than one authorization. The Option is exercisable
only in the event that the CommcoCCC Acquisition is consummated and Commco LLC
receives authorizations pursuant to pending applications covering a minimum
specified population and expires in August 1997. The price of authorizations to
be purchased under the Option is based upon a formula that considers the market
price of the Common Stock on the date of exercise.
 
    In connection with the agreement to acquire the CommcoCCC Assets, certain
stockholders of CommcoCCC loaned the Company $3,000,000 in cash in exchange for
notes due September 30, 1996 (the "CommcoCCC Notes") with interest at the prime
rate and received three year warrants to purchase 18,182 shares of Common Stock
at a price of $15.00 per share, as adjusted and after giving effect to anti-
dilution adjustments. As a result of a delay in the September 30, 1996
repayment, the Company obtained waivers from the lenders to extend the payment
terms. In exchange, the Company issued additional warrants to purchase 69,091
shares of the Common Stock at a price of $15.00 per share (as adjusted after
giving effect to anti-dilution adjustments) and increased the interest rate to
14.75%. During November 1996, the Company repaid the principal balance and
accrued interest with proceeds from the initial public offering.
 
8.  FINANCINGS:
 
AMERITECH FINANCING
 
    On February 2, 1996, Telecom sold 48,893 shares of serial preferred stock
(converted into 231,131 shares of Common Stock concurrent with the initial
public offering) for an aggregate purchase price of $2.5 million to Ameritech
Development Corporation ("Ameritech"). In addition, Telecom entered into a
 
                                      F-35
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
 
   NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS, CONTINUED
 
8.  FINANCINGS, CONTINUED:
strategic distribution agreement with Ameritech Corp., the parent of Ameritech,
and, as partial consideration, granted warrants to Ameritech to purchase up to
318,959 shares of Common Stock at a nominal price per share, exercisable on
February 2, 1996 through February 2, 2006. The Company recorded the value of
$1,053,000 ascribed to the strategic distribution agreement as market
development expense in the first quarter of 1996. The Company incurred fees of
$150,000 in connection with this transaction. On December 5, 1996, Ameritech
surrendered its warrants to purchase 318,959 shares of Common Stock in full
exercise of the warrants and was issued 318,374 shares of Common Stock by the
Company.
 
MARCH BRIDGE FINANCING
 
    On March 8, 1996, the Company issued in a private placement a portion of
which was issued to certain holders of serial preferred stock, $5,000,000 of two
year, 10% notes, interest payable on a semi-annual basis, and warrants to
purchase up to an aggregate of 400,000 shares of Common Stock at a price of
$17.1875 per share. During November 1996, the Company repaid the principal
balance and accrued interest with proceeds from the initial public offering.
 
EQUIPMENT FINANCING
 
    On April 29, 1996, the Company completed a $2,445,000 equipment financing
for the purchase of wireless transmission equipment. The Company issued a
$2,445,000 promissory note, payable in 24 monthly installments of $92,694 with a
final payment of $642,305 due April 29, 1998. In connection with the equipment
financing, the Company issued five year warrants to purchase up to an aggregate
of 118,181 shares of Common Stock and paid $225,000 in fees to certain
stockholders to partially guarantee the equipment financing. In addition, the
Company was required to invest $1,000,000 in a certificate of deposit assigned
to the lender as collateral. The $1,000,000 is reflected as restricted cash in
the balance sheet.
 
SEPTEMBER BRIDGE FINANCING
 
    During September and October, 1996, the Company issued in a private
placement, a portion of which was issued to certain stockholders, $4,000,000 in
notes due March 1998 with interest at 14.75%, payable quarterly, and warrants to
purchase 116,363 shares of Common Stock at a purchase price of $15.00 per share,
as adjusted after giving effect to anti-dilution adjustments. During November
1996, the Company repaid the principal balance and accrued interest with
proceeds from the initial public offering.
 
CIBC FINANCING COMMITMENT
 
    During November 1996, the Company entered into agreements with certain
lenders which provide for the issuance of up to $50,000,000 of Senior Secured
Notes, at any time at the Company's option through February 10, 1997 (the "CIBC
Financing Commitment"). The initial interest rate on the Senior Secured Notes is
12.5%, which rate increases by 0.50% three months after the closing of the
initial public offering and by an additional 0.50% for each three-month period
thereafter. The Senior Secured Notes are due in full in November 1998.
 
    The Senior Secured Notes are to be collateralized by a first priority
security interest in substantially all the assets of the Company, including a
pledge of the Company's stock in its subsidiaries. The Senior Secured Notes
contain covenants that restrict the ability of the Company to pay dividends and
make other restricted payments, to incur additional debt, guarantees and liens,
to sell its assets, to enter into mergers and consolidations, to conduct sale
and leaseback transactions and to enter into affiliate transactions, among other
restrictions.
 
    Upon completion of the initial public offering, the Company delivered
warrants to purchase 300,257 shares of Common Stock at a nominal exercise price.
The Company also is committed to deliver
 
                                      F-36
<PAGE>
                 ADVANCED RADIO TELECOM CORP. AND SUBSIDIARIES
 
   NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS, CONTINUED
 
8.  FINANCINGS, CONTINUED:
additional warrants to purchase 1.5% of the fully diluted Common Stock upon the
first draw down of the Senior Secured Notes. If the Senior Secured Notes are
outstanding six months after the initial public offering, the Company shall
issue to the lenders additional warrants to purchase 3% of the fully diluted
Common Stock, and an additional 3% for each additional six month period such
notes are outstanding.
 
    In connection with the CIBC Financing Commitment, the Company paid placement
and commitment fees and other expenses of approximately $1,900,000 and is
obligated to pay approximately $1,800,000 upon the drawdown of the Senior
Secured Notes.
 
9.  STOCKHOLDERS' DEFICIT:
 
    On May 30, 1996, the Board of Directors authorized a 29,450.16 for 1 stock
split, increased the number of authorized shares of preferred stock and Common
Stock to 10,000,000 and 100,000,000, respectively, and changed the par value of
common stock from $.01 to $.001. On October 11, 1996, the Board of Directors
authorized a 1 for 2.75 reverse stock split of shares of Common Stock issued and
outstanding. All references to the number of shares and per share amounts in the
accompanying financial statements have been restated to reflect the stock split
and the reverse stock split, unless otherwise indicated.
 
    Pursuant to a February 2, 1996 reorganization, the terms of the escrow
shares arrangement were terminated and all of the remaining escrow shares
thereunder were released to the stockholders of the Company. The related
compensation expense of $6,795,514, based on the then estimated fair value of
the escrow shares was recognized, the effect of which was recorded as additional
paid-in capital.
 
10. RELATED PARTY TRANSACTION:
 
    In November 1996, Landover Holdings Corporation ("LHC"), one of the
principal stockholders of the Company was paid an aggregate of approximately
$300,000 in conjunction with various services provided in connection with
certain acquisitions under the consulting agreement with LHC.
 
11. COMMITMENTS AND CONTINGENCIES:
 
DCT AGREEMENT
 
    During April 1996, the Company entered into an agreement with DCT
Communications, Inc. ("DCT") (the "DCT Agreement") to acquire DCT's interest in
certain FCC authorizations and licenses in exchange for $3,600,000 in cash, of
which the Company paid a deposit of $100,000. DCT has alleged that the Company
has failed to satisfy a provision of the DCT Agreement which provides that if
the Company failed to obtain debt or equity proceeds by August 31, 1996 in an
amount at least equal to $3,600,000, the DCT Agreement would terminate and DCT
could retain the $100,000 deposit paid by the Company. The Company and DCT are
currently discussing a settlement under the DCT Agreement. There can be no
assurance as to the outcome of such dispute or settlement discussions and,
therefore, no assurance that the Company will be in a position to consummate the
acquisition of the DCT Systems, even if the Company wishes to do so. Although
the Company believes that it has satisfied such provision of the DCT Agreement
and is legally entitled to proceed to consummate the transactions contemplated
thereby, the Company does not currently plan to purchase the DCT Systems as
contemplated by the DCT Agreement.
 
                                      F-37
<PAGE>
                              [INSIDE BACK COVER]
 
                      38 GHz TECHNOLOGY PROVIDES SUPERIOR
                BANDWIDTH PER CHANNEL WHICH ALLOWS SIGNIFICANTLY
                          FASTER DATA TRANSFER RATES.
 
                   [GRAPHIC DISPLAYING BANDWIDTH PER CHANNEL
                  OF FREQUENCIES BETWEEN 530 KHz AND 38 GHz.]
<PAGE>
- --------------------------------------------------------------------------------
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    NO DEALER, SALESPERSON, OR OTHER INDIVIDUAL HAS BEEN AUTHORIZED TO GIVE ANY
INFORMATION OR TO MAKE ANY REPRESENTATIONS, OTHER THAN THOSE CONTAINED IN THIS
PROSPECTUS IN CONNECTION WITH THE OFFERING COVERED BY THIS PROSPECTUS. IF GIVEN
OR MADE, SUCH INFORMATION OR REPRESENTATIONS MUST NOT BE RELIED UPON AS HAVING
BEEN AUTHORIZED BY THE COMPANY OR THE UNDERWRITERS. THIS PROSPECTUS DOES NOT
CONSTITUTE AN OFFER TO SELL, OR A SOLICITATION OF AN OFFER TO BUY, THE
SECURITIES OFFERED HEREBY IN ANY JURISDICTION WHERE, OR TO ANY PERSON TO WHOM,
IT IS UNLAWFUL TO MAKE SUCH OFFER OR SOLICITATION. NEITHER THE DELIVERY OF THIS
PROSPECTUS NOR ANY SALE MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES, CREATE AN
IMPLICATION THAT THERE HAS NOT BEEN ANY CHANGE IN THE FACTS SET FORTH IN THIS
PROSPECTUS OR IN THE AFFAIRS OF THE COMPANY SINCE THE DATE HEREOF.
 
                            ------------------------
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                   PAGE
                                                                   ----
<S>                                                                <C>
Prospectus Summary...............................................    3
Risk Factors.....................................................   13
The Company......................................................   28
Use of Proceeds..................................................   29
Price Range of Common Stock and Dividend Policy..................   30
Capitalization...................................................   31
Selected Historical and Pro Forma Financial Data.................   32
Management's Discussion and Analysis of Financial Condition and
 Results of Operations...........................................   35
Business.........................................................   42
Management.......................................................   70
Principal Stockholders...........................................   80
Certain Transactions.............................................   82
Description of Units.............................................   87
Description of Notes.............................................   87
Description of Warrants..........................................  116
Description of Capital Stock.....................................  118
Description of Certain Indebtedness..............................  120
Certain Federal Income Tax Considerations........................  122
Underwriting.....................................................  126
Legal Matters....................................................  127
Experts..........................................................  127
Available Information............................................  127
Special Note Regarding Forward-Looking Statements................  128
Glossary.........................................................  129
Index to Financial Statements....................................  F-1
</TABLE>
 
                                  $135,000,000
 
                                     [LOGO]
 
                          135,000 UNITS CONSISTING OF
                            14% SENIOR NOTES DUE 2007
                                      AND
                         2,025,000 WARRANTS TO PURCHASE
                             SHARES OF COMMON STOCK
 
                              -------------------
 
                              P R O S P E C T U S
 
                              -------------------
 
                              MERRILL LYNCH & CO.
 
                        CIBC WOOD GUNDY SECURITIES CORP.
 
                                FEBRUARY 3, 1997
 
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