SBA COMMUNICATIONS CORP
8-K, 1999-02-24
CONSTRUCTION - SPECIAL TRADE CONTRACTORS
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<PAGE>

 
                                 UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549


                                   FORM 8-K


CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF
                                     1934.
                                        


               Date of Report                    February 24, 1999

                                        
                        SBA COMMUNICATIONS CORPORATION
                        ------------------------------
            (Exact name of registrant as specified in its charter)

<TABLE> 
<S>                                                               <C>                          <C> 
                 Florida                                                  333-50219                          65-0716501
- ------------------------------------------------------------------------------------------------------------------------------------
 (State or other jurisdiction of incorporation or organization)   Commission File Number       (I.R.S. Employer Identification No.)


     One Town Center Road, Boca Raton, Florida                                                               33486
- ------------------------------------------------------------------------------------------------------------------------------------
      (Address of principal executive offices)                                                             (Zip code)


                                                          (561) 995-7670
- ------------------------------------------------------------------------------------------------------------------------------------
                                       (Registrant's telephone number, including area code)
</TABLE>
<PAGE>
 
Item 5    Other Events
 
          SBA Communications Corporation's ("SBA) wholly-owned subsidiary, SBA
          Telecommunications, Inc. has successfully closed on a new $125 million
          senior credit facility. The new credit facility replaces the prior $55
          million credit facility and will be used to fund the construction and
          acquisition of wireless communications towers and related assets, as
          well as for general corporate purposes. A copy of the press release
          issued by SBA, on February 16, 1999 with respect to this financing is
          attached hereto as Exhibit 99.1 and is incorporated herein by
          reference.



Item 7    Financial Statements and Exhibits

          (c)  Exhibits

          99.1  Press release dated February 16, 1999

          99.2  AMENDED AND RESTATED CREDIT AGREEMENT, dated as of February 5,
                1999, among SBA COMMUNICATIONS CORPORATION, a Florida
                corporation ("Holdings"), SBA TELECOMMUNICATIONS, INC., a
                              --------
                Florida corporation (the "Borrower"), the several banks and
                                          --------
                other financial institutions or entities from time to time
                parties to this Agreement (the "Lenders"), LEHMAN BROTHERS INC.,
                                                -------
                as advisor and book manager (`LBI"), LEHMAN BROTHERS INC., as a
                                              ----
                co-arranger (in such capacity, a "Co-Arranger"), GENERAL
                                                  -----------
                ELECTRIC CAPITAL CORPORATION, as a co-arranger (in such
                capacity, a "Co-Arranger") and as syndication agent (in such
                             -----------
                capacity, the "Syndication Agent"), TORONTO DOMINION (TEXAS),
                               -----------------
                INC., as documentation agent (in such capacity, the
                "Documentation Agent"), BARCLAYS BANK PLC (in such capacity, the
                 -------------------
                "Co-Documentation Agent") and LEHMAN COMMERCIAL PAPER INC., as
                 ----------------------
                administrative agency (in such capacity, the "Administrative
                                                              --------------
                Agent").
                -----
<PAGE>
 
                                   SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.



February 24, 1999                    /s/  Jeffrey A. Stoops
                                     ----------------------
                                     Jeffrey A. Stoops
                                     Chief Financial Officer



                                        

<PAGE>
 
                                     NEWS
                                                  For additional information:
                                                  Jeffrey A. Stoops
                                                  Chief Financial Officer
                                                  (561) 995-7670

                             FOR IMMEDIATE RELEASE
                             ---------------------
                                        
                   SBA COMMUNICATIONS CORPORATION ANNOUNCES
                CLOSING OF $125 MILLION SENIOR CREDIT FACILITY
                                        

SBA COMMUNICATIONS CORPORATION; BOCA RATON, FL; TUESDAY, FEBRUARY 16, 1999
- ---------------------------------------------------------------------------

SBA Communications Corporation ("SBA") announced that its wholly-owned
subsidiary, SBA Telecommunications, Inc., has successfully closed on a new $125
million senior credit facility, consisting of a $100 million revolving credit
facility and a $25 million term loan.  SBA has the option for a period of time
to increase the revolving credit facility to $150 million subject to the
satisfaction of certain conditions.  The new credit facility replaces SBA's
prior $55 million credit facility, and will be used to fund the construction and
acquisition of wireless communications towers and related assets, as well as for
other general corporate purposes.  The new credit facility, originally committed
by Lehman Brothers Inc., was arranged by Lehman Brothers Inc. and General
Electric Capital Corporation, and includes twelve institutions as agents or
syndicate members.

SBA is a leading independent provider of communication site services to the
wireless communications industry.  SBA's primary focus is the construction of
new towers and acquisition of existing towers for its own account.  Since it was
founded in 1989, SBA has participated in the development of over 10,000 antenna
sites in the United States.  SBA currently owns over 500 towers and is involved
in the acquisition or development for its ownership of over 400 additional
towers throughout the nation.



Information Concerning Forward-Looking Statements

Some information in this release is forward looking.  These forward looking
statements may be affected by the risks and uncertainties in the company's
business.  This information is qualified in its entirety by cautionary
statements and risk factors disclosure contained in certain of the company's
Securities and Exchange Commission filings.  The company wishes to caution
readers that certain important factors may have affected and could in the future
affect the company's actual results and could cause the company's actual results
for subsequent periods to differ materially from those expressed in any forward-
looking statement made by or on behalf of the company.  The company undertakes
no obligation to update forward-looking statements to reflect events or
circumstances after the date hereof.

<PAGE>
 
                                                            EXECUTION COPY

 


                                  $125,000,000

                              AMENDED AND RESTATED
                                CREDIT AGREEMENT

                                     among

                        SBA COMMUNICATIONS CORPORATION,

                         SBA TELECOMMUNICATIONS, INC.,
                                  as Borrower,

                              The Several Lenders
                       from Time to Time Parties Hereto,

                             LEHMAN BROTHERS INC.,
                                 as Co-Arranger

                     GENERAL ELECTRIC CAPITAL CORPORATION,
                    as Co-Arranger and as Syndication Agent

                        TORONTO DOMINION (TEXAS), INC.,
                             as Documentation Agent

                               BARCLAYS BANK PLC,
                           as Co-Documentation Agent

                                      and

                         LEHMAN COMMERCIAL PAPER INC.,
                            as Administrative Agent

                          Dated as of February 5, 1999
                                        
 
<PAGE>
 
                                 TABLE OF CONTENTS

<TABLE>
<CAPTION>
<S>                                                                                                             <C>
                                                                                                               Page
SECTION 1.  DEFINITIONS.........................................................................................1
     1.1  Defined Terms.........................................................................................1
     1.2  Other Definitional Provisions.........................................................................26   
                                                                                                                     
SECTION 2.  AMOUNT AND TERMS OF COMMITMENTS.....................................................................26  
     2.1  Term Loan Commitments.................................................................................26               
     2.2  Procedure for Term Loan Borrowing.....................................................................26           
     2.4  Revolving Credit Commitments..........................................................................27           
     2.5  Procedure for Revolving Credit Borrowing..............................................................28           
     2.6  Repayment of Loans; Evidence of Debt..................................................................29        
     2.7  Commitment Fees, etc..................................................................................30       
     2.8  Optional Termination or Reduction of Revolving Credit Commitments; Scheduled                         
                Reductions of Revoloving Credit Commitments.....................................................30               
     2.9  Optional Prepayments; Mandatory Prepayments of Loans..................................................31        
     2.10  Mandatory Prepayments and Commitments Reductions.....................................................32        
     2.11  Conversion and Continuation Options..................................................................33       
     2.12  Minimum Amounts and Maximum Number of Eurodollar Tranches............................................34          
     2.13  Interest Rates and Payment Dates.....................................................................34   
     2.14  Computation of Interest and Fees.....................................................................34   
     2.15  Inability to Determine Interest Rate.................................................................35
     2.16  Pro Rata Treatment and Payments......................................................................35
     2.17  Requirements of Law..................................................................................37
     2.18  Taxes................................................................................................38
     2.19  Indemnity............................................................................................40
     2.20  Illegality...........................................................................................40
     2.21  Change of Lending Office.............................................................................40
                                                                                                                
SECTION 3.  LETTERS OF CREDIT...................................................................................41
     3.1  L/C Commitment........................................................................................41
     3.2  Procedure for Issuance of Letter of Credit............................................................41
     3.3  Fees and Other Charges................................................................................41
     3.4  L/C Participations....................................................................................42
     3.5  Reimbursement Obligation of the Borrower..............................................................43
     3.6  Obligations Absolute..................................................................................43
     3.7  Letter of Credit Payments.............................................................................43
     3.8  Applications..........................................................................................44
                                                                                                                
SECTION 4.  REPRESENTATIONS AND WARRANTIES......................................................................44
     4.1  Financial Condition...................................................................................44
     4.2  No Change.............................................................................................45
     4.3  Corporate Existence; Compliance with Law..............................................................45
     4.4  Corporate Power; Authorization; Enforceable Obligations...............................................45
     4.5  No Legal Bar..........................................................................................45
</TABLE> 

                                       i
<PAGE>

<TABLE> 
 
<S>                                                                                                             <C>
     4.6  No Material Litigation................................................................................46
     4.7  No Default............................................................................................46
     4.8  Ownership of Property; Liens..........................................................................46
     4.9  Intellectual Property.................................................................................46
     4.10  Taxes................................................................................................46
     4.11  Federal Regulations..................................................................................46
     4.12  Labor Matters........................................................................................47
     4.13  ERISA................................................................................................47
     4.14  Investment Company Act; Other Regulations............................................................47
     4.15  Subsidiaries.........................................................................................47
     4.16  Use of Proceeds......................................................................................48
     4.17  Environmental Matters................................................................................48
     4.18  Accuracy of Information, etc.........................................................................49
     4.19  Security Documents...................................................................................49
     4.20  Solvency.............................................................................................50
     4.21  Regulation H.........................................................................................50
     4.22  Year 2000 Matters....................................................................................50
     4.23  Initial Tower Report.................................................................................51
     4.24  Tower Sites..........................................................................................51
     4.25  Real Property Leases.................................................................................51
     4.26  FCC and FAA Matters; State Regulatory Compliance.....................................................51
                                                                                                                
SECTION 5.  CONDITIONS PRECEDENT................................................................................52
     5.1  Conditions to Initial Extension of Credit.............................................................52
     5.2  Conditions to Each Extension of Credit................................................................54
                                                                                                                
SECTION 6.  AFFIRMATIVE COVENANTS...............................................................................55
     6.1  Financial Statements..................................................................................55
     6.2  Certificates; Other Information.......................................................................56
     6.3  Payment of Obligations................................................................................58
     6.4  Conduct of Business and Maintenance of Existence, etc.................................................58
     6.5  Maintenance of Property; Insurance....................................................................58
     6.6  Inspection of Property; Books and Records; Discussions................................................60
     6.7  Notices...............................................................................................61
     6.8  Environmental Laws....................................................................................61
     6.9  Interest Rate Protection..............................................................................62
     6.10  Additional Collateral, etc...........................................................................62
     6.11  Further Assurances...................................................................................63
     6.12  Initial Tower Report Supplement......................................................................64
     6.13  Mortgages............................................................................................64
                                                                                                                
SECTION 7.  NEGATIVE COVENANTS..................................................................................64
     7.1  Financial Condition Covenants.........................................................................64
     7.2  Limitation on Indebtedness............................................................................67
     7.3  Limitation on Liens...................................................................................68
     7.4  Limitation on Fundamental Changes.....................................................................69
     7.5  Limitation on Disposition of Property.................................................................69
     7.6  Limitation on Restricted Payments.....................................................................70
     7.7  Limitation on Capital Expenditures....................................................................70
     7.8  Limitation on Investments.............................................................................71
     7.9  Limitation on Modifications of Certain Documents......................................................71
     7.10  Limitation on Transactions with Affiliates...........................................................71
</TABLE> 

                                      ii
<PAGE>

<TABLE> 
 
<S>                                                                                                             <C>
     7.11  Limitation on Sales and Leasebacks...................................................................72
     7.12  Limitation on Negative Pledge Clauses................................................................72
     7.13  Limitation on Restrictions on Subsidiary Distributions...............................................72
     7.14  Limitation on Lines of Business......................................................................72
     7.15  Limitation on Activities of Holdings.................................................................72
     7.16  Limitation on Hedge Agreements.......................................................................73
     7.17  Limitation on Speculative Sites......................................................................73
                                                                                                                
SECTION 8.  EVENTS OF DEFAULT...................................................................................73
                                                                                                                
SECTION 9.  THE AGENTS..........................................................................................76
     9.1  Appointment...........................................................................................76
     9.2  Delegation of Duties..................................................................................77
     9.3  Exculpatory Provisions................................................................................77
     9.4  Reliance by Agents....................................................................................77
     9.5  Notice of Default.....................................................................................78
     9.6  Non-Reliance on Agents and Other Lenders..............................................................78
     9.7  Indemnification.......................................................................................78
     9.8  Agent in Its Individual Capacity......................................................................79
     9.9  Successor Agents......................................................................................79
     9.10  Authorization to Release Liens.......................................................................79
     9.11  The Co-Arranger......................................................................................80
                                                                                                                
SECTION 10.  MISCELLANEOUS......................................................................................80
     10.1  Amendments and Waivers...............................................................................80
     10.2  Notices..............................................................................................81
     10.3  No Waiver; Cumulative Remedies.......................................................................82
     10.4  Survival of Representations and Warranties...........................................................82
     10.5  Payment of Expenses..................................................................................82
     10.6  Successors and Assigns; Participations and Assignments...............................................83
     10.7  Adjustments; Set-off.................................................................................85
     10.8  Counterparts.........................................................................................86
     10.9  Severability.........................................................................................86
     10.10  Integration.........................................................................................86
     10.11  GOVERNING LAW.......................................................................................87
     10.12  Submission To Jurisdiction; Waivers.................................................................87
     10.13  Acknowledgments.....................................................................................87
     10.14  Confidentiality.....................................................................................88
     10.15  Release of Collateral Security and Guarantee Obligations............................................88
     10.16  Accounting Changes..................................................................................88
     10.17 Delivery of Lender Addenda...........................................................................89
     10.18  WAIVERS OF JURY TRIAL...............................................................................89
     10.19 Intercreditor Provisions.............................................................................89
     10.20 Purchase of Loans Under Existing Credit Agreement....................................................89
     10.21 Subordination, Non-Disturbance and Attornment........................................................90
</TABLE>
                                      iii
<PAGE>
 
ANNEXES:

A           Pricing Grid
B           Acceptable Tenants


SCHEDULES:

1.1         Mortgaged Properties on Closing Date
4.4         Consents, Authorizations, Filings and Notices
4.15        Subsidiaries
4.19(a)-1   UCC Filing Jurisdictions
4.19(a)-2   UCC Financing Statements to Remain on File
4.19(a)-3   UCC Financing Statements to be Terminated
4.19(b)     Mortgage Filing Jurisdictions
4.26        Governmental Proceedings
7.2(d)      Existing Indebtedness
7.2(f)      Subordinated Indebtedness
7.3(f)      Existing Liens

                                      iv
<PAGE>
 
          AMENDED AND RESTATED CREDIT AGREEMENT, dated as of February 5, 1999,
among SBA COMMUNICATIONS CORPORATION, a Florida corporation ("Holdings"), SBA
                                                              --------       
TELECOMMUNICATIONS, INC., a Florida corporation (the "Borrower"), the several
                                                      --------               
banks and other financial institutions or entities from time to time parties to
this Agreement (the "Lenders"), LEHMAN BROTHERS INC.,  as advisor and book
                     -------                                              
manager ("LBI"), LEHMAN BROTHERS INC., as a co-arranger (in such capacity, a
          ---                                                               
"Co-Arranger"), GENERAL ELECTRIC CAPITAL CORPORATION, as a co-arranger (in such
- ------------                                                                   
capacity, a "Co-Arranger") and as syndication agent (in such capacity, the
             ----------                                                   
"Syndication Agent"), TORONTO DOMINION (TEXAS), INC., as documentation agent (in
- ------------------                                                              
such capacity, the "Documentation Agent"), BARCLAYS BANK PLC (in such capacity,
                    -------------------                                        
the "Co-Documentation Agent") and LEHMAN COMMERCIAL PAPER INC., as
     ----------------------                                       
administrative agent (in such capacity, the "Administrative Agent").
                                             --------------------   


                                 W I T N E S S E T H:
                                 ------------------- 

          WHEREAS, the Borrower is a party to the Amended and Restated Credit
Agreement, dated as of June 29, 1998, by and among the Borrower, BankBoston,
N.A., as agent, First Union National Bank, as co-agent, Fleet National Bank, as
co-agent, and BancBoston Securities Inc., as syndication agent and manager (the
"Existing Credit Agreement");
 -------------------------   

          WHEREAS, the Borrower has requested the Lenders, and the Lenders have
agreed, to purchase all outstanding loans, and the related collateral, under the
Existing Credit Agreement and to restate the Existing Credit Agreement to
provide for senior secured credit facilities in the aggregate principal amount
of $125,000,000 (which amount may be increased to $175,000,000 pursuant to
Section 2.4A); and

          WHEREAS, the proceeds of such credit facilities will be used to
refinance existing indebtedness of the Borrower and to finance (i) the
acquisition and/or construction of wireless transmission towers, tower sites and
related assets, (ii) the acquisition of rights to place antennae on the sides
and rooftops of buildings owned by others, (iii) the acquisition of leasehold
interests in existing transmission towers to be subleased to others, (iv) the
acquisition of or investments in entities the principal assets of which are
towers, tower sites and related assets, (v) the Borrower's business of managing
transmission towers owned by others, (vi) the Borrower's existing wireless
transmission towers and related assets and (vii) other working capital needs and
general corporate purposes of the Borrower and its Subsidiaries.

          NOW, THEREFORE, in consideration of the premises and the agreements
hereinafter set forth, the parties hereto hereby agree that on the Closing Date
the Existing Credit Agreement shall be amended and restated in its entirety as
follows:

                                 SECTION 1.  DEFINITIONS

          1.1  Defined Terms.  As used in this Agreement, the terms listed in
               -------------                                                 
this Section 1.1 shall have the respective meanings set forth in this Section
1.1.
<PAGE>
 
                                                                               2


          "Acceptable Tenant":  any Person that (a) has a contract with the
           -----------------                                               
     Borrower or any of its Subsidiaries to locate wireless transmission
     antennae on a Tower and (b) either (i) is listed on Annex B or (ii) has
     been approved in writing by the Required Lenders.

          "Adjusted EBITDA":  for any period, Consolidated EBITDA for such
           ---------------                                                
     period; provided, however, that for purposes of calculating Non-Tower
             --------  -------                                            
     EBITDA, Mature Tower EBITDA and Developmental Tower EBITDA for any period,
     Consolidated EBITDA shall be adjusted by allocating sales and marketing and
     general and administrative expenses (as such expenses are reflected in the
     financial statements referred to in Section 4.1(b) on the date hereof)
     reflected in Consolidated EBITDA as follows:  (a) to  Non-Tower EBITDA, 28%
     of such expenses, (b) to Mature Tower EBITDA,  72% of such expenses,
     multiplied by the ratio of  the aggregate number of Mature Towers to the
     aggregate number of Towers, and (c) to Developmental Tower EBITDA, 72% of
     such expenses, multiplied by the ratio of the aggregate number of
     Developmental Towers to the aggregate number of Towers.

          "Adjustment Date":  as defined in the Pricing Grid.
           ---------------                                   

          "Administrative Agent":  as defined in the preamble hereto.
           --------------------                                      

          "Affiliate":  as to any Person, any other Person which, directly or
           ---------                                                         
     indirectly, is in control of, is controlled by, or is under common control
     with, such Person.  For purposes of this definition, "control" of a Person
     means the power, directly or indirectly, either to (a) vote 10% or more of
     the securities having ordinary voting power for the election of directors
     (or persons performing similar functions) of such Person or (b) direct or
     cause the direction of the management and policies of such Person, whether
     by contract or otherwise.

          "Agents":  the collective reference to the Syndication Agent, the
           ------                                                          
     Documentation Agent, the Co-Documentation Agent and the Administrative
     Agent.

          "Aggregate Exposure":  with respect to any Lender at any time, an
           ------------------                                              
     amount equal to (a) until the Closing Date, the aggregate amount of such
     Lender's Commitments at such time and (b) thereafter, the sum of (i) the
     aggregate then unpaid principal amount of such Lender's Term Loans and (ii)
     amount of such Lender's Revolving Credit Commitment then in effect or, if
     the Revolving Credit Commitments have been terminated, the amount of such
     Lender's Revolving Extensions of Credit then outstanding.

          "Aggregate Exposure Percentage"  with respect to any Lender at any
           -----------------------------                                    
     time, the ratio (expressed as a percentage) of such Lender's Aggregate
     Exposure at such time to the Aggregate Exposure of all Lenders at such
     time.
<PAGE>
 
                                                                               3

          "Agreement":  this Credit Agreement, as amended, supplemented or
           ---------                                                      
     otherwise modified from time to time.

          "Annualized Adjusted EBITDA":  for any period, the sum of
           --------------------------                              
     Developmental Tower EBITDA,  Mature Tower EBITDA and Non-Tower EBITDA for
     such period.

          "Applicable Margin":  for each Loan, the rate per annum set forth
           -----------------                                               
     under the relevant column heading below:

                                     Base Rate    Eurodollar
                                       Loans      Loans
                                     ---------    ----------

                                       2.50%    3.50%;

     provided, that on and after the date that is six months following the
     --------                                                             
     Closing Date, the Applicable Margin will be determined pursuant to the
     Pricing Grid.

          "Application":  an application, in such form as the Issuing Lender may
           -----------                                                          
     specify from time to time, requesting the Issuing Lender to open a Letter
     of Credit.

          "Asset Coverage Test Amount": at any date of calculation thereof, the
           --------------------------                                          
     sum of (a) the lesser of (i) $125,000 for each Tower which is a
     Developmental Tower on such date of calculation and (ii) 55% of Tower Cost
     with respect to such Tower, plus (b) the product of (i) the aggregate
     Mature Tower EBITDA for the period of twelve consecutive calendar months
     most recently ended prior to such date of calculation and (ii) six, plus
     (c) the product of (i) the aggregate Non-Tower EBITDA for the period of
     twelve consecutive calendar months most recently ended prior to such date
     of calculation and (ii) four; provided, that in calculating the Asset
                                   --------                               
     Coverage Test Amount on any date, no amount may be attributed to the Mature
     Tower EBITDA or Non-Tower EBITDA, as the case may be, attributable to
     assets Disposed of prior to such date of calculation.

          "Asset Sale":  any Disposition of Property or series of related
           ----------                                                    
     Dispositions of Property (excluding any such Disposition permitted by
     clauses (b), (c) or (d) of Section 7.5) which yields gross proceeds to
     Holdings, the Borrower or any of its Subsidiaries (valued at the initial
     principal amount thereof in the case of non-cash proceeds consisting of
     notes or other debt securities and valued at fair market value in the case
     of other non-cash proceeds) in excess of $10,000.

          "Assignee":  as defined in Section 10.6(c).
           --------                                  

          "Assignor":  as defined in Section 10.6(c).
           --------                                  

          "Available Revolving Credit Commitment":  as to any Revolving Credit
           -------------------------------------                              
     Lender at any time, an amount equal to the excess, if any, of (a) such
     Lender's Revolving Credit Commitment then in effect over (b) such Lender's
                                                         ----                  
     Revolving Extensions of Credit then outstanding.
<PAGE>
 
                                                                               4

          "Base Rate":  for any day, a rate per annum (rounded upwards, if
           ---------                                                      
     necessary, to the next 1/16 of 1%) equal to the greatest of (a) the Prime
     Rate in effect on such day, (b) the Base CD Rate in effect on such day plus
     1% and (c) the Federal Funds Effective Rate in effect on such day plus  1/2
     of 1%.  For purposes hereof:  "Prime Rate" shall mean the rate of interest
                                    ----------                                 
     per annum publicly announced from time to time by the Reference Lender as
     its prime or base rate in effect at its principal office in New York City
     (the Prime Rate not being intended to be the lowest rate of interest
     charged by the Reference Lender in connection with extensions of credit to
     debtors); "Base CD Rate" shall mean the sum of (a) the product of (i) the
                ------------                                                  
     Three-Month Secondary CD Rate and (ii) a fraction, the numerator of which
     is one and the denominator of which is one minus the C/D Reserve Percentage
     and (b) the C/D Assessment Rate; and "Three-Month Secondary CD Rate" shall
                                           -----------------------------       
     mean, for any day, the secondary market rate for three-month certificates
     of deposit reported as being in effect on such day (or, if such day shall
     not be a Business Day, the next preceding Business Day) by the Board
     through the public information telephone line of the Federal Reserve Bank
     of New York (which rate will, under the current practices of the Board, be
     published in Federal Reserve Statistical Release H.15(519) during the week
     following such day), or, if such rate shall not be so reported on such day
     or such next preceding Business Day, the average of the secondary market
     quotations for three-month certificates of deposit of major money center
     banks in New York City received at approximately 10:00 A.M., New York City
     time, on such day (or, if such day shall not be a Business Day, on the next
     preceding Business Day) by the Reference Lender from three New York City
     negotiable certificate of deposit dealers of recognized standing selected
     by it.  Any change in the Base Rate due to a change in the Prime Rate, the
     Three-Month Secondary CD Rate or the Federal Funds Effective Rate shall be
     effective as of the opening of business on the effective day of such change
     in the Prime Rate, the Three-Month Secondary CD Rate or the Federal Funds
     Effective Rate, respectively.

          "Base Rate Loans":  Loans for which the applicable rate of interest is
           ---------------                                                      
     based upon the Base Rate.

          "Benefitted Lender":  as defined in Section 10.7.
           -----------------                               

          "Board":  the Board of Governors of the Federal Reserve System of the
           -----                                                               
     United States (or any successor).

          "Borrower":  as defined in the preamble hereto.
           --------                                      

          "Borrowing Date":  any Business Day specified by the Borrower as a
           --------------                                                   
     date on which the Borrower requests the relevant Lenders to make Loans
     hereunder.

          "Business Day":  (i) for all purposes other than as covered by clause
           ------------                                                        
     (ii) below, a day other than a Saturday, Sunday or other day on which
     commercial banks in New York City are authorized or required by law to
     close and (ii) with respect to all notices and determinations in connection
     with, and payments of principal and interest on, Eurodollar 
<PAGE>
 
                                                                               5

     Loans, any day which is a Business Day described in clause (i) and which is
     also a day for trading by and between banks in Dollar deposits in the
     interbank eurodollar market.

          "Capital Expenditures":  for any period, with respect to any Person,
           --------------------                                               
     the aggregate of all expenditures by such Person and its Subsidiaries for
     the acquisition or leasing (pursuant to a capital lease) of fixed or
     capital assets or additions to equipment (including replacements,
     construction costs, capitalized repairs and improvements during such
     period) which should be capitalized under GAAP on a consolidated balance
     sheet of such Person and its Subsidiaries.

          "Capital Lease Obligations":  as to any Person, the obligations of
           -------------------------                                        
     such Person to pay rent or other amounts under any lease of (or other
     arrangement conveying the right to use) real or personal property, or a
     combination thereof, which obligations are required to be classified and
     accounted for as capital leases on a balance sheet of such Person under
     GAAP, and, for the purposes of this Agreement, the amount of such
     obligations at any time shall be the capitalized amount thereof at such
     time determined in accordance with GAAP.

          "Capital Stock":  any and all shares, interests, participations or
           -------------                                                    
     other equivalents (however designated) of capital stock of a corporation,
     any and all equivalent ownership interests in a Person (other than a
     corporation) and any and all warrants, rights or options to purchase any of
     the foregoing.

          "Cash Equivalents":  (a) marketable direct obligations issued by, or
           ----------------                                                   
     unconditionally guaranteed by, the United States Government or issued by
     any agency thereof and backed by the full faith and credit of the United
     States, in each case maturing within one year from the date of acquisition;
     (b) certificates of deposit, time deposits, eurodollar time deposits or
     overnight bank deposits having maturities of six months or less from the
     date of acquisition issued by any Lender or by any commercial bank
     organized under the laws of the United States of America or any state
     thereof having combined capital and surplus of not less than $500,000,000;
     (c) commercial paper of an issuer rated at least A-2 by Standard & Poor's
     Ratings Services ("S&P") or P-2 by Moody's Investors Service, Inc.
                        ---                                            
     ("Moody's"), or carrying an equivalent rating by a nationally recognized
     ---------                                                               
     rating agency, if both of the two named rating agencies cease publishing
     ratings of commercial paper issuers generally, and maturing within six
     months from the date of acquisition; (d) repurchase obligations of any
     Lender or of any commercial bank satisfying the requirements of clause (b)
     of this definition, having a term of not more than 30 days with respect to
     securities issued or fully guaranteed or insured by the United States
     government; (e) securities with maturities of one year or less from the
     date of acquisition issued or fully guaranteed by any state, commonwealth
     or territory of the United States, by any political subdivision or taxing
     authority of any such state, commonwealth or territory or by any foreign
     government, the securities of which state, commonwealth, territory,
     political subdivision, taxing authority or foreign government (as the case
     may be) are rated at least A by S&P or A by Moody's; (f) securities with
     maturities of six months or less from the date of acquisition backed by
<PAGE>
 
                                                                               6

     standby letters of credit issued by any Lender or any commercial bank
     satisfying the requirements of clause (b) of this definition; or (g) shares
     of money market mutual or similar funds which invest exclusively in assets
     satisfying the requirements of clauses (a) through (f) of this definition.

          "C/D Assessment Rate":  for any day as applied to any Base Rate Loan,
           -------------------                                                 
     the annual assessment rate in effect on such day that is payable by a
     member of the Bank Insurance Fund maintained by the Federal Deposit
     Insurance Corporation (the "FDIC") classified as well-capitalized and
                                 ----                                     
     within supervisory subgroup "B" (or a comparable successor assessment risk
     classification) within the meaning of 12 C.F.R. (S) 327.4 (or any successor
     provision) to the FDIC (or any successor) for the FDIC's (or such
     successor's) insuring time deposits at offices of such institution in the
     United States.

          "C/D Reserve Percentage":  for any day as applied to any Base Rate
           ----------------------                                           
     Loan, that percentage (expressed as a decimal) which is in effect on such
     day, as prescribed by the Board, for determining the maximum reserve
     requirement for a Depositary Institution (as defined in Regulation D of the
     Board as in effect from time to time) in respect of new non-personal time
     deposits in Dollars having a maturity of 30 days or more.

          "Closing Date":  the date on which the conditions precedent set forth
           ------------                                                        
     in Section 5.1 shall have been satisfied, which date is February 5, 1999.

          "Co-Arranger":  as defined in the preamble hereto.
           -----------                                      

          "Code":  the Internal Revenue Code of 1986, as amended from time to
           ----                                                              
     time.

          "Collateral":  all Property of the Loan Parties, now owned or
           ----------                                                  
     hereafter acquired, upon which a Lien is purported to be created by any
     Security Document.

          "Commitment":  as to any Lender, the sum of the Term Loan Commitment
           ----------                                                         
     and the Revolving Credit Commitment of such Lender.

          "Commitment Fee Rate":  1.25% per annum; provided, that on and after
           -------------------                     --------                   
     the date that is six months following the Closing Date, the Commitment Fee
     Rate will be determined pursuant to the Pricing Grid.

          "Commonly Controlled Entity":  an entity, whether or not incorporated,
           --------------------------                                           
     which is under common control with the Borrower within the meaning of
     Section 4001 of ERISA or is part of a group that includes the Borrower and
     that is treated as a single employer under Section 414 of the Code.

          "Compliance Certificate":  a certificate duly executed by a
           ----------------------                                    
     Responsible Officer substantially in the form of Exhibit B.
<PAGE>
 
                                                                               7

          "Communications Act": the Communications Act of 1934, and any similar
           ------------------                                                  
     or successor federal statute, and the rules and regulations of the FCC
     thereunder, all as amended and as may be in effect from time to time.

          "Confidential Information Memorandum":  the Confidential Information
           -----------------------------------                                
     Memorandum dated January 1999 and furnished to the initial Lenders.

          "Consolidated Current Assets":  at any date, all amounts (other than
           ---------------------------                                        
     cash and Cash Equivalents) which would, in conformity with GAAP, be set
     forth opposite the caption "total current assets" (or any like caption) on
     a consolidated balance sheet of the Borrower and its Subsidiaries at such
     date.

          "Consolidated Current Liabilities":  at any date, all amounts that
           --------------------------------                                 
     would, in conformity with GAAP, be set forth opposite the caption "total
     current liabilities" (or any like caption) on a consolidated balance sheet
     of the Borrower and its Subsidiaries at such date, but excluding (a) the
     current portion of any Funded Debt of the Borrower and its Subsidiaries and
     (b) without duplication of clause (a) above, all Indebtedness consisting of
     Revolving Credit Loans to the extent otherwise included therein.

          "Consolidated EBITDA":  for any period, Consolidated Net Income for
           -------------------                                               
     such period plus, without duplication and to the extent reflected as a
                 ----                                                      
     charge in the statement of such Consolidated Net Income for such period,
     the sum of (a) income tax expense, (b) Consolidated Interest Expense,
     amortization or writeoff of debt discount and debt issuance costs and
     commissions, discounts and other fees and charges associated with
     Indebtedness (including the Loans), (c) depreciation and amortization
     expense, (d) amortization of intangibles (including, but not limited to,
     goodwill) and organization costs, (e) any extraordinary, unusual or non-
     recurring expenses or losses (including, whether or not otherwise
     includable as a separate item in the statement of such Consolidated Net
     Income for such period, losses on sales of assets outside of the ordinary
     course of business) and (f) any other non-cash charges, and minus, to the
                                                                 -----        
     extent included in the statement of such Consolidated Net Income for such
     period, the sum of (a) interest income (except to the extent deducted in
     determining Consolidated Interest Expense), (b) any extraordinary, unusual
     or non-recurring income or gains (including, whether or not otherwise
     includable as a separate item in the statement of such Consolidated Net
     Income for such period, gains on the sales of assets outside of the
     ordinary course of business) and (c) any other non-cash income, all as
     determined on a consolidated basis; provided that for purposes of
                                         --------                     
     calculating Consolidated EBITDA of the Borrower and its Subsidiaries for
     any period, (i) the Consolidated EBITDA of any Mature Tower or Person
     acquired by the Borrower or its Subsidiaries during such period shall be
     included on a pro forma basis for such period (assuming the consummation of
                   --- -----                                                    
     such acquisition and the incurrence or assumption of any Indebtedness in
     connection therewith occurred on the first day of such period) if, with
     respect to any acquisition of any Person,  the consolidated balance sheet
     of such acquired Person and its consolidated Subsidiaries as at the end of
     the period preceding the acquisition of such Person and the related
     consolidated statements of income and stockholders' equity and of cash
     flows for the 
<PAGE>
 
                                                                               8

     period in respect of which Consolidated EBITDA is to be calculated (x) have
     been previously provided to the Administrative Agent and the Lenders and
     (y) either (1) have been reported on without a qualification arising out of
     the scope of the audit by independent certified public accountants of
     nationally recognized standing or (2) have been found acceptable by the
     Administrative Agent and (ii) the Consolidated EBITDA of any Person
     Disposed of by the Borrower or its Subsidiaries during such period shall be
     excluded for such period (assuming the consummation of such Disposition and
     the repayment of any Indebtedness in connection therewith occurred on the
     first day of such period).

          "Consolidated Fixed Charge Coverage Ratio":  for any period, the ratio
           ----------------------------------------                             
     of (a) the sum of (i) Consolidated EBITDA for such period, (ii) the Net
     Cash Proceeds from issuances of Capital Stock or Indebtedness during such
     period, (iii) the aggregate of the Available Revolving Credit Commitments,
     as determined in accordance with this Agreement, as of the date of the most
     recently ended fiscal quarter and (iv) without duplication, cash of the
     Borrower and its Subsidiaries as of the date of the most recently ended
     fiscal quarter to (b) Consolidated Fixed Charges for such period.

          "Consolidated Fixed Charges":  for any period, the sum (without
           --------------------------                                    
     duplication) of (a) Consolidated Interest Expense for such period, (b)
     provision for cash income taxes made by the Borrower or any of its
     Subsidiaries on a consolidated basis in respect of such period, (c)
     scheduled payments made during such period on account of principal of
     Indebtedness of the Borrower or any of its Subsidiaries (including
     scheduled principal payments in respect of the Term Loans and scheduled
     reductions of the Revolving Credit Commitments) and (d) Capital
     Expenditures for such period.

          "Consolidated Interest Expense":  for any period, total cash interest
           -----------------------------                                       
     expense (including that attributable to Capital Lease Obligations) of the
     Borrower and its Subsidiaries for such period with respect to all
     outstanding Indebtedness of the Borrower and its Subsidiaries (including,
     without limitation, all commissions, discounts and other fees and charges
     owed with respect to letters of credit and bankers' acceptance financing
     and net costs under Hedge Agreements in respect of interest rates to the
     extent such net costs are allocable to such period in accordance with
     GAAP).

          "Consolidated Net Income":  for any period, the consolidated net
           -----------------------                                        
     income (or loss) of the Borrower and its Subsidiaries, determined on a
     consolidated basis in accordance with GAAP; provided that there shall be
                                                 --------                    
     excluded (a) the income (or deficit) of any Person accrued prior to the
     date it becomes a Subsidiary of the Borrower or is merged into or
     consolidated with the Borrower or any of its Subsidiaries, (b) the income
     (or deficit) of any Person (other than a Subsidiary of the Borrower) in
     which the Borrower or any of its Subsidiaries has an ownership interest,
     except to the extent that any such income is actually received by the
     Borrower or such Subsidiary in the form of dividends or similar
     distributions and (c) the undistributed earnings of any Subsidiary of the
     Borrower to the extent that the declaration or payment of dividends or
     similar distributions by such Subsidiary is not at the time permitted by
     the terms of any 
<PAGE>
 
                                                                               9

     Contractual Obligation (other than under any Loan Document) or Requirement
     of Law applicable to such Subsidiary; provided, that Consolidated Net
                                           --------
     Income shall include income from Excluded Entities only to the extent that
     such income is actually received by the Borrower and its Subsidiaries in
     cash.

          "Consolidated Total Debt":  at any date, the aggregate principal
           -----------------------                                        
     amount of all Indebtedness of the Borrower and its Subsidiaries at such
     date, determined on a consolidated basis in accordance with GAAP.

          "Consolidated Working Capital":  at any date, the excess of
           ----------------------------                              
     Consolidated Current Assets on such date over Consolidated Current
     Liabilities on such date.

          "Contractual Obligation":  as to any Person, any provision of any
           ----------------------                                          
     security issued by such Person or of any agreement, instrument or other
     undertaking to which such Person is a party or by which it or any of its
     Property is bound.

          "Control Investment Affiliate":  as to any Person, any other Person
           ----------------------------                                      
     that (a) directly or indirectly, is in control of, is controlled by, or is
     under common control with, such Person and (b) is organized by such Person
     primarily for the purpose of making equity or debt investments in one or
     more companies.  For purposes of this definition, "control" of a Person
     means the power, directly or indirectly, to direct or cause the direction
     of the management and policies of such Person whether by contract or
     otherwise.

          "Default":  any of the events specified in Section 8, whether or not
           -------                                                            
     any requirement for the giving of notice, the lapse of time, or both, has
     been satisfied.

          "Derivatives Counterparty":  as defined in Section 7.6.
           ------------------------                              

          "Developmental Tower":  at any date of determination thereof, each
           -------------------                                              
     Tower which (a) has been operational for 12 months or a shorter period of
     time, (b) during such period has had, and continues to have on such date of
     determination, at least one broadband Acceptable Tenant under a contract
     having an original term of not less than five years, (c) has capacity for
     at least two additional broadband tenants and at least two additional
     narrowband tenants and (d) has not been designated by the Borrower by
     written notice to the Administrative Agent, as a Mature Tower.

          "Developmental Tower EBITDA":  for any period of twelve consecutive
           --------------------------                                        
     calendar months, the product of (a) Adjusted EBITDA derived from
     Developmental Towers for the last three calendar months of such period
     (whether or not a fiscal quarter) and (b) four.

          "Disposition":  with respect to any Property, any sale, lease, sale
           -----------                                                       
     and leaseback, assignment, conveyance, transfer or other disposition
     thereof; and the terms "Dispose" and "Disposed of" shall have correlative
                             -------       -----------                        
     meanings.
<PAGE>
 
                                                                              10

          "Dollars" and "$":  dollars in lawful currency of the United States of
           -------       -                                                      
     America.

          "Domestic Subsidiary":  any Subsidiary of the Borrower organized under
           -------------------                                                  
     the laws of any jurisdiction within the United States of America.

          "Environmental Laws":  any and all laws, rules, orders, regulations,
           ------------------                                                 
     statutes, ordinances, guidelines, codes, decrees, or other legally
     enforceable requirements (including, without limitation, common law) of any
     international authority, foreign government, the United States, or any
     state, local, municipal or other governmental authority having jurisdiction
     over the Borrower, any Subsidiary of the Borrower or any Tower, regulating,
     relating to or imposing liability or standards of conduct concerning
     protection of the environment or of human health, or employee health and
     safety, as has been, is now, or may at any time hereafter be, in effect.

          "Environmental Permits":  any and all permits, licenses, approvals,
           ---------------------                                              
     registrations, notifications, exemptions and any other authorization
     required under any Environmental Law.

          "ERISA":  the Employee Retirement Income Security Act of 1974, as
           -----                                                           
     amended from time to time.

          "Eurocurrency Reserve Requirements":  for any day as applied to a
           ---------------------------------                               
     Eurodollar Loan, the aggregate (without duplication) of the maximum rates
     (expressed as a decimal fraction) of reserve requirements in effect on such
     day (including, without limitation, basic, supplemental, marginal and
     emergency reserves under any regulations of the Board or other Governmental
     Authority having jurisdiction with respect thereto) dealing with reserve
     requirements prescribed for eurocurrency funding (currently referred to as
     "Eurocurrency Liabilities" in Regulation D of the Board) maintained by a
     member bank of the Federal Reserve System.

          "Eurodollar Base Rate":  with respect to each day during each Interest
           --------------------                                                 
     Period pertaining to a Eurodollar Loan, the rate per annum determined on
     the basis of the rate for deposits in Dollars for a period equal to such
     Interest Period commencing on the first day of such Interest Period
     appearing on Page 3750 of the Telerate screen as of 11:00 A.M., London
     time, two Business Days prior to the beginning of such Interest Period.  In
     the event that such rate does not appear on Page 3750 of the Telerate
     screen (or otherwise on such screen), the "Eurodollar Base Rate" for
                                                --------------------     
     purposes of this definition shall be determined by reference to such other
     comparable publicly available service for displaying eurodollar rates as
     may be selected by the Administrative Agent or, in the absence of such
     availability, by reference to the rate at which the Administrative Agent is
     offered Dollar deposits at or about 11:00 A.M., New York City time, two
     Business Days prior to the beginning of such Interest Period in the
     interbank eurodollar market where its eurodollar and foreign currency and
     exchange operations are then being conducted for delivery on the first day
     of such Interest Period for the number of days comprised therein.
<PAGE>
 
                                                                              11

          "Eurodollar Loans":  Loans the rate of interest applicable to which is
           ----------------                                                     
     based upon the Eurodollar Rate.

          "Eurodollar Rate":  with respect to each day during each Interest
           ---------------                                                 
     Period pertaining to a Eurodollar Loan, a rate per annum determined for
     such day in accordance with the following formula (rounded upward to the
     nearest 1/100th of 1%):

                             Eurodollar Base Rate
                -----------------------------------------------
                   1.00 - Eurocurrency Reserve Requirements

          "Eurodollar Tranche":  the collective reference to Eurodollar Loans
           ------------------                                                
     the then current Interest Periods with respect to all of which begin on the
     same date and end on the same later date (whether or not such Eurodollar
     Loans shall originally have been made on the same day).

          "Event of Default":  any of the events specified in Section 8,
           ----------------                                             
     provided that any requirement for the giving of notice, the lapse of time,
     --------                                                                  
     or both, has been satisfied.

          "Excess Cash Flow":  for any fiscal year of the Borrower, the excess,
           ----------------                                                    
     if any, of (a) the sum, without duplication, of (i) Consolidated Net Income
     for such fiscal year, (ii) an amount equal to the amount of all non-cash
     charges (including depreciation and amortization) deducted in arriving at
     such Consolidated Net Income, (iii) decreases in Consolidated Working
     Capital for such fiscal year, (iv) an amount equal to the aggregate net
     non-cash loss on the Disposition of Property by the Borrower and its
     Subsidiaries during such fiscal year (other than sales of inventory in the
     ordinary course of business), to the extent deducted in arriving at such
     Consolidated Net Income and (v) the net increase during such fiscal year
     (if any) in deferred tax accounts of the Borrower over (b) the sum, without
                                                       ----                     
     duplication, of (i) an amount equal to the amount of all non-cash credits
     included in arriving at such Consolidated Net Income, (ii) the aggregate
     amount actually paid by the Borrower and its Subsidiaries in cash during
     such fiscal year on account of Capital Expenditures (excluding the
     principal amount of Indebtedness incurred in connection with such
     expenditures and any such expenditures financed with the proceeds of any
     Reinvestment Deferred Amount), (iii) the aggregate amount of all
     prepayments of Revolving Credit Loans during such fiscal year to the extent
     accompanying permanent optional reductions of the Revolving Credit
     Commitments and all optional prepayments of the Term Loans during such
     fiscal year, (iv) the aggregate amount of all regularly scheduled principal
     payments of Funded Debt (including, without limitation, the Term Loans) of
     the Borrower and its Subsidiaries made during such fiscal year (other than
     in respect of any revolving credit facility to the extent there is not an
     equivalent permanent reduction in commitments thereunder), (v) increases in
     Consolidated Working Capital for such fiscal year, (vi) an amount equal to
     the aggregate net non-cash gain on the Disposition of Property by the
     Borrower and its Subsidiaries during such fiscal year (other than sales of
     inventory in the ordinary course of business), to the extent included in
     arriving at such Consolidated Net Income, and (vii) the net decrease during
     such fiscal year (if any) in deferred tax accounts of the Borrower.
<PAGE>
 
                                                                              12

          "Excess Cash Flow Application Date":  as defined in Section 2.10(c).
           ---------------------------------                                  

          "Excluded Entities":  SBA Brazil and Metro Joint Venture, L.C. (or
           -----------------                                                
     such other partnership, limited liability company or other entity formed by
     and between SBA Towers New York, Inc. and Site Tech, Inc.)

          "Excluded Foreign Subsidiaries":  any Foreign Subsidiary in respect of
           -----------------------------                                        
     which either (i) the pledge of all of the Capital Stock of such Subsidiary
     as Collateral or (ii) the guaranteeing by such Subsidiary of the
     Obligations, would, in the good faith judgment of the Borrower, result in
     adverse tax consequences to the Borrower.

          "Existing Credit Agreement": as defined in the Recitals.
           -------------------------                              

          "FAA":  the Federal Aviation Administration, and any successor agency
           ---                                                                 
     of the United States Government exercising substantially equivalent powers.

          "Facility":  each of (a) the Term Loan Commitments and the Term Loans
           --------                                                            
     made thereunder (the "Term Loan Facility") and (b) the Revolving Credit
                           ------------------                               
     Commitments and the extensions of credit made thereunder (the "Revolving
                                                                    ---------
     Credit Facility").
     ---------------   

          "FCC":  the Federal Communications Commission, and any successor
           ---                                                            
     agency of the United States Government exercising substantially equivalent
     powers.

          "Federal Funds Effective Rate":  for any day, the weighted average of
           ----------------------------                                        
     the rates on overnight federal funds transactions with members of the
     Federal Reserve System arranged by federal funds brokers, as published on
     the next succeeding Business Day by the Federal Reserve Bank of New York,
     or, if such rate is not so published for any day which is a Business Day,
     the average of the quotations for the day of such transactions received by
     the Reference Lender from three federal funds brokers of recognized
     standing selected by it.

          "Foreign Subsidiary":  any Subsidiary of the Borrower that is not a
           ------------------                                                
     Domestic Subsidiary.

          "Funded Debt":  as to any Person, all Indebtedness of such Person of
           -----------                                                        
     the types described in clauses (a) through (e) of the definition of
     "Indebtedness" in this Section.

          "Funding Office":  the office designated from time to time by the
           --------------                                                  
     Administrative Agent, by written notice to the Borrower and the Lenders, as
     the Funding Office.

          "GAAP":  generally accepted accounting principles in the United States
           ----                                                                 
     of America as in effect from time to time, except that for purposes of
     Section 7.1, GAAP shall be determined on the basis of such principles in
     effect on the date hereof and consistent with those used in the preparation
     of the most recent audited financial statements delivered pursuant to
     Section 4.1(b).
<PAGE>
 
                                                                              13

          "Governmental Authority":  any nation or government, any state or
           ----------------------                                          
     other political subdivision thereof and any entity exercising executive,
     legislative, judicial, regulatory or administrative functions of or
     pertaining to government.

          "Guarantee and Collateral Agreement":  the Guarantee and Collateral
           ----------------------------------                                
     Agreement to be executed and delivered by Holdings, the Borrower and each
     Subsidiary Guarantor, substantially in the form of Exhibit A, as the same
     may be amended, supplemented or otherwise modified from time to time.

          "Guarantee Obligation":  as to any Person (the "guaranteeing person"),
           --------------------                           -------------------   
     any obligation of (a) the guaranteeing person or (b) another Person
     (including, without limitation, any bank under any letter of credit) to
     induce the creation of which the guaranteeing person has issued a
     reimbursement, counterindemnity or similar obligation, in either case
     guaranteeing or in effect guaranteeing any Indebtedness, leases, dividends
     or other obligations (the "primary obligations") of any other third Person
                                -------------------                            
     (the "primary obligor") in any manner, whether directly or indirectly,
           ---------------                                                 
     including, without limitation, any obligation of the guaranteeing person,
     whether or not contingent, (i) to purchase any such primary obligation or
     any Property constituting direct or indirect security therefor, (ii) to
     advance or supply funds (1) for the purchase or payment of any such primary
     obligation or (2) to maintain working capital or equity capital of the
     primary obligor or otherwise to maintain the net worth or solvency of the
     primary obligor, (iii) to purchase Property, securities or services
     primarily for the purpose of assuring the owner of any such primary
     obligation of the ability of the primary obligor to make payment of such
     primary obligation or (iv) otherwise to assure or hold harmless the owner
     of any such primary obligation against loss in respect thereof; provided,
                                                                     -------- 
     however, that the term Guarantee Obligation shall not include endorsements
     -------                                                                   
     of instruments for deposit or collection in the ordinary course of
     business.  The amount of any Guarantee Obligation of any guaranteeing
     person shall be deemed to be the lower of (a) an amount equal to the stated
     or determinable amount of the primary obligation in respect of which such
     Guarantee Obligation is made and (b) the maximum amount for which such
     guaranteeing person may be liable pursuant to the terms of the instrument
     embodying such Guarantee Obligation, unless such primary obligation and the
     maximum amount for which such guaranteeing person may be liable are not
     stated or determinable, in which case the amount of such Guarantee
     Obligation shall be such guaranteeing person's maximum reasonably
     anticipated liability in respect thereof as determined by the Borrower in
     good faith.

          "Guarantors":  the collective reference to Holdings and the Subsidiary
           ----------                                                           
     Guarantors.

          "Hedge Agreements":  all interest rate swaps, caps or collar
           ----------------                                           
     agreements or similar arrangements entered into by the Borrower providing
     for protection against fluctuations in interest rates or currency exchange
     rates or the exchange of nominal interest obligations, either generally or
     under specific contingencies.
<PAGE>
 
                                                                              14

          "Increased Commitment Availability Period":  as defined in Section
           ----------------------------------------                         
     2.4A.

          "Increased Revolving Commitment Date":  as defined in Section 2.4A.
           -----------------------------------                               

          "Increased Revolving Credit Commitments":  as defined in Section 2.4A.
           --------------------------------------                               

          "Indebtedness":  of any Person at any date, without duplication, (a)
           ------------                                                       
     all indebtedness of such Person for borrowed money, (b) all obligations of
     such Person for the deferred purchase price of Property or services (other
     than trade payables incurred in the ordinary course of such Person's
     business), (c) all obligations of such Person evidenced by notes, bonds,
     debentures or other similar instruments (other than performance bonds and
     other obligations of a like nature incurred in the ordinary course of such
     Person's business), (d) all indebtedness created or arising under any
     conditional sale or other title retention agreement with respect to
     Property acquired by such Person (even though the rights and remedies of
     the seller or lender under such agreement in the event of default are
     limited to repossession or sale of such Property), (e) all Capital Lease
     Obligations of such Person, (f) all obligations of such Person, contingent
     or otherwise, as an account party under acceptance, letter of credit or
     similar facilities, (g) all obligations of such Person, contingent or
     otherwise, to purchase, redeem, retire or otherwise acquire for value any
     Capital Stock of such Person, (h) all Guarantee Obligations of such Person
     in respect of obligations of the kind referred to in clauses (a) through
     (g) above; (i) all obligations of the kind referred to in clauses (a)
     through (h) above secured by (or for which the holder of such obligation
     has an existing right, contingent or otherwise, to be secured by) any Lien
     on Property (including, without limitation, accounts and contract rights)
     owned by such Person, whether or not such Person has assumed or become
     liable for the payment of such obligation, (j) for the purposes of Section
     8(e) only, all obligations of such Person in respect of Hedge Agreements
     and (k) the liquidation value of any preferred Capital Stock of such Person
     or its Subsidiaries held by any Person other than such Person and its
     Wholly Owned Subsidiaries.

          "Indemnified Liabilities":  as defined in Section 10.5.
           -----------------------                               

          "Indemnitee":  as defined in Section 10.5.
           ----------                               

          "Initial Tower Report":  the report of Arthur Andersen LLP,
           --------------------                                      
     independent certified public accountants of Holdings, dated November 30,
     1998 stating that the procedures that such accountants have used to verify
     information with respect to leases in existence for Developmental Towers
     and Mature Towers and which report (i) demonstrates that Total Tower
     Revenue for the eleven months ended November 30, 1998 was at least
     $10,500,000 and that total Tower gross profit for such period was at least
     $4,000,000, (ii) confirms that on the last day of such period there were at
     least 418 Towers,  (iii) confirms the total number of tenants on the Towers
     on the last day of such period and (iv) confirms such other information as
     reasonably requested by the Administrative Agent.
<PAGE>
 
                                                                              15

          "Initial Tower Report Supplement":  the report of Arthur Andersen LLP
           -------------------------------                                     
     supplementing the Initial Tower Report which shall (a) verify cash
     collections of the Borrower in respect of a statistical sample of Towers,
     and describe the methods and procedures used for such verification and (b)
     verify that Towers classified by the Borrower as Developmental Towers met
     the criteria specified in the definition of "Developmental Towers" in this
     Section 1.1 at the time such Towers were so classified by the Borrower.

          "Insolvency":  with respect to any Multiemployer Plan, the condition
           ----------                                                         
     that such Plan is insolvent within the meaning of Section 4245 of ERISA.

          "Insolvent":  pertaining to a condition of Insolvency.
           ---------                                            

          "Intellectual Property":  the collective reference to all rights,
           ---------------------                                           
     priorities and privileges relating to intellectual property, whether
     arising under United States, multinational or foreign laws or otherwise,
     including, without limitation, copyrights, copyright licenses, patents,
     patent licenses, trademarks, trademark licenses, technology, know-how and
     processes, and all rights to sue at law or in equity for any infringement
     or other impairment thereof, including the right to receive all proceeds
     and damages therefrom.

          "Interest Payment Date":  (a) as to any Base Rate Loan, the last day
           ---------------------                                              
     of each March, June, September and December to occur while such Base Rate
     Loan is outstanding and the final maturity date of such Loan, (b) as to any
     Eurodollar Loan having an Interest Period of three months or less, the last
     day of such Interest Period, (c) as to any Eurodollar Loan having an
     Interest Period longer than three months, each day which is three months,
     or a whole multiple thereof, after the first day of such Interest Period
     and the last day of such Interest Period and (d) as to any Loan (other than
     any Revolving Credit Loan that is a Base Rate Loan), the date of any
     repayment or prepayment made in respect thereof.

          "Interest Period":  as to any Eurodollar Loan, (a) initially, the
           ---------------                                                 
     period commencing on the borrowing or conversion date, as the case may be,
     with respect to such Eurodollar Loan and ending one, two, three or six
     months thereafter, as selected by the Borrower in its notice of borrowing
     or notice of conversion, as the case may be, given with respect thereto;
     and (b) thereafter, each period commencing on the last day of the next
     preceding Interest Period applicable to such Eurodollar Loan and ending
     one, two, three or six months thereafter, as selected by the Borrower by
     irrevocable notice to the Administrative Agent not less than three Business
     Days prior to the last day of the then current Interest Period with respect
     thereto; provided that, all of the foregoing provisions relating to
              --------                                                  
     Interest Periods are subject to the following:

                    (i0    if any Interest Period would otherwise end on a day
          that is not a Business Day, such Interest Period shall be extended to
          the next succeeding Business Day unless the result of such extension
          would be to carry such Interest 
<PAGE>
 
                                                                              16

          Period into another calendar month in which event such Interest Period
          shall end on the immediately preceding Business Day;

                    (ii0    any Interest Period that would otherwise extend
          beyond the Revolving Credit Termination Date or beyond the date final
          payment is due on the Term Loans shall end on the Revolving Credit
          Termination Date or such due date, as applicable;

                    (iii0    any Interest Period that begins on the last
          Business Day of a calendar month (or on a day for which there is no
          numerically corresponding day in the calendar month at the end of such
          Interest Period) shall end on the last Business Day of a calendar
          month; and

                    (iv0    the Borrower shall select Interest Periods so as not
          to require a payment or prepayment of any Eurodollar Loan during an
          Interest Period for such Loan.
          "Investments":  as defined in Section 7.8.
           -----------                              

          "Issuing Lender":  Toronto Dominion (Texas), Inc., in its capacity as
           --------------                                                      
     issuer of any Letter of Credit.

          "L/C Commitment":  $25,000,000.
           --------------                

          "L/C Fee Payment Date":  the last day of each March, June, September
           --------------------                                               
     and December and the last day of the Revolving Credit Commitment Period.

          "L/C Obligations":  at any time, an amount equal to the sum of (a) the
           ---------------                                                      
     aggregate then undrawn and unexpired amount of the then outstanding Letters
     of Credit and (b) the aggregate amount of drawings under Letters of Credit
     that have not then been reimbursed pursuant to Section 3.5.

          "L/C Participants":  the collective reference to all the Revolving
           ----------------                                                 
     Credit Lenders other than the Issuing Lender.

          "Lender Addendum":  with respect to any initial Lender, a Lender
           ---------------                                                
     Addendum, substantially in the form of Exhibit I, to be executed and
     delivered by such Lender on the Closing Date as provided in Section 10.17.

          "Lenders":  as defined in the preamble hereto.
           -------                                      

          "Letters of Credit":  as defined in Section 3.1(a).
           -----------------                                 

          "Lien":  any mortgage, pledge, hypothecation, assignment, deposit
           ----                                                            
     arrangement, encumbrance, lien (statutory or other), charge or other
     security interest or any preference, priority or other security agreement
     or preferential arrangement of any kind or nature 
<PAGE>
 
                                                                              17

     whatsoever (including, without limitation, any conditional sale or other
     title retention agreement and any capital lease having substantially the
     same economic effect as any of the foregoing).

          "Loan":  any loan made by any Lender pursuant to this Agreement.
           ----                                                           

          "Loan Documents":  this Agreement, the Security Documents, the
           --------------                                               
     Applications and the Notes.

          "Loan Parties":  Holdings, the Borrower and each Subsidiary of the
           ------------                                                     
     Borrower which is a party to a Loan Document.

          "Majority Facility Lenders":  with respect to any Facility, the
           -------------------------                                     
     holders of more than 50% of the aggregate unpaid principal amount of the
     Term Loans or the Total Revolving Extensions of Credit, as the case may be,
     outstanding under such Facility (or, in the case of the Revolving Credit
     Facility, prior to any termination of the Revolving Credit Commitments, the
     holders of more than 50% of the Total Revolving Credit Commitments);
     provided, that, for purposes of this definition, during the Increased
     --------                                                             
     Commitment Availability Period, the Revolving Credit Commitments of each
     Lender shall include such Lender's Increased Revolving Credit Commitment,
     and the Total Revolving Credit Commitments shall include the Increased
     Revolving Credit Commitments of all Lenders.

          "Majority Revolving Credit Facility Lenders":  the Majority Facility
           ------------------------------------------                         
     Lenders in respect of the Revolving Credit Facility.

          "Material Adverse Effect":  a material adverse effect on (a) the
           -----------------------                                        
     business, assets, property, condition (financial or otherwise) or prospects
     of Holdings, the Borrower and its Subsidiaries taken as a whole or (b) the
     validity or enforceability of this Agreement or any of the other Loan
     Documents or the rights or remedies of the Agents or the Lenders hereunder
     or thereunder.

          "Material Environmental Amount":  an amount or amounts payable by the
           -----------------------------                                       
     Borrower and/or any of its Subsidiaries, in the aggregate in excess of
     $1,000,000, for: costs to comply with any Environmental Law; costs of any
     investigation, and any remediation, of any Material of Environmental
     Concern; and compensatory damages (including, without limitation damages to
     natural resources), punitive damages, fines, and penalties pursuant to any
     Environmental Law; provided that any amounts expended for environmental
                        --------                                            
     site assessments pursuant to customary due diligence conducted in
     connection with the acquisition of towers and/or tower sites shall be
     excluded from the calculation of any Material Environmental Amount.

          "Materials of Environmental Concern":  any gasoline or petroleum
           ----------------------------------                             
     (including crude oil or any fraction thereof) or petroleum products,
     polychlorinated biphenyls, urea-formaldehyde insulation, asbestos,
     pollutants, contaminants, radioactivity, and any other 
<PAGE>
 
                                                                              18

     substances or forces of any kind, whether or not any such substance or
     force is defined as hazardous or toxic under any Environmental Law, that is
     regulated pursuant to or could give rise to liability under any
     Environmental Law.

          "Mature Tower":   any  Tower other than a Developmental Tower.
           ------------                                                 

          "Mature Tower EBITDA":  for any period of twelve consecutive calendar
           -------------------                                                 
     months, the product of (a) Adjusted EBITDA derived for the last three
     calendar months of such period (whether or not a fiscal quarter) from
     Mature Towers, from the Borrower's lease/sublease business (excluding
     revenue derived from Developmental Towers) and the Borrower's businesses of
     leasing antennae space on buildings and managing towers and antennae space
     on buildings owned by others and (b) four.

          "Mortgaged Properties":  the real properties upon which the
           --------------------                                      
     Administrative Agent for the benefit of the Lenders shall be granted a Lien
     pursuant to the Mortgages. The properties required to be Mortgaged
     Properties as of the Closing Date based upon Total Tower Revenue and number
     of Developmental Towers as of September 30, 1998 are described in Schedule
     1.1.

          "Mortgage Requirement":  the requirement that, within 45 days of the
           --------------------                                               
     Closing Date and 45 days after the end of each fiscal quarter thereafter,
     there shall have been executed and delivered to the Administrative Agent,
     and duly recorded in the appropriate recording offices, Mortgages (i)
     covering Mature Towers which during such fiscal quarter most recently ended
     contributed at least 80% of Total Tower Revenue (excluding revenue from the
     Borrower's lease/sublease business) and (ii) Developmental Towers on such
     date which constitute at least 80% in number of all Developmental Towers on
     such date (it being understood that the Borrower will execute and deliver
     Mortgages within 45 days of the Closing Date based upon Total Tower Revenue
     and number of Developmental Towers as of November 30, 1998)

          "Mortgages":  each of the mortgages and deeds of trust made by any
           ---------                                                        
     Loan Party in favor of, or for the benefit of, the Administrative Agent for
     the benefit of the Lenders, substantially in the form of Exhibit D (with
     such changes thereto as shall be advisable under the law of the
     jurisdiction in which such mortgage or deed of trust is to be recorded), as
     the same may be amended, supplemented or otherwise modified from time to
     time.

          "Multiemployer Plan":  a Plan that is a multiemployer plan as defined
           ------------------                                                  
     in Section 4001(a)(3) of ERISA.

          "National Data Transaction":  the Borrower's purchase of c company
           -------------------------                                        
     which owns 29 towers located in Tampa, Florida, central Florida and
     Atlanta, Georgia from National Data & Comm. for aggregate cash
     consideration of $13,100,000.

          "Net Cash Proceeds":  (a) in connection with any Asset Sale or any
           -----------------                                                
     Recovery Event, the proceeds thereof in the form of cash and Cash
     Equivalents (including any such 
<PAGE>
 
                                                                              19

     proceeds received by way of deferred payment of principal pursuant to a
     note or installment receivable or purchase price adjustment receivable or
     otherwise, but only as and when received) of such Asset Sale or Recovery
     Event, net of attorneys' fees, accountants' fees, investment banking fees,
     amounts required to be applied to the repayment of Indebtedness secured by
     a Lien expressly permitted hereunder on any asset which is the subject of
     such Asset Sale or Recovery Event (other than any Lien pursuant to a
     Security Document) and other customary fees and expenses (including
     commissions, transfer taxes and other customary expenses) actually incurred
     in connection therewith and net of taxes paid or reasonably estimated to be
     payable as a result thereof (after taking into account any available tax
     credits or deductions and any tax sharing arrangements) and (b) in
     connection with any issuance or sale of equity securities or debt
     securities or instruments or the incurrence of loans, the cash proceeds
     received from such issuance or incurrence, net of attorneys' fees,
     investment banking fees, accountants' fees, underwriting discounts and
     commissions and other customary fees and expenses (including commissions,
     transfer taxes and other customary expenses) actually incurred in
     connection therewith.

          "Non-Excluded Taxes":  as defined in Section 2.18(a).
           ------------------                                  

          "Non-Tower EBITDA":  for any period of twelve consecutive calendar
           ----------------                                                 
     months, the difference of (i) Adjusted EBITDA for such period minus (ii)
     the sum of (a) Developmental Tower EBITDA for such period plus (b) Mature
     Tower EBITDA for such period.

          "Non-U.S. Lender":  as defined in Section 2.18(d).
           ---------------                                  

          "Notes":  the collective reference to any promissory note evidencing
           -----                                                              
     Loans.

          "Obligations":  the unpaid principal of and interest on (including,
           -----------                                                       
     without limitation, interest accruing after the maturity of the Loans and
     Reimbursement Obligations and interest accruing after the filing of any
     petition in bankruptcy, or the commencement of any insolvency,
     reorganization or like proceeding, relating to the Borrower, whether or not
     a claim for post-filing or post-petition interest is allowed in such
     proceeding) the Loans and all other obligations and liabilities of the
     Borrower to the Administrative Agent or to any Lender (or, in the case of
     Specified Hedge Agreements, any Affiliate of any Lender), whether direct or
     indirect, absolute or contingent, due or to become due, or now existing or
     hereafter incurred, which may arise under, out of, or in connection with,
     this Agreement, any other Loan Document, the Letters of Credit, any
     Specified Hedge Agreement or any other document made, delivered or given in
     connection herewith or therewith, whether on account of principal,
     interest, reimbursement obligations, fees, indemnities, costs, expenses
     (including, without limitation, all fees, charges and disbursements of
     counsel to the Administrative Agent or to any Lender that are required to
     be paid by the Borrower pursuant hereto) or otherwise.
<PAGE>
 
                                                                              20

          "Other Taxes":  any and all present or future stamp or documentary
           -----------                                                      
     taxes or any other excise or property taxes, charges or similar levies
     arising from any payment made hereunder or from the execution, delivery or
     enforcement of, or otherwise with respect to, this Agreement or any other
     Loan Document.

          "Participant":  as defined in Section 10.6(b).
           -----------                                  

          "Payment Office":  the office designated from time to time by the
           --------------                                                  
     Administrative Agent, by written notice to the Borrower, as the Payment
     Office.

          "PBGC":  the Pension Benefit Guaranty Corporation established pursuant
           ----                                                                 
     to Subtitle A of Title IV of ERISA (or any successor).

          "Person":  an individual, partnership, corporation, limited liability
           ------                                                              
     company, business trust, joint stock company, trust, unincorporated
     association, joint venture, Governmental Authority or other entity of
     whatever nature.

          "Plan":  at a particular time, any employee benefit plan that is
           ----                                                           
     covered by ERISA and in respect of which the Borrower or a Commonly
     Controlled Entity is (or, if such plan were terminated at such time, would
     under Section 4069 of ERISA be deemed to be) an "employer" as defined in
     Section 3(5) of ERISA.

          "Preferred Stock":  the collective reference to the Series A Preferred
           ---------------                                                      
     Stock, the Series B Preferred Stock, the Series C Preferred Stock and the
     Series D Preferred Stock.

          "Pricing Grid":  the pricing grid attached hereto as Annex A.
           ------------                                                

          "Pricing Ratio":  (a) on the last day of any fiscal quarter ending on
           -------------                                                       
     or before the Transition Date, the ratio of (i) Consolidated Total Debt on
     such last day to (ii) Annualized Adjusted EBITDA for the period of twelve
     consecutive calendar months ended on such day, and (b) on the last day of
     any fiscal quarter ending after the Transition Date, the ratio of (i)
     Consolidated Total Debt on such last day to (ii) Consolidated EBITDA for
     the period of four consecutive fiscal quarters ended on such day.

          "Pro Forma Balance Sheet":  as defined in Section 4.1(a).
           -----------------------                                 

          "Pro Forma Consolidated Debt Service Coverage Ratio":  for any period,
           --------------------------------------------------                   
     the ratio of (a) Consolidated EBITDA for such period to (b) Pro Forma
     Consolidated Debt Service for such period.

          "Pro Forma Consolidated Debt Service":  for any period, the sum
          ------------------------------------                           
     (without duplication) of (a) Pro Forma Consolidated Interest Expense plus
     (b) scheduled payments to be made during the next succeeding four fiscal
     quarters of the Borrower and its Subsidiaries on account of principal of
     Indebtedness of the Borrower or any of its Subsidiaries (including
     scheduled principal payments in respect of the Term Loans and scheduled
     reductions of the Revolving Credit Commitments).
<PAGE>
 
                                                                              21

          "Pro Forma Consolidated Interest Expense":  for any period, total cash
           ---------------------------------------                              
     interest expense of the Borrower and its Subsidiaries for the next
     succeeding four fiscal quarters with respect to all outstanding
     Indebtedness of the Borrower and its Subsidiaries (including, without
     limitation, all commissions, discounts and other fees and charges owed with
     respect to letters of credit and bankers' acceptance financing and net
     costs under Hedge Agreements in respect of interest rates to the extent
     such net costs are allocable to such period in accordance with GAAP).

          "Projections":  as defined in Section 6.2(c).
           -----------                                 

          "Property":  any right or interest in or to property of any kind
           --------                                                       
     whatsoever, whether real, personal or mixed and whether tangible or
     intangible, including, without limitation, Capital Stock.

          "Recovery Event":  any settlement of or payment in respect of any
           --------------                                                  
     property or casualty insurance claim or any condemnation proceeding
     relating to any asset of Holdings, the Borrower or any of its Subsidiaries.

          "Reference Lender":  Bankers Trust Company.
           ----------------                          

          "Register":  as defined in Section 10.6(d).
           --------                                  
          "Regulation U":  Regulation U of the Board as in effect from time to
           ------------                                                       
     time.

          "Reimbursement Obligation":  the obligation of the Borrower to
           ------------------------                                     
     reimburse the Issuing Lender pursuant to Section 3.5 for amounts drawn
     under Letters of Credit.

          "Reinvestment Deferred Amount":  with respect to any Reinvestment
           ----------------------------                                    
     Event, the aggregate Net Cash Proceeds received by Holdings, the Borrower
     or any of its Subsidiaries in connection therewith that are not applied to
     prepay the Term Loans or reduce the Revolving Credit Commitments pursuant
     to Section 2.10(b) as a result of the delivery of a Reinvestment Notice.

          "Reinvestment Event":  any Asset Sale or Recovery Event in respect of
           ------------------                                                  
     which the Borrower has delivered a Reinvestment Notice.

          "Reinvestment Notice":  a written notice executed by a Responsible
           -------------------                                              
     Officer stating that no Default or Event of Default has occurred and is
     continuing and that the Borrower (directly or indirectly through a
     Subsidiary) intends and expects to use all or a specified portion of the
     Net Cash Proceeds of an Asset Sale or Recovery Event to acquire assets
     useful in its business or make capitalized repairs and improvements with
     respect to such assets.

          "Reinvestment Prepayment Amount":  with respect to any Reinvestment
           ------------------------------                                    
     Event, the Reinvestment Deferred Amount relating thereto less any amount
     expended prior to 
<PAGE>
 
                                                                              22

     the relevant Reinvestment Prepayment Date to acquire assets useful in the
     Borrower's business.

          "Reinvestment Prepayment Date":  with respect to any Reinvestment
           ----------------------------                                    
     Event, the earlier of (a) the date occurring six months after such
     Reinvestment Event and (b) the date on which the Borrower shall have
     determined not to, or shall have otherwise ceased to, acquire assets useful
     in the Borrower's business with all or any portion of the relevant
     Reinvestment Deferred Amount.

          "Reorganization":  with respect to any Multiemployer Plan, the
           --------------                                               
     condition that such plan is in reorganization within the meaning of Section
     4241 of ERISA.

          "Reportable Event":  any of the events set forth in Section 4043(c) of
           ----------------                                                     
     ERISA, other than those events as to which the thirty day notice period is
     waived under subsections .27, .28, .29, .30, .31, .32, .34 or .35 of PBGC
     Reg. (S) 4043.

          "Required Lenders":  at any time, the holders of more than 50% of (a)
           ----------------                                                    
     until the Closing Date, the Commitments and (b) thereafter, the sum of (i)
     the aggregate unpaid principal amount of the Term Loans then outstanding
     and (ii) the Total Revolving Credit Commitments then in effect (provided,
                                                                     -------- 
     that, for purposes of this definition, during the Increased Commitment
     Availability Period, prior to the date which is 45 days after the Closing
     Date, the Revolving Credit Commitments of each Lender shall include such
     Lender's Increased Revolving Credit Commitment, and the Total Revolving
     Credit Commitments shall include the Increased Revolving Credit Commitments
     of all Lenders) or, if the Revolving Credit Commitments have been
     terminated, the Total Revolving Extensions of Credit then outstanding.

          "Required Prepayment Lenders":  the Majority Facility Lenders in
           ---------------------------                                    
     respect of each Facility.

          "Requirement of Law":  as to any Person, the Certificate of
           ------------------                                        
     Incorporation and By-Laws or other organizational or governing documents of
     such Person, and any law, treaty, rule or regulation or determination of an
     arbitrator or a court or other Governmental Authority, in each case
     applicable to or binding upon such Person or any of its Property or to
     which such Person or any of its Property is subject.

          "Responsible Officer":  the chief executive officer, president or
           -------------------                                             
     chief financial officer of the Borrower, but in any event, with respect to
     financial matters, the chief financial officer of the Borrower.

          "Restricted Payments":  as defined in Section 7.6.
           -------------------                              

          "Revolving Credit Commitment":  as to any Lender, the obligation of
           ---------------------------                                       
     such Lender, if any, to make Revolving Credit Loans and participate in
     Letters of Credit, in an aggregate principal and/or face amount not to
     exceed the amount set forth under the 
<PAGE>
 
                                                                              23

     heading "Revolving Credit Commitment" opposite such Lender's name on
     Schedule 1 to the Lender Addendum delivered by such Lender, or, as the case
     may be, in the Assignment and Acceptance pursuant to which such Lender
     became a party hereto, as the same may be changed from time to time
     pursuant to the terms hereof (including, without limitation, Section 2.4A).
     The original amount of the Total Revolving Credit Commitments on the
     Closing Date is $100,000,000.

          "Revolving Credit Commitment Period":  the period from and including
           ----------------------------------                                 
     the Closing Date to the Revolving Credit Termination Date.

          "Revolving Credit Lender":  each Lender that has a Revolving Credit
           -----------------------                                           
     Commitment or that is the holder of Revolving Credit Loans.

          "Revolving Credit Loans":  as defined in Section 2.4.
           ----------------------                              

          "Revolving Credit Percentage":  as to any Revolving Credit Lender at
           ---------------------------                                        
     any time, the percentage which such Lender's Revolving Credit Commitment
     then constitutes of the Total Revolving Credit Commitments (or, at any time
     after the Revolving Credit Commitments shall have expired or terminated,
     the percentage which the aggregate amount of such Lender's Revolving
     Extensions of Credit then outstanding constitutes of the aggregate amount
     of the Revolving Extensions of Credit then outstanding).

          "Revolving Credit Termination Date": December 31, 2004.
           ---------------------------------                     

          "Revolving Extensions of Credit":  as to any Revolving Credit Lender
           ------------------------------                                     
     at any time, an amount equal to the sum of (a) the aggregate principal
     amount of all Revolving Credit Loans made by such Lender then outstanding
     and (b) such Lender's Revolving Credit Percentage of the L/C Obligations
     then outstanding.

          "SBA Brazil":  SBA Telecommunicacoes do Brasil, LTDA, a company
           ----------                                                    
     organized under the laws of Brazil.

          "SEC":  the Securities and Exchange Commission (or successors thereto
           ---                                                                 
     or an analogous Governmental Authority).

          "Security Documents":  the collective reference to the Guarantee and
           ------------------                                                 
     Collateral Agreement, the Mortgages and all other security documents
     hereafter delivered to the Administrative Agent granting a Lien on any
     Property of any Person to secure the obligations and liabilities of any
     Loan Party under any Loan Document.

          "Senior Discount Notes":  the 12% Senior Discount Notes of Holdings
           ---------------------                                             
     due 2008 in the initial aggregate face amount of $269,000,000.

          "Senior Discount Notes Indenture":  the Indenture entered into by
           -------------------------------                                 
     Holdings in connection with the issuance of the Senior Discount Notes,
     together with all instruments 
<PAGE>
 
                                                                              24

     and other agreements entered into by Holdings in connection therewith, as
     in effect on the date hereof.

          "Series A Preferred Stock":  the 4% Series A Convertible Preferred
           ------------------------                                         
     Stock, par value $0.01 per share, of Holdings.

          "Series B Preferred Stock":  the 4% Series B Redeemable Preferred
           ------------------------                                        
     Stock, par value $0.01 per share, of Holdings issuable upon conversion of
     the Series A Preferred Stock.

          "Series C Preferred Stock":  the 4% Series C Convertible Preferred
           ------------------------                                         
     Stock, par value $0.01 per share, of Holdings.

          "Series D Preferred Stock":  the 4% Series D Redeemable Preferred
           ------------------------                                        
     Stock, par value $0.01 per share, of Holdings issuable upon conversion of
     the Series C Preferred Stock.

          "Single Employer Plan":  any Plan that is covered by Title IV of
           --------------------                                           
     ERISA, but which is not a Multiemployer Plan.

          "Solvent":  when used with respect to any Person, means that, as of
           -------                                                           
     any date of determination, (a) the amount of the "present fair saleable
     value" of the assets of such Person will, as of such date, exceed the
     amount of all "liabilities of such Person, contingent or otherwise", as of
     such date, as such quoted terms are determined in accordance with
     applicable federal and state laws governing determinations of the
     insolvency of debtors, (b) the present fair saleable value of the assets of
     such Person will, as of such date, be greater than the amount that will be
     required to pay the liability of such Person on its debts as such debts
     become absolute and matured, (c) such Person will not have, as of such
     date, an unreasonably small amount of capital with which to conduct its
     business, and (d) such Person will be able to pay its debts as they mature.
     For purposes of this definition, (i) "debt" means liability on a "claim",
     and (ii) "claim" means any (x) right to payment, whether or not such a
     right is reduced to judgment, liquidated, unliquidated, fixed, contingent,
     matured, unmatured, disputed, undisputed, legal, equitable, secured or
     unsecured or (y) right to an equitable remedy for breach of performance if
     such breach gives rise to a right to payment, whether or not such right to
     an equitable remedy is reduced to judgment, fixed, contingent, matured or
     unmatured, disputed, undisputed, secured or unsecured.

          "Specified Hedge Agreement":  any Hedge Agreement (a) entered into by
           -------------------------                                           
     (i) the Borrower or any of its Subsidiaries and (ii) any Lender or any
     Affiliate thereof, as counterparty and (b) which has been designated by
     such Lender and the Borrower, by notice to the Administrative Agent and the
     Syndication Agent, as a Specified Hedge Agreement.
<PAGE>
 
                                                                              25

          "Subsidiary":  as to any Person, a corporation, partnership, limited
           ----------                                                         
     liability company or other entity of which shares of stock or other
     ownership interests having ordinary voting power (other than stock or such
     other ownership interests having such power only by reason of the happening
     of a contingency) to elect a majority of the board of directors or other
     managers of such corporation, partnership or other entity are at the time
     owned, or the management of which is otherwise controlled, directly or
     indirectly through one or more intermediaries, or both, by such Person (it
     being understood that an Excluded Entity shall not be a Subsidiary).
     Unless otherwise qualified, all references to a "Subsidiary" or to
     "Subsidiaries" in this Agreement shall refer to a Subsidiary or
     Subsidiaries of the Borrower.

          "Subsidiary Guarantor":  each Subsidiary of Holdings other than the
           --------------------                                              
     Borrower and any Excluded Foreign Subsidiary.

          "Term Loan":  as defined in Section 2.1.
           ---------                              

          "Term Loan Commitment":  as to any Term Loan Lender, the obligation of
           --------------------                                                 
     such Lender, if any, to make a Term Loan to the Borrower hereunder in a
     principal amount not to exceed the amount set forth under the heading "Term
     Loan Commitment" opposite such Lender's name on Schedule 1 to the Lender
     Addendum delivered by such Lender, or, as the case may be, in the
     Assignment and Acceptance pursuant to which such Lender became a party
     hereto, as the same may be changed from time to time pursuant to the terms
     hereof.  The original aggregate amount of the Term Loan Commitments is
     $25,000,000.

          "Term Loan Lender":  each Lender that has a Term Loan Commitment or is
           ----------------                                                     
     the holder of a Term Loan.

          "Term Loan Percentage":  as to any Term Loan Lender at any time, the
           --------------------                                               
     percentage which such Lender's Term Loan Commitment then constitutes of the
     aggregate Term Loan Commitments (or, at any time after the Closing Date,
     the percentage which the aggregate principal amount of such Lender's Term
     Loans then outstanding constitutes of the aggregate principal amount of the
     Term Loans then outstanding).

          "Total Capitalization":  the sum of shareholder's equity and
           --------------------                                       
     Consolidated Total Debt of the Borrower and its Subsidiaries, as reflected
     in a consolidated balance sheet of the Borrower and its Subsidiaries
     prepared in accordance with GAAP.

          "Total Revolving Credit Commitments":  at any time, the aggregate
           ----------------------------------                              
     amount of the Revolving Credit Commitments then in effect.

          "Total Revolving Extensions of Credit":  at any time, the aggregate
           ------------------------------------                              
     amount of the Revolving Extensions of Credit of the Revolving Credit
     Lenders outstanding at such time.
<PAGE>
 
                                                                              26

          "Total Tower Revenue":  for any period, the Borrower's revenue from
           -------------------                                               
     all Towers for such period, plus the Borrower's revenue for such period
     from its lease/sublease business and its business of leasing or managing
     antennae space on buildings, Towers or other structures.

          "Tower":  any wireless transmission tower, and related assets that are
           -----                                                                
     located on the site of such wireless transmission tower, owned by the
     Borrower or any of its Subsidiaries or leased by the Borrower or any of its
     Subsidiaries pursuant to a lease required to be classified and accounted
     for as a capital lease on a balance sheet of the Borrower and its
     Subsidiaries under GAAP.

          "Tower Company":  a corporation or any other entity engaged primarily
           -------------                                                       
     in the business of owning, managing, leasing and/or operating towers and
     leasing space thereon to tenants.

          "Tower Cost":  with respect to any Tower, the aggregate cost of
           ----------                                                    
     construction thereof, plus the aggregate cost of all zoning and other
     regulatory approvals required for the construction and/or operation of such
     Tower, plus, without duplication, the cost of Capital Expenditures with
     respect to such Tower.

          "Transferee":  as defined in Section 10.15.
           ----------                                

          "Transition Date": the date which is 30 months after the Closing Date.
           ---------------                                                      

          "Type":  as to any Loan, its nature as a Base Rate Loan or a
           ----                                                       
     Eurodollar Loan.

          "Wholly Owned Subsidiary":  as to any Person, any other Person all of
           -----------------------                                             
     the Capital Stock of which (other than directors' qualifying shares
     required by law) is owned by such Person directly and/or through other
     Wholly Owned Subsidiaries.

          "Wholly Owned Subsidiary Guarantor":  any Subsidiary Guarantor that is
           ---------------------------------                                    
     a Wholly Owned Subsidiary of Holdings.

          1.2  Other Definitional Provisions.  (a)  Unless otherwise specified
               -----------------------------                                  
therein, all terms defined in this Agreement shall have the defined meanings
when used in the other Loan Documents or any certificate or other document made
or delivered pursuant hereto or thereto.

          (b   As used herein and in the other Loan Documents, and any
certificate or other document made or delivered pursuant hereto or thereto,
accounting terms relating to Holdings, the Borrower and its Subsidiaries not
defined in Section 1.1 and accounting terms partly defined in Section 1.1, to
the extent not defined, shall have the respective meanings given to them under
GAAP.

          (c   The words "hereof", "herein" and "hereunder" and words of similar
import when used in this Agreement shall refer to this Agreement as a whole and
not to any particular 
<PAGE>
 
                                                                              27

provision of this Agreement, and Section, Schedule and Exhibit references are to
this Agreement unless otherwise specified.

          (d   The meanings given to terms defined herein shall be equally
applicable to both the singular and plural forms of such terms.

                  SECTION 2.  AMOUNT AND TERMS OF COMMITMENTS


          2.1  Term Loan Commitments.  Subject to the terms and conditions
               ---------------------                                      
hereof, each Term Loan Lender severally agrees to make a term loan (a "Term
                                                                       ----
Loan") to the Borrower on the Closing Date in an amount not to exceed the lesser
of  (i) the amount of the Term Loan Commitment of such Lender or (ii) the
product of (a) such Lender's Term Loan Percentage and (b) the Asset Coverage
Test Amount less the aggregate principal amount outstanding under the Revolving
Credit Facility as calculated on the Closing Date.  The Term Loans may from time
to time be Eurodollar Loans or Base Rate Loans, as determined by the Borrower
and notified to the Administrative Agent in accordance with Sections 2.2 and
2.11.

          2.2  Procedure for Term Loan Borrowing.  The Borrower shall give the
               ---------------------------------                              
Administrative Agent irrevocable notice (which notice must be received by the
Administrative Agent prior to 10:00 A.M., New York City time, one Business Day
prior to the anticipated Closing Date) requesting that the Term Loan Lenders
make the Term Loans on the Closing Date and specifying the amount to be
borrowed.  The Term Loans made on the Closing Date shall initially be Base Rate
Loans, and no Term Loan may be converted into or continued as a Eurodollar Loan
having an Interest Period in excess of one month prior to the date which is 60
days after the Closing Date.  Upon receipt of such notice the Administrative
Agent shall promptly notify each Term Loan Lender thereof.  Not later than 12:00
Noon, New York City time, on the Closing Date each Term Loan Lender shall make
available to the Administrative Agent at the Funding Office an amount in
immediately available funds equal to the Term Loan or Term Loans to be made by
such Lender.  The Administrative Agent shall make available to the Borrower the
aggregate of the amounts made available to the Administrative Agent by the Term
Loan Lenders in like funds.

          2.3  Repayment of Term Loans.  The Term Loan of each Term Loan Lender
               -----------------------                                         
shall mature in consecutive quarterly installments, commencing on March 31,
2001, each of which shall be in an amount equal to such Lender's Term Loan
Percentage multiplied by the amount set forth below opposite such installment:

<TABLE>
<CAPTION>
          Quarterly Installment        Principal Amount
          ---------------------        ----------------
       <S>                             <C>
          March 31, 2001                $  625,000
          June 30, 2001                 $  625,000
          September 30, 2001            $  625,000
          December 31, 2001             $  625,000
          March 31, 2002                $  625,000
</TABLE> 
<PAGE>
 
                                                                              28
<TABLE> 
<CAPTION> 

<S>                                     <C> 
          June 30, 2002                 $  625,000
          September 30, 2002            $  625,000
          December 31, 2002             $  625,000
          March 31, 2003                $1,875,000
          June 30, 2003                 $1,875,000
          September 30, 2003            $1,875,000
          December 30, 2003             $1,875,000
          March 31, 2004                $3,125,000
          June 30, 2004                 $3,125,000
          September 30, 2004            $3,125,000
          December 31, 2004             $3,125,000
</TABLE>

          2.4  Revolving Credit Commitments.  Subject to the terms and
               ----------------------------                           
conditions hereof, each Revolving Credit Lender severally agrees to make
revolving credit loans ("Revolving Credit Loans") to the Borrower from time to
                         ----------------------                               
time during the Revolving Credit Commitment Period in an aggregate principal
amount at any one time outstanding which, when added to such Lender's Revolving
Credit Percentage of the L/C Obligations then outstanding, does not exceed (i)
the amount of such Lender's Revolving Credit Commitment or (ii) prior to the
Transition Date, the product of (a) such Lender's Revolving Credit Percentage
and (b) the Asset Coverage Test Amount, as most recently calculated prior to the
date of such Revolving Credit Loans pursuant to Section 6.2(h), less the
aggregate principal amount outstanding under the Term Loan Facility.  During the
Revolving Credit Commitment Period the Borrower may use the Revolving Credit
Commitments by borrowing, prepaying the Revolving Credit Loans in whole or in
part, and reborrowing, all in accordance with the terms and conditions hereof.
The Revolving Credit Loans may from time to time be Eurodollar Loans or Base
Rate Loans, as determined by the Borrower and notified to the Administrative
Agent in accordance with Sections 2.5 and 2.11, provided that no Revolving
                                                --------                  
Credit Loan shall be made as a Eurodollar Loan after the day that is one month
prior to the Revolving Credit Termination Date.

          2.4A  Revolving Credit Commitments Increase.  Subject to the terms and
                -------------------------------------                           
conditions of this Section, if during the period (the "Increased Commitment
                                                       --------------------
Availability Period") between the Closing Date and the earlier of (a) the date
- -------------------                                                           
which is 45 days after the Closing Date and (b) the date on which the Borrower
notifies the Administrative Agent that it will not increase the Revolving Credit
Commitments pursuant to this Section, the Borrower delivers a certificate signed
by a Responsible Officer of the Borrower in form and substance satisfactory to
the Administrative Agent (the date of such delivery, the "Increased Revolving
                                                          -------------------
Credit Commitment Date") (and the Administrative Agent shall provide copies of
- ----------------------                                                        
such certificate to the Revolving Credit Lenders) that it has received consents
from holders of the Senior Discount Notes necessary and sufficient to permit the
Borrower to increase the aggregate principal amount of Indebtedness (as defined
in the Senior Discount Notes Indenture) hereunder pursuant to Section 4.09(i) of
the Senior Discount Notes Indenture to an aggregate principal amount not
exceeding $175,000,000 in accordance with the terms of the Senior Discount Notes
Indenture, then, at such time, without any further action by the Administrative
Agent or any Revolving Credit Lender, the Revolving Credit Commitments of each
Revolving Credit Lender shall automatically increase by an amount specified on
Schedule 2 to the Lender Addendum of such Lender (the 
<PAGE>
 
                                                                              29

aggregate of such amounts, the "Increased Revolving Credit Commitments") such
                                -------------------------------------- 
that the amount of the Total Revolving Credit Commitments shall be $150,000,000.
The increase referred to in the immediately preceding sentence shall not be
effective unless, on the Increased Revolving Credit Commitment Date, the
Borrower (i) pays to the Administrative Agent an underwriting fee on the
aggregate amount of the Increased Revolving Credit Commitments at a rate equal
to the rate payable on the aggregate amount of the Commitments prior to the
Increased Revolving Commitment Date and (ii) delivers to the Administrative
Agent an opinion of counsel to the Borrower, in form and substance satisfactory
to the Administrative Agent, that the increase referred to in the immediately
preceding sentence does not violate the terms of the Senior Discount Indenture,
in form and substance satisfactory to the Administrative Agent. The Borrower
shall also pay to the Administrative Agent for the account of each Revolving
Credit Lender a commitment fee for the period from the Closing Date to the
earlier of (x) the Increased Revolving Credit Commitment Date and (y) the last
day of the Increased Commitment Availability Period calculated at the Commitment
Fee Rate on the amount by which such Revolving Credit Lender's Revolving Credit
Commitment is increased pursuant to this Section, payable on the earlier of (x)
the Increased Revolving Credit Commitment Date and (y) the last day of the
Increased Commitment Availability Period.

          2.5  Procedure for Revolving Credit Borrowing.   The Borrower may
               ----------------------------------------                    
borrow under the Revolving Credit Commitments during the Revolving Credit
Commitment Period on any Business Day, provided that the Borrower shall give the
                                       --------                                 
Administrative Agent irrevocable notice (which notice must be received by the
Administrative Agent prior to 12:00 Noon, New York City time, (a) three Business
Days prior to the requested Borrowing Date, in the case of Eurodollar Loans, or
(b) one Business Day prior to the requested Borrowing Date, in the case of Base
Rate Loans), specifying (i) the amount and Type of Revolving Credit Loans to be
borrowed, (ii) the requested Borrowing Date and (iii) in the case of Eurodollar
Loans, the length of the initial Interest Period therefor.  Any Revolving Credit
Loans made on the Closing Date shall initially be Base Rate Loans, and no
Revolving Credit Loan may be made as, converted into or continued as a
Eurodollar Loan having an Interest Period in excess of one month prior to the
date which is 60 days after the Closing Date.  Each borrowing under the
Revolving Credit Commitments shall be in an amount equal to (x) in the case of
Base Rate Loans, $1,000,000 or a whole multiple thereof (or, if the then
aggregate Available Revolving Credit Commitments are less than $1,000,000, such
lesser amount) and (y) in the case of Eurodollar Loans, $2,500,000 or a whole
multiple of $500,000 in excess thereof.  Upon receipt of any such notice from
the Borrower, the Administrative Agent shall promptly notify each Revolving
Credit Lender thereof.  Each Revolving Credit Lender will make the amount of its
pro rata share of each borrowing available to the Administrative Agent for the
- --- ----                                                                      
account of the Borrower at the Funding Office prior to 12:00 Noon, New York City
time, on the Borrowing Date requested by the Borrower in funds immediately
available to the Administrative Agent.  The Administrative Agent shall make
available to the Borrower the aggregate of the amounts made available to the
Administrative Agent by the Revolving Credit Lenders in like funds as received
by the Administrative Agent.

          2.6  Repayment of Loans; Evidence of Debt.  (a)  The Borrower hereby
               ------------------------------------                           
unconditionally promises to pay to the Administrative Agent for the account of
the appropriate Revolving Credit Lender or Term Loan Lender, as the case may be,
(i) the then unpaid principal 
<PAGE>
 
                                                                              30

amount of each Revolving Credit Loan of such Revolving Credit Lender on the
Revolving Credit Termination Date (or such earlier date on which the Loans
become due and payable pursuant to Section 8) and (ii) the principal amount of
each Term Loan of such Term Loan Lender in installments according to the
amortization schedule set forth in Section 2.3. The Borrower hereby further
agrees to pay interest on the unpaid principal amount of the Loans from time to
time outstanding from the date hereof until payment in full thereof at the rates
per annum, and on the dates, set forth in Section 2.13.

          (b   Each Lender shall maintain in accordance with its usual practice
an account or accounts evidencing indebtedness of the Borrower to such Lender
resulting from each Loan of such Lender from time to time, including the amounts
of principal and interest payable and paid to such Lender from time to time
under this Agreement.

          (c   The Administrative Agent, on behalf of the Borrower, shall
maintain the Register pursuant to Section 10.6(e), and a subaccount therein for
each Lender, in which shall be recorded (i) the amount of each Loan made
hereunder and any Note evidencing such Loan, the Type thereof and each Interest
Period applicable thereto, (ii) the amount of any principal or interest due and
payable or to become due and payable from the Borrower to each Lender hereunder
and (iii) both the amount of any sum received by the Administrative Agent
hereunder from the Borrower and each Lender's share thereof.

          (d   The entries made in the Register and the accounts of each Lender
maintained pursuant to Section 2.6(b) shall, to the extent permitted by
applicable law, be prima facie evidence of the existence and amounts of the
                   ----- -----                                             
obligations of the Borrower therein recorded; provided, however, that the
                                              --------  -------          
failure of any Lender or the Administrative Agent to maintain the Register or
any such account, or any error therein, shall not in any manner affect the
obligation of the Borrower to repay (with applicable interest) the Loans made to
such Borrower by such Lender in accordance with the terms of this Agreement.

          (e   The Borrower agrees that, upon the request to the Administrative
Agent by any Lender, the Borrower will execute and deliver to such Lender a
promissory note of the Borrower evidencing any Term Loans or Revolving Credit
Loans of such Lender, substantially in the forms of Exhibit G-1 or G-2,
respectively, with appropriate insertions as to date and principal amount.

          2.7  Commitment Fees, etc.  (a)  The Borrower agrees to pay to the
               ---------------------                                        
Administrative Agent for the account of each Revolving Credit Lender a
commitment fee for the period from and including the Closing Date to the last
day of the Revolving Credit Commitment Period, computed at the Commitment Fee
Rate on the average daily amount of the Available Revolving Credit Commitment of
such Lender during the period for which payment is made, payable quarterly in
arrears on the last day of each March, June, September and December and on the
Revolving Credit Termination Date, commencing on the first of such dates to
occur after the date hereof.
<PAGE>
 
                                                                              31

          (b   The Borrower agrees to pay to LBI the fees in the amounts and on
the dates previously agreed to in writing by the Borrower and LBI.

          (c   The Borrower agrees to pay to the Administrative Agent the fees
in the amounts and on the dates from time to time agreed to in writing by the
Borrower and the Administrative Agent.

          2.8  Optional Termination or Reduction of Revolving Credit
               -----------------------------------------------------
Commitments; Scheduled Reductions of Revolving Credit Commitments.  (a)  The
- -----------------------------------------------------------------           
Borrower shall have the right, upon not less than three Business Days' notice to
the Administrative Agent, to terminate the Revolving Credit Commitments or, from
time to time, to reduce the amount of the Revolving Credit Commitments; provided
                                                                        --------
that no such termination or reduction of Revolving Credit Commitments shall be
permitted if, after giving effect thereto and to any prepayments of the
Revolving Credit Loans made on the effective date thereof, the Total Revolving
Extensions of Credit would exceed the Total Revolving Credit Commitments.  Any
such reduction shall be in an amount equal to $1,000,000, or a whole multiple
thereof, and shall reduce permanently the Revolving Credit Commitments then in
effect.

          (b)  The Revolving Credit Commitments shall be reduced automatically
in quarterly installments, commencing on March  31, 2001, by the percentage of
the Total Revolving Credit Commitments (or, if the Borrower delivers the
certificate referred to in Section 2.4A, the Total Revolving Credit Commitments
after giving effect to the increase effected pursuant to Section 2.4A) set forth
below opposite such period:

<TABLE>
<CAPTION>
                                         Amount of Reduction of
          Quarterly Installment          Total  Revolving
          ---------------------
          <S>                            <C>
          March 31, 2001                      2.5%
          June 30, 2001                       2.5%
          September 30, 2001                  2.5%
          December 31, 2001                   2.5%
          March 31, 2002                        5%
          June 30, 2002                         5%
          September 30, 2002                    5%
          December 31, 2002                     5%
          March 31, 2003                      7.5%
          June 30, 2003                       7.5%
          September 30, 2003                  7.5%
          December 31, 2003                   7.5%
          March 31, 2004                       10%
          June 30, 2004                        10%
          September 30, 2004                   10%
          December 31, 2004                    10%
</TABLE>
<PAGE>
 
                                                                              32

          2.9  Optional Prepayments; Mandatory Prepayments of Loans.  (a) The
               ----------------------------------------------------          
Borrower may at any time and from time to time prepay the Loans, in whole or in
part, without premium or penalty, upon irrevocable notice delivered to the
Administrative Agent at least three Business Days prior thereto in the case of
Eurodollar Loans and at least one Business Day prior thereto in the case of Base
Rate Loans, which notice shall specify the date and amount of prepayment and
whether the prepayment is of Eurodollar Loans or Base Rate Loans; provided, that
                                                                  --------      
if a Eurodollar Loan is prepaid on any day other than the last day of the
Interest Period applicable thereto, the Borrower shall also pay any amounts
owing pursuant to Section 2.19.  Upon receipt of any such notice the
Administrative Agent shall promptly notify each relevant Lender thereof.  If any
such notice is given, the amount specified in such notice shall be due and
payable on the date specified therein, together with (except in the case of
Revolving Credit Loans that are Base Rate Loans) accrued interest to such date
on the amount prepaid.  Optional partial prepayments of Term Loans and Revolving
Credit Loans shall be in an aggregate principal amount of $1,000,000 or a whole
multiple thereof.

          (b)(i)  Any optional, scheduled or mandatory reduction of the
Revolving Credit Commitments pursuant to Section 2.8 or 2.10 shall be
accompanied by prepayment of the Revolving Credit Loans to the extent, if any,
that the Total Revolving Extensions of Credit exceed the amount of the Total
Revolving Credit Commitments as so reduced; and (ii) if any Asset Coverage Test
Certificate delivered pursuant to Section 6.2(h) shows that, as of the date
thereof, the Total Revolving Extensions of Credit, together with the aggregate
principal amount of outstanding Term Loans, exceeded the Asset Coverage Test
Amount, the Borrower shall prepay Revolving Credit Loans (or, if insufficient
Revolving Credit Loans are then outstanding, the Term Loans to the extent of
such insufficiency) on the date of delivery of such Asset Coverage Test
Certificate, to the extent, if any, that the Total Revolving Extensions of
Credit, together with the aggregate principal amount of outstanding Term Loans,
exceed the Asset Coverage Test Amount; provided that, in each case, if the
                                       --------                           
aggregate principal amount of Revolving Credit Loans (in the case of clause (i))
or Loans (in the case of clause (ii)) then outstanding is less than the amount
of either such excess (because L/C Obligations constitute a portion thereof),
the Borrower shall, to the extent of the balance of such excess, replace
outstanding Letters of Credit and/or deposit an amount in cash in a cash
collateral account established with the Administrative Agent for the benefit of
the Lenders on terms and conditions reasonably satisfactory to the
Administrative Agent.  The application of any optional, scheduled or mandatory
prepayment shall be made, first, to Base Rate Loans and, second, to Eurodollar
                          -----                          ------               
Loans.  Each prepayment of Eurodollar Loans shall be accompanied by accrued
interest to the date of such prepayment on the amount prepaid.

          2.10  Mandatory Prepayments and Commitments Reductions.  (a)  Unless
                ------------------------------------------------              
the Required Prepayment Lenders shall otherwise agree, if any Capital Stock
shall be issued (other than the issuance of common stock of Holdings upon the
exercise of the common stock options of Holdings held by directors, officers and
employees of Holdings, the Borrower and its Subsidiaries), or Indebtedness
incurred, by Holdings, the Borrower or any of its Subsidiaries, an amount equal
to 100% of the Net Cash Proceeds thereof shall be applied on the date of such
issuance or incurrence toward the prepayment of the Term Loans and the repayment
of 
<PAGE>
 
                                                                              33

Revolving Credit Loans (which repayment shall not be required to be accompanied
by any reduction of the Revolving Credit Commitments) in accordance with Section
2.10(d); provided, that the proceeds of an initial public offering of the common
         --------
stock of Holdings may be used within 5 days of the receipt thereof (i) to redeem
the outstanding Series A Preferred Stock to the extent required by the
provisions of the Series A Preferred Stock in effect on the date hereof and (ii)
to redeem outstanding shares of Capital Stock of Holdings issued after the date
hereof if required by the provisions thereof and to the extent the proceeds from
such issuance constitute Net Cash Proceeds applied toward prepayment of Loans as
provided above in this Section; provided, further, that the aggregate amount of
                                -----------------
the redemptions referred to in clauses (i) and (ii) of the immediately preceding
proviso shall not exceed $100,000,000.
- -------                               

          (b)  Unless the Required Prepayment Lenders shall otherwise agree, if
on any date Holdings, the Borrower or any of its Subsidiaries shall receive Net
Cash Proceeds from any Asset Sale or Recovery Event then, unless a Reinvestment
Notice shall be delivered in respect thereof, such Net Cash Proceeds shall be
applied on such date toward the prepayment of the Term Loans and the permanent
reduction of the Revolving Credit Commitments in accordance with Section
2.10(d); provided, that, notwithstanding the foregoing, (i) the aggregate Net
         --------                                                            
Cash Proceeds of Asset Sales that may be held by the Borrower for reinvestment
and excluded from the foregoing requirement pursuant to a Reinvestment Notice
shall not exceed $5,000,000 at any time and (ii) on each Reinvestment Prepayment
Date, an amount equal to the Reinvestment Prepayment Amount with respect to the
relevant Reinvestment Event shall be applied toward the prepayment of the Term
Loans and the reduction of the Revolving Credit Commitments in accordance with
Section 2.10(d).

          (c)  Unless the Required Prepayment Lenders shall otherwise agree, if,
for any fiscal year of the Borrower commencing with the fiscal year ending
December 31, 1999, there shall be Excess Cash Flow, the Borrower shall, on the
relevant Excess Cash Flow Application Date, apply 75% of such Excess Cash Flow
toward the prepayment of the Term Loans and the permanent reduction of the
Revolving Credit Commitments in accordance with Section 2.10(d).  Each such
prepayment and commitment reduction shall be made on a date (an "Excess Cash
                                                                 -----------
Flow Application Date") no later than five days after the earlier of (i) the
- ---------------------                                                       
date on which the financial statements of the Borrower referred to in Section
6.1(a), for the fiscal year with respect to which such prepayment is made, are
required to be delivered to the Lenders and (ii) the date such financial
statements are actually delivered.

          (d)  Amounts required by this Section to be applied to the prepayment
of the Loans and/or the permanent reduction of the Revolving Credit Commitments
shall be allocated between the Term Loan Facility and the Revolving Credit
Facility pro rata based upon the aggregate principal amount of Term Loans
outstanding and the aggregate amount of the Revolving Credit Commitments.  Any
such permanent reduction of the Revolving Credit Commitments shall be
accompanied by prepayment of the Revolving Credit Loans to the extent, if any,
that the Total Revolving Extensions of Credit exceed the amount of the Total
Revolving Credit Commitments as so reduced, provided that if the aggregate
                                            --------                      
principal amount of Revolving Credit Loans then outstanding is less than the
amount of such excess (because L/C Obligations constitute a portion thereof),
the Borrower shall, to the extent of the balance of such excess, 
<PAGE>
 
                                                                              34

replace outstanding Letters of Credit and/or deposit an amount in cash in a cash
collateral account established with the Administrative Agent for the benefit of
the Lenders on terms and conditions reasonably satisfactory to the
Administrative Agent. The application of any prepayment pursuant to this Section
shall be made, first, to Base Rate Loans and, second, to Eurodollar Loans. Each
               -----                          ------   
prepayment of the Loans under this Section (except in the case of Revolving
Credit Loans that are Base Rate Loans) shall be accompanied by accrued interest
to the date of such prepayment on the amount prepaid.

          2.11  Conversion and Continuation Options. (a)  The Borrower may elect
                -----------------------------------                             
from time to time to convert Eurodollar Loans to Base Rate Loans by giving the
Administrative Agent at least two Business Days' prior irrevocable notice of
such election, provided that any such conversion of Eurodollar Loans may only be
               --------                                                         
made on the last day of an Interest Period with respect thereto.  The Borrower
may elect from time to time to convert Base Rate Loans to Eurodollar Loans by
giving the Administrative Agent at least three Business Days' prior irrevocable
notice of such election (which notice shall specify the length of the initial
Interest Period therefor), provided that no Base Rate Loan under a particular
                           --------                                          
Facility may be converted into a Eurodollar Loan (i) when any Event of Default
has occurred and is continuing and the Administrative Agent or the Majority
Facility Lenders in respect of such Facility have determined in its or their
sole discretion not to permit such conversions or (ii) after the date that is
one month prior to the final scheduled termination or maturity date of such
Facility.  Upon receipt of any such notice the Administrative Agent shall
promptly notify each relevant Lender thereof.

          (b)  Any Eurodollar Loan may be continued as such upon the expiration
of the then current Interest Period with respect thereto by the Borrower giving
irrevocable notice to the Administrative Agent, in accordance with the
applicable provisions of the term "Interest Period" set forth in Section 1.1, of
the length of the next Interest Period to be applicable to such Loans, provided
                                                                       --------
that no Eurodollar Loan under a particular Facility may be continued as such (i)
when any Event of Default has occurred and is continuing and the Administrative
Agent has or the Majority Facility Lenders in respect of such Facility have
determined in its or their sole discretion not to permit such continuations or
(ii) after the date that is one month prior to the final scheduled termination
or maturity date of such Facility; and provided, further, that if the Borrower
                                       --------  -------                      
shall fail to give any required notice as described above in this paragraph or
if such continuation is not permitted pursuant to the preceding proviso such
Loans shall be automatically converted to Base Rate Loans on the last day of
such then expiring Interest Period.  Upon receipt of any such notice the
Administrative Agent shall promptly notify each relevant Lender thereof.

          2.12  Minimum Amounts and Maximum Number of Eurodollar Tranches.
                ---------------------------------------------------------  
Notwithstanding anything to the contrary in this Agreement, all borrowings,
conversions, continuations and optional prepayments of Eurodollar Loans
hereunder and all selections of Interest Periods hereunder shall be in such
amounts and be made pursuant to such elections so that, (a) after giving effect
thereto, the aggregate principal amount of the Eurodollar Loans comprising each
Eurodollar Tranche shall be equal to $2,500,000 or a whole multiple of 
<PAGE>
 
                                                                              35

$500,000 in excess thereof and (b) no more than ten Eurodollar Tranches shall be
outstanding at any one time.

          2.13  Interest Rates and Payment Dates.  (a)  Each Eurodollar Loan
                --------------------------------                            
shall bear interest for each day during each Interest Period with respect
thereto at a rate per annum equal to the Eurodollar Rate determined for such day
plus the Applicable Margin.

          (b)  Each Base Rate Loan shall bear interest at a rate per annum equal
to the Base Rate plus the Applicable Margin.

          (c)  (i) If all or a portion of the principal amount of any Loan or
Reimbursement Obligation shall not be paid when due (whether at the stated
maturity, by acceleration or otherwise), such overdue amount shall bear interest
at a rate per annum that is equal to (x) in the case of the Loans, the rate that
would otherwise be applicable thereto pursuant to the foregoing provisions of
this Section plus 2% or (y) in the case of Reimbursement Obligations, the rate
             ----                                                             
applicable to Base Rate Loans under the Revolving Credit Facility plus 2%, and
                                                                  ----        
(ii) if all or a portion of any interest payable on any Loan or Reimbursement
Obligation or any commitment fee or other amount payable hereunder shall not be
paid when due (whether at the stated maturity, by acceleration or otherwise),
such overdue amount shall bear interest at a rate per annum equal to the rate
then applicable to Base Rate Loans under the relevant Facility plus 2% (or, in
                                                               ----           
the case or any such other amounts that do not relate to a particular Facility,
the rate then applicable to Base Rate Loans under the Revolving Credit Facility
plus 2%), in each case, with respect to clauses (i) and (ii) above, from the
- ----                                                                        
date of such non-payment until such amount is paid in full (after as well as
before judgment).

          (d)  Interest shall be payable in arrears on each Interest Payment
Date, provided that interest accruing pursuant to paragraph (c) of this Section
      --------                                                                 
shall be payable from time to time on demand.

          2.14  Computation of Interest and Fees.  (a)  Interest, fees and
                --------------------------------                          
commissions payable pursuant hereto shall be calculated on the basis of a 360-
day year for the actual days elapsed, except that, with respect to Base Rate
Loans the rate of interest on which is calculated on the basis of the Prime
Rate, the interest thereon shall be calculated on the basis of a 365- (or 366-,
as the case may be) day year for the actual days elapsed.  The Administrative
Agent shall as soon as practicable notify the Borrower and the relevant Lenders
of each determination of a Eurodollar Rate.  Any change in the interest rate on
a Loan resulting from a change in the Base Rate or the Eurocurrency Reserve
Requirements shall become effective as of the opening of business on the day on
which such change becomes effective.  The Administrative Agent shall as soon as
practicable notify the Borrower and the relevant Lenders of the effective date
and the amount of each such change in interest rate.

          (b)  Each determination of an interest rate by the Administrative
Agent pursuant to any provision of this Agreement shall be conclusive and
binding on the Borrower and the Lenders in the absence of manifest error.  The
Administrative Agent shall, at the request of the 
<PAGE>
 
                                                                              36

Borrower, deliver to the Borrower a statement showing the quotations used by the
Administrative Agent in determining any interest rate pursuant to Section
2.13(a).

          2.15  Inability to Determine Interest Rate.  If prior to the first day
                ------------------------------------                            
of any Interest Period:

          (a)  the Administrative Agent shall have determined (which
     determination shall be conclusive and binding upon the Borrower) that, by
     reason of circumstances affecting the relevant market, adequate and
     reasonable means do not exist for ascertaining the Eurodollar Rate for such
     Interest Period, or

          (b)  the Administrative Agent shall have received notice from the
     Majority Facility Lenders in respect of the relevant Facility that the
     Eurodollar Rate determined or to be determined for such Interest Period
     will not adequately and fairly reflect the cost to such Lenders (as
     conclusively certified by such Lenders) of making or maintaining their
     affected Loans during such Interest Period,

the Administrative Agent shall give telecopy or telephonic notice thereof to the
Borrower and the relevant Lenders as soon as practicable thereafter.  If such
notice is given (x) any Eurodollar Loans under the relevant Facility requested
to be made on the first day of such Interest Period shall be made as Base Rate
Loans, (y) any Loans under the relevant Facility that were to have been
converted on the first day of such Interest Period to Eurodollar Loans shall be
continued as Base Rate Loans and (z) any outstanding Eurodollar Loans under the
relevant Facility shall be converted, on the last day of the then current
Interest Period with respect thereto, to Base Rate Loans.  Until such notice has
been withdrawn by the Administrative Agent, no further Eurodollar Loans under
the relevant Facility shall be made or continued as such, nor shall the Borrower
have the right to convert Loans under the relevant Facility to Eurodollar Loans.

          2.16  Pro Rata Treatment and Payments.  (a)  Each borrowing by the
                -------------------------------                             
Borrower from the Lenders hereunder, each payment by the Borrower on account of
any commitment fee and any reduction of the Commitments of the Lenders shall be
made pro rata according to the respective Term Loan Percentages or Revolving
     --- ----                                                               
Credit Percentages, as the case may be, of the relevant Lenders.  Each payment
(other than prepayments) in respect of principal or interest in respect of the
Loans, each payment in respect of fees payable hereunder, and each payment in
respect of Reimbursement Obligations, shall be applied to the amounts of such
obligations owing to the Lenders pro rata according to the respective amounts
                                 --- ----                                    
then due and owing to the Lenders.

          (b)  Each payment (including each prepayment) by the Borrower on
account of principal and interest on the Term Loans shall be allocated among the
Term Loan Lenders pro rata based on the outstanding principal amounts of the
                  --- ----                                                  
Term Loans then held by the Term Loan Lenders, and shall be applied to the
installments of the Term Loans pro rata based on the remaining outstanding
                               --- ----                                   
principal amount of such installments.  Amounts prepaid on account of the Term
Loans may not be reborrowed.
<PAGE>
 
                                                                              37

          (c)  Each payment (including each prepayment) by the Borrower on
account of principal of and interest on the Revolving Credit Loans shall be
allocated among the Revolving Credit Lenders pro rata based on the outstanding
                                             --- ----                         
principal amounts of the Revolving Credit Loans then held by the Revolving
Credit Lenders.

          (d)  All payments (including prepayments) to be made by the Borrower
hereunder, whether on account of principal, interest, fees or otherwise, shall
be made without setoff or counterclaim and shall be made prior to 12:00 Noon,
New York City time, on the due date thereof to the Administrative Agent, for the
account of the Lenders, at the Payment Office, in Dollars and in immediately
available funds.  The Administrative Agent shall distribute such payments to the
Lenders promptly upon receipt in like funds as received.  If any payment
hereunder (other than payments on the Eurodollar Loans) becomes due and payable
on a day other than a Business Day, such payment shall be extended to the next
succeeding Business Day.  If any payment on a Eurodollar Loan becomes due and
payable on a day other than a Business Day, the maturity thereof shall be
extended to the next succeeding Business Day unless the result of such extension
would be to extend such payment into another calendar month, in which event such
payment shall be made on the immediately preceding Business Day.  In the case of
any extension of any payment of principal pursuant to the preceding two
sentences, interest thereon shall be payable at the then applicable rate during
such extension.

          (e)  Unless the Administrative Agent shall have been notified in
writing by any Lender prior to a borrowing that such Lender will not make the
amount that would constitute its share of such borrowing available to the
Administrative Agent, the Administrative Agent may assume that such Lender is
making such amount available to the Administrative Agent, and the Administrative
Agent may, in reliance upon such assumption, make available to the Borrower a
corresponding amount.  If such amount is not made available to the
Administrative Agent by the required time on the Borrowing Date therefor, such
Lender shall pay to the Administrative Agent, on demand, such amount with
interest thereon at a rate equal to the daily average Federal Funds Effective
Rate for the period until such Lender makes such amount immediately available to
the Administrative Agent.  A certificate of the Administrative Agent submitted
to any Lender with respect to any amounts owing under this paragraph shall be
conclusive in the absence of manifest error.  If such Lender's share of such
borrowing is not made available to the Administrative Agent by such Lender
within three Business Days of such Borrowing Date, the Administrative Agent
shall also be entitled to recover such amount with interest thereon at the rate
per annum applicable to Base Rate Loans under the relevant Facility, on demand,
from the Borrower.

          (f)  Unless the Administrative Agent shall have been notified in
writing by the Borrower prior to the date of any payment being made hereunder
that the Borrower will not make such payment to the Administrative Agent, the
Administrative Agent may assume that the Borrower is making such payment, and
the Administrative Agent may, but shall not be required to, in reliance upon
such assumption, make available to the Lenders their respective pro rata shares
                                                                --- ----       
of a corresponding amount.  If such payment is not made to the Administrative
Agent by the Borrower within three Business Days of such required date, the
Administrative Agent shall be entitled to recover, on demand, from each Lender
to which any amount which was made 
<PAGE>
 
                                                                              38

available pursuant to the preceding sentence, such amount with interest thereon
at the rate per annum equal to the daily average Federal Funds Effective Rate.
Nothing herein shall be deemed to limit the rights of the Administrative Agent
or any Lender against the Borrower.

          2.17  Requirements of Law.  (a)  If the adoption of or any change in
                -------------------                                           
any Requirement of Law or in the interpretation or application thereof or
compliance by any Lender with any request or directive (whether or not having
the force of law) from any central bank or other Governmental Authority made
subsequent to the date hereof:

               (i)  shall subject any Lender to any tax of any kind whatsoever
     with respect to this Agreement, any Letter of Credit, any Application or
     any Eurodollar Loan made by it, or change the basis of taxation of payments
     to such Lender in respect thereof (except for Non-Excluded Taxes covered by
     Section 2.18 and changes in the rate of tax on the overall net income of
     such Lender);

               (ii)  shall impose, modify or hold applicable any reserve,
     special deposit, compulsory loan or similar requirement against assets held
     by, deposits or other liabilities in or for the account of, advances, loans
     or other extensions of credit by, or any other acquisition of funds by, any
     office of such Lender that is not otherwise included in the determination
     of the Eurodollar Rate hereunder; or

               (iii)    shall impose on such Lender any other condition;

and the result of any of the foregoing is to increase the cost to such Lender,
by an amount which such Lender deems to be material, of making, converting into,
continuing or maintaining Eurodollar Loans or issuing or participating in
Letters of Credit, or to reduce any amount receivable hereunder in respect
thereof, then, in any such case, the Borrower shall promptly pay such Lender,
upon its demand, any additional amounts necessary to compensate such Lender for
such increased cost or reduced amount receivable.  If any Lender becomes
entitled to claim any additional amounts pursuant to this Section, it shall
promptly notify the Borrower (with a copy to the Administrative Agent) of the
event by reason of which it has become so entitled provided that the Borrower
                                                   --------                  
shall not be required to compensate a Lender pursuant to this paragraph for any
amounts incurred more than six months prior to the date on which such Lender
notifies the Borrower of such Lender's intention to claim compensation therefor;
and provided further that, if the circumstances giving rise to such claim have a
    -------- -------                                                            
retroactive effect, then such six-month period shall be extended to include the
period of such retroactive effect.

          (b)  If any Lender shall have determined that the adoption of or any
change in any Requirement of Law regarding capital adequacy or in the
interpretation or application thereof or compliance by such Lender or any
corporation controlling such Lender with any request or directive regarding
capital adequacy (whether or not having the force of law) from any Governmental
Authority made subsequent to the date hereof shall have the effect of reducing
the rate of return on such Lender's or such corporation's capital as a
consequence of its obligations hereunder or under or in respect of any Letter of
Credit to a level below that which such Lender or such corporation could have
achieved but for such adoption, change or compliance (taking 
<PAGE>
 
                                                                              39

into consideration such Lender's or such corporation's policies with respect to
capital adequacy) submission by such Lender to the Borrower (with a copy to the
Administrative Agent) of a written request therefor, the Borrower shall pay to
such Lender such additional amount or amounts as will compensate such Lender for
such reduction; provided that the Borrower shall not be required to compensate a
                --------
Lender pursuant to this paragraph for any amounts incurred more than six months
prior to the date on which such Lender notifies the Borrower of such Lender's
intention to claim compensation therefor; and provided further that, if the
                                              ----------------
circumstances giving rise to such claim have a retroactive effect, then such 
six-month period shall be extended to include the period of such retroactive
effect. If any Lender becomes entitled to claim any additional amounts pursuant
to this Section, it shall promptly notify the Borrower (with a copy to the
Administrative Agent) of the event by reason of which it has become so entitled.

          (c)  A certificate as to any additional amounts payable pursuant to
this Section submitted by any Lender to the Borrower (with a copy to the
Administrative Agent) shall be conclusive in the absence of manifest error.  The
obligations of the Borrower pursuant to this Section shall survive the
termination of this Agreement and the payment of the Revolving Credit Loans and
all other amounts payable hereunder.

          2.18  Taxes.  (a)  All payments made by the Borrower under this
                -----                                                    
Agreement shall be made free and clear of, and without deduction or withholding
for or on account of, any present or future income, stamp or other taxes,
levies, imposts, duties, charges, fees, deductions or withholdings, now or
hereafter imposed, levied, collected, withheld or assessed by any Governmental
Authority, excluding net income taxes and franchise taxes (imposed in lieu of
net income taxes) imposed on any Agent or any Lender as a result of a present or
former connection between such Agent or such Lender and the jurisdiction of the
Governmental Authority imposing such tax or any political subdivision or taxing
authority thereof or therein (other than any such connection arising solely from
such Agent's or such Lender's having executed, delivered or performed its
obligations or received a payment under, or enforced, this Agreement or any
other Loan Document).  If any such non-excluded taxes, levies, imposts, duties,
charges, fees, deductions or withholdings ("Non-Excluded Taxes") or Other Taxes
                                            ------------------                 
are required to be withheld from any amounts payable to any Agent or any Lender
hereunder, the amounts so payable to such Agent or such Lender shall be
increased to the extent necessary to yield to such Agent or such Lender (after
payment of all Non-Excluded Taxes and Other Taxes) interest or any such other
amounts payable hereunder at the rates or in the amounts specified in this
Agreement, provided, however, that the Borrower shall not be required to
           --------  -------                                            
increase any such amounts payable to any Lender with respect to any Non-Excluded
Taxes (i) that are attributable to such Lender's failure to comply with the
requirements of paragraph (d) or (e) of this Section or (ii) that are United
States withholding taxes imposed on amounts payable to such Lender at the time
the Lender becomes a party to this Agreement, except to the extent that such
Lender's assignor (if any) was entitled, at the time of assignment, to receive
additional amounts from the Borrower with respect to such Non-Excluded Taxes
pursuant to Section 2.18(a).

          (b)  In addition, the Borrower shall pay any Other Taxes to the
relevant Governmental Authority in accordance with applicable law.
<PAGE>
 
                                                                              40



          (c)  Whenever any Non-Excluded Taxes or Other Taxes are payable by the
Borrower, as promptly as possible thereafter the Borrower shall send to the
Administrative Agent for the account of the relevant Agent or Lender, as the
case may be, a certified copy of an original official receipt received by the
Borrower showing payment thereof.  If the Borrower fails to pay any Non-Excluded
Taxes or Other Taxes when due to the appropriate taxing authority or fails to
remit to the Administrative Agent the required receipts or other required
documentary evidence, the Borrower shall indemnify the Agents and the Lenders
for any incremental taxes, interest or penalties that may become payable by any
Agent or any Lender as a result of any such failure.  The agreements in this
Section 2.18 shall survive the termination of this Agreement and the payment of
the Loans and all other amounts payable hereunder.

          (d)  Each Lender (or Transferee) that is not a citizen or resident of
the United States of America, a corporation, partnership or other entity created
or organized in or under the laws of the United States of America (or any
jurisdiction thereof), or any estate or trust that is subject to federal income
taxation regardless of the source of its income (a "Non-U.S. Lender") shall
                                                    ---------------        
deliver to the Borrower and the Administrative Agent (or, in the case of a
Participant, to the Lender from which the related participation shall have been
purchased) two copies of either U.S. Internal Revenue Service Form 1001 or Form
4224, or, in the case of a Non-U.S. Lender claiming exemption from U.S. federal
withholding tax under Section 871(h) or 881(c) of the Code with respect to
payments of "portfolio interest" a statement substantially in the form of
Exhibit H and a Form W-8, or any subsequent versions thereof or successors
thereto properly completed and duly executed by such Non-U.S. Lender claiming
complete exemption from, or a reduced rate of, U.S. federal withholding tax on
all payments by the Borrower under this Agreement and the other Loan Documents.
Such forms shall be delivered by each Non-U.S. Lender on or before the date it
becomes a party to this Agreement (or, in the case of any Participant, on or
before the date such Participant purchases the related participation).  In
addition, each Non-U.S. Lender shall deliver such forms promptly upon the
obsolescence or invalidity of any form previously delivered by such Non-U.S.
Lender.  Each Non-U.S. Lender shall promptly notify the Borrower at any time it
determines that it is no longer in a position to provide any previously
delivered certificate to the Borrower (or any other form of certification
adopted by the U.S. taxing authorities for such purpose).  Notwithstanding any
other provision of this paragraph, a Non-U.S. Lender shall not be required to
deliver any form pursuant to this paragraph that such Non-U.S. Lender is not
legally able to deliver.

          (e)  A Lender that is entitled to an exemption from or reduction of
non-U.S. withholding tax under the law of the jurisdiction in which the Borrower
is located, or any treaty to which such jurisdiction is a party, with respect to
payments under this Agreement shall deliver to the Borrower (with a copy to the
Administrative Agent), at the time or times prescribed by applicable law or
reasonably requested by the Borrower, such properly completed and executed
documentation prescribed by applicable law as will permit such payments to be
made without withholding or at a reduced rate, provided that such Lender is
                                               --------                    
legally entitled to complete, execute and deliver such documentation and in such
Lender's reasonable judgment such completion, execution or submission would not
materially prejudice the legal position of such Lender.
<PAGE>
 
                                                                              41

          2.19  Indemnity.  The Borrower agrees to indemnify each Lender and to
                ---------                                                      
hold each Lender harmless from any loss or expense that such Lender may sustain
or incur as a consequence of (a) default by the Borrower in making a borrowing
of, conversion into or continuation of Eurodollar Loans after the Borrower has
given a notice requesting the same in accordance with the provisions of this
Agreement, (b) default by the Borrower in making any prepayment after the
Borrower has given a notice thereof in accordance with the provisions of this
Agreement or (c) the making of a prepayment or conversion of Eurodollar Loans on
a day that is not the last day of an Interest Period with respect thereto.  Such
indemnification may include an amount equal to the excess, if any, of (i) the
amount of interest that would have accrued on the amount so prepaid, or not so
borrowed, converted or continued, for the period from the date of such
prepayment or of such failure to borrow, convert or continue to the last day of
such Interest Period (or, in the case of a failure to borrow, convert or
continue, the Interest Period that would have commenced on the date of such
failure) in each case at the applicable rate of interest for such Loans provided
for herein (excluding, however, the Applicable Margin included therein, if any)
over (ii) the amount of interest (as reasonably determined by such Lender) that
- ----                                                                           
would have accrued to such Lender on such amount by placing such amount on
deposit for a comparable period with leading banks in the interbank eurodollar
market.  A certificate as to any amounts payable pursuant to this Section
submitted to the Borrower by any Lender shall be conclusive in the absence of
manifest error.  This covenant shall survive the termination of this Agreement
and the payment of the Loans and all other amounts payable hereunder.

          2.20  Illegality.  Notwithstanding any other provision herein, if the
                ----------                                                     
adoption of or any change in any Requirement of Law or in the interpretation or
application thereof shall make it unlawful for any Lender to make or maintain
Eurodollar Loans as contemplated by this Agreement, (a) the commitment of such
Lender hereunder to make Eurodollar Loans, continue Eurodollar Loans as such and
convert Base Rate Loans to Eurodollar Loans shall forthwith be canceled and (b)
such Lender's Loans then outstanding as Eurodollar Loans, if any, shall be
converted automatically to Base Rate Loans on the respective last days of the
then current Interest Periods with respect to such Loans or within such earlier
period as required by law.  If any such conversion of a Eurodollar Loan occurs
on a day which is not the last day of the then current Interest Period with
respect thereto, the Borrower shall pay to such Lender such amounts, if any, as
may be required pursuant to Section 2.19.

          2.21  Change of Lending Office.  Each Lender agrees that, upon the
                ------------------------                                    
occurrence of any event giving rise to the operation of Section 2.17, 2.18(a) or
2.20 with respect to such Lender, it will, if requested by the Borrower, use
reasonable efforts (subject to overall policy considerations of such Lender) to
designate another lending office for any Loans affected by such event with the
object of avoiding the consequences of such event; provided, that such
                                                   --------           
designation is made on terms that, in the sole judgment of such Lender, cause
such Lender and its lending office(s) to suffer no economic, legal or regulatory
disadvantage, and provided, further, that nothing in this Section shall affect
                  --------  -------                                           
or postpone any of the obligations of any Borrower or the rights of any Lender
pursuant to Section 2.17, 2.18(a) or 2.20.

                         SECTION 3.  LETTERS OF CREDIT
<PAGE>
 
                                                                              42

          3.1  L/C Commitment.  (a)  Subject to the terms and conditions hereof,
               --------------                                                   
the Issuing Lender, in reliance on the agreements of the other Revolving Credit
Lenders set forth in Section 3.4(a), agrees to issue letters of credit ("Letters
                                                                         -------
of Credit") for the account of the Borrower on any Business Day during the
- ---------                                                                 
Revolving Credit Commitment Period in such form as may be approved from time to
time by the Issuing Lender; provided that the Issuing Lender shall have no
                            --------                                      
obligation to issue any Letter of Credit if, after giving effect to such
issuance, (i) the L/C Obligations would exceed the L/C Commitment, (ii) the
aggregate amount of the Available Revolving Credit Commitments would be less
than zero or (iii) prior to the Transition Date, the Total Revolving Extensions
of Credit would exceed the Asset Coverage Test Amount, as most recently
determined prior to the date of issuance of such Letter of Credit pursuant to
Section 6.2(h).  Each Letter of Credit shall (i) be denominated in Dollars and
(ii) expire no later than the earlier of (x) the first anniversary of its date
of issuance and (y) the date which is five Business Days prior to the Revolving
Credit Termination Date, provided that any Letter of Credit with a one-year term
                         --------                                               
may provide for the renewal thereof for additional one-year periods (which shall
in no event extend beyond the date referred to in clause (y) above).

          (b)  The Issuing Lender shall not at any time be obligated to issue
any Letter of Credit hereunder if such issuance would conflict with, or cause
the Issuing Lender or any L/C Participant to exceed any limits imposed by, any
applicable Requirement of Law.

          3.2  Procedure for Issuance of Letter of Credit.  The Borrower may
               ------------------------------------------                   
from time to time request that the Issuing Lender issue a Letter of Credit by
delivering to the Issuing Lender at its address for notices specified herein an
Application therefor, completed to the satisfaction of the Issuing Lender, and
such other certificates, documents and other papers and information as the
Issuing Lender may request.  Upon receipt of any Application, the Issuing Lender
will process such Application and the certificates, documents and other papers
and information delivered to it in connection therewith in accordance with its
customary procedures and, within 5 Business Days of receipt of such Application,
shall issue the Letter of Credit requested thereby (but in no event shall the
Issuing Lender be required to issue any Letter of Credit earlier than three
Business Days after its receipt of the Application therefor and all such other
certificates, documents and other papers and information relating thereto) by
issuing the original of such Letter of Credit to the beneficiary thereof or as
otherwise may be agreed to by the Issuing Lender and the Borrower.  The Issuing
Lender shall furnish a copy of such Letter of Credit to the Borrower promptly
following the issuance thereof.  The Issuing Lender shall promptly furnish to
the Administrative Agent, which shall in turn promptly furnish to the Lenders,
notice of the issuance of each Letter of Credit (including the amount thereof).

          3.3  Fees and Other Charges.  (a)  The Borrower will pay a fee on the
               ----------------------                                          
aggregate drawable amount of all outstanding Letters of Credit at a per annum
rate equal to the Applicable Margin then in effect with respect to Eurodollar
Loans under the Revolving Credit Facility, shared ratably among the Revolving
Credit Lenders and payable quarterly in arrears on each L/C Fee Payment Date
after the issuance date.
<PAGE>
 
                                                                              43

          (b)  In addition to the foregoing fees, the Borrower shall pay or
reimburse the Issuing Lender for such normal and customary costs and expenses as
are incurred or charged by the Issuing Lender in issuing, negotiating, effecting
payment under, amending or otherwise administering any Letter of Credit.

          3.4  L/C Participations.  (a)  The Issuing Lender irrevocably agrees
               ------------------                                             
to grant and hereby grants to each L/C Participant, and, to induce the Issuing
Lender to issue Letters of Credit hereunder, each L/C Participant irrevocably
agrees to accept and purchase and hereby accepts and purchases from the Issuing
Lender, on the terms and conditions hereinafter stated, for such L/C
Participant's own account and risk an undivided interest equal to such L/C
Participant's Revolving Credit Percentage in the Issuing Lender's obligations
and rights under each Letter of Credit issued hereunder and the amount of each
draft paid by the Issuing Lender thereunder.  Each L/C Participant
unconditionally and irrevocably agrees with the Issuing Lender that, if a draft
is paid under any Letter of Credit for which the Issuing Lender is not
reimbursed in full by the Borrower in accordance with the terms of this
Agreement, such L/C Participant shall pay to the Issuing Lender upon demand at
the Issuing Lender's address for notices specified herein an amount equal to
such L/C Participant's Revolving Credit Percentage of the amount of such draft,
or any part thereof, that is not so reimbursed.

          (b)  If any amount required to be paid by any L/C Participant to the
Issuing Lender pursuant to Section 3.4(a) in respect of any unreimbursed portion
of any payment made by the Issuing Lender under any Letter of Credit is paid to
the Issuing Lender within three Business Days after the date such payment is
due, such L/C Participant shall pay to the Issuing Lender on demand an amount
equal to the product of (i) such amount, times (ii) the daily average Federal
Funds Effective Rate during the period from and including the date such payment
is required to the date on which such payment is immediately available to the
Issuing Lender, times (iii) a fraction the numerator of which is the number of
days that elapse during such period and the denominator of which is 360.  If any
such amount required to be paid by any L/C Participant pursuant to Section
3.4(a) is not made available to the Issuing Lender by such L/C Participant
within three Business Days after the date such payment is due, the Issuing
Lender shall be entitled to recover from such L/C Participant, on demand, such
amount with interest thereon calculated from such due date at the rate per annum
applicable to Base Rate Loans under the Revolving Credit Facility.  A
certificate of the Issuing Lender submitted to any L/C Participant with respect
to any amounts owing under this Section shall be conclusive in the absence of
manifest error.

          (c)  Whenever, at any time after the Issuing Lender has made payment
under any Letter of Credit and has received from any L/C Participant its pro
                                                                         ---
rata share of such payment in accordance with Section 3.4(a), the Issuing Lender
- ----                                                                            
receives any payment related to such Letter of Credit (whether directly from the
Borrower or otherwise, including proceeds of collateral applied thereto by the
Issuing Lender), or any payment of interest on account thereof, the Issuing
Lender will distribute to such L/C Participant its pro rata share thereof;
                                                   --- ----               
provided, however, that in the event that any such payment received by the
- --------  -------                                                         
Issuing Lender shall be required to be returned by the Issuing Lender, such L/C
Participant shall return to the Issuing Lender the portion thereof previously
distributed by the Issuing Lender to it.
<PAGE>
 
                                                                              44

          3.5  Reimbursement Obligation of the Borrower.  The Borrower agrees to
               ----------------------------------------                         
reimburse the Issuing Lender on each date on which the Issuing Lender notifies
the Borrower of the date and amount of a draft presented under any Letter of
Credit and paid by the Issuing Lender for the amount of (a) such draft so paid
and (b) any taxes, fees, charges or other costs or expenses incurred by the
Issuing Lender in connection with such payment.  Each such payment shall be made
to the Issuing Lender at its address for notices specified herein in lawful
money of the United States of America and in immediately available funds.
Interest shall be payable on the amount of any drawing under any Letter of
Credit (plus any taxes, fees, charges or other costs payable by the Borrower
pursuant to clause (b) of the preceding sentence) from the date of such drawing
until payment in full at the rate set forth in (i) until the second Business Day
following the date of the applicable drawing, Section 2.13(b) and (ii)
thereafter, Section 2.13(c).  Each drawing under any Letter of Credit shall
(unless an event of the type described in clause (i) or (ii) of Section 8(f)
shall have occurred and be continuing with respect to the Borrower, in which
case the procedures specified in Section 3.4 for funding by L/C Participants
shall apply) constitute a request by the Borrower to the Administrative Agent
for a borrowing pursuant to Section 2.5 of Base Rate Loans  in the amount of
such drawing.  The Borrowing Date with respect to such borrowing shall be the
first date on which a borrowing of Revolving Credit Loans could be made pursuant
to Section 2.5 if the Administrative Agent had received a notice of such
borrowing at the time of such drawing under such Letter of Credit.

          3.6  Obligations Absolute.  The Borrower's obligations under this
               --------------------                                        
Section 3 shall be absolute and unconditional under any and all circumstances
and irrespective of any setoff, counterclaim or defense to payment that the
Borrower may have or have had against the Issuing Lender, any beneficiary of a
Letter of Credit or any other Person.  The Borrower also agrees with the Issuing
Lender that the Issuing Lender shall not be responsible for, and the Borrower's
Reimbursement Obligations under Section 3.5 shall not be affected by, among
other things, the validity or genuineness of documents or of any endorsements
thereon, even though such documents shall in fact prove to be invalid,
fraudulent or forged, or any dispute between or among the Borrower and any
beneficiary of any Letter of Credit or any other party to which such Letter of
Credit may be transferred or any claims whatsoever of the Borrower against any
beneficiary of such Letter of Credit or any such transferee.  The Issuing Lender
shall not be liable for any error, omission, interruption or delay in
transmission, dispatch or delivery of any message or advice, however
transmitted, in connection with any Letter of Credit, except for errors or
omissions found by a final and nonappealable decision of a court of competent
jurisdiction to have resulted from the gross negligence or willful misconduct of
the Issuing Lender.  The Borrower agrees that any action taken or omitted by the
Issuing Lender under or in connection with any Letter of Credit or the related
drafts or documents, if done in the absence of gross negligence or willful
misconduct and in accordance with the standards or care specified in the Uniform
Commercial Code of the State of New York, shall be binding on the Borrower and
shall not result in any liability of the Issuing Lender to the Borrower.

          3.7  Letter of Credit Payments.  If any draft shall be presented for
               -------------------------                                      
payment under any Letter of Credit, the Issuing Lender shall promptly notify the
Borrower of the date and amount thereof.  The responsibility of the Issuing
Lender to the Borrower in connection with any 
<PAGE>
 
                                                                              45

draft presented for payment under any Letter of Credit shall, in addition to any
payment obligation expressly provided for in such Letter of Credit, be limited
to determining that the documents (including each draft) delivered under such
Letter of Credit in connection with such presentment are substantially in
conformity with such Letter of Credit.

          3.8  Applications.  To the extent that any provision of any
               ------------                                          
Application related to any Letter of Credit is inconsistent with the provisions
of this Section 3, the provisions of this Section 3 shall apply.

            SECTION 4.  REPRESENTATIONS AND WARRANTIES

          To induce the Agents and the Lenders to enter into this Agreement and
to make the Revolving Credit Loans and issue or participate in the Letters of
Credit, Holdings and the Borrower hereby jointly and severally represent and
warrant to each Agent and each Lender that:

          4.1  Financial Condition.  (a)  The unaudited pro forma consolidated
               -------------------                      --- -----             
balance sheet of Holdings, the Borrower and its consolidated Subsidiaries as at
September 30, 1998 (including the notes thereto) (the "Pro Forma Balance
                                                       -----------------
Sheet"), copies of which have heretofore been furnished to each Lender, has been
prepared giving effect (as if such events had occurred on such date) to (i) the
Loans to be made on the Closing Date and the use of $17,001,000 of the proceeds
thereof to refinance the credit facilities under the Existing Credit Agreement
and (ii) the payment of fees and expenses in connection with the foregoing.  The
Pro Forma Balance Sheet has been prepared based on the best information
available to the Borrower as of the date of delivery thereof, and presents
fairly in all material respects on a pro forma basis the estimated financial
                                     --- -----                              
position of Holdings, the Borrower and its consolidated Subsidiaries as at
September 30, 1998, assuming that the events specified in the preceding sentence
had actually occurred at such date.

          (b)  The audited consolidated balance sheets of Holdings and its
Subsidiaries as at December 31, 1997 and December 31, 1996 and the related
statements of income and of cash flows for the three fiscal years ended December
31, 1997, reported on by and accompanied by an unqualified report from Arthur
Andersen LLP, present fairly in all material respects the consolidated financial
condition of Holdings and its Subsidiaries as at such date, and the consolidated
results of its operations and its consolidated cash flows for the respective
fiscal years then ended.  The unaudited consolidated balance sheet of Holdings
and its Subsidiaries and of the Borrower and its Subsidiaries as at September
30, 1998, and the related unaudited consolidated statements of income and cash
flows for the 9-month period ended on such date, present fairly in all material
respects the consolidated financial condition of Holdings and its Subsidiaries
and of the Borrower and its Subsidiaries, as the case may be, as at such date,
and the consolidated results of its operations and its consolidated cash flows
for the 9-month period then ended (subject to normal year-end audit
adjustments).  All such financial statements, including the related schedules
and notes thereto, have been prepared in accordance with GAAP applied
consistently throughout the periods involved (except as approved by the
aforementioned firm of accountants and disclosed therein).  Holdings, the
Borrower and its Subsidiaries do not have any material Guarantee Obligations,
contingent liabilities and liabilities for taxes, or any long-term 
<PAGE>
 
                                                                              46

leases or unusual forward or long-term commitments, including, without
limitation, any interest rate or foreign currency swap or exchange transaction
or other obligation in respect of derivatives, that are not reflected in the
most recent financial statements referred to in this paragraph. During the
period from September 30, 1998 to and including the date hereof there has been
no Disposition by Holdings or the Borrower of any material part of its business
or Property.

          4.2  No Change.  Since December 31, 1997 there has been no development
               ---------                                                        
or event that has had or could reasonably be expected to have a Material Adverse
Effect.

          4.3  Corporate Existence; Compliance with Law.  Each of Holdings, the
               ----------------------------------------                        
Borrower and its Subsidiaries (a) is duly organized, validly existing and in
good standing under the laws of the jurisdiction of its organization, (b) has
the corporate power and authority, and the legal right, to own and operate its
Property, to lease the Property it operates as lessee and to conduct the
business in which it is currently engaged, (c) is duly qualified as a foreign
corporation and in good standing under the laws of each jurisdiction where its
ownership, lease or operation of Property or the conduct of its business
requires such qualification except to the extent the failure to be so qualified
could not, in the aggregate, reasonably be expected to have a Material Adverse
Effect and (d) is in compliance with all Requirements of Law except to the
extent that the failure to comply therewith could not, in the aggregate,
reasonably be expected to have a Material Adverse Effect.

          4.4  Corporate Power; Authorization; Enforceable Obligations.  Each
               -------------------------------------------------------       
Loan Party has the corporate power and authority, and the legal right, to make,
deliver and perform the Loan Documents to which it is a party and, in the case
of the Borrower, to borrow hereunder.  Each Loan Party has taken all necessary
corporate action to authorize the execution, delivery and performance of the
Loan Documents to which it is a party and, in the case of the Borrower, to
authorize the borrowings on the terms and conditions of this Agreement.  No
consent or authorization of, filing with, notice to or other act by or in
respect of, any Governmental Authority or any other Person is required in
connection with the borrowings hereunder or with the execution, delivery,
performance, validity or enforceability of this Agreement or any of the Loan
Documents, except (i) consents, authorizations, filings and notices described in
Schedule 4.4, which consents, authorizations, filings and notices have been
obtained or made and are in full force and effect and (ii) the filings referred
to in Section 4.19.  Each Loan Document has been duly executed and delivered on
behalf of each Loan Party party thereto.  This Agreement constitutes, and each
other Loan Document upon execution will constitute, a legal, valid and binding
obligation of each Loan Party party thereto, enforceable against each such Loan
Party in accordance with its terms, except as enforceability may be limited by
applicable bankruptcy, insolvency, reorganization, moratorium or similar laws
affecting the enforcement of creditors' rights generally and by general
equitable principles (whether enforcement is sought by proceedings in equity or
at law).

          4.5  No Legal Bar.  The execution, delivery and performance of this
               ------------                                                  
Agreement and the other Loan Documents, the issuance of Letters of Credit, the
borrowings hereunder and the use of the proceeds thereof will not violate any
Requirement of Law or any Contractual 
<PAGE>
 
                                                                              47

Obligation of Holdings, the Borrower or any of its Subsidiaries except as could
not, in the aggregate, reasonably be expected to have a Material Adverse Effect
and except for such Contractual Obligations pursuant to which the Administrative
Agent is required to execute and deliver a non-disturbance agreement and will
not result in, or require, the creation or imposition of any Lien on any of
their respective properties or revenues pursuant to any Requirement of Law or
any such Contractual Obligation (other than the Liens created by the Security
Documents). Nothwithstanding the foregoing, it is understood that the Borrower
will obtain the consent of BellSouth Personal Communications, Inc. pursuant to
the Master Lease Agreement, dated as of October 30, 1998, by and among SBA
Towers, Inc., SBA Sites, Inc. and BellSouth Personal Communications, Inc. within
10 Business Days of the Closing Date. No Requirement of Law or Contractual
Obligation applicable to the Borrower or any of its Subsidiaries could
reasonably be expected to have a Material Adverse Effect.

          4.6  No Material Litigation. No litigation, investigation or
               ----------------------                                  
proceeding of or before any arbitrator or Governmental Authority is pending or,
to the knowledge of Holdings or the Borrower, threatened by or against Holdings,
the Borrower or any of its Subsidiaries or against any of their respective
properties or revenues (a) with respect to any of the Loan Documents or any of
the transactions contemplated hereby or thereby, or (b) that could reasonably be
expected to have a Material Adverse Effect.

          4.7  No Default.  Neither Holdings, the Borrower nor any of its
               ----------                                                
Subsidiaries is in default under or with respect to any of its Contractual
Obligations in any respect that could reasonably be expected to have a Material
Adverse Effect.  No Default or Event of Default has occurred and is continuing.

          4.8  Ownership of Property; Liens.  Each of Holdings, the Borrower and
               ----------------------------                                     
its Subsidiaries has title in fee simple to, a valid leasehold interest in, or
an easement, license or permit to occupy, all its real property, and good title
to, a valid leasehold interest in, or an easement, license or permit to occupy,
all its other Property, and none of such Property is subject to any Lien except
as permitted by Section 7.3.

          4.9  Intellectual Property.  Holdings, the Borrower and each of its
               ---------------------                                         
Subsidiaries owns, or is licensed to use, all Intellectual Property necessary
for the conduct of its business as currently conducted.  No material claim has
been asserted and is pending by any Person challenging or questioning the use of
any Intellectual Property or the validity or effectiveness of any Intellectual
Property, nor does Holdings or the Borrower know of any valid basis for any such
claim.  The use of Intellectual Property by Holdings, the Borrower and its
Subsidiaries does not infringe on the rights of any Person in any material
respect.

          4.10 Taxes.  Each of Holdings, the Borrower and each of its
               -----                                                 
Subsidiaries has filed or caused to be filed all Federal, state and other
material tax returns that are required to be filed and has paid all taxes shown
to be due and payable on said returns or on any assessments made against it or
any of its Property and all other taxes, fees or other charges imposed on it or
any of its Property by any Governmental Authority (other than any the amount or
validity of which are currently being contested in good faith by appropriate
proceedings and with respect to which
<PAGE>
 
                                                                              48

reserves in conformity with GAAP have been provided on the books of Holdings,
the Borrower or its Subsidiaries, as the case may be); no tax Lien has been
filed, and, to the knowledge of Holdings and the Borrower, no claim is being
asserted, with respect to any such tax, fee or other charge.

          4.11  Federal Regulations.  No part of the proceeds of any Loans will
                -------------------                                            
be used for "purchasing" or "carrying" any "margin stock" within the respective
meanings of each of the quoted terms under Regulation U as now and from time to
time hereafter in effect or for any purpose that violates the provisions of the
Regulations of the Board.  If requested by any Lender or the Administrative
Agent, the Borrower will furnish to the Administrative Agent and each Lender a
statement to the foregoing effect in conformity with the requirements of FR Form
G-3 or FR Form U-1 referred to in Regulation U.

          4.12  Labor Matters. There are no strikes or other labor disputes
                -------------                                              
against Holdings, the Borrower or any of its Subsidiaries pending or, to the
knowledge of Holdings or the Borrower, threatened that (individually or in the
aggregate) could reasonably be expected to have a Material Adverse Effect.
Hours worked by and payment made to employees of Holdings, the Borrower and its
Subsidiaries have not been in violation of the Fair Labor Standards Act or any
other applicable Requirement of Law dealing with such matters that (individually
or in the aggregate) could reasonably be expected to have a Material Adverse
Effect.  All payments due from Holdings, the Borrower or any of its Subsidiaries
on account of employee health and welfare insurance that (individually or in the
aggregate) could reasonably be expected to have a Material Adverse Effect if not
paid have been paid or accrued as a liability on the books of Holdings, the
Borrower or the relevant Subsidiary.

          4.13  ERISA.  Neither a Reportable Event nor an "accumulated funding
                -----                                                         
deficiency" (within the meaning of Section 412 of the Code or Section 302 of
ERISA) has occurred during the five-year period prior to the date on which this
representation is made or deemed made with respect to any Plan, and each Plan
has complied in all material respects with the applicable provisions of ERISA
and the Code.  No termination of a Single Employer Plan has occurred, and no
Lien in favor of the PBGC or a Plan has arisen, during such five-year period.
The present value of all accrued benefits under each Single Employer Plan (based
on those assumptions used to fund such Plans) did not, as of the last annual
valuation date prior to the date on which this representation is made or deemed
made, exceed the value of the assets of such Plan allocable to such accrued
benefits by a material amount.  Neither the Borrower nor any Commonly Controlled
Entity has had a complete or partial withdrawal from any Multiemployer Plan that
has resulted or could reasonably be expected to result in a material liability
under ERISA, and neither the Borrower nor any Commonly Controlled Entity would
become subject to any material liability under ERISA if the Borrower or any such
Commonly Controlled Entity were to withdraw completely from all Multiemployer
Plans as of the valuation date most closely preceding the date on which this
representation is made or deemed made.  No such Multiemployer Plan is in
Reorganization or Insolvent.

          4.14  Investment Company Act; Other Regulations.  No Loan Party is an
                -----------------------------------------                      
"investment company", or a company "controlled" by an "investment company",
within the
<PAGE>
 
                                                                              49

meaning of the Investment Company Act of 1940, as amended.  No Loan
Party is subject to regulation under any Requirement of Law (other than
Regulation X of the Board) which limits its ability to incur Indebtedness.

          4.15  Subsidiaries.  (a) The Subsidiaries listed on Schedule 4.15
                ------------                                               
constitute all the Subsidiaries of the Borrower as of the Closing Date.
Schedule 4.15 sets forth as of the Closing Date the name and jurisdiction of
incorporation of each Subsidiary and, as to each such Subsidiary, the percentage
of each class of Capital Stock owned by any Loan Party.

          (b)  There are no outstanding subscriptions, options, warrants, calls,
rights or other agreements or commitments (other than stock options granted to
employees or directors and directors' qualifying shares) of any nature relating
to any Capital Stock of the Borrower or any Subsidiary.

          4.16  Use of Proceeds. The proceeds of the Loans and the Letters of
                ---------------                                              
Credit shall be used to refinance the credit facilities under the Existing
Credit Agreement and to finance (i) the acquisition and/or construction of
wireless transmission towers, tower sites and related assets, (ii) the
acquisition of rights to place antennae on the sides and rooftops of buildings
owned by others, (iii) the acquisition of leasehold interests in existing
transmission towers to be subleased to others, (iv) the acquisition of or
investments in entities the principal assets of which are towers, tower sites
and related assets, (v) the Borrower's business of managing transmission towers
owned by others, (vi) the Borrower's existing wireless transmission towers and
related assets and (vii) other working capital needs and general corporate
purposes of the Borrower and its Subsidiaries.

          4.17  Environmental Matters.  Other than exceptions to any of the
                ---------------------                                      
following that could not, individually or in the aggregate, reasonably be
expected to have a Material Adverse Effect:

          (a)  the Borrower and its Subsidiaries:  (i) are, and within the
     period of all applicable statutes of limitation have been, in compliance
     with all applicable Environmental Laws; (ii) hold all Environmental Permits
     (each of which is in full force and effect) required for any of their
     current or intended operations or for any property owned, leased, or
     otherwise operated by any of them; (iii) are, and within the period of all
     applicable statutes of limitation have been, in compliance with all of
     their Environmental Permits; and (iv) reasonably believe that: each of
     their Environmental Permits will be timely renewed and complied with,
     without material expense; any additional Environmental Permits that may be
     required of any of them will be timely obtained and complied with, without
     material expense; and compliance with any Environmental Law that is or is
     expected to become applicable to any of them will be timely attained and
     maintained, without material expense.

          (b)  Materials of Environmental Concern are not present at, on, under,
     in, or about any real property now or formerly owned, leased or operated by
     the Borrower or any of its Subsidiaries, or at any other location
     (including, without limitation, any location to 
<PAGE>
 
                                                                              50

     which Materials of Environmental Concern have been sent for re-use or
     recycling or for treatment, storage, or disposal) which could reasonably be
     expected to (i) give rise to liability of the Borrower or any of its
     Subsidiaries under any applicable Environmental Law or otherwise result in
     costs to the Borrower or any of its Subsidiaries, or (ii) interfere with
     the Borrower's or any of its Subsidiaries' continued operations, or (iii)
     impair the fair saleable value of any real property owned or leased by the
     Borrower or any of its Subsidiaries.

          (c)  There is no judicial, administrative, or arbitral proceeding
     (including any notice of violation or alleged violation) under or relating
     to any Environmental Law to which the Borrower or any of its Subsidiaries
     is, or to the knowledge of the Borrower or any of its Subsidiaries will be,
     named as a party that is pending or, to the knowledge of the Borrower or
     any of its Subsidiaries, threatened.

          (d)  Neither the Borrower nor any of its Subsidiaries has received any
     written request for information, or been notified that it is a potentially
     responsible party under or relating to the federal Comprehensive
     Environmental Response, Compensation, and Liability Act or any similar
     Environmental Law, or with respect to any Materials of Environmental
     Concern.

          (e)  Neither the Borrower nor any of its Subsidiaries has entered into
     or agreed to any consent decree, order, or settlement or other agreement,
     or is subject to any judgment, decree, or order or other agreement, in any
     judicial, administrative, arbitral, or other forum for dispute resolution,
     relating to compliance with or liability under any Environmental Law.

          (f)  Neither the Borrower nor any of its Subsidiaries has assumed or
     retained, by contract or operation of law, any liabilities of any kind,
     fixed or contingent, known or unknown, under any Environmental Law or with
     respect to any Material of Environmental Concern.

          4.18  Accuracy of Information, etc.  No statement or information
                -----------------------------                             
contained in this Agreement, any other Loan Document, the Confidential
Information Memorandum or any other written document, certificate or statement
furnished to the Administrative Agent or the Lenders or any of them, by or on
behalf of any Loan Party for use in connection with the transactions
contemplated by this Agreement or the other Loan Documents, contained as of the
date such statement, information, document or certificate was so furnished (or,
in the case of the Confidential Information Memorandum, as of the date of this
Agreement), any untrue statement of a material fact or omitted to state a
material fact necessary in order to make the statements contained herein or
therein not misleading.  The projections and pro forma financial information
                                             --- -----                      
contained in the materials referenced above are based upon good faith estimates
and assumptions believed by management of the Borrower to be reasonable at the
time made, it being recognized by the Lenders that such financial information as
it relates to future events is not to be viewed as fact and that actual results
during the period or periods covered by such financial information may differ
from the projected results set forth therein by a material amount. There is no
fact actually known to any Loan Party that could reasonably be expected to have
a Material Adverse 
<PAGE>
 
                                                                              51

Effect that has not been expressly disclosed herein, in the other Loan
Documents, in the Confidential Information Memorandum or in any other documents,
certificates and statements furnished to the Agents and the Lenders for use in
connection with the transactions contemplated hereby and by the other Loan
Documents.

          4.19  Security Documents.  (a)  The Guarantee and Collateral Agreement
                ------------------                                              
is effective to create in favor of the Administrative Agent, for the benefit of
the Lenders, a legal, valid and enforceable security interest in the Collateral
described therein and proceeds thereof.  In the case of the Pledged Stock
described in the Guarantee and Collateral Agreement, when any stock certificates
representing such Pledged Stock are delivered to the Administrative Agent, and
in the case of the other Collateral described in the Guarantee and Collateral
Agreement, when financing statements in appropriate form are filed in the
offices specified on Schedule 4.19(a)-1 (which financing statements have been
duly completed and executed and delivered to the Administrative Agent) and such
other filings as are specified on Schedule 3 to the Guarantee and Collateral
Agreement (all of which filings have been duly completed), the Guarantee and
Collateral Agreement shall constitute a fully perfected Lien on, and security
interest in, all right, title and interest of the Loan Parties in such
Collateral and the proceeds thereof, as security for the Obligations (as defined
in the Guarantee and Collateral Agreement), in each case prior and superior in
right to any other Person (except, in the case of Collateral other than Pledged
Stock, Liens permitted by Section 7.3).  Notwithstanding the foregoing, it is
understood that UCC-1 financing statements are not being filed in respect of
equipment in locations where the value of such equipment is less than $5000 or
in local jurisdictions requiring dual filings, and that fixture filings are not
being made in respect of Tower locations which are not Mortgaged Properties.
Schedule 4.19(a)-2 lists each UCC Financing Statement that (i) names any Loan
Party as debtor and (ii) will remain on file after the Closing Date.  Schedule
4.19(a)-3 lists each UCC Financing Statement that (i) names any Loan Party as
debtor and (ii) will be terminated on or prior to the Closing Date; and on or
prior to the Closing Date, the Borrower will have delivered to the
Administrative Agent, or caused to be filed, duly completed UCC termination
statements, signed by the relevant secured party, in respect of each such UCC
Financing Statement.

          (b)  Each of the Mortgages executed and delivered on the Closing Date
is, and each of the Mortgages executed and delivered after the Closing Date will
be when so executed and delivered, effective to create in favor of the
Administrative Agent, for the benefit of the Lenders, a legal, valid and
enforceable Lien on the Mortgaged Properties described therein and proceeds
thereof, and when such Mortgages are recorded in the appropriate recording
office (which offices are specified on Schedule 4.19(b), in the case of
Mortgages executed and delivered on the Closing Date), each such Mortgage shall
constitute a fully perfected Lien on, and security interest in, all right, title
and interest of the Loan Parties in the Mortgaged Properties and the proceeds
thereof, as security for the Obligations (as defined in the relevant Mortgage),
in each case prior and superior in right to any other Person.

          4.20  Solvency.  Each Loan Party is, and after giving effect to the
                --------                                                     
incurrence of all Indebtedness and obligations being incurred in connection
herewith will be and will continue to be, Solvent.
<PAGE>
 
                                                                              52

          4.21  Regulation H.   No Mortgage encumbers improved real property
                ------------                                               
which is located in an area that has been identified by the Secretary of Housing
and Urban Development as an area having special flood hazards and in which flood
insurance has been made available under the National Flood Insurance Act of
1968, unless such flood insurance either has been obtained and evidence thereof
provided to the Administrative Agent or is unavailable based upon the nature of
the improvements located on such real property.

          4.22  Year 2000 Matters.  Any reprogramming required to permit the
                -----------------                                           
proper functioning, in and following the year 2000, of (i) the Borrower's
computer systems and (ii) equipment containing embedded microchips (including
systems and equipment supplied by others or with which Borrower's systems
interface) and the testing of all such systems and equipment, as so
reprogrammed, will be completed by September 30, 1999.  The cost to the Borrower
of such reprogramming and testing and of the reasonably foreseeable consequences
of year 2000 to the Borrower (including, without limitation, reprogramming
errors and the failure of others' systems or equipment) will not result in a
Default or a Material Adverse Effect.  Except for such of the reprogramming
referred to in the preceding sentence as may be necessary, the computer and
management information systems of the Borrower and its Subsidiaries are and,
with ordinary course upgrading and maintenance, will continue for the term of
this Agreement to be, sufficient to permit the Borrower to conduct its business
without Material Adverse Effect.

          4.23  Initial Tower Report.  The information set forth in the Initial
                --------------------                                           
Tower Report is true and correct in all material respects as of the date
thereof.

          4.24  Tower Sites.  At least a majority of the Towers that do not
                -----------                                                
constitute Mortgaged Properties are constructed so as to be capable of being
moved from their present locations and except to the extent (i) recordation of
any renewal, extension, amendment, assignment or other instrument in connection
with any lease of real property in the applicable public records may be required
in order to permit removal of a Tower and (ii) removal and/or disassembly of a
Tower may require the Borrower and its Subsidiaries to obtain the consent of, or
a permit from, the applicable Governmental Authority (which consent or permit
the Borrower believes is reasonably likely to be issued if requested by the
Borrower or any of its Subsidiaries), the Borrower and its Subsidiaries have the
right to remove such Towers from their present locations.

          4.25  Real Property Leases.  The present and contemplated use of the
                --------------------                                          
real property owned or leased by the Borrower or any of its Subsidiaries for the
operation of Towers is in compliance in all material respects with all
applicable zoning ordinances and regulations and other laws and regulations
where failure so to comply would result, or create reasonable risk of resulting,
in a Material Adverse Effect.  Each lease pursuant to which the Borrower or any
of its Subsidiaries, as lessee, acquired rights in real property upon which any
Tower is situated is in full force and effect, the Borrower or such Subsidiary
has all rights of the lessee thereunder, there has been no default in the
performance of any of its terms or conditions by the Borrower or any such
Subsidiary nor (to the best of the Borrower's knowledge) any other party
thereto, and no claims of default have been asserted with respect thereto where
such default would result, or create a reasonable risk of resulting, in a
Material Adverse Effect.
<PAGE>
 
                                                                              53

          4.26  FCC and FAA Matters; State Regulatory Compliance.  (a)  The
                ------------------------------------------------           
Borrower (i) has duly and timely filed all material reports, registrations and
other material filings, if any, which are required to be filed by it or any of
its Subsidiaries under the Communications Act or any other applicable law, rule
or regulation of any Governmental Authority, including the FCC and the FAA, the
non-filing of which would not result, or be reasonably likely to result, in a
Material Adverse Effect and (ii) is in compliance with all such laws, rules,
regulations and ordinances, including those promulgated by the FCC and the FAA,
to the extent the non-compliance with which would result, or be reasonably
likely to result, in a Material Adverse Effect.  All information provided by or
on behalf of the Borrower or any Affiliate in any material filing, if any, with
the FCC and the FAA relating to the business of the Borrower and its
Subsidiaries was, to the knowledge of such Person at the time of filing,
complete and correct in all material respects when made, and the FCC and the FAA
have been notified of any substantial or significant changes in such information
as may be required in accordance with applicable Requirements of Law.

          (b)  The Borrower and its Subsidiaries have all permits, certificates,
licenses, tariff approvals and other authorizations from all state and federal
Governmental Authorities required to conduct their current business except for
such permits, certificates, licenses, tariff approvals and other authorizations
as could not, in the aggregate, reasonably be expected to have a Material
Adverse Effect.

          (c)  Except as described on Schedule 4.26, the Borrower has no
knowledge of any investigation, notice of apparent liability, violation,
forfeiture or other order or complaint issued by or before any state or federal
Governmental Authority, or of any other proceedings of or before any state or
federal Governmental Authority, which could reasonably be expected to have a
Material Adverse Effect.

                       SECTION 5.  CONDITIONS PRECEDENT

          5.1  Conditions to Initial Extension of Credit.  The agreement of each
               -----------------------------------------                        
Lender to make the initial extension of credit requested to be made by it is
subject to the satisfaction, prior to or concurrently with the making of such
extension of credit on the Closing Date, of the following conditions precedent:

          (a)  Loan Documents.  The Administrative Agent shall have received (i)
               --------------                                                   
     this Agreement, executed and delivered by a duly authorized officer of
     Holdings and the Borrower, (ii) the Guarantee and Collateral Agreement,
     executed and delivered by a duly authorized officer of Holdings, the
     Borrower and each Subsidiary Guarantor, (iii) subject to Section 6.13, a
     Mortgage covering each of the Mortgaged Properties described in Schedule
     1.1, executed and delivered by a duly authorized officer of each party
     thereto, and (iv) for the account of each relevant Lender, Notes conforming
     to the requirements hereof and executed and delivered by a duly authorized
     officer of the Borrower.
<PAGE>
 
                                                                              54

          (b)  Pro Forma Balance Sheet; Financial Statements.  The Lenders shall
               ---------------------------------------------                    
     have received (i) the Pro Forma Balance Sheet and (ii) the consolidated
     financial statements of Holdings and the Borrower described in Section 4.1,
     and such financial statements shall not, in the reasonable judgment of the
     Lenders, reflect any material adverse change in the consolidated financial
     condition of Holdings, the Borrower and its Subsidiaries, as reflected in
     the financial statements or projections contained in the Confidential
     Information Memorandum.

          (c)  Initial Tower Report.  The Lenders shall have received the
               --------------------                                      
     Initial Tower Report, in form, scope and substance satisfactory to them.

          (d)  Approvals.  All governmental and third party approvals (including
               ---------                                                        
     landlords' and other consents) necessary or, in the discretion of the
     Administrative Agent, advisable in connection with the continuing
     operations of Holdings, the Borrower and its Subsidiaries and the
     transactions contemplated hereby shall have been obtained and be in full
     force and effect, except for such approvals as could not reasonably be
     expected to have a Material Adverse Effect.

          (e)  Related Agreements.  The Administrative Agent shall have received
               ------------------                                               
     (in a form reasonably satisfactory to the Administrative Agent), with a
     copy for each Lender, true and correct copies, certified as to authenticity
     by the Borrower, of the Senior Discount Notes Indenture and such other
     documents or instruments as may be reasonably requested by the
     Administrative Agent, including, without limitation, a copy of any debt
     instrument, security agreement or other material contract to which any of
     the Loan Parties may be a party.

          (f)  Existing Credit Agreement.  All loans outstanding, and all
               -------------------------                                 
     security interests securing such loans, under the Existing Credit Agreement
     shall have been assigned to the Lenders in a manner satisfactory to the
     Administrative Agent or, with respect to such security interests, at the
     request of the Administrative Agent, arrangements satisfactory to the
     Administrative Agent shall have been made for the termination of such
     security interests.

          (g)  Fees.  The Lenders, LBI, the Co-Arrangers and the Administrative
               ----                                                            
     Agent shall have received all fees required to be paid, and all expenses
     for which invoices have been presented (including reasonable fees,
     disbursements and other charges of counsel to the Agents), on or before the
     Closing Date.  All such amounts will be paid with proceeds of Loans made on
     the Closing Date and will be reflected in the funding instructions given by
     the Borrower to the Administrative Agent on or before the Closing Date.

          (h)  Business Plan.  The Lenders shall have received a reasonably
               -------------                                               
     satisfactory business plan for fiscal years 1997-2007 and a reasonably
     satisfactory written analysis of the business and prospects of Holdings,
     the Borrower and its Subsidiaries for the period from the Closing Date
     through fiscal year 2005.
<PAGE>
 
                                                                              55

          (i)  Solvency Analysis.  The Lenders shall have received a reasonably
               -----------------                                               
     satisfactory solvency analysis certified by the chief financial officer of
     Holdings or other senior executive officer of Holdings satisfactory to the
     Lenders which shall document the solvency of Holdings, the Borrower and its
     Subsidiaries considered as a whole after giving effect to the transactions
     contemplated hereby.

          (j)  Lien Searches.  The Administrative Agent shall have received the
               -------------                                                   
     results of a recent lien search in each of the jurisdictions where assets
     of the Loan Parties are located, and such search shall reveal no liens on
     any of the assets of Holdings, the Borrower or its Subsidiaries except for
     liens permitted by Section 7.3 or liens to be discharged on or prior to the
     Closing Date pursuant to documentation satisfactory to the Administrative
     Agent.

          (k)  Closing Certificate.  The Administrative Agent shall have
               -------------------                                      
     received a certificate of each Loan Party, dated the Closing Date,
     substantially in the form of Exhibit C, with appropriate insertions and
     attachments.

          (l)  Legal Opinions. The Administrative Agent shall have received the
     following executed legal opinions:

                      (i)  the legal opinion of Gunster, Yoakley, Valdes-Fauli &
          Stewart, P.A., counsel to the Borrower and its Subsidiaries,
          substantially in the form of Exhibit F;  and

                      (ii) subject to Section 6.13, the legal opinion of local
          counsel in each of Georgia, Indiana, Maryland and Tennessee and of
          such other special and local counsel as may be required by the
          Administrative Agent.

     Each such legal opinion shall cover such other matters incident to the
     transactions contemplated by this Agreement as the Administrative Agent may
     reasonably require.

          (m)  Pledged Stock; Stock Power; Pledged Notes.  The Administrative
               -----------------------------------------                     
     Agent shall have received (i) the certificates representing the shares of
     Capital Stock pledged pursuant to the Guarantee and Collateral Agreement,
     together with an undated stock power for each such certificate executed in
     blank by a duly authorized officer of the pledgor thereof and (ii) each
     promissory note pledged to the Administrative Agent pursuant to the
     Guarantee and Collateral Agreement endorsed (without recourse) in blank (or
     accompanied by an executed transfer form in blank satisfactory to the
     Administrative Agent) by the pledgor thereof.

          (n)  Filings, Registrations and Recordings.  Subject to Section 6.13,
               -------------------------------------                           
     each document (including, without limitation, any Uniform Commercial Code
     financing statement) required by the Security Documents or under law or
     reasonably requested by the Administrative Agent to be filed, registered or
     recorded in order to create in favor of the Administrative Agent, for the
     benefit of the Lenders, a perfected Lien on the Collateral described
     therein, prior and superior in right to any other Person (other than 
<PAGE>
 
                                                                              56

     with respect to Liens expressly permitted by Section 7.3), shall be in
     proper form for filing, registration or recordation.

          (o)  Insurance.  The Administrative Agent shall have received
               ---------                                               
     insurance certificates satisfying the requirements of Section 5.3 of the
     Guarantee and Collateral Agreement.

          5.2  Conditions to Each Extension of Credit.  The agreement of each
               --------------------------------------                        
Lender to make any extension of credit requested to be made by it on any date
(including, without limitation, its initial extension of credit) is subject to
the satisfaction of the following conditions precedent:

          (a)  Representations and Warranties.  Each of the representations and
               ------------------------------                                  
     warranties made by any Loan Party in or pursuant to the Loan Documents
     shall be true and correct on and as of such date as if made on and as of
     such date except for such representations and warranties expressly stated
     to be made as of a specific earlier date, in which case such
     representations and warranties shall be true and correct as of such earlier
     date.

          (b)  No Default.  No Default or Event of Default shall have occurred
               ----------                                                     
     and be continuing on such date or after giving effect to the extensions of
     credit requested to be made on such date.

Each borrowing by and issuance of a Letter of Credit on behalf of the Borrower
hereunder shall constitute a representation and warranty by the Borrower as of
the date of such extension of credit that the conditions contained in this
Section 5.2 have been satisfied.

                       SECTION 6.  AFFIRMATIVE COVENANTS

          Holdings and the Borrower hereby jointly and severally agree that, so
long as the Commitments remain in effect, any Letter of Credit remains
outstanding or any Loan or other amount is owing to any Lender or any Agent
hereunder, each of Holdings and the Borrower shall and shall cause each of its
Subsidiaries to:

          6.1  Financial Statements.  Furnish to the Administrative Agent (and
               --------------------                                           
the Administrative Agent shall furnish to each other Agent and to each Lender):

          (a)  as soon as available, but in any event within 90 days after the
     end of each fiscal year of the Borrower, a copy of the audited consolidated
     and unaudited consolidating balance sheets of Holdings and its consolidated
     Subsidiaries and of the Borrower and its consolidated Subsidiaries, in each
     case as at the end of such year and the related audited consolidated and
     unaudited consolidating statements of income and of cash flows for such
     year, setting forth in each case in comparative form the figures for the
     previous year, reported on, in the case of such audited financial
     statements, without a "going concern" or like qualification or exception,
     or qualification arising out of the 
<PAGE>
 
                                                                              57

     scope of the audit, by Arthur Andersen LLP or other independent certified
     public accountants of nationally recognized standing;

          (b)  as soon as available, but in any event not later than 45 days
     after the end of each of the first three quarterly periods of each fiscal
     year of the Borrower, the unaudited consolidated and consolidating balance
     sheets of Holdings and its consolidated Subsidiaries and of the Borrower
     and its consolidated Subsidiaries, in each case as at the end of such
     quarter, and the related unaudited consolidated and consolidating
     statements of income and of cash flows for such quarter and the portion of
     the fiscal year through the end of such quarter, setting forth in each case
     in comparative form the figures for the previous year, certified by a
     Responsible Officer as being fairly stated in all material respects
     (subject to normal year-end audit adjustments); and

          (c)  as soon as available, but in any event not later than 45 days
     after the end of each month occurring during each fiscal year of the
     Borrower (other than the third, sixth, ninth and twelfth such month), the
     unaudited consolidated and consolidating balance sheets of Holdings and its
     Subsidiaries and of the Borrower and its Subsidiaries, in each case as at
     the end of such month and the related unaudited consolidated statements of
     income for such month and the portion of the fiscal year through the end of
     such month, setting forth in each case in comparative form the figures for
     the previous year, certified by a Responsible Officer as being fairly
     stated in all material respects (subject to normal year-end audit
     adjustments);

all such financial statements shall be complete and correct in all material
respects and shall be prepared in reasonable detail and in accordance with GAAP
applied consistently throughout the periods reflected therein and with prior
periods (except as approved by such accountants or officer, as the case may be,
and disclosed therein).

          6.2  Certificates; Other Information.  Furnish to the Administrative
               -------------------------------                                
Agent (and the Administrative Agent shall furnish to each other Agent and to
each Lender) or, in the case of clause (l), to the relevant Lender:

          (a)  concurrently with the delivery of the financial statements
     referred to in Section 6.1(a), a certificate of the independent certified
     public accountants reporting on such financial statements stating that in
     making the examination necessary therefor no knowledge was obtained of any
     Default or Event of Default in respect of the financial covenants contained
     in Section 7.1, except as specified in such certificate;

          (b)  concurrently with the delivery of any financial statements
     pursuant to Section 6.1, (i) a certificate of a Responsible Officer stating
     that, to the best of each such Responsible Officer's knowledge, each Loan
     Party during such period has observed or performed all of its covenants and
     other agreements, and satisfied every condition, contained in this
     Agreement and the other Loan Documents to which it is a party to be
     observed, performed or satisfied by it, and that such Responsible Officer
     has obtained no knowledge of any Default or Event of Default except as
     specified in such certificate and 
<PAGE>
 
                                                                              58

     (ii) in the case of quarterly or annual financial statements, a Compliance
     Certificate containing all information and calculations necessary for
     determining compliance by Holdings, the Borrower and its Subsidiaries with
     the provisions of this Agreement referred to therein as of the last day of
     the fiscal quarter or fiscal year of the Borrower, as the case may be;

          (c)  concurrently with the delivery of any financial statements
     pursuant to Section 6.1 prior to the Transition Date, a certificate of a
     Responsible Officer stating that, as of the date of such delivery, the
     Total Revolving Extensions of Credit do not exceed the Asset Coverage Test
     Amount and setting forth all information and calculations necessary to
     demonstrate compliance therewith;

          (d)  as soon as available, and in any event no later than 45 days
     after the end of each fiscal year of the Borrower, a detailed consolidated
     budget for the following fiscal year (including a projected consolidated
     balance sheet of Holdings, the Borrower and its Subsidiaries as of the end
     of the following fiscal year, and the related consolidated statements of
     projected cash flow, projected changes in financial position and projected
     income), and, as soon as available, significant revisions, if any, of such
     budget and projections with respect to such fiscal year (collectively, the
     "Projections"), which Projections shall in each case be accompanied by a
      -----------                                                            
     certificate of a Responsible Officer stating that such Projections are
     based on reasonable estimates, information and assumptions and that such
     Responsible Officer has no reason to believe that such Projections are
     incorrect or misleading in any material respect;

          (e)  within 45 days after the end of each fiscal quarter of the
     Borrower, a narrative discussion and analysis of the financial condition
     and results of operations of Holdings, the Borrower and its Subsidiaries
     for such fiscal quarter and for the period from the beginning of the then
     current fiscal year to the end of such fiscal quarter, as compared to the
     portion of the Projections covering such periods and to the comparable
     periods of the previous year;

          (f)  concurrently with the delivery of any financial statement
     pursuant to Sections 6.1(a) or 6.1(b), a certificate of a Responsible
     Officer showing as of the end of the period covered by such financial
     statement (i) the location of all Towers, whether each Tower or the real
     property on which it is located is owned or leased by the Borrower and its
     Subsidiaries, the contribution by each Tower to Total Tower Revenue as then
     estimated in good faith by the Borrower, which Towers were acquired during
     the most recently completed fiscal quarter and the status of all Towers
     under construction and (ii) an open bid summary report and a site
     development backlog report with respect to Towers;

          (g)  other than in connection with the National Data Transaction, not
     later than 10 Business Days prior to any proposed acquisition of any new
     Towers (including real property sites for Towers), written notice of such
     proposed acquisition if the proposed cost exceeds $1,000,000 for any
     acquisition or series of related acquisitions and the proposed cost and
     projected revenue thereof (whether or not the costs of such acquisition 
<PAGE>
 
                                                                              59

     are to be funded by the Company from its own sources or from the proceeds
     of Revolving Credit Loans) (provided, that if the proposed cost of such
                                 --------
     acquisition does not exceed $2,500,000, 5 Business Days' prior written
     notice shall be required). Such notice shall specify a description and the
     locations of the new Towers (including Towers owned by Tower Companies),
     the name and address of the owner or lessee, as appropriate, of the real
     property on which they are located and, if the proposed cost exceeds
     $2,500,000 for any acquisition or series of related acquisitions, a
     memorandum summarizing the results of the due diligence review of such
     acquisition or series of related acquisitions (including, without
     limitation, a discussion of the capacity and contemplated use of such new
     Towers) and such other documents or information owned or within the control
     of the Borrower and its Subsidiaries as the Required Lenders may reasonably
     require;

          (h)  within 45 days after the end of each calendar month ending on or
     before the Transition Date, a certificate of a Responsible Officer setting
     forth calculations of the Asset Coverage Test Amount as of the date of such
     certificate (an "Asset Coverage Test Certificate");
                      -------------------------------   

          (i)  within 45 days of the Closing Date and within 45 days after the
     end of each fiscal quarter thereafter, a certificate of a Responsible
     Officer demonstrating that the Borrower is in compliance with the Mortgage
     Requirement;

          (j)  within five days after the same are sent, copies of all financial
     statements and reports that Holdings sends to the holders of any class of
     its debt securities or public equity securities and, within five days after
     the same are filed, copies of all financial statements and reports that
     Holdings may make to, or file with, the SEC;

          (k)  as soon as possible and in any event within 10 days of obtaining
     knowledge thereof:  (i) any development, event, or condition that,
     individually or in the aggregate with other developments, events or
     conditions, could reasonably be expected to result in the payment by the
     Borrower and its Subsidiaries, in the aggregate, of a Material
     Environmental Amount; and (ii) any notice that any governmental authority
     may deny any application for an Environmental Permit sought by, or revoke
     or refuse to renew any Environmental Permit held by, the Borrower; and

          (l)  promptly, such additional financial and other information as any
     Lender may from time to time reasonably request.

          6.3  Payment of Obligations.  Pay, discharge or otherwise satisfy at
               ----------------------                                         
or before maturity or before they become delinquent, as the case may be, all its
material obligations of whatever nature, except where the amount or validity
thereof is currently being contested in good faith by appropriate proceedings
and reserves in conformity with GAAP with respect thereto have been provided on
the books of Holdings, the Borrower or its Subsidiaries, as the case may be.
<PAGE>
 
                                                                              60

          6.4  Conduct of Business and Maintenance of Existence, etc.    (a) (i)
               ------------------------------------------------------           
Preserve, renew and keep in full force and effect its corporate existence and
(ii) take all reasonable action to maintain all rights, privileges and
franchises necessary or desirable in the normal conduct of its business, except,
in each case, as otherwise permitted by Section 7.4 and except, in the case of
clause (ii) above, to the extent that failure to do so could not reasonably be
expected to have a Material Adverse Effect; and (b) comply with all Contractual
Obligations and Requirements of Law except to the extent that failure to comply
therewith could not, in the aggregate, reasonably be expected to have a Material
Adverse Effect.

          6.5  Maintenance of Property; Insurance.
               ---------------------------------- 

          (a)  Keep all Property and systems useful and necessary in its
business in good working order and condition, ordinary wear and tear excepted.

          (b)  Maintain with financially sound and reputable insurance companies
insurance on all its Property in at least such amounts and against at least such
risks (but including in any event public liability, product liability and
business interruption) as are usually insured against in the same general area
by companies engaged in the same or a similar business.

          (c)  Maintain or cause to be maintained on all of the Mortgaged
Property:

          (i) property insurance against loss or damage by fire, lightning,
     windstorm, tornado, water damage, flood, earthquake and by such other
     further risks and hazards as now are or subsequently may be covered by an
     "all risk" policy or a fire policy covering "special" causes of loss, and
     the policy limits shall be automatically reinstated after each loss;

               (ii) commercial general liability insurance under a policy
     including the "broad form CGL endorsement" (or which incorporates the
     language of such endorsement), covering all claims for personal injury,
     bodily injury or death, or property damage occurring on, in or about the
     Premises in an amount not less than $10,000,000 combined single limit with
     respect to injury and property damage relating to any one occurrence plus
     such excess limits as the Administrative Agent shall request from time to
     time;

               (iii) if any portion of the Mortgaged Property is located in an
     area identified as a special flood hazard area by the Federal Emergency
     Management Agency or other applicable agency, flood insurance in an amount
     reasonably satisfactory to the Administrative Agent, but in no event less
     than the maximum limit of coverage available under the National Flood
     Insurance Act of 1968, as amended (unless such flood insurance is
     unavailable based upon the nature of improvements located on such Mortgaged
     Property); and

               (iv) such other insurance in such amounts as the Administrative
     Agent may reasonably request from time to time against loss or damage by
     any other risk 
<PAGE>
 
                                                                              61

     commonly insured against by persons occupying or using like properties in
     the locality or localities in which the Mortgaged Property is situated.

          (d)  Ensure that each insurance policy (other than flood insurance)
shall (i) provide that it shall not be canceled, non-renewed or materially
amended without 30-days' prior written notice to the Administrative Agent, and
(ii) with respect to all property insurance, provide for deductibles in an
amount reasonably satisfactory to the Administrative Agent and contain a
"Replacement Cost Endorsement" without any deduction made for depreciation and
with no co-insurance penalty (or attaching an agreed amount endorsement
reasonably satisfactory to Administrative Agent), with loss payable solely to
the Administrative Agent (modified, if necessary, to provide that proceeds in
the amount of replacement cost may be retained by the Administrative Agent
without the obligation to rebuild) as its interest may appear, without
contribution, under a "standard" or "New York" mortgagee clause acceptable to
the Administrative Agent.  Liability insurance policies shall name the
Administrative Agent as an additional insured and contain a waiver of
subrogation against the Administrative Agent.  Each policy shall expressly
provide that any proceeds which are payable to the Administrative Agent shall be
paid by check payable to the order of the Administrative Agent only and
requiring the endorsement of the Administrative Agent only.

          (e)  Deliver to the Administrative Agent an original of each insurance
policy required to be maintained, or a certificate of such insurance acceptable
to the Administrative Agent, together with a copy of the declaration page for
each such policy.  The Borrower shall (i) pay as they become due all premiums
for such insurance, and (ii) not later than 15 days prior to the expiration of
each policy to be furnished pursuant to the provisions of this Section, deliver
a renewed policy or policies, or duplicate original or originals thereof, marked
"premium paid," or accompanied by such other evidence of payment reasonably
satisfactory to the Administrative Agent.

          (f)  If the Borrower is in default of its obligations to insure or
deliver any such prepaid policy or policies, then the Administrative Agent, at
its option and without notice, may effect such insurance from year to year, and
pay the premium or premiums therefor, and the Borrower shall pay to the
Administrative Agent  on demand such premium or premiums so paid by the
Administrative Agent with interest from the time of payment at the Default Rate.

          (g)  Promptly comply with and conform to (i) all provisions of each
such insurance policy, and (ii) all requirements of the insurers applicable to
the Borrower or to any of the Mortgaged Property or to the use, manner of use,
occupancy, possession, operation, maintenance, alteration or repair of any of
the Mortgaged Property.  The Borrower shall not use or permit the use of the
Mortgaged Property in any manner which would permit any insurer to cancel any
insurance policy or void coverage required to be maintained by this Section.

          (h)  If the Mortgaged Property, or any part thereof, shall be
destroyed or damaged, give immediate notice thereof to the Administrative Agent.
All insurance proceeds shall be paid to the Administrative Agent to be held by
the Administrative Agent as collateral to secure the payment and performance of
the Indebtedness and the Obligations.  Notwithstanding the 
<PAGE>
 
                                                                              62

preceding sentence, provided that no Event of Default shall have occurred and be
continuing, the Borrower shall have the right to adjust such loss, and the
insurance proceeds relating to such loss shall be paid over to the Borrower and
the Borrower shall, promptly after any such damage and the receipt of such
proceeds from the Administrative Agent, repair all such damage regardless of
whether such proceeds are sufficient to pay for the costs of repair.

          (i)  The Borrower may maintain insurance required under this Section
by means of one or more blanket insurance policies maintained by the Borrower;
                                                                              
provided, however, that (A) any such policy shall specify, or the Borrower shall
- --------  -------                                                               
furnish to the Administrative Agent a written statement from the insurer so
specifying, the maximum amount of the total insurance afforded by such blanket
policy that is allocated to the Mortgaged Property and any sublimits in such
blanket policy applicable to the Mortgaged Property, (B) each such blanket
policy shall include an endorsement providing that, in the event of a loss
resulting from an insured peril, insurance proceeds shall be allocated to the
Mortgaged Property in an amount equal to the coverages required to be maintained
by the Borrower as provided above and (C) the protection afforded under any such
blanket policy shall be no less than that which would have been afforded under a
separate policy or policies relating only to the Mortgaged Property.

          6.6  Inspection of Property; Books and Records; Discussions.  (a)
               ------------------------------------------------------       
Keep proper books of records and account in which full, true and correct entries
in conformity with GAAP and all Requirements of Law shall be made of all
dealings and transactions in relation to its business and activities and (b)
permit representatives of any Lender to visit and inspect any of its properties
and examine and make abstracts from any of its books and records at any
reasonable time and as often as may reasonably be desired (such visits and
inspections to be coordinated by the Lenders to the extent reasonably
practicable) and to discuss the business, operations, properties and financial
and other condition of Holdings, the Borrower and its Subsidiaries with officers
of Holdings, the Borrower and its Subsidiaries and with its independent
certified public accountants; provided that if no Default or Event of Default
                              --------                                       
has occurred, such visits shall be limited to once per fiscal quarter and such
discussions shall be limited to once per week.

          6.7  Notices.  Promptly give notice to the Administrative Agent and
               -------                                                       
each Lender of:

          (a)  the occurrence of any Default or Event of Default;

          (b)  any (i) default or event of default under any Contractual
     Obligation of Holdings, the Borrower or any of its Subsidiaries beyond any
     period of grace provided in such Contractual Obligation or (ii) litigation,
     investigation or proceeding which may exist at any time between Holdings,
     the Borrower or any of its Subsidiaries and any Governmental Authority,
     that in either case, if not cured or if adversely determined, as the case
     may be, could reasonably be expected to have a Material Adverse Effect;

          (c)  any litigation or proceeding affecting Holdings, the Borrower or
     any of its Subsidiaries in which the amount involved is $1,000,000 or more
     and not covered by insurance or in which injunctive or similar relief is
     sought;
<PAGE>
 
                                                                              63

          (d)  the following events, as soon as possible and in any event within
     30 days after the Borrower knows or has reason to know thereof:  (i) the
     occurrence of any Reportable Event with respect to any Plan, a failure to
     make any required contribution to a Plan, the creation of any Lien in favor
     of the PBGC or a Plan or any withdrawal from, or the termination,
     Reorganization or Insolvency of, any Multiemployer Plan or (ii) the
     institution of proceedings or the taking of any other action by the PBGC or
     the Borrower or any Commonly Controlled Entity or any Multiemployer Plan
     with respect to the withdrawal from, or the termination, Reorganization or
     Insolvency of, any Plan; and

          (e)  any development or event that has had or could reasonably be
     expected to have a Material Adverse Effect.

Each notice pursuant to this Section shall be accompanied by a statement of a
Responsible Officer setting forth details of the occurrence referred to therein
and stating what action Holdings, the Borrower or the relevant Subsidiary
proposes to take with respect thereto.

          6.8  Environmental Laws.  (a)  Comply in all material respects with,
               ------------------                                             
and use commercially reasonable efforts to ensure compliance in all material
respects by all tenants and subtenants, if any, with, all applicable
Environmental Laws, and obtain and comply in all material respects with and
maintain, and use commercially reasonable efforts to ensure that all tenants and
subtenants obtain and comply in all material respects with and maintain, any and
all licenses, approvals, notifications, registrations or permits required by
applicable Environmental Laws.

          (b)  Conduct and complete all investigations, studies, sampling and
testing, and all remedial, removal and other actions required under
Environmental Laws and promptly comply in all material respects with all lawful
orders and directives of all Governmental Authorities regarding Environmental
Laws.

          6.9  Interest Rate Protection.  In the case of the Borrower, on or
               ------------------------                                     
prior to the date upon which at least 50% of the aggregate amount of the
Commitments has been utilized, enter into one or more Hedge Agreements pursuant
to which the interest rates on then-outstanding Loans shall be effectively fixed
or capped on terms and conditions satisfactory to the Administrative Agent.

          6.10 Additional Collateral, etc.  (a)  With respect to any Property
               ---------------------------                                   
acquired after the Closing Date by Holdings, the Borrower or any of its
Subsidiaries (other than (x) any Property described in paragraph (b) or
paragraph (c) of this Section, (y) any Property subject to a Lien expressly
permitted by Section 7.3(g) and (z) Property acquired by an Excluded Foreign
Subsidiary) as to which the Administrative Agent, for the benefit of the
Lenders, does not have a perfected Lien, promptly (i) execute and deliver to the
Administrative Agent such amendments to the Guarantee and Collateral Agreement
or such other documents as the Administrative Agent deems necessary or advisable
to grant to the Administrative Agent, for the benefit of the Lenders, a security
interest in such Property and (ii) take all actions necessary or advisable to
grant to the Administrative Agent, for the benefit of the Lenders, a perfected
first priority security interest in
<PAGE>
 
                                                                              64

such Property, including without limitation, the filing of Uniform Commercial
Code financing statements in such jurisdictions as may be required by the
Guarantee and Collateral Agreement or by law or as may be requested by the
Administrative Agent.

          (b)  With respect to any fee or leasehold interest in any real
property or fixtures acquired after the Closing Date by Holdings, the Borrower
or any of its Subsidiaries, promptly (i) execute and deliver a first priority
Mortgage in favor of the Administrative Agent, for the benefit of the Lenders,
covering such real property, if and to the extent required in order to cause the
Mortgage Requirement to continue to be satisfied, (ii) if requested by the
Administrative Agent, provide the Lenders with any consents or estoppels
reasonably deemed necessary or advisable by the Administrative Agent in
connection with such Mortgage, each of the foregoing in form and substance
reasonably satisfactory to the Administrative Agent and (iii) if requested by
the Administrative Agent, deliver to the Administrative Agent legal opinions
relating to the matters described above, which opinions shall be in form and
substance, and from counsel, reasonably satisfactory to the Administrative
Agent.

          (c)  With respect to any new Subsidiary (other than an Excluded
Foreign Subsidiary) created or acquired after the Closing Date (which, for the
purposes of this paragraph, shall include any existing Subsidiary that ceases to
be an Excluded Foreign Subsidiary), by Holdings, the Borrower or any of its
Subsidiaries, promptly (i) execute and deliver to the Administrative Agent such
amendments to the Guarantee and Collateral Agreement as the Administrative Agent
deems necessary or advisable to grant to the Administrative Agent, for the
benefit of the Lenders, a perfected first priority security interest in the
Capital Stock of such new Subsidiary that is owned by Holdings, the Borrower or
any of its Subsidiaries, (ii) deliver to the Administrative Agent the
certificates representing such Capital Stock, together with undated stock
powers, in blank, executed and delivered by a duly authorized officer of
Holdings, the Borrower or such Subsidiary, as the case may be, (iii) cause such
new Subsidiary (A) to become a party to the Guarantee and Collateral Agreement
and (B) to take such actions necessary or advisable to grant to the
Administrative Agent for the benefit of the Lenders a perfected first priority
security interest in the Collateral described in the Guarantee and Collateral
Agreement with respect to such new Subsidiary, including, without limitation,
the filing of Uniform Commercial Code financing statements in such jurisdictions
as may be required by the Guarantee and Collateral Agreement or by law or as may
be requested by the Administrative Agent, and (iv) if requested by the
Administrative Agent, deliver to the Administrative Agent legal opinions
relating to the matters described above, which opinions shall be in form and
substance, and from counsel, reasonably satisfactory to the Administrative
Agent.

          (d)  With respect to any new Excluded Foreign Subsidiary created or
acquired after the Closing Date by Holdings, the Borrower or any of its
Subsidiaries, promptly (i) execute and deliver to the Administrative Agent such
amendments to the Guarantee and Collateral Agreement as the Administrative Agent
deems necessary or advisable in order to grant to the Administrative Agent, for
the benefit of the Lenders, a perfected first priority security interest in the
Capital Stock of such new Subsidiary that is owned by Holdings, the Borrower or
any of its Subsidiaries (provided that in no event shall more than 65% of the
total outstanding Capital Stock of any such new Subsidiary be required to be so
pledged), (ii) deliver to the Administrative 
<PAGE>
 
                                                                              65

Agent the certificates representing such Capital Stock, together with undated
stock powers, in blank, executed and delivered by a duly authorized officer of
Holdings, the Borrower or such Subsidiary, as the case may be, and take such
other action as may be necessary or, in the opinion of the Administrative Agent,
desirable to perfect the Lien of the Administrative Agent thereon, and (iii) if
requested by the Administrative Agent, deliver to the Administrative Agent legal
opinions relating to the matters described above, which opinions shall be in
form and substance, and from counsel, reasonably satisfactory to the
Administrative Agent.

          6.11 Further Assurances.  From time to time execute and deliver, or
               ------------------                                            
cause to be executed and delivered, such additional instruments, certificates or
documents, and take all such actions, as the Administrative Agent may reasonably
request, for the purposes of implementing or effectuating the provisions of this
Agreement and the other Loan Documents, or of more fully perfecting or renewing
the rights of the Administrative Agent and the Lenders with respect to the
Collateral (or with respect to any additions thereto or replacements or proceeds
thereof or with respect to any other property or assets hereafter acquired by
the Borrower or any Subsidiary which may be deemed to be part of the Collateral)
pursuant hereto or thereto.  Upon the exercise by the Administrative Agent or
any Lender of any power, right, privilege or remedy pursuant to this Agreement
or the other Loan Documents which requires any consent, approval, recording,
qualification or authorization of any Governmental Authority, the Borrower will
execute and deliver, or will cause the execution and delivery of, all
applications, certifications, instruments and other documents and papers that
the Administrative Agent or such Lender may be required to obtain from the
Borrower or any of its Subsidiaries for such governmental consent, approval,
recording, qualification or authorization.

          6.12 Initial Tower Report Supplement.  Not later than 20 Business
               -------------------------------                             
Days after the Closing Date, deliver to the Administrative Agent a copy of the
Initial Tower Report Supplement.

          6.13 Mortgages.  Within 45 days after the Closing Date, (a) execute
               ---------                                                     
and deliver to the Administrative Agent Mortgages in respect of any properties
listed on Schedule 1.1 with respect to which Mortgages were not executed and
delivered on the Closing Date and (b) cause to be delivered to the
Administrative Agent the local counsel opinions described in Section 5.1(l)(ii),
to the extent such opinions were not delivered on the Closing Date.

                        SECTION 7.  NEGATIVE COVENANTS

          Holdings and the Borrower hereby jointly and severally agree that, so
long as the  Commitments remain in effect, any Letter of Credit remains
outstanding or any Loan or other amount is owing to any Lender or any Agent
hereunder, each of Holdings and the Borrower shall not, and shall not permit any
of its Subsidiaries to, directly or indirectly (provided, that Section 7.1 shall
                                                --------                        
apply to the Borrower and its Subsidiaries only):

          7.1  Financial Condition Covenants.  (a)  Prior to the Transition
               -----------------------------                               
Date:
<PAGE>
 
                                                                              66

          (i)  Consolidated Total Debt to Annualized Adjusted EBITDA Ratio.
               -----------------------------------------------------------  
Permit the ratio of (x) Consolidated Total Debt on any date during any period
set forth below to (y) Annualized Adjusted EBITDA for the period of twelve
consecutive calendar months most recently ended on or prior to such date, to
exceed the ratio set forth below opposite such period:

<TABLE> 
<CAPTION>  
                                              
          Period                         Annualized Adjusted EBITDA Ratio
          ------                         --------------------------------
<S>                                      <C>    
     Closing Date - March 31, 1999              11.25x
     April 1, 1999 - June 30, 1999       11.25x
     July 1, 1999 - September 30, 1999          11.25x
     October 1, 1999 - December 31, 1999        9.00x
     January 1, 2000 - March 31, 2000           6.50x
     April 1, 2000 - June 30, 2000       6.00x
     July 1, 2000 - September 30, 2000          5.50x
     October 1, 2000 - December 31, 2000        5.00x
     January 1, 2001 - March 31, 2001           5.00x
     April 1, 2001 - June 30, 2001       4.75x

</TABLE> 
          (ii)  Annualized Adjusted EBITDA to Consolidated Interest Expense
                -----------------------------------------------------------
Ratio.  Permit the ratio of (x) Annualized Adjusted EBITDA for any period of
- -----                                                                       
twelve consecutive calendar months ending during any period set forth below to
(y) Consolidated Interest Expense for such period, to be less than the ratio set
forth below opposite such period:
<TABLE> 
                                         Annualized Adjusted EBITDA to
            Period                       Consolidated Interest Expense Ratio
            ------                       -----------------------------------
<S>                                      <C>      
     Closing Date - March 31, 1999              1.10x
     April 1, 1999 - June 30, 1999       1.10x
     July 1, 1999 - September 30, 1999          1.10x
     October 1, 1999 - December 31, 1999        1.10x
     January 1, 2000 - March 31, 2000           1.75x
     April 1, 2000 - June 30, 2000       1.75x
     July 1, 2000 - September 30, 2000          2.25x
     October 1, 2000 - December 31, 2000        2.50x
     January 1, 2001 - March 31, 2001           2.50x
     April 1, 2001 - June 30, 2001       2.50x

</TABLE> 
          (iii) Consolidated Total Debt Per Tower.  Permit on any date the
                 ---------------------------------                         
quotient of (a) Consolidated Total Debt on such date divided by (b) the
aggregate number of Towers owned by the Borrower and its Subsidiaries on such
date, to exceed $150,000; provided, that, the foregoing covenant shall not be
                          --------                                           
applicable for any period if the ratio of Consolidated Total Debt to Annualized
Adjusted EBITDA does not exceed 5.0x on any date during such period.
<PAGE>
 
                                                                              67

          (iv)  Maintenance of Annualized Adjusted EBITDA.  Permit Annualized
                -----------------------------------------                    
Adjusted EBITDA for any period of twelve consecutive calendar months ending
during any period set forth below to be less than the amount set forth below
opposite such period:

<TABLE>
<CAPTION>
                                  
Period                                    Annualized
- ------                                    ----------   
                                        Adjusted EBITDA
                                        ---------------

<S>                                    <C>
Closing Date - March 31, 1999                  $225,000

April 1, 1999 - June 30, 1999                  $900,000

July 1, 1999 - September 30, 1999            $1,650,000

October 1, 1999 - December 31,               $2,800,000 

1999

January 1, 2000 - March 31, 2000             $4,200,000

April 1, 2000 - June 30, 2000                $4,800,000

July 1, 2000 - September 30, 2000            $5,500,000

October 1, 2000 - December 31,               $6,000,000

2000                        

January 1, 2001 - March 31, 2001             $6,850,000

April 1, 2001 - June 30, 2001               $7,500,000;

</TABLE>

provided, that, the foregoing covenant shall not be applicable for any period
- --------                                                                     
set forth above if the ratio of Consolidated Total Debt to Annualized Adjusted
EBITDA does not exceed 5.0x on any date during such period.

          (v)  Maintenance of Total Tower Revenue.  Permit Total Tower Revenue
               ----------------------------------                             
for any period of twelve consecutive calendar months ending during any period
set forth below to be less than the amount set forth below opposite such period:
<TABLE>
<CAPTION>
 
Total
Period                                              Tower Revenue
- ------                                              -------------
<S>                                                <C>
          Closing Date - March 31, 1999             $4,500,000
          April 1, 1999 - June 30, 1999             $5,500,000
          July 1, 1999 - September 30, 1999         $6,500,000
          October 1, 1999 - December 31, 1999       $7,500,000
          January 1, 2000 - March 31, 2000          $8,000,000
          April 1, 2000 - June 30, 2000             $8,750,000
          July 1, 2000 - September 30, 2000         $9,250,000
          October 1, 2000 - December 31, 2000       $9,850,000
          January 1, 2001 - March 31, 2001          $10,500,000
          April 1, 2001 - June 30, 2001             $11,000,000;
</TABLE>
<PAGE>
 
                                                                              68

provided, that, the foregoing covenant shall not be applicable for any period
- --------                                                                     
set forth above if the ratio of Consolidated Total Debt to Annualized Adjusted
EBITDA does not exceed 5.0x on any date during such period.

          (vi)  Consolidated Total Debt to Total Capitalization Ratio.  Permit
                -----------------------------------------------------         
on any date the ratio of (a) Consolidated Total Debt on such date to (b) Total
Capitalization on such date to exceed 0.55 to 1.00.

          (b)   From and after the Transition Date:

          (i)   Consolidated Total Debt to Consolidated EBITDA Ratio.  Permit 
                ----------------------------------------------------   
the ratio of (x) Consolidated Total Debt on any date during any period set forth
below to to (y) Consolidated EBITDA for the period of four consecutive fiscal
quarters of the Borrower most recently ended on or prior to such date, to exceed
the ratio set forth below opposite such period:

                                           
          Period                            Consolidated EBITDA Ratio
          ------                            -------------------------

     July 1, 2001 - September 30, 2001             4.25x
     October 1, 2001 - December 31, 2001           4.00x
     January 1, 2002 - March 31, 2002              3.00x
     April 1, 2002 - June 30, 2002          3.00x
     July 1, 2002 - September 30, 2002             3.00x
     October 1, 2002 - December 31, 2002           3.00x
     January 1, 2003 and thereafter                2.50x

          (ii)  Consolidated EBITDA to Consolidated Interest Expense Ratio.
                ----------------------------------------------------------  
Permit the ratio of (x) Consolidated EBITDA for the period of four consecutive
fiscal quarters of the Borrower most recently ended on or prior to such date to
(y) Consolidated Interest Expense for such period, to be less than the ratio set
forth below opposite such period:

                                            Consolidated EBITDA to
          Period                            Consolidated Interest Expense Ratio
          ------                            -----------------------------------

          July 1, 2001 and thereafter              2.50x


          (iii) Consolidated Fixed Charge Coverage Ratio.  Permit the
                 ----------------------------------------             
Consolidated Fixed Charge Coverage Ratio for any period of four consecutive
fiscal quarters of the Borrower ending with any fiscal quarter set forth below
to be less than the ratio set forth below opposite such period:

                                            Consolidated Fixed
          Fiscal Quarter                    Charge Coverage Ratio
          --------------                    ---------------------

          July 1, 2001 and thereafter              1.00x
<PAGE>
 
                                                                              69

          (iv)  Pro Forma Consolidated Debt Service Coverage Ratio.  Permit the
                --------------------------------------------------             
Pro Forma Consolidated Debt Service Coverage Ratio for any period of four
consecutive fiscal quarters of the Borrower ending with any fiscal quarter set
forth below to be less than the ratio set forth below opposite such period:

                                            Pro Forma Consolidated Debt
          Fiscal Quarter                    Service Coverage Ratio
          --------------                     ----------------------

          July 1, 2001 - September 30, 2001        1.00x
          October 1, 2001 and thereafter           1.10x


          7.2   Limitation on Indebtedness.  Create, incur, assume or suffer to
                --------------------------                                     
exist any Indebtedness, except:

          (a)   Indebtedness of any Loan Party pursuant to any Loan Document;

          (b)   Indebtedness of the Borrower to any Subsidiary Guarantor and of
     any Wholly Owned Subsidiary Guarantor to the Borrower or any other
     Subsidiary;

          (c)   Indebtedness (including, without limitation, Capital Lease
     Obligations) secured by Liens permitted by Section 7.3(g) in an aggregate
     principal amount not to exceed $1,000,000 at any one time outstanding;

          (d)   Indebtedness outstanding on the date hereof and listed on
     Schedule 7.2(d) and any refinancings, refundings, renewals or extensions
     thereof (without any increase in the principal amount thereof or any
     shortening of the maturity of any principal amount thereof); 

          (e)   Guarantee Obligations made in the ordinary course of business by
     Holdings, the Borrower or any of its Subsidiaries of obligations of the
     Borrower or any Subsidiary Guarantor;

          (f)   unsecured Indebtedness owing to sellers of Towers and Tower
     Companies and constituting a portion of the consideration for the
     acquisition of such Towers or Tower Companies by the Borrower or a
     Subsidiary Guarantor, so long as either (i) such Indebtedness is
     subordinated to the Obligations on substantially the terms of Schedule
     7.2(f) and the aggregate principal amount of all Indebtedness under this
     clause (i) any one time outstanding shall not exceed $5,000,000 or (ii) the
     aggregate principal amount of Indebtedness owing to such sellers is covered
     by Letters of Credit; and

          (g)   Indebtedness of Holdings permitted by Section 7.15(b).
<PAGE>
 
                                                                              70

          7.3  Limitation on Liens.  Create, incur, assume or suffer to exist
               -------------------                                           
any Lien upon any of its Property, whether now owned or hereafter acquired,
except for:

          (a)  Liens for taxes not yet due or which are being contested in good
     faith by appropriate proceedings, provided that adequate reserves with
                                       --------                            
     respect thereto are maintained on the books of the Borrower or its
     Subsidiaries, as the case may be, in conformity with GAAP;

          (b)  carriers', warehousemen's, mechanics', materialmen's, repairmen's
     or other like Liens arising in the ordinary course of business which are
     not overdue for a period of more than 30 days or that are being contested
     in good faith by appropriate proceedings;

          (c)  pledges or deposits in connection with workers' compensation,
     unemployment insurance and other social security legislation;

          (d)  deposits to secure the performance of bids, trade contracts
     (other than for borrowed money), leases, statutory obligations, surety and
     appeal bonds, performance bonds and other obligations of a like nature
     incurred in the ordinary course of business, and deposits to secure
     obligations under contracts to purchase towers or other related assets;

          (e)  easements, rights-of-way, restrictions and other similar
     encumbrances incurred in the ordinary course of business that, in the
     aggregate, are not substantial in amount and which do not in any case
     materially detract from the value of the Property subject thereto or
     materially interfere with the ordinary conduct of the business of the
     Borrower or any of its Subsidiaries;

          (f)  Liens in existence on the date hereof listed on Schedule 7.3(f),
     securing Indebtedness permitted by Section 7.2(d), provided that no such
                                                        --------             
     Lien is spread to cover any additional Property after the Closing Date and
     that the amount of Indebtedness secured thereby is not increased;

          (g)  Liens securing Indebtedness of the Borrower or any other
     Subsidiary incurred pursuant to Section 7.2(c) to finance the acquisition
     of fixed or capital assets, provided that (i) such Liens shall be created
                                 --------                                     
     substantially simultaneously with the acquisition of such fixed or capital
     assets, (ii) such Liens do not at any time encumber any Property other than
     the Property financed by such Indebtedness and (iii) the amount of
     Indebtedness secured thereby is not increased;

          (h)  Liens created pursuant to the Security Documents; and

          (i)  any interest or title of a lessor under any lease entered into by
     the Borrower or any other Subsidiary in the ordinary course of its business
     and covering only the assets so leased (including landlord's Liens on any
     property placed on the property subject to such lease).
<PAGE>
 
                                                                              71

          7.4  Limitation on Fundamental Changes.  Enter into any merger,
               ---------------------------------                         
consolidation or amalgamation, or liquidate, wind up or dissolve itself (or
suffer any liquidation or dissolution), or Dispose of all or substantially all
of its Property or business, except that:

          (a)  any Subsidiary of the Borrower may be merged or consolidated with
     or into the Borrower (provided that the Borrower shall be the continuing or
                           --------                                             
     surviving corporation) or with or into any Subsidiary Guarantor (provided
                                                                      --------
     that the Subsidiary Guarantor shall be the continuing or surviving
     corporation); and

          (b)  any Subsidiary of the Borrower may Dispose of any or all of its
     assets (upon voluntary liquidation or otherwise) to the Borrower or any
     Subsidiary Guarantor.

          7.5  Limitation on Disposition of Property.  Dispose of any of its
               -------------------------------------                        
Property (including, without limitation, receivables and leasehold interests),
whether now owned or hereafter acquired, or, in the case of any Subsidiary,
issue or sell any shares of such Subsidiary's Capital Stock to any Person,
except:

          (a)  the Disposition in the ordinary course of business of obsolete or
     worn out property, or surplus real property not needed in the Borrower's
     business;

          (b)  the sale of inventory in the ordinary course of business
     (including, without limitation, the leasing of space on Towers);

          (c)  Dispositions permitted by Section 7.4(b) and Dispositions of Cash
     Equivalents;

          (d)  the sale or issuance of any Subsidiary's Capital Stock to the
     Borrower or any Subsidiary Guarantor;

          (e)  the Disposition of other assets having a fair market value not to
     exceed $500,000 in the aggregate for any fiscal year of the Borrower;


          (f)  the Disposition of Towers in exchange for towers with revenue at
     least equal in amount to the revenue of such Disposed Towers; and

          (g)  any Asset Sale or Recovery Event, provided, in each case, that
                                                 --------                    
     the requirements of Section 2.10(b) are complied with in connection
     therewith.

          7.6  Limitation on Restricted Payments.  Declare or pay any dividend
               ---------------------------------                              
(other than dividends payable solely in common stock of the Person making such
dividend) on, or make any payment on account of, or set apart assets for a
sinking or other analogous fund for, the purchase, redemption, defeasance,
retirement or other acquisition of, any Capital Stock of Holdings, the Borrower
or any Subsidiary, whether now or hereafter outstanding, or make any other
<PAGE>
 
                                                                              72

distribution in respect thereof, either directly or indirectly, whether in cash
or property or in obligations of Holdings, the Borrower or any Subsidiary, or
enter into any derivatives or other transaction with any financial institution,
commodities or stock exchange or clearinghouse (a "Derivatives Counterparty")
                                                   ------------------------  
obligating Holdings, the Borrower or any Subsidiary to make payments to such
Derivatives Counterparty as a result of any change in market value of any such
Capital Stock (collectively, "Restricted Payments"), except that so long as no
                              -------------------                             
Default or Event of Default exists immediately before and after giving effect
thereto:

          (a)  any Subsidiary may make Restricted Payments to the Borrower or
     any Subsidiary Guarantor;

          (b)  the Borrower may make Restricted Payments to Holdings to enable
     Holdings to pay mandatory cash interest on the Senior Discount Notes in
     accordance with their terms; provided, however, that no such Restricted
                                  --------  -------                         
     Payments shall be made unless the ratio of (i) Consolidated Total Debt on
     the date of such Restricted Payment to (ii) Consolidated EBITDA for the
     period of four fiscal quarters of the Borrower most recently ended on or
     prior to such date does not exceed 4.0x;

          (c)  the Borrower may pay dividends to Holdings (i) to permit Holdings
     to pay corporate overhead expenses incurred in the ordinary course of
     business not to exceed $2,500,000 in any fiscal year, (ii) in an amount
     equal to the lesser of (A) the amount of Holdings' actual tax liability and
     (B) the amount of taxes which are attributable to the Borrower and its
     Subsidiaries as part of the consolidated group that includes Holdings and
     (iii) not later than 10 Business Days after the Increased Revolving
     Commitment Date, on terms and conditions satisfactory to the Administrative
     Agent; and

          (d)  Holdings may make Restricted Payments with the proceeds of an
     initial public offering of its common stock in accordance with Section
     2.10(a).

          7.7  Limitation on Capital Expenditures.  Make or commit to make any
               ----------------------------------                             
Capital Expenditure, except Capital Expenditures of the Borrower and its
Subsidiaries in the ordinary course of business not exceeding while this
Agreement is in effect the sum of (a) $175,000,000 plus (b) the aggregate amount
                                                   ----                         
of cash equity received by the Borrower from Holdings and not required by
Section 2.10 to be used to prepay Loans.

          7.8  Limitation on Investments.  Make any advance, loan, extension of
               -------------------------                                       
credit (by way of guaranty or otherwise) or capital contribution to, or purchase
any Capital Stock, bonds, notes, debentures or other debt securities of, or any
assets constituting an ongoing business from, or make any other investment in,
any other Person (all of the foregoing, "Investments"), except:
                                         -----------           

          (a)  extensions of trade credit in the ordinary course of business;

          (b)  Investments in Cash Equivalents;

          (c)  Investments arising in connection with the incurrence of
     Indebtedness permitted by Section 7.2(b) and (e);
<PAGE>
 
                                                                              73

          (d)  loans and advances to employees of Holdings, the Borrower or any
     Subsidiaries of the Borrower in the ordinary course of business (including,
     without limitation, for travel, entertainment and relocation expenses) in
     an aggregate amount for Holdings, the Borrower and Subsidiaries of the
     Borrower not to exceed $250,000 at any one time outstanding;

          (e)  Investments (other than those relating to the incurrence of
     Indebtedness permitted by Section 7.8(c)) by Holdings, the Borrower or any
     of its Subsidiaries in the Borrower or any Person that, prior to such
     investment, is a  Subsidiary Guarantor;

          (f)  Investments by the Borrower or any of its Subsidiaries in Tower
     Companies and other entities the principal assets of which are towers,
     tower sites and related assets, (provided, that in each case such Tower
                                      --------                              
     Company or other entity becomes a Subsidiary Guarantor); and other
     Investments in Tower Companies and other related entities and Excluded
     Entities, not exceeding in the aggregate, during the term of this
     Agreement, $10,000,000 (of which amount not more than $7,500,000 may be
     invested in fiscal year 1999); provided that notwithstanding anything
                                    --------                              
     herein to the contrary, no additional Investments shall be permitted in SBA
     Brazil; and

          (g)  Investments by Holdings in the promissory note of Steven E.
     Bernstein, dated March 8, 1997, in the principal amount of $3,500,000
     payable to Holdings.

          7.9  Limitation on Modifications of Certain Documents.  Amend its
               ------------------------------------------------            
certificate of incorporation or the Senior Discount Note Indenture in any manner
determined by the Administrative Agent to be adverse to the Lenders.

          7.10  Limitation on Transactions with Affiliates.  Enter into any
                ------------------------------------------                 
transaction, including, without limitation, any purchase, sale, lease or
exchange of Property, the rendering of any service or the payment of any
management, advisory or similar fees, with any Affiliate (other than the
Borrower or any Subsidiary Guarantor) unless such transaction is (a) otherwise
permitted under this Agreement, (b) in the ordinary course of business of
Holdings, the Borrower or such Subsidiary, as the case may be, and (c) upon fair
and reasonable terms no less favorable to Holdings, the Borrower or such
Subsidiary, as the case may be, than it would obtain in a comparable arm's
length transaction with a Person that is not an Affiliate.

          7.11  Limitation on Sales and Leasebacks.  Enter into any arrangement
                ----------------------------------                             
with any Person providing for the leasing by Holdings, the Borrower or any
Subsidiary of real or personal property which has been or is to be sold or
transferred by Holdings, the Borrower or such Subsidiary to such Person or to
any other Person to whom funds have been or are to be advanced by such Person on
the security of such property or rental obligations of Holdings, the Borrower or
such Subsidiary, except to the extent permitted by Section 7.2(c) or Section
7.5(g).

          7.12  Limitation on Negative Pledge Clauses.  Enter into or suffer to
                -------------------------------------                          
exist or become effective any agreement that prohibits or limits the ability of
Holdings, the Borrower or 
<PAGE>
 
                                                                              74

any of its Subsidiaries to create, incur, assume or suffer to exist any Lien
upon any of its Property or revenues, whether now owned or hereafter acquired,
to secure the Obligations or, in the case of any guarantor, its obligations
under the Guarantee and Collateral Agreement, other than (a) this Agreement and
the other Loan Documents and (b) any agreements governing any purchase money
Liens or Capital Lease Obligations otherwise permitted hereby (in which case,
any prohibition or limitation shall only be effective against the assets
financed thereby).

          7.13  Limitation on Restrictions on Subsidiary Distributions.  Enter
                ------------------------------------------------------        
into or suffer to exist or become effective any consensual encumbrance or
restriction on the ability of any Subsidiary to (a) make Restricted Payments in
respect of any Capital Stock of such Subsidiary held by, or pay any Indebtedness
owed to, the Borrower or any other Subsidiary, (b) make Investments in the
Borrower or any other Subsidiary or (c) transfer any of its assets to the
Borrower or any other Subsidiary, except for such encumbrances or restrictions
existing under or by reason of (i) any restrictions existing under the Loan
Documents and (ii) any restrictions with respect to a Subsidiary imposed
pursuant to an agreement that has been entered into in connection with the
Disposition of all or substantially all of the Capital Stock or assets of such
Subsidiary.

          7.14  Limitation on Lines of Business.  Enter into any business,
                -------------------------------                           
either directly or through any Subsidiary, except for those businesses in which
the Borrower and its Subsidiaries are engaged on the date of this Agreement or
that are reasonably related thereto.

          7.15  Limitation on Activities of Holdings.  In the case of Holdings,
                ------------------------------------                           
notwithstanding anything to the contrary in this Agreement or any other Loan
Document, (a) conduct, transact or otherwise engage in, or commit to conduct,
transact or otherwise engage in, any business or operations other than those
incidental to its ownership of the Capital Stock of the Borrower, (b) incur,
create, assume or suffer to exist any Indebtedness or other liabilities or
financial obligations, except (i) nonconsensual obligations imposed by operation
of law, (ii) pursuant to the Loan Documents to which it is a party, (iii)
obligations with respect to its Capital Stock, (iv) obligations in respect of
the Senior Discount Notes and (v) Indebtedness permitted under Section 7.2(e)
                                                                             
(provided, however, that Holdings may incur Indebtedness if on the date thereof
- ---------  -------                                                             
after giving effect thereto the ratio of (x) Consolidated Total Debt (which, for
the purposes of this proviso, shall include the aggregate principal amount of
                     -------                                                 
all Indebtedness of Holdings) to (y) Consolidated EBITDA does not exceed 5.0x),
or (c) own, lease, manage or otherwise operate any properties or assets
(including cash (other than cash received in connection with dividends made by
the Borrower in accordance with Section 7.6 pending application in the manner
contemplated by said Section) and cash equivalents) other than the ownership of
shares of Capital Stock of the Borrower.

          7.16  Limitation on Hedge Agreements.  Enter into any Hedge Agreement
                ------------------------------                                 
other than Hedge Agreements entered into in the ordinary course of business, and
not for speculative purposes, to protect against changes in interest rates or
foreign exchange rates.

          7.17  Limitation on Speculative Sites.  Permit there to be, at any
                -------------------------------                             
time, more than 17 Tower sites (i) for which the Borrower has incurred
construction costs and (ii) in respect of
<PAGE>
 
                                                                              75

which the Borrower has not entered into a lease with at least one anchor tenant
under a lease having an original term of not less than five years.


                         SECTION 8.  EVENTS OF DEFAULT

          If any of the following events shall occur and be continuing:

          (a)   The Borrower shall fail to pay any principal of any Loan or
     Reimbursement Obligation when due in accordance with the terms hereof; or
     the Borrower shall fail to pay any interest on any Loan or Reimbursement
     Obligation, or any other amount payable hereunder or under any other Loan
     Document, within five days after any such interest or other amount becomes
     due in accordance with the terms hereof; or

          (b)   Any representation or warranty made or deemed made by any Loan
     Party herein or in any other Loan Document or that is contained in any
     certificate, document or financial or other statement furnished by it at
     any time under or in connection with this Agreement or any such other Loan
     Document shall prove to have been inaccurate in any material respect on or
     as of the date made or deemed made; or

          (c)  (i)  Any Loan Party shall default in the observance or
     performance of any agreement contained in clause (i) or (ii) of Section
     6.4(a) (with respect to Holdings and the Borrower only), Section 6.7(a),
     Section 6.12, Section 6.13 or Section 7 of this Agreement or Section 5 of
     the Guarantee and Collateral Agreement or (ii) any Loan Party shall default
     in the observance or performance of any covenant or agreement contained in
     any Mortgage and such default, together with any other such default under
     any other Mortgage or Mortgages, shall have continued unremedied beyond any
     applicable notice and cure periods that may be provided for therein and the
     aggregate book value of the Mortgaged Property or Mortgaged Properties
     encumbered by such Mortgage of Mortgages exceeds $2,500,000; or

          (d)   Any Loan Party shall default in the observance or performance of
     any other agreement contained in this Agreement or any other Loan Document
     (other than as provided in paragraphs (a) through (c) of this Section), and
     such default shall continue unremedied for a period of 30 days; or

          (e)   Holdings, the Borrower or any of its Subsidiaries shall (i)
     default in making any payment of any principal of any Indebtedness
     (including, without limitation, any Guarantee Obligation, but excluding the
     Loans) on the scheduled or original due date with respect thereto; or (ii)
     default in making any payment of any interest on any such Indebtedness
     beyond the period of grace, if any, provided in the instrument or agreement
     under which such Indebtedness was created; or (iii) default in the
     observance or performance of any other agreement or condition relating to
     any such Indebtedness or contained in any instrument or agreement
     evidencing, securing or relating thereto, or any other event shall occur or
     condition exist, the effect of which default or other event or     
<PAGE>
 
                                                                              76


     condition is to cause, or to permit the holder or beneficiary of such
     Indebtedness (or a trustee or agent on behalf of such holder or
     beneficiary) to cause, with the giving of notice if required, such
     Indebtedness to become due prior to its stated maturity or (in the case of
     any such Indebtedness constituting a Guarantee Obligation) to become
     payable; provided, that a default, event or condition described in clause
              --------
     (i), (ii) or (iii) of this paragraph (e) shall not at any time constitute
     an Event of Default unless, at such time, one or more defaults, events or
     conditions of the type described in clauses (i), (ii) and (iii) of this
     paragraph (e) shall have occurred and be continuing with respect to
     Indebtedness the outstanding principal amount of which exceeds in the
     aggregate $1,000,000; or

          (f)  (i) Holdings, the Borrower or any of its Subsidiaries shall
     commence any case, proceeding or other action (A) under any existing or
     future law of any jurisdiction, domestic or foreign, relating to
     bankruptcy, insolvency, reorganization or relief of debtors, seeking to
     have an order for relief entered with respect to it, or seeking to
     adjudicate it a bankrupt or insolvent, or seeking reorganization,
     arrangement, adjustment, winding-up, liquidation, dissolution, composition
     or other relief with respect to it or its debts, or (B) seeking appointment
     of a receiver, trustee, custodian, conservator or other similar official
     for it or for all or any substantial part of its assets, or Holdings, the
     Borrower or any of its Subsidiaries shall make a general assignment for the
     benefit of its creditors; or (ii) there shall be commenced against
     Holdings, the Borrower or any of its Subsidiaries any case, proceeding or
     other action of a nature referred to in clause (i) above that (A) results
     in the entry of an order for relief or any such adjudication or appointment
     or (B) remains undismissed, undischarged or unbonded for a period of 60
     days; or (iii) there shall be commenced against Holdings, the Borrower or
     any of its Subsidiaries any case, proceeding or other action seeking
     issuance of a warrant of attachment, execution, distraint or similar
     process against all or any substantial part of its assets that results in
     the entry of an order for any such relief that shall not have been vacated,
     discharged, or stayed or bonded pending appeal within 60 days from the
     entry thereof; or (iv) Holdings, the Borrower or any of its Subsidiaries
     shall take any action in furtherance of, or indicating its consent to,
     approval of, or acquiescence in, any of the acts set forth in clause (i),
     (ii), or (iii) above; or (v) Holdings, the Borrower or any of its
     Subsidiaries shall generally not, or shall be unable to, or shall admit in
     writing its inability to, pay its debts as they become due; or

          (g)  (i) Any Person shall engage in any "prohibited transaction" (as
     defined in Section 406 of ERISA or Section 4975 of the Code) involving any
     Plan, (ii) any "accumulated funding deficiency" (as defined in Section 302
     of ERISA), whether or not waived, shall exist with respect to any Plan or
     any Lien in favor of the PBGC or a Plan shall arise on the assets of the
     Borrower or any Commonly Controlled Entity, (iii) a Reportable Event shall
     occur with respect to, or proceedings shall commence to have a trustee
     appointed, or a trustee shall be appointed, to administer or to terminate,
     any Single Employer Plan, which Reportable Event or commencement of
     proceedings or appointment of a trustee is, in the reasonable opinion of
     the Required Lenders, likely to result in the termination of such Plan for
     purposes of Title IV of ERISA, (iv) any Single Employer Plan shall
     terminate for purposes of Title IV of ERISA, (v) the Borrower or 
<PAGE>
 
                                                                              77

     any Commonly Controlled Entity shall, or in the reasonable opinion of the
     Required Lenders is likely to, incur any liability in connection with a
     withdrawal from, or the Insolvency or Reorganization of, a Multiemployer
     Plan or (vi) any other event or condition shall occur or exist with respect
     to a Plan; and in each case in clauses (i) through (vi) above, such event
     or condition, together with all other such events or conditions, if any,
     could, in the sole judgment of the Required Lenders, reasonably be expected
     to have a Material Adverse Effect; or

          (h)  One or more judgments or decrees shall be entered against
     Holdings, the Borrower or any of its Subsidiaries involving for Holdings,
     the Borrower and its Subsidiaries taken as a whole a liability (not paid or
     fully covered by insurance as to which the relevant insurance company has
     acknowledged coverage) of $1,000,000 or more, and all such judgments or
     decrees shall not have been vacated, discharged, stayed or bonded pending
     appeal within 30 days from the entry thereof; or

          (i)  Any of the Security Documents shall cease, for any reason, to be
     in full force and effect, or any Loan Party or any Affiliate of any Loan
     Party shall so assert, or any Lien created by any of the Security Documents
     shall cease to be enforceable and of the same effect and priority purported
     to be created thereby; or

          (j)  The guarantee contained in Section 2 of the Guarantee and
     Collateral Agreement shall cease, for any reason, to be in full force and
     effect or any Loan Party or any Affiliate of any Loan Party shall so
     assert; or

          (k)  (i) Any "person" or "group" (as such terms are used in Sections
     13(d) and 14(d) of the Securities Exchange Act of 1934, as amended (the
     "Exchange Act")), other than Steven Bernstein, shall become, or obtain
     rights (whether by means or warrants, options or otherwise) to become, the
     "beneficial owner" (as defined in Rules 13(d)-3 and 13(d)-5 under the
     Exchange Act), directly or indirectly, of more than 20% of the outstanding
     common stock of Holdings; (ii) Holdings shall cease to own and control, of
     record and beneficially, directly, 100% of each class of outstanding
     Capital Stock of the Borrower free and clear of all Liens (except Liens
     created by the Guarantee and Collateral Agreement); (iii) Steven Bernstein
     shall at any time own less than 65% of the outstanding shares of Holdings'
     common stock owned by him on the Closing Date; or (iv) a "Change of
     Control" as defined in the Master Lease Agreement, dated as of October 30,
     1998, by and among SBA Towers, Inc., SBA Sites, Inc. and BellSouth Personal
     Communications, Inc. shall occur or be reasonably likely to occur;


then, and in any such event, (A) if such event is an Event of Default specified
in clause (i) or (ii) of paragraph (f) above with respect to the Borrower,
automatically the Commitments shall immediately terminate and the Loans
hereunder (with accrued interest thereon) and all other amounts owing under this
Agreement and the other Loan Documents (including, without limitation, all
amounts of L/C Obligations, whether or not the beneficiaries of the then
outstanding Letters of Credit shall have presented the documents required
thereunder) shall 
<PAGE>
 
                                                                              78

immediately become due and payable, and (B) if such event is any other Event of
Default, either or both of the following actions may be taken: (i) with the
consent of the Majority Revolving Credit Facility Lenders, the Administrative
Agent may, or upon the request of the Majority Revolving Credit Facility
Lenders, the Administrative Agent shall, by notice to the Borrower declare the
Revolving Credit Commitments to be terminated forthwith, whereupon the Revolving
Credit Commitments shall immediately terminate; and (ii) with the consent of the
Required Lenders, the Administrative Agent may, or upon the request of the
Required Lenders, the Administrative Agent shall, by notice to the Borrower,
declare the Loans hereunder (with accrued interest thereon) and all other
amounts owing under this Agreement and the other Loan Documents (including,
without limitation, all amounts of L/C Obligations, whether or not the
beneficiaries of the then outstanding Letters of Credit shall have presented the
documents required thereunder) to be due and payable forthwith, whereupon the
same shall immediately become due and payable. With respect to all Letters of
Credit with respect to which presentment for honor shall not have occurred at
the time of an acceleration pursuant to this paragraph, the Borrower shall at
such time deposit in a cash collateral account opened by the Administrative
Agent an amount equal to the aggregate then undrawn and unexpired amount of such
Letters of Credit. Amounts held in such cash collateral account shall be applied
by the Administrative Agent to the payment of drafts drawn under such Letters of
Credit, and the unused portion thereof after all such Letters of Credit shall
have expired or been fully drawn upon, if any, shall be applied to repay other
obligations of the Borrower hereunder and under the other Loan Documents. After
all such Letters of Credit shall have expired or been fully drawn upon, all
Reimbursement Obligations shall have been satisfied and all other obligations of
the Borrower hereunder and under the other Loan Documents shall have been paid
in full, the balance, if any, in such cash collateral account shall be returned
to the Borrower (or such other Person as may be lawfully entitled thereto).

                            SECTION 9.  THE AGENTS

          9.1  Appointment.  Each Lender hereby irrevocably designates and
               -----------                                                
appoints the Agents as the agents of such Lender under this Agreement and the
other Loan Documents, and each such Lender irrevocably authorizes each Agent, in
such capacity, to take such action on its behalf under the provisions of this
Agreement and the other Loan Documents and to exercise such powers and perform
such duties as are expressly delegated to the such Agent by the terms of this
Agreement and the other Loan Documents, together with such other powers as are
reasonably incidental thereto.   Notwithstanding any provision to the contrary
elsewhere in this Agreement, no Agent shall have any duties or responsibilities,
except those expressly set forth herein, or any fiduciary relationship with any
Lender, and no implied covenants, functions, responsibilities, duties,
obligations or liabilities shall be read into this Agreement or any other Loan
Document or otherwise exist against any Agent.

          9.2  Delegation of Duties.  Each Agent may execute any of its duties
               --------------------                                           
under this Agreement and the other Loan Documents by or through agents or
attorneys-in-fact and shall be entitled to advice of counsel concerning all
matters pertaining to such duties.  No Agent shall be responsible for the
negligence or misconduct of any agents or attorneys in-fact selected by it with
reasonable care.
<PAGE>
 
                                                                              79



          9.3  Exculpatory Provisions.  Neither any Agent nor any of their
               ----------------------                                     
respective officers, directors, employees, agents, attorneys-in-fact or
affiliates shall be (i) liable for any action lawfully taken or omitted to be
taken by it or such Person under or in connection with this Agreement or any
other Loan Document (except to the extent that any of the foregoing are found by
a final and nonappealable decision of a court of competent jurisdiction to have
resulted from its or such Person's own gross negligence or willful misconduct)
or (ii) responsible in any manner to any of the Lenders for any recitals,
statements, representations or warranties made by any Loan Party or any officer
thereof contained in this Agreement or any other Loan Document or in any
certificate, report, statement or other document referred to or provided for in,
or received by the Agents under or in connection with, this Agreement or any
other Loan Document or for the value, validity, effectiveness, genuineness,
enforceability or sufficiency of this Agreement or any other Loan Document or
for any failure of any Loan Party a party thereto to perform its obligations
hereunder or thereunder.  The Agents shall not be under any obligation to any
Lender to ascertain or to inquire as to the observance or performance of any of
the agreements contained in, or conditions of, this Agreement or any other Loan
Document, or to inspect the properties, books or records of any Loan Party.

          9.4  Reliance by Agents.  Each Agent shall be entitled to rely, and
               ------------------                                            
shall be fully protected in relying, upon any instrument, writing, resolution,
notice, consent, certificate, affidavit, letter, telecopy, telex or teletype
message, statement, order or other document or conversation believed by it to be
genuine and correct and to have been signed, sent or made by the proper Person
or Persons and upon advice and statements of legal counsel (including, without
limitation, counsel to Holdings or the Loan Parties), independent accountants
and other experts selected by such Agent.  The Agents may deem and treat the
payee of any Note as the owner thereof for all purposes unless a written notice
of assignment, negotiation or transfer thereof shall have been filed with the
Administrative Agent.  Each Agent shall be fully justified in failing or
refusing to take any action under this Agreement or any other Loan Document
unless it shall first receive such advice or concurrence of the Required Lenders
(or, if so specified by this Agreement, all Lenders) as it deems appropriate or
it shall first be indemnified to its satisfaction by the Lenders against any and
all liability and expense that may be incurred by it by reason of taking or
continuing to take any such action.  Each Agent shall in all cases be fully
protected in acting, or in refraining from acting, under this Agreement and the
other Loan Documents in accordance with a request of the Required Lenders (or,
if so specified by this Agreement, all Lenders), and such request and any action
taken or failure to act pursuant thereto shall be binding upon all the Lenders
and all future holders of the Loans.

          9.5  Notice of Default.  No Agent shall be deemed to have knowledge or
               -----------------                                                
notice of the occurrence of any Default or Event of Default hereunder unless
such Agent has received notice from a Lender, Holdings or the Borrower referring
to this Agreement, describing such Default or Event of Default and stating that
such notice is a "notice of default".  In the event that the Administrative
Agent receives such a notice, the Administrative Agent shall give notice thereof
to the Lenders.  The Administrative Agent shall take such action with respect to
such Default or Event of Default as shall be reasonably directed by the Required
Lenders (or, if so specified by this Agreement, all Lenders); provided that
                                                              --------     
<PAGE>
 
                                                                              80

unless and until the Administrative Agent shall have received such directions,
the Administrative Agent may (but shall not be obligated to) take such action,
or refrain from taking such action, with respect to such Default or Event of
Default as it shall deem advisable in the best interests of the Lenders.

          9.6  Non-Reliance on Agents and Other Lenders.  Each Lender expressly
               -----------------------------------------                        
acknowledges that neither the Agents nor any of their respective officers,
directors, employees, agents, attorneys-in-fact or affiliates have made any
representations or warranties to it and that no act by any Agent hereinafter
taken, including any review of the affairs of a Loan Party or any affiliate of a
Loan Party, shall be deemed to constitute any representation or warranty by any
Agent to any Lender.  Each Lender represents to the Agents that it has,
independently and without reliance upon any Agent or any other Lender, and based
on such documents and information as it has deemed appropriate, made its own
appraisal of and investigation into the business, operations, property,
financial and other condition and creditworthiness of the Loan Parties and their
affiliates and made its own decision to make its Loans hereunder and enter into
this Agreement.  Each Lender also represents that it will, independently and
without reliance upon any Agent or any other Lender, and based on such documents
and information as it shall deem appropriate at the time, continue to make its
own credit analysis, appraisals and decisions in taking or not taking action
under this Agreement and the other Loan Documents, and to make such
investigation as it deems necessary to inform itself as to the business,
operations, property, financial and other condition and creditworthiness of the
Loan Parties and their affiliates.  Except for notices, reports and other
documents expressly required to be furnished to the Lenders by the
Administrative Agent hereunder, no Agent shall have any duty or responsibility
to provide any Lender with any credit or other information concerning the
business, operations, property, condition (financial or otherwise), prospects or
creditworthiness of any Loan Party or any affiliate of a Loan Party that may
come into the possession of such Agent or any of its officers, directors,
employees, agents, attorneys-in-fact or affiliates.

          9.7  Indemnification.  The Lenders agree to indemnify each Agent in
               ---------------                                               
its capacity as such (to the extent not reimbursed by Holdings or the Borrower
and without limiting the obligation of Holdings or the Borrower to do so),
ratably according to their respective Aggregate Exposure Percentages in effect
on the date on which indemnification is sought under this Section (or, if
indemnification is sought after the date upon which the Commitments shall have
terminated and the Loans shall have been paid in full, ratably in accordance
with such Aggregate Exposure Percentages immediately prior to such date), from
and against any and all liabilities, obligations, losses, damages, penalties,
actions, judgments, suits, costs, expenses or disbursements of any kind
whatsoever that may at any time (including, without limitation, at any time
following the payment of the Loans) be imposed on, incurred by or asserted
against such Agent in any way relating to or arising out of, the Commitments,
this Agreement, any of the other Loan Documents or any documents contemplated by
or referred to herein or therein or the transactions contemplated hereby or
thereby or any action taken or omitted by such Agent under or in connection with
any of the foregoing; provided that no Lender shall be liable for the payment of
                      --------                                                  
any portion of such liabilities, obligations, losses, damages, penalties,
actions, judgments, suits, costs, expenses or disbursements that are found by a
final and nonappealable decision of a court of competent jurisdiction to have
resulted from such Agent's gross negligence
<PAGE>
 
                                                                              81

or willful misconduct. The agreements in this Section 9.7 shall survive the
payment of the Loans and all other amounts payable hereunder.

          9.8  Agent in Its Individual Capacity.  Each Agent and its affiliates
               --------------------------------                                
may make loans to, accept deposits from and generally engage in any kind of
business with any Loan Party as though such Agent was not an Agent.  With
respect to its Loans made or renewed by it and with respect to any Letter of
Credit issued or participated in by it, each Agent shall have the same rights
and powers under this Agreement and the other Loan Documents as any Lender and
may exercise the same as though it were not an Agent, and the terms "Lender" and
"Lenders" shall include each Agent in its individual capacity.

          9.9  Successor Agents.  The Administrative Agent may resign as
               ----------------                                         
Administrative Agent upon 10 days' notice to the Lenders and the Borrower.  If
the Administrative Agent shall resign as Administrative Agent under this
Agreement and the other Loan Documents, then the Required Lenders shall appoint
from among the Lenders a successor agent for the Lenders, which successor agent
shall (unless an Event of Default under Section 8(a) or Section 8(f) with
respect to the Borrower shall have occurred and be continuing) be subject to
approval by the Borrower (which approval shall not be unreasonably withheld or
delayed), whereupon such successor agent shall succeed to the rights, powers and
duties of the Administrative Agent, and the term "Administrative Agent" shall
mean such successor agent effective upon such appointment and approval, and the
former Administrative Agent's rights, powers and duties as Administrative Agent
shall be terminated, without any other or further act or deed on the part of
such former Administrative Agent or any of the parties to this Agreement or any
holders of the Loans.  If no successor agent has accepted appointment as
Administrative Agent by the date that is 10 days following a retiring
Administrative Agent's notice of resignation, the retiring Administrative
Agent's resignation shall nevertheless thereupon become effective, and the
Lenders shall assume and perform all of the duties of the Administrative Agent
hereunder until such time, if any, as the Required Lenders appoint a successor
agent as provided for above.  The Syndication Agent may, at any time, by notice
to the Lenders and the Administrative Agent, resign as Syndication Agent
hereunder, whereupon the duties, rights, obligations and responsibilities of the
Syndication Agent hereunder shall automatically be assumed by, and inure to the
benefit of, the Administrative Agent, without any further act by the Syndication
Agent, the Administrative Agent or any Lender.  After any retiring Agent's
resignation as Agent, the provisions of this Section 9 shall inure to its
benefit as to any actions taken or omitted to be taken by it while it was Agent
under this Agreement and the other Loan Documents.

          9.10 Authorization to Release Liens.  The Administrative Agent is
               ------------------------------                              
hereby irrevocably authorized by each of the Lenders to release any Lien
covering any Property of Holdings or any of its Subsidiaries that is the subject
of a Disposition which is permitted by this Agreement or which has been
consented to in accordance with Section 10.1.

          9.11 The Co-Arranger.  Each Co-Arranger, in its capacity as such,
               ---------------                                             
shall have no duties or responsibilities, and shall incur no liability, under
this Agreement and the other Loan Documents.
<PAGE>
 
                                                                              82

                                 SECTION 10.  MISCELLANEOUS

          10.1 Amendments and Waivers.  Neither this Agreement or any other
               ----------------------                                      
Loan Document, nor any terms hereof or thereof may be amended, supplemented or
modified except in accordance with the provisions of this Section 10.1.  The
Required Lenders and each Loan Party party to the relevant Loan Document may, or
(with the written consent of the Required Lenders) the Administrative Agent and
each Loan Party party to the relevant Loan Document may, from time to time, (a)
enter into written amendments, supplements or modifications hereto and to the
other Loan Documents (including amendments and restatements hereof or thereof)
for the purpose of adding any provisions to this Agreement or the other Loan
Documents or changing in any manner the rights of the Lenders or of the Loan
Parties hereunder or thereunder or (b) waive, on such terms and conditions as
may be specified in the instrument of waiver, any of the requirements of this
Agreement or the other Loan Documents or any Default or Event of Default and its
consequences; provided, however, that no such waiver and no such amendment,
              --------  -------                                            
supplement or modification shall (i) forgive the principal amount or extend the
final scheduled date of maturity of any Revolving Credit Loan or Reimbursement
Obligation, extend the scheduled date of any amortization payment in respect of
any Term Loan, reduce the stated rate of any interest or fee payable hereunder
or extend the scheduled date of any payment thereof, or increase the amount or
extend the expiration date of any Commitment of any Lender, in each case without
the consent of each Lender directly affected thereby; (ii) amend, modify or
waive any provision of this Section or reduce any percentage specified in the
definition of Required Lenders or Required Prepayment Lenders, consent to the
assignment or transfer by the Borrower of any of its rights and obligations
under this Agreement and the other Loan Documents, release all or substantially
all of the Collateral or release all or substantially all of the Guarantors from
their guarantee obligations under the Guarantee and Collateral Agreement, in
each case without the consent of all Lenders; (iii) reduce the percentage
specified in the definition of Majority Facility Lenders with respect to any
Facility without the consent of all Lenders under such Facility; (iv) amend,
modify or waive any provision of Section 9 without the consent of any Agent
directly affected thereby; or (v) amend, modify or waive any provision of
Section 3 without the consent of the Issuing Lender.  Any such waiver and any
such amendment, supplement or modification shall apply equally to each of the
Lenders and shall be binding upon the Loan Parties, the Lenders, the
Administrative Agent and all future holders of the Loans.  In the case of any
waiver, the Loan Parties, the Lenders and the Agents shall be restored to their
former position and rights hereunder and under the other Loan Documents, and any
Default or Event of Default waived shall be deemed to be cured and not
continuing; but no such waiver shall extend to any subsequent or other Default
or Event of Default, or impair any right consequent thereon.  Any such waiver,
amendment, supplement or modification shall be effected by a written instrument
signed by the parties required to sign pursuant to the foregoing provisions of
this Section; provided, that delivery of an executed signature page of any such
              --------                                                         
instrument by facsimile transmission shall be effective as delivery of a
manually executed counterpart thereof.  For the avoidance of doubt, this
Agreement may be amended (or amended and restated) with the written consent of
the Required Lenders, the Agents and each Loan Party to each relevant Loan
Document (x) to add one or more additional credit facilities to this Agreement
(or, with the consent of each Lender affected thereby, to increase the Total
Revolving Credit Commitments) and to permit the extensions of credit from time
to time outstanding 
<PAGE>
 
                                                                              83

thereunder and the accrued interest and fees in respect thereof (collectively,
the "Additional Extensions of Credit") to share ratably
     -------------------------------                   
in the benefits of this Agreement and the other Loan Documents with the Term
Loans and Revolving Extensions of Credit and the accrued interest and fees in
respect thereof and (y) to include appropriately the Lenders holding such credit
facilities in any determination of the Required Lenders, Required Prepayment
Lenders and Majority Revolving Facility Lenders; provided, however, that no such
                                                 --------  -------              
amendment shall permit the Additional Extensions of Credit to share ratably with
or with preference to the Term Loans in the application of mandatory prepayments
without the consent of the Required Prepayment Lenders or otherwise share
ratably with or with preference to the Revolving Extensions of Credit without
the consent of the Majority Revolving Facility Lenders.

          10.2 Notices.  All notices, requests and demands to or upon the
               -------                                                   
respective parties hereto to be effective shall be in writing (including by
telecopy), and, unless otherwise expressly provided herein, shall be deemed to
have been duly given or made when delivered, or three Business Days after being
deposited in the mail, postage prepaid, or, in the case of telecopy notice, when
received, addressed (a) in the case of Holdings, the Borrower and the Agents, as
follows and (b) in the case of the Lenders, as set forth in an administrative
questionnaire delivered to the Administrative Agent or on Schedule I to the
Lender Addendum to which such Lender is a party or, in the case of a Lender
which becomes a party to this Agreement pursuant to an Assignment and
Acceptance, in such Assignment and Acceptance or (c) in the case of any party,
to such other address as such party may hereafter notify to the other parties
hereto:

     Holdings:                    SBA Communications Corporation
                                  One Town Center Road
                                  Boca Raton, Florida 33486
                                  Attention:  Jeffrey A. Stoops
                                  Telecopy:   (561) 997-0343
                                  Telephone:  (561) 995-7670


     The Borrower:                SBA Telecommunications, Inc.
                                  One Town Center Road
                                  Boca Raton, Florida 33486
                                  Attention:  Jeffrey A. Stoops
                                  Telecopy:   (561) 997-0343
                                  Telephone:  (561) 995-7670


     The Administrative Agent:    Lehman Commercial Paper Inc.
                                  3 World Financial Center
                                  New York, New York 10285
                                  Attention:  Michael O'Brien
                                  Telecopy:   (212) 528-0819
                                  Telephone:  (212) 526-0437
<PAGE>
 
                                                                              84

provided that any notice, request or demand to or upon the any Agent or any
- --------                                                                   
Lender shall not be effective until received.

          10.3 No Waiver; Cumulative Remedies.  No failure to exercise and no
               ------------------------------                                
delay in exercising, on the part of the any Agent or any Lender, any right,
remedy, power or privilege hereunder or under the other Loan Documents shall
operate as a waiver thereof; nor shall any single or partial exercise of any
right, remedy, power or privilege hereunder preclude any other or further
exercise thereof or the exercise of any other right, remedy, power or privilege.
The rights, remedies, powers and privileges herein provided are cumulative and
not exclusive of any rights, remedies, powers and privileges provided by law.

          10.4 Survival of Representations and Warranties.  All representations
               ------------------------------------------                      
and warranties made hereunder, in the other Loan Documents and in any document,
certificate or statement delivered pursuant hereto or in connection herewith
shall survive the execution and delivery of this Agreement and the making of the
Revolving Credit Loans and other extensions of credit hereunder.

          10.5 Payment of Expenses.  The Borrower agrees (a) to pay or
               -------------------                                    
reimburse LBI, the Administrative Agent for all their reasonable out-of-pocket
costs and expenses incurred in connection with the syndication of the Facilities
(other than fees payable to syndicate members) and the development, preparation
and execution of, and any amendment, supplement or modification to, this
Agreement and the other Loan Documents and any other documents prepared in
connection herewith or therewith, and the consummation and administration of the
transactions contemplated hereby and thereby, including, without limitation, the
reasonable fees and disbursements and other charges of counsel to the
Administrative Agent, (b) to pay or reimburse each Lender, LBI and the
Administrative Agent for all its costs and expenses incurred in connection with
the enforcement or preservation of any rights under this Agreement, the other
Loan Documents and any such other documents, including, without limitation, the
fees and disbursements of counsel (including the allocated fees and
disbursements and other charges of in-house counsel) to each Lender and of
counsel to the Agents, (c) to pay, indemnify, and hold each Lender and the
Agents harmless from, any and all recording and filing fees and any and all
liabilities with respect to, or resulting from any delay in paying, stamp,
excise and other taxes, if any, which may be payable or determined to be payable
in connection with the execution and delivery of, or consummation or
administration of any of the transactions contemplated by, or any amendment,
supplement or modification of, or any waiver or consent under or in respect of,
this Agreement, the other Loan Documents and any such other documents, and (d)
to pay, indemnify, and hold each Lender, each Agent, their respective
affiliates, and their respective officers, directors, trustees, employees,
advisors, agents and controlling persons (each, an "Indemnitee") harmless from
                                                    ----------                
and against any and all other liabilities, obligations, losses, damages,
penalties, actions, judgments, suits, costs, expenses or disbursements of any
kind or nature whatsoever with respect to the execution, delivery, enforcement,
performance and administration of this Agreement, the other Loan Documents and
any such other documents, including, without limitation, any of the foregoing
relating to the use of proceeds of the Loans or the violation of, noncompliance
with or liability under, any Environmental Law applicable to the operations of
Holdings, the Borrower, any of its Subsidiaries or any of the Properties and the
fees
<PAGE>
 
                                                                              85

and disbursements and other charges of legal counsel in connection with claims,
actions or proceedings by any Indemnitee against the Borrower hereunder (all the
foregoing in this clause (d), collectively, the "Indemnified Liabilities"),
                                                 -----------------------
provided, that the Borrower shall have no obligation hereunder to any Indemnitee
- -------
with respect to Indemnified Liabilities to the extent such Indemnified
Liabilities are found by a final and nonappealable decision of a court of
competent jurisdiction to have resulted from the gross negligence or willful
misconduct of such Indemnitee. Without limiting the foregoing, and to the extent
permitted by applicable law, the Borrower agrees not to assert and to cause its
Subsidiaries not to assert, and hereby waives and agrees to cause its
Subsidiaries so to waive, all rights for contribution or any other rights of
recovery with respect to all claims, demands, penalties, fines, liabilities,
settlements, damages, costs and expenses of whatever kind or nature, under or
related to Environmental Laws, that any of them might have by statute or
otherwise against any indemnitee. All amounts due under this Section shall be
payable not later than 30 days after written demand therefor. Statements payable
by the Borrower pursuant to this Section shall be submitted to Pam Kline
(Telephone No. (561) 995-7670) (Fax No. (561) 989-2940), at the address of the
Borrower set forth in Section 10.2, or to such other Person or address as may be
hereafter designated by the Borrower in a written notice to the Administrative
Agent. The agreements in this Section shall survive repayment of the Loans and
all other amounts payable hereunder.

          10.6 Successors and Assigns; Participations and Assignments.  (a)
               ------------------------------------------------------       
This Agreement shall be binding upon and inure to the benefit of Holdings, the
Borrower, the Lenders, the Agents, all future holders of the Loans and their
respective successors and assigns, except that the Borrower may not assign or
transfer any of its rights or obligations under this Agreement without the prior
written consent of the Agents and each Lender.

          (b)  Any Lender may, without the consent of the Borrower, in
accordance with applicable law, at any time sell to one or more banks, financial
institutions or other entities (each, a "Participant") participating interests
                                         -----------                          
in any Loan owing to such Lender, any Commitment of such Lender or any other
interest of such Lender hereunder and under the other Loan Documents.  In the
event of any such sale by a Lender of a participating interest to a Participant,
such Lender's obligations under this Agreement to the other parties to this
Agreement shall remain unchanged, such Lender shall remain solely responsible
for the performance thereof, such Lender shall remain the holder of any such
Loan for all purposes under this Agreement and the other Loan Documents, and the
Borrower and the Agents shall continue to deal solely and directly with such
Lender in connection with such Lender's rights and obligations under this
Agreement and the other Loan Documents.  In no event shall any Participant under
any such participation have any right to approve any amendment or waiver of any
provision of any Loan Document, or any consent to any departure by any Loan
Party therefrom, except to the extent that such amendment, waiver or consent
would reduce the principal of, or interest on, the Loans or any fees payable
hereunder, release all or substantially of the Collateral or the Guarantors from
their obligations under the Guarantee and Collateral Agreement, or postpone the
date of the final maturity of the Loans, in each case to the extent subject to
such participation.  The Borrower agrees that if amounts outstanding under this
Agreement and the Loans are due or unpaid, or shall have been declared or shall
have become due and payable upon the occurrence of an Event of Default, each
Participant shall, to the maximum extent permitted by applicable law, be deemed
to have the 
<PAGE>
 
                                                                              86

right of setoff in respect of its participating interest in amounts owing under
this Agreement to the same extent as if the amount of its participating interest
were owing directly to it as a Lender under this Agreement, provided that, in
                                                            --------
purchasing such participating interest, such Participant shall be deemed to have
agreed to share with the Lenders the proceeds thereof as provided in Section
10.7(a) as fully as if it were a Lender hereunder. The Borrower also agrees that
each Participant shall be entitled to the benefits of Sections 2.17, 2.18 and
2.19 with respect to its participation in the Commitments and the Loans
outstanding from time to time as if it was a Lender; provided that, in the case
                                                     --------
of Section 2.18, such Participant shall have complied with the requirements of
said Section and provided, further, that no Participant shall be entitled to
                 --------  -------
receive any greater amount pursuant to any such Section than the transferor
Lender would have been entitled to receive in respect of the amount of the
participation transferred by such transferor Lender to such Participant had no
such transfer occurred.

          (c)  Any Lender (an "Assignor") may, in accordance with applicable law
                               --------                                         
and upon written notice to the Administrative Agent, at any time and from time
to time assign to any Lender or any affiliate or Control Investment Affiliate
thereof or, with the consent of the Borrower, the Administrative Agent and (with
respect to assignments of Revolving Credit Commitments only) the Issuing Lender
(which, in each case, shall not be unreasonably withheld or delayed) (provided
                                                                      --------
(x) that no such consent need be obtained by Lehman Commercial Paper Inc. for a
period of 180 days following the Closing Date and (y) the consent of the
Borrower need not be obtained with respect to any assignment of Term Loans), to
an additional bank, financial institution or other entity (an "Assignee") all or
                                                               --------         
any part of its rights and obligations under this Agreement pursuant to an
Assignment and Acceptance, substantially in the form of Exhibit E, executed by
such Assignee and such Assignor (and, where the consent of the Borrower , the
Administrative Agent or the Issuing Lender is required pursuant to  the
foregoing provisions, by the Borrower and such other Persons) and delivered to
the Administrative Agent for its acceptance and recording in the Register; 
provided that no such assignment to an Assignee (other than any Lender or any
- --------                                                                     
affiliate thereof) shall be in an aggregate principal amount of less than
$2,500,000 (other than in the case of an assignment of all of a Lender's
interests under this Agreement), unless otherwise agreed by the Borrower and the
Administrative Agent; provided further that, after giving effect to such
                      -------- -------                                  
assignment, the aggregate principal amount of such Assignor's Commitment shall
be at least $2,500,000 (other than in the case of an assignment of all of a
Lender's interests under this Agreement), unless otherwise agreed by the
Borrower and the Administrative Agent.  Upon such execution, delivery,
acceptance and recording, from and after the effective date determined pursuant
to such Assignment and Acceptance, (x) the Assignee thereunder shall be a party
hereto and, to the extent provided in such Assignment and Acceptance, have the
rights and obligations of a Lender hereunder with a Commitment and/or Loans as
set forth therein, and (y) the Assignor thereunder shall, to the extent provided
in such Assignment and Acceptance, be released from its obligations under this
Agreement (and, in the case of an Assignment and Acceptance covering all of an
Assignor's rights and obligations under this Agreement, such Assignor shall
cease to be a party hereto).  Notwithstanding any provision of this Section, the
consent of the Borrower shall not be required for any assignment that occurs at
any time when any Event of Default shall have occurred and be continuing.
<PAGE>
 
                                                                              87

          (d)  The Administrative Agent shall, on behalf of the Borrower,
maintain at its address referred to in Section 10.2 a copy of each Assignment
and Acceptance delivered to it and a register (the "Register") for the
                                                    --------          
recordation of the names and addresses of the Lenders and the Commitment of, and
principal amount of the Loans owing to, each Lender from time to time.  The
entries in the Register shall be conclusive, in the absence of manifest error,
and the Borrower, the Administrative Agent and the Lenders shall treat each
Person whose name is recorded in the Register as the owner of the Loans and any
Notes evidencing such Loans recorded therein for all purposes of this Agreement.
Any assignment of any Loan, whether or not evidenced by a Note, shall be
effective only upon appropriate entries with respect thereto being made in the
Register (and each Note shall expressly so provide).  Any assignment or transfer
of all or part of a Loan evidenced by a Note shall be registered on the Register
only upon surrender for registration of assignment or transfer of the Note
evidencing such Loan, accompanied by a duly executed Assignment and Acceptance;
thereupon one or more new Notes in the same aggregate principal amount shall be
issued to the designated Assignee, and the old Notes shall be returned by the
Administrative Agent to the Borrower marked "canceled".  The Register shall be
available for inspection by the Borrower or any Lender or Agent at any
reasonable time and from time to time upon reasonable prior notice.

          (e)  Upon its receipt of an Assignment and Acceptance executed by an
Assignor and an Assignee (and, in any case where the consent of any other Person
is required by Section 10.6(c), by each such other Person) together with payment
to the Administrative Agent of a registration and processing fee of $3,500
(except that no such registration and processing fee shall be payable (y) in
connection with an assignment by or to Lehman Commercial Paper Inc. or any of
its Affiliates or (z) in the case of an Assignee which is already a Lender or is
an affiliate of a Lender or a Person under common management with a Lender), the
Administrative Agent shall (i) promptly accept such Assignment and Acceptance
and (ii) on the effective date determined pursuant thereto record the
information contained therein in the Register and give notice of such acceptance
and recordation to the Lenders, the Agents and the Borrower.  On or prior to
such effective date, the Borrower, at its own expense, upon request, shall
execute and deliver to the Administrative Agent (in exchange for the Revolving
Credit Note and/or Term Note, as the case may be, of the assigning Lender) a new
Revolving Credit Note or Term Note, as the case may be,  to the order of such
Assignee in an amount equal to the Revolving Credit Commitment and/or applicable
Term Loan, as the case may be, assumed or acquired by it pursuant to such
Assignment and Acceptance and, if the Assignor has retained a Revolving Credit
Commitment and/or Term Loan, as the case may be, upon request, a new Revolving
Credit Note and/or Term Note, as the case may be, to the order of the Assignor
in an amount equal to the Revolving Credit Commitment and/or applicable Term
Loan, as the case may be, retained by it hereunder.  Such new Note or Notes
shall be dated the Closing Date and shall otherwise be in the form of the Note
or Notes replaced thereby.

          (f)  For avoidance of doubt, the parties to this Agreement acknowledge
that the provisions of this Section concerning assignments of Loans and Notes
relate only to absolute assignments and that such provisions do not prohibit
assignments creating security interests, including, without limitation, any
pledge or assignment by a Lender of any Loan or Note to any Federal Reserve Bank
in accordance with applicable law.
<PAGE>
 
                                                                              88

          10.7 Adjustments; Set-off.  (a)  Except to the extent that this
               ---------------------                                      
Agreement provides for payments to be allocated to a particular Lender or to the
Lenders under a particular Facility, if any Lender (a "Benefitted Lender") shall
                                                       -----------------        
at any time receive any payment of all or part of the Obligations owing to it,
or receive any collateral in respect thereof (whether voluntarily or
involuntarily, by set-off, pursuant to events or proceedings of the nature
referred to in Section 8(f), or otherwise), in a greater proportion than any
such payment to or collateral received by any other Lender, if any, in respect
of such other Lender's Obligations, such Benefitted Lender shall purchase for
cash from the other Lenders a participating interest in such portion of each
such other Lender's Obligations, or shall provide such other Lenders with the
benefits of any such collateral, as shall be necessary to cause such Benefitted
Lender to share the excess payment or benefits of such collateral ratably with
each of the Lenders; provided, however, that if all or any portion of such
                     --------  -------                                    
excess payment or benefits is thereafter recovered from such Benefitted Lender,
such purchase shall be rescinded, and the purchase price and benefits returned,
to the extent of such recovery, but without interest.

          (b)  In addition to any rights and remedies of the Lenders provided by
law, each Lender shall have the right, without prior notice to Holdings or the
Borrower, any such notice being expressly waived by Holdings and the Borrower to
the extent permitted by applicable law, upon any amount becoming due and payable
by Holdings or the Borrower hereunder (whether at the stated maturity, by
acceleration or otherwise), to set off and appropriate and apply against such
amount any and all deposits (general or special, time or demand, provisional or
final), in any currency, and any other credits, indebtedness or claims, in any
currency, in each case whether direct or indirect, absolute or contingent,
matured or unmatured, at any time held or owing by such Lender or any branch or
agency thereof to or for the credit or the account of Holdings or the Borrower,
as the case may be.  Each Lender agrees promptly to notify the Borrower and the
Administrative Agent after any such setoff and application made by such Lender,
provided that the failure to give such notice shall not affect the validity of
- --------
such setoff and application.

          10.8 Counterparts.  This Agreement may be executed by one or more of
               ------------                                                   
the parties to this Agreement on any number of separate counterparts, and all of
said counterparts taken together shall be deemed to constitute one and the same
instrument.  Delivery of an executed signature page of this Agreement by
facsimile transmission shall be effective as delivery of a manually executed
counterpart hereof. A set of the copies of this Agreement signed by all the
parties shall be lodged with the Borrower and the Administrative Agent.

          10.9 Severability.  Any provision of this Agreement that is
               ------------                                          
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

          10.10 Integration.  This Agreement and the other Loan Documents
                -----------                                              
represent the agreement of Holdings, the Borrower, the Agents, the Co-Arrangers
and the Lenders with respect
<PAGE>
 
                                                                              89

to the subject matter hereof, and there are no promises, undertakings,
representations or warranties by any Co-Arranger, any Agent or any Lender
relative to subject matter hereof not expressly set forth or referred to herein
or in the other Loan Documents.

          10.11 GOVERNING LAW.  THIS AGREEMENT AND THE RIGHTS AND OBLIGATIONS
                -------------                                                
OF THE PARTIES UNDER THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

          10.12  Submission To Jurisdiction; Waivers.  Each of Holdings and the
                 -----------------------------------                           
Borrower hereby irrevocably and unconditionally:

          (a)  submits for itself and its Property in any legal action or
     proceeding relating to this Agreement and the other Loan Documents to which
     it is a party, or for recognition and enforcement of any judgment in
     respect thereof, to the non-exclusive general jurisdiction of the courts of
     the State of New York, the courts of the United States of America for the
     Southern District of New York, and appellate courts from any thereof;

          (b)  consents that any such action or proceeding may be brought in
     such courts and waives any objection that it may now or hereafter have to
     the venue of any such action or proceeding in any such court or that such
     action or proceeding was brought in an inconvenient court and agrees not to
     plead or claim the same;

          (c)  agrees that service of process in any such action or proceeding
     may be effected by mailing a copy thereof by registered or certified mail
     (or any substantially similar form of mail), postage prepaid, to Holdings
     or the Borrower, as the case may be at its address set forth in Section
     10.2 or at such other address of which the Administrative Agent shall have
     been notified pursuant thereto;

          (d)  agrees that nothing herein shall affect the right to effect
     service of process in any other manner permitted by law or shall limit the
     right to sue in any other jurisdiction; and

          (e)  waives, to the maximum extent not prohibited by law, any right it
     may have to claim or recover in any legal action or proceeding referred to
     in this Section any special, exemplary, punitive or consequential damages.

          10.13 Acknowledgments.  Each of Holdings and the Borrower hereby
                ---------------                                           
acknowledges that:

          (a)  it has been advised by counsel in the negotiation, execution and
     delivery of this Agreement and the other Loan Documents;

          (b)  neither Co-Arranger, any Agent nor any Lender has any fiduciary
     relationship with or duty to Holdings or the Borrower arising out of or in
     connection with this
<PAGE>
 
                                                                              90

     Agreement or any of the other Loan Documents, and the relationship between
     the Co- Arrangers, the Agents and Lenders, on one hand, and Holdings and
     the Borrower, on the other hand, in connection herewith or therewith is
     solely that of debtor and creditor; and

          (c)  no joint venture is created hereby or by the other Loan Documents
     or otherwise exists by virtue of the transactions contemplated hereby among
     the Co-Arrangers, the Agents and the Lenders or among Holdings, the
     Borrower and the Lenders.

          10.14 Confidentiality.  Each of the Agents and the Lenders agrees to
                ---------------                                               
keep confidential all non-public information provided to it by any Loan Party
pursuant to this Agreement that is designated by such Loan Party as
confidential; provided that nothing herein shall prevent any Agent or any Lender
              --------                                                          
from disclosing any such information (a) to any Co-Arranger, any Agent, any
other Lender or any affiliate of any thereof, (b) to any Participant or Assignee
(each, a "Transferee") or prospective Transferee that agrees to comply with the
          ----------                                                           
provisions of this Section, (c) any of its employees, directors, agents,
attorneys, accountants and other professional advisors, (d) upon the request or
demand of any Governmental Authority having jurisdiction over it, (e) in
response to any order of any court or other Governmental Authority or as may
otherwise be required pursuant to any Requirement of Law, (f) if requested or
required to do so in connection with any litigation or similar proceeding, (g)
that has been publicly disclosed other than in breach of this Section, (h) to
the National Association of Insurance Commissioners or any similar organization
or any nationally recognized rating agency that requires access to information
about a Lender's investment portfolio in connection with ratings issued with
respect to such Lender or (i) in connection with the exercise of any remedy
hereunder or under any other Loan Document.

          10.15 Release of Collateral Security and Guarantee Obligations.
                --------------------------------------------------------  
Notwithstanding anything to the contrary contained herein or in the Guarantee
and Collateral Agreement, upon request of the Borrower, the Administrative Agent
shall (without notice to or vote or consent of any Lender or any other Person)
take action having the effect of releasing any Collateral and/or guarantee
obligations provided for in the Guarantee and Collateral Agreement in any of the
following circumstances: (a) to the extent necessary to permit consummation, by
the relevant Person in accordance with the terms of this Agreement and the other
Loan Documents, of any Disposition transaction not prohibited hereunder, (b) to
the extent the Administrative Agent is directed to do so by the Required Lenders
and (c) to the extent that all Obligations outstanding hereunder and under the
other Loan Documents have been paid in full, all Commitments have been
terminated and no Letters of Credit are outstanding.

          10.16 Accounting Changes.  In the event that any "Accounting Change"
                ------------------                                            
(as defined below) shall occur and such change results in a change in the method
of calculation of financial covenants, standards or terms in this Agreement,
then the Borrower and the Administrative Agent agree to enter into negotiations
in order to amend such provisions of this Agreement so as to equitably reflect
such Accounting Changes with the desired result that the criteria for evaluating
the Borrower's financial condition shall be the same after such Accounting
Changes as if such Accounting Changes had not been made. Until such time as such
an
<PAGE>
 
                                                                              91

amendment shall have been executed and delivered by the Borrower, the
Administrative Agent and the Required Lenders, all financial covenants,
standards and terms in this Agreement shall continue to be calculated or
construed as if such Accounting Changes had not occurred. "Accounting Changes"
refers to changes in accounting principles required by the promulgation of any
rule, regulation, pronouncement or opinion by the Financial Accounting Standards
Board of the American Institute of Certified Public Accountants or, if
applicable, the SEC.

          10.17 Delivery of Lender Addenda.  Each initial Lender shall become a
                --------------------------                                     
party to this Agreement by delivering to the Administrative Agent a Lender
Addendum duly executed by such Lender, the Borrower and the Administrative
Agent.

          10.18 WAIVERS OF JURY TRIAL.  HOLDINGS, THE BORROWER, THE AGENTS AND
                 ---------------------                                         
THE LENDERS HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVE TRIAL BY JURY IN ANY
LEGAL ACTION OR PROCEEDING RELATING TO THIS AGREEMENT OR ANY OTHER LOAN DOCUMENT
AND FOR ANY COUNTERCLAIM THEREIN.

          10.19 Intercreditor Provisions.  Notwithstanding (i) any provision
                ------------------------                                    
hereof or of any other Loan Document and (ii) the priority of any Lien on the
Collateral arising by virtue of the assignment of Liens securing obligations of
the Borrower and its Subsidiaries under the Existing Credit Agreement and the
other documents executed in connection therewith, all proceeds received by the
Administrative Agent from the Collateral or from the guarantee contained in the
Guarantee and Collateral Agreement or from the exercise by the Administrative
Agent of any of its remedies under any of the Security Documents shall be
applied by the Administrative Agent as follows:

          First, to reimburse the Administrative Agent for all costs and
          -----                                                         
     expenses incurred by it in administering the Collateral and the Security
     Documents and in enforcing rights thereunder;

          Second, to the Lenders (or, in the case of Specified Hedge Agreements,
          ------                                                                
     any affiliates thereof) to pay principal of, accrued and unpaid interest
     on, and other amounts payable hereunder with respect to, the Loans and the
     L/C Obligations (and to cash collateralize any L/C Obligations not then due
     and payable, to the extent such L/C Obligations are not already cash
     collateralized), and all other outstanding Obligations, ratably among the
     Lenders (or, in the case of Specified Hedge Agreements, any affiliates
     thereof) according to the amounts owing to the Lender (or such affiliate,
     as the case may be) hereunder or under such Specified Hedge Agreements; and

          Third, after payment in full of all of the amounts described in
          -----                                                          
     clauses First and Second above, to the Borrower or the other Loan Parties
     entitled thereto or as otherwise may be required under applicable law.
<PAGE>
 
                                                                              92

          10.20 Purchase of Loans Under Existing Credit Agreement.
                -------------------------------------------------  
Notwithstanding the express terms of Section 2.1 and any other contrary
provision contained in Section 2, the Term Loan Lenders shall fund their Term
Loans (or such portion thereof as shall equal the principal amount of all loans
then outstanding under the Existing Credit Agreement) on the Closing Date
through the purchase, ratably by the Term Loan Lenders in accordance with their
respective Term Loan Percentages, of all loans outstanding under the Existing
Credit Agreement on the Closing Date immediately prior to the effectiveness of
this Agreement, and such loans so purchased shall thereafter be deemed to be
Term Loans and be subject to all terms and conditions hereof.  The Borrower
hereby expressly confirms that such loans so purchased shall constitute Term
Loans hereunder and that the representations and warranties set forth in Section
4 apply to such Term Loans.

          10.21 Subordination, Non-Disturbance and Attornment.  Within fifteen
                ---------------------------------------------                 
(15) Business Days following receipt from any Loan Party of the lease, license
or other occupancy arrangement (a "Lease") of any Tower and related property
                                   -----                                    
owned or leased by such Loan Party (the "Leased Property") with any person or
                                         ---------------                     
entity not prohibited by this Agreement (a "Tenant") and either (x) the Approved
                                            ------                              
Form of SNDA (as defined below) or (y) the Tenant's requested version thereof,
the Administrative Agent, individually and on behalf of each of the Lenders,
shall execute and deliver to such Loan Party an agreement (an "SNDA") in form
                                                               ----          
and substance reasonably satisfactory to the Administrative Agent pursuant to
which (a) the Tenant subordinates the Lease and all of Tenant's rights and
estates thereunder to the Security Document held by the Administrative Agent and
encumbering the Leased Property, (b) the Tenant agrees that Tenant will attorn
to and recognize the Administrative Agent or the purchaser at any foreclosure
sale or any sale under a power of sale contained in any such Security Document
as the landlord under the Lease for the balance of the leasehold term then
remaining '', (c) the Administrative Agent consents to the Lease and (d) the
Administrative Agent agrees that, notwithstanding the terms of the applicable
Security Document held by the Administrative Agent, or any default, expiration,
termination. foreclosure, sale, entry or other act or omission under or pursuant
to such Security Document or a transfer on lieu of foreclosure, so long as the
Tenant is not in default under such Lease, the Tenant shall not be disturbed in
the peaceful enjoyment of the Leased Property nor shall the Lease be terminated
or canceled at any time, except in the event the Loan Party shall have the right
to terminate the Lease under the terms and provisions expressly set forth
therein.  Without limiting the generality of the foregoing, Administrative
Agent, individually and on behalf of each of the Lenders, acknowledges and
agrees that the form of SNDA attached hereto as Exhibit J (the "Approved Form
                                                                -------------
of SNDA") is acceptable to it and the Lenders.
- -------
<PAGE>
 
                                                                              93

          IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed and delivered by their proper and duly authorized officers as
of the day and year first above written.

                              SBA COMMUNICATIONS CORPORATION


                              By:  --------------------------------
                                   Name:
                                   Title:


                              SBA TELECOMMUNICATIONS, INC.


                              By:  --------------------------------
                                   Name:
                                   Title:


                              LEHMAN BROTHERS INC.,
                              as Advisor, Co-Arranger and Book Manager


                              By:  --------------------------------
                                   Name:
                                   Title:


                              LEHMAN COMMERCIAL PAPER INC., as
                              Administrative Agent


                              By:  --------------------------------
                                   Name:
                                   Title:


                              GENERAL ELECTRIC CAPITAL 
                              CORPORATION, as Co-Arranger and as 
                              Syndication Agent

                              
                              By:  --------------------------------
                                   Name:
                                   Title:
<PAGE>
 
                                                                              94

                              TORONTO DOMINION (TEXAS), INC., as Documentation
                              Agent


                              By:  --------------------------------
                                   Name:
                                   Title:
<PAGE>
 
                                                                              95

                              BARCLAYS BANK PLC, as
                              Co-Documentation Agent


                              By:  --------------------------------
                                   Name:
                                   Title:
   
<PAGE>
 
                                                                              

                                                                         Annex A
                                                                         -------

    PRICING GRID FOR TERM LOANS, REVOLVING CREDIT LOANS AND COMMITMENT FEES
<TABLE>
<CAPTION>
==============================================================================================
   
   Pricing Ratio                  Applicable Margin         Applicable       Commitment Fee
                                 for Eurodollar Loans       Margin for            Rate
                                                          Base Rate Loans
==============================================================================================
<S>                                      <C>                 <C>                  <C>
x greater than 5.5                       3.50%               2.50%                1.25%
5.5 greater than x greater than 5.       3.25%               2.25%               1.125%
5.0 greater than x greater than 4.5      3.00%               2.00%                1.00%
4.5 greater than x greater than 4.0      2.50%               1.50%                0.75%
x less than 4.0                          2.25%               1.25%                0.50%
==============================================================================================
</TABLE>

Changes in the Applicable Margin and Commitment Fee Rate resulting from changes
in the Pricing Ratio shall become effective (a) on the date which is six months
after the Closing Date (based upon financial statements delivered on the most
recent Adjustment Date) and (b) thereafter, on each Adjustment Date, and any
such change shall remain in effect until the next Adjustment Date.  The
"Adjustment Date" in respect of each fiscal period shall be the date on which
financial statements are delivered to the Lenders pursuant to Section 6.1 (but
in any event not later than the 45th day after the end of each of the first
three quarterly periods of each fiscal year or the 90th day after the end of
each fiscal year, as the case may be).  If any financial statements referred to
above are not delivered within the time periods specified above, then, until
such financial statements are delivered, the Pricing Ratio as at the end of the
fiscal period that would have been covered thereby shall for the purposes of
this definition be deemed to be greater than 5.5 to 1.  In addition, at all
times while an Event of Default shall have occurred and be continuing, the
Pricing Ratio shall for the purposes of this definition be deemed to be greater
than 5.5 to 1.  Each determination of the Pricing Ratio pursuant to this
definition shall be made with respect to the period of four consecutive fiscal
quarters of the Borrower ending at the end of the period covered by the relevant
financial statements.
                                                  
<PAGE>
 
                                                                              

                                                                         Annex B
                                                                         -------

                               ACCEPTABLE TENANTS
                               ------------------


AT&T Wireless
Sprint PCS
Primeco
Vanguard
Bell South
Bell Atlantic
Airtouch
Nextel
Omnipoint
SBC
US West
Western Wireless
Voicestream Wireless Corporation (successor by name change to Western Wireless)
Motorola
360 Communications
Powertel
Pacific Bell
Comnet Cellular
Leases signed with investment grade lessees
Triton
Nextel Partners
Telecorp
<PAGE>
 
                                                                              

                                                            SCHEDULE 1.1


                     MORTGAGED PROPERTIES ON CLOSING DATE
<PAGE>
 
                                                                              

                                                            SCHEDULE 4.4


                 CONSENTS, AUTHORIZATIONS, FILINGS AND NOTICES
<PAGE>
 
                                                                             

                                                            SCHEDULE 4.15


                                  SUBSIDIARIES
<PAGE>
 
                                                                             

                                                            SCHEDULE 4.19(a)-1


                            UCC FILING JURISDICTIONS
<PAGE>
 
                                                                             

                                                            SCHEDULE 4.19(a)-2



                   UCC FILING JURISDICTIONS TO REMAIN ON FILE
<PAGE>
 
                                                                             

                                                              SCHEDULE 4.19(a)-3



                   UCC FILING JURISDICTIONS TO BE TERMINATED
<PAGE>
 
                                                                             

                                SCHEDULE 4.19(b)


                         MORTGAGE FILING JURISDICTIONS
<PAGE>
 
                                                                             

                                 SCHEDULE 4.26


                            GOVERNMENTAL PROCEEDINGS
<PAGE>
 
                                                                             


                                SCHEDULE 7.2(d)


                             EXISTING INDEBTEDNESS
<PAGE>
 
                                                                             

                                                            SCHEDULE 7.3(f)


                                 EXISTING LIENS


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