<PAGE>   1
                                                                    Exhibit 4.17




                           SPECTRASITE HOLDINGS, INC.


                                    as Issuer


                                       and


                     UNITED STATES TRUST COMPANY OF NEW YORK

                                   as Trustee



                                    INDENTURE

                          Dated as of December 20, 2000




                          12 1/2% Senior Notes due 2010




<PAGE>   2



                                TABLE OF CONTENTS

                                                                          Page

ARTICLE I

         SECTION 1.1.  Definitions                                         1
                       ------------
         SECTION 1.2.  Other Definitions                                   18
                       -----------------
         SECTION 1.3.  Incorporation by Reference of Trust Indenture Act   19
                       -------------------------------------------------

         SECTION 1.4.  Rules of Construction                               19
                       ---------------------
         SECTION 1.5.  One Class of Notes                                  20
                       ------------------

ARTICLE II

         SECTION 2.1.  Form and Dating                                     20
                       ---------------
         SECTION 2.2.  Execution and Authentication                        20
                       ----------------------------
         SECTION 2.3.  Registrar and Paying Agent                          21
                       --------------------------

         SECTION 2.4.  Paying Agent to Hold Money in Trust                 21
                       -----------------------------------

         SECTION 2.5.  Noteholder Lists                                    22
                       ----------------
         SECTION 2.6.  [Intentionally Omitted]                             22
                       -----------------------
         SECTION 2.7.  Replacement Notes                                   22
                       -----------------
         SECTION 2.8.  Outstanding Notes                                   22
                       -----------------
         SECTION 2.9.  Temporary Notes                                     22
                       -----------------
         SECTION 2.10.  Cancellation                                       23
                        -----------------
         SECTION 2.11.  Defaulted Interest                                 23
                        ------------------
         SECTION 2.12.  CUSIP Numbers                                      23
                        -------------
ARTICLE III

         SECTION 3.1.  Notices to Trustee                                  24
                       ------------------
         SECTION 3.2.  Selection of Notes to Be Redeemed                   24
                       ---------------------------------

                                       i
<PAGE>   3

         SECTION 3.3.  Notice of Redemption                                24
                       --------------------
         SECTION 3.4.  Effect of Notice of Redemption                      25
                       ------------------------------

         SECTION 3.5.  Deposit of Redemption Price                         25
                       ---------------------------

         SECTION 3.6.  Notes Redeemed in Part                              25
                       ----------------------

ARTICLE IV

         SECTION 4.1.  Payment of Notes                                    25
                       ----------------
         SECTION 4.2.  SEC Reports                                         26
                       ------------
         SECTION 4.3.  Limitation on Indebtedness                          26
                       --------------------------
         SECTION 4.4.  Limitation on Indebtedness and Preferred Stock of
                       Restricted Subsidiaries                             28
                       --------------------------------------------------

         SECTION 4.5.  Limitation on Restricted Payments                   30
                       ---------------------------------

         SECTION 4.6.  Limitation on Restrictions on Distributions from
                       Restricted Subsidiaries.                            32
                       ---------------------------------------------------

         SECTION 4.7.  Limitation on Sale of Assets and Subsidiary Stock   32
                       -------------------------------------------------

         SECTION 4.8.  Limitation on Transactions with Affiliates          35
                       ------------------------------------------

         SECTION 4.9.  Change of Control                                   36
                       -----------------
         SECTION 4.10.  Limitation on Sale or Issuance of Capital Stock of
                        Restricted Subsidiaries                            37
                        --------------------------------------------------
         SECTION 4.11.  Limitation on Liens                                38
                        -------------------
         SECTION 4.12.  Limitation on Sale/Leaseback Transactions          38
                        -----------------------------------------

         SECTION 4.13.  Compliance with Laws                               38
                        --------------------
         SECTION 4.14.  Compliance Certificate                             38
                        ----------------------
         SECTION 4.15.  Further Instruments and Acts                       38
                        ----------------------------

         SECTION 4.16.  Maintenance of Office or Agency                    39
                        -------------------------------

         SECTION 4.17.  Corporate Existence                                39
                        -------------------
         SECTION 4.18.  Payment of Taxes and Other Claims                  39
                        ---------------------------------

                                       ii
<PAGE>   4

         SECTION 4.19.  Maintenance of Properties and Insurance            39
                        ---------------------------------------

ARTICLE V

         SECTION 5.1.  When the Issuer May Merge or Transfer Assets        40
                       --------------------------------------------

ARTICLE VI

         SECTION 6.1.  Events of Default                                   41
                       -----------------
         SECTION 6.2.  Acceleration                                        43
                       ------------
         SECTION 6.3.  Other Remedies                                      43
                       --------------
         SECTION 6.4.  Waiver of Past Defaults                             43
                       -----------------------

         SECTION 6.5.  Control by Majority                                 43
                       -------------------
         SECTION 6.6.  Limitation on Suits                                 44
                       -------------------
         SECTION 6.7.  Rights of Holders to Receive Payment                44
                       ------------------------------------

         SECTION 6.8.  Collection Suit by Trustee                          44
                       --------------------------

         SECTION 6.9.  Trustee May File Proofs of Claim                    44
                       --------------------------------

         SECTION 6.10.  Priorities                                         45
                        -----------
         SECTION 6.11.  Undertaking for Costs                              45
                        ---------------------
         SECTION 6.12.  Waiver of Stay or Extension Laws                   45
                        --------------------------------

ARTICLE VII

         SECTION 7.1.  Duties of Trustee                                   46
                       -----------------
         SECTION 7.2.  Rights of Trustee                                   47
                       -----------------
         SECTION 7.3.  Individual Rights of Trustee                        47
                       ----------------------------

         SECTION 7.4.  Trustee's Disclaimer                                47
                       --------------------
         SECTION 7.5.  Notice of Defaults                                  48
                       ------------------
         SECTION 7.6.  Reports by Trustee to Holders                       48
                       -----------------------------

         SECTION 7.7.  Compensation and Indemnity                          48
                       --------------------------
         SECTION 7.8.  Replacement of Trustee                              49
                       ----------------------
                                      iii
<PAGE>   5

         SECTION 7.9.  Successor Trustee by Merger                         50
                       ---------------------------

         SECTION 7.10.  Eligibility; Disqualification                      50
                        -----------------------------
         SECTION 7.11.  Preferential Collection of Claims Against Issuer   50
                        ------------------------------------------------

ARTICLE VIII

         SECTION 8.1.  Discharge of Liability on Notes; Defeasance         50
                       -------------------------------------------

         SECTION 8.2.  Conditions to Defeasance                            51
                       ------------------------
         SECTION 8.3.  Application of Trust Money                          52
                       --------------------------

         SECTION 8.4.  Repayment to Issuer                                 53
                       -------------------
         SECTION 8.5.  Indemnity for Government Obligations                53
                       ------------------------------------

         SECTION 8.6.  Reinstatement                                       53
                       -------------
ARTICLE IX

         SECTION 9.1.  Without Consent of Holders                          53
                       --------------------------

         SECTION 9.2.  With Consent of Holders                             54
                       -----------------------

         SECTION 9.3.  Compliance with Trust Indenture Act                 55
                       -----------------------------------

         SECTION 9.4.  Revocation and Effect of Consents and Waivers       55
                       ---------------------------------------------

         SECTION 9.5.  Notation on or Exchange of Notes                    55
                       --------------------------------

         SECTION 9.6.  Trustee to Sign Amendments                          55
                       --------------------------

         SECTION 9.7.  Payment for Consent                                 56
                       -------------------
ARTICLE X

         SECTION 10.1.  Trust Indenture Act Controls                       56
                        ----------------------------

         SECTION 10.2.  Notices                                            56
                        -------
         SECTION 10.3.  Communication by Holders with Other Holders        57
                        -------------------------------------------

         SECTION 10.4.  Certificate and Opinion as to Conditions Precedent 57
                        --------------------------------------------------

         SECTION 10.5.  Statements Required in Certificate or Opinion      57
                        ---------------------------------------------

         SECTION 10.6.  When Notes Disregarded                             57
                        ----------------------
                                       iv
<PAGE>   6

         SECTION 10.7.  Rules by Trustee, Paying Agent and Registrar       58
                        --------------------------------------------

         SECTION 10.8.  Legal Holidays                                     58
                        --------------
         SECTION 10.9.  Governing Law                                      58
                        -------------
         SECTION 10.10.  No Recourse Against Others                        58
                         --------------------------

         SECTION 10.11.  Successors                                        58
                         ----------
         SECTION 10.12.  Multiple Originals                                58
                         ------------------

Rule 144A/Regulation S Appendix
Exhibit 1 to Appendix - Form of Initial Note
Exhibit A - Form of Exchange Note and Private Exchange Note

                                       v



<PAGE>   7

                  INDENTURE,  dated as of December 20, 2000, between SPECTRASITE
HOLDINGS, INC., a Delaware corporation (as further defined below, the "Issuer"),
and UNITED STATES TRUST COMPANY OF NEW YORK, a bank and trust company  organized
under New York banking law, as trustee (the "Trustee").

                  Each  party  agrees as  follows  for the  benefit of the other
party and for the equal and  ratable  benefit  of the  Holders  of the  Issuer's
$200,000,000  aggregate  principal  amount of 12 1/2% Senior Notes due 2010 (the
"Initial  Notes")  and,  if and when issued in  exchange  for  Initial  Notes as
provided  in the  Registration  Rights  Agreement  (as  defined in the  Appendix
hereto),  the  Issuer's  Series B 12 1/2% Senior  Notes due 2010 (the  "Exchange
Notes")  and, if and when  issued  pursuant  to a private  exchange  for Initial
Notes,  the  Issuer's  Series B 12 1/2%  Senior  Notes  Due 2010  (the  "Private
Exchange  Notes,"  together with the Initial Notes and the Exchange  Notes,  the
"Notes"):

                                    ARTICLE I
                   DEFINITIONS AND INCORPORATION BY REFERENCE

                  SECTION 1.1.  Definitions

                  "Adjusted  EBITDA" as of any date of  determination  means the
sum of (i) the  EBITDA  of the  Issuer  for the four  most  recent  full  fiscal
quarters  ending  prior to such date,  less the  Issuer's  Tower EBITDA for such
four-quarter  period,  plus (ii) the  product of four times the  Issuer's  Tower
EBITDA for the most recent  quarterly  period,  which Tower  EBITDA for the most
recent  quarterly  period shall be  determined on a pro forma basis after giving
effect to (A) all  acquisitions or dispositions of assets made by the Issuer and
its  Subsidiaries  from the beginning of such quarter through and including such
date of determination  (including any related financing transactions) as if such
acquisitions and dispositions had occurred at the beginning of such quarter, (B)
any new lease or Site  Management  Contract  entered  into by the  Issuer or any
Restricted  Subsidiary in the ordinary  course of business with respect to Tower
Assets from the  beginning of such quarter  through and  including  such date of
determination  as if such new lease or Site Management  Contract had been signed
at the  beginning  of such  quarter  and the rent  required by the terms of such
lease or Site  Management  Contract  for such  quarter had been  received by the
Issuer or a Restricted  Subsidiary  during such  quarter,  (C) the loss from the
beginning of such quarter  through and including such date of  determination  of
any lease or Site Management  Contract of the Issuer or a Restricted  Subsidiary
with  respect  to any Tower  Assets  that was in effect on the first day of such
quarter  as if such  lease or Site  Management  Contract  had not been in effect
during such quarter and no rent under such lease had been  received  during such
quarter  and (D) any rent  increases  received  by the Issuer or any  Restricted
Subsidiary  during the period  beginning  on the first day of such  quarter  and
ending  on the  date of  determination  related  to  leases  or Site  Management
Contracts on Tower Assets as if such increased rental rate had been in effect at
the  beginning  of such  quarter  and  such  increased  amount  of rent had been
received  by the Issuer or a  Restricted  Subsidiary  during such  quarter.  For
purposes of making the computation referred to above, (1) acquisitions that have
been made by the Issuer or any of its Restricted Subsidiaries, including through
mergers or  consolidations
                                       1
<PAGE>   8

and including any related financing transactions, during the reference period or
subsequent to such reference period and on or prior to the date of determination
shall be deemed to have  occurred on the first day of the  reference  period and
EBITDA for such  reference  period shall be calculated  without giving effect to
clause (ii) of the  proviso  set forth in the  definition  of  Consolidated  Net
Income,  and  (2)  the  EBITDA  attributable  to  discontinued  operations,   as
determined in accordance  with GAAP,  and  operations or businesses  disposed of
prior to the date of determination shall be excluded.

                  "Affiliate"  of any  specified  Person means any other Person,
directly or indirectly, controlling or controlled by or under direct or indirect
common control with such specified Person.  For the purposes of this definition,
"control"  when used with  respect to any  Person  means the power to direct the
management and policies of such Person, directly or indirectly,  whether through
the  ownership of voting  securities,  by contract or  otherwise;  and the terms
"controlling" and "controlled" have meanings correlative to the foregoing.

                  "Asset  Disposition" means any sale, lease,  transfer or other
disposition (or series of related sales,  leases,  transfers or dispositions) by
the Issuer or any Restricted Subsidiary, including any disposition by means of a
merger,  consolidation or similar transaction (each referred to for the purposes
of this definition as a "disposition"),  of (i) any shares of Capital Stock of a
Restricted  Subsidiary  (other  than  directors'  qualifying  shares  or  shares
required  by  applicable  law to be held by a Person  other than the Issuer or a
Restricted Subsidiary), (ii) all or substantially all the assets of any division
or line of  business  of the Issuer or any  Restricted  Subsidiary  or (iii) any
other assets of the Issuer or any Restricted  Subsidiary outside of the ordinary
course of business of the Issuer or such Restricted  Subsidiary  (other than, in
the  case of (i),  (ii) and  (iii)  above,  (u) a  disposition  by a  Restricted
Subsidiary to the Issuer or by the Issuer or a Restricted  Subsidiary to another
Restricted  Subsidiary,  (v) a disposition that constitutes a Restricted Payment
permitted by Section 4.5, (w) a  disposition  of assets with a fair market value
of less than $5.0 million,  (x) any transaction not prohibited by Section 4.5 or
that constitutes a Permitted Investment, (y) grants of leases or licenses in the
ordinary course of business, and (z) disposals of cash equivalents).

                  "Attributable  Indebtedness"  in respect  of a  Sale/Leaseback
Transaction  means,  as  at  the  time  of  determination,   the  present  value
(discounted at the interest rate borne by the Notes, compounded annually) of the
total obligations of the lessee for rental payments during the remaining term of
the lease included in such Sale/Leaseback  Transaction (including any period for
which such lease has been extended).

                  "Average Life" means,  as of the date of  determination,  with
respect to any  Indebtedness  or  Preferred  Stock,  the  quotient  obtained  by
dividing  (i) the sum of the  product  of the  numbers of years from the date of
determination  to the dates of each successive  scheduled  principal  payment of
such  Indebtedness  or  redemption  or  similar  payment  with  respect  to such
Preferred Stock  multiplied by the amount of such payment by (ii) the sum of all
such payments.

                  "Board  of  Directors"  means the  Board of  Directors  of the
Issuer or any committee thereof duly authorized to act on behalf of such Board.

                                       2
<PAGE>   9

                  "Business  Day" means a day other than a  Saturday,  Sunday or
other day on which  banking  institutions  in New York State are  authorized  or
required by law to close.

                  "Capitalized  Lease  Obligation"  means an obligation  that is
required to be classified and accounted for as a capitalized lease for financial
reporting  purposes  in  accordance  with GAAP,  and the amount of  Indebtedness
represented  by  such  obligation  shall  be  the  capitalized  amount  of  such
obligation determined in accordance with GAAP.

                  "Capital  Stock"  of any  Person  means  any and  all  shares,
interests,  rights  to  purchase,  warrants,  options,  participation  or  other
equivalents  of or  interests  in (however  designated)  equity of such  Person,
including any Preferred  Stock,  but excluding any debt  securities  convertible
into such equity.

                  "Change of Control" means the occurrence of any of the
following events:

                  (i) any "person"  (as such term is used in Sections  13(d) and
         14(d) of the Exchange Act),  other than one or more Permitted  Holders,
         is or  becomes  the  beneficial  owner  (as such  term is used in Rules
         13(d)-3 and 13(d)-5 of the  Exchange  Act,  except that for purposes of
         this  clause  (i) such  Person  shall  be  deemed  to have  "beneficial
         ownership" of all shares that any such person has the right to acquire,
         whether such right is exercisable immediately or only after the passage
         of time), directly or indirectly,  of more than 35% of the total voting
         power of the Voting Stock of the Issuer;  provided,  however,  that the
         Permitted Holders  "beneficially own",  directly or indirectly,  in the
         aggregate a lesser  percentage  of the total voting power of the Voting
         Stock of the Issuer than such other Person and do not have the right or
         ability by voting  power,  contract or  otherwise to elect or designate
         for election a majority of the Board of Directors  (for the purposes of
         this clause (i), (a) such other person shall be deemed to  beneficially
         own any Voting Stock of a specified entity held by a parent entity,  if
         such other person is the beneficial owner,  directly or indirectly,  of
         more than 35% of the voting  power of the Voting  Stock of such  parent
         entity  and the  Permitted  Holders  "beneficially  own",  directly  or
         indirectly,  in the  aggregate a lesser  percentage of the total voting
         power of the Voting Stock of such parent entity than such other Person,
         and do not have the right or  ability  by  voting  power,  contract  or
         otherwise to elect or designate for election a majority of the board of
         directors of such parent entity; and (b) the Permitted Holders shall be
         deemed to  beneficially  own any Voting  Stock of an entity held by any
         other parent entity, so long as the Permitted Holders beneficially own,
         directly  or  indirectly,  in the  aggregate,  a majority of the voting
         power of the parent entity's Voting Stock);

                  (ii)  during any period of two  consecutive  years (or, in the
         case this event occurs within the first two years after the Issue Date,
         such shorter period as shall have begun on the Issue Date), individuals
         who at the beginning of such period  constituted the Board of Directors
         (together  with  any new  directors  whose  election  by such  Board of
         Directors or whose  nomination for election by the  shareholders of the
         Issuer was  approved  by a vote of a majority of the  directors  of the
         Issuer then still in office who were either  directors at the beginning
         of such  period  or whose  election  or  nomination  for  election  was
         previously  so approved)  cease for any reason to constitute a majority
         of the Board of Directors then in office;

                                      3
<PAGE>   10

                  (iii) the merger or  consolidation  of the Issuer with or into
         another Person or the merger of another Person with or into the Issuer,
         and, in the case of any such merger or consolidation, the securities of
         the Issuer that are outstanding  immediately  prior to such transaction
         and which  represent  100% of the aggregate  voting power of the Voting
         Stock of the Issuer are changed into or exchanged for cash,  securities
         or property,  unless pursuant to such  transaction  such securities are
         changed into or exchanged for, in addition to any other  consideration,
         securities  of the surviving  corporation  that  represent  immediately
         after such  transaction,  at least a majority of the  aggregate  voting
         power of the Voting Stock of the surviving corporation; and

                  (iv)  the  sale of all or  substantially  all of the  Issuer's
         assets to another  person,  other than a  Permitted  Holder or a Person
         that is controlled by the Permitted Holders.

                  "Code" means the Internal Revenue Code of 1986, as amended.

                  "Completed Broadcast Tower" means a communications tower of at
least  500  feet,  other  than  a  Completed  Tower,  with,  as of the  date  of
determination,  (i) at least one broadcast tenant that has executed a definitive
lease or Site  Management  Contract  with the  Issuer  or any of its  Restricted
Subsidiaries and (ii) capacity for at least one other tenant.

                  "Completed  Tower" means a communications  transmission  tower
with, as of any date of  determination,  (i) at least one anchor tenant that has
executed a definitive  lease or Site Management  Contract with the Issuer or any
of its Restricted Subsidiaries and (ii) capacity for at least three tenants.

                  "Consolidated  Indebtedness"  as of any date of  determination
means (without  duplication)  (i) the total amount of Indebtedness of the Issuer
and its Restricted  Subsidiaries,  (ii) the total amount of  Indebtedness of any
other Person,  to the extent that such  Indebtedness  has been Guaranteed by the
Issuer or one or more of its  Restricted  Subsidiaries,  and (iii) the aggregate
liquidation  value of all  Disqualified  Stock of the Issuer  and all  preferred
stock of  Restricted  Subsidiaries  of the  Issuer  not owned by the Issuer or a
Restricted  Subsidiary,  in each case,  determined  on a  consolidated  basis in
accordance with GAAP.

                  "Consolidated  Interest  Expense" means,  for any period,  the
total  interest   expense  of  the  Issuer  and  its   consolidated   Restricted
Subsidiaries,  plus, to the extent not included in such total interest  expense,
and to the extent incurred by the Issuer or its Restricted Subsidiaries, without
duplication,  (i) interest expense  attributable to capital leases and to leases
constituting  part of a Sale/Leaseback  Transaction,  (ii)  amortization of debt
discount and debt  issuance  cost,  (iii)  capitalized  interest,  (iv) non-cash
interest  expense,  (v)  commissions,  discounts and other fees and charges owed
with respect to letters of credit and bankers'  acceptance  financing,  (vi) net
costs  associated  with Hedging  Obligations  (including  amortization of fees),
(vii)  Preferred  Stock  dividends paid in respect of all Preferred Stock of the
Issuer and its  Subsidiaries  held by Persons  other than the Issuer or a Wholly
Owned  Subsidiary,  (viii) interest  incurred in connection with  Investments in
discontinued operations, (ix) interest accruing on any Indebtedness of any other
Person to the extent  such  Indebtedness  is  Guaranteed  by (or  secured by the
assets  of)  the  Issuer  or  any   Restricted   Subsidiary  and  (x)  the  cash
contributions  to any  employee  stock  ownership  plan or similar  trust to the
extent such contributions are used by such plan or trust to pay interest

                                       4
<PAGE>   11

or fees to any Person  (other than the Issuer) in connection  with  Indebtedness
Incurred by such plan or trust.

                  "Consolidated  Net  Income"  means,  for any  period,  the net
income  (loss)  of the  Issuer  and  its  consolidated  Subsidiaries;  provided,
however, that there shall not be included in such Consolidated Net Income:

                  (i) any net  income  (loss)  of any  Person  (other  than  the
         Issuer) if such Person is not a  Restricted  Subsidiary,  except  that,
         subject to the exclusion  contained in (iv) below,  the Issuer's equity
         in the net income of any such Person for such period  shall be included
         in such  Consolidated  Net  Income up to the  aggregate  amount of cash
         actually distributed by such Person during such period to the Issuer or
         a Restricted  Subsidiary as a dividend or other distribution  (subject,
         in the case of a dividend or other  distribution  paid to a  Restricted
         Subsidiary, to the limitations contained in clause (iii) below);

                  (ii) any net  income  (loss)  of any  Person  acquired  by the
         Issuer or a Subsidiary  in a pooling of interests  transaction  for any
         period prior to the date of such acquisition;

                  (iii) any net  income  of any  Restricted  Subsidiary  if such
         Restricted  Subsidiary  is  subject  to  restrictions  (other  than any
         restrictions permitted in Section 4.6), directly or indirectly,  on the
         payment of dividends or the making of  distributions by such Restricted
         Subsidiary,  directly or  indirectly,  to the  Issuer,  except that (A)
         subject to the  exclusion  contained  in clause (iv) below the Issuer's
         equity in the net  income of any such  Restricted  Subsidiary  for such
         period  shall be  included  in such  Consolidated  Net Income up to the
         aggregate  amount  of cash  actually  distributed  by  such  Restricted
         Subsidiary  during  such  period to the  Issuer or  another  Restricted
         Subsidiary as a dividend or other distribution (subject, in the case of
         a dividend or other distribution paid to another Restricted Subsidiary,
         to the limitation contained in this clause) and (B) solely for purposes
         of calculating the  Indebtedness to Adjusted EBITDA Ratio, the Issuer's
         equity in a net loss of any such Restricted  Subsidiary for such period
         shall be included in determining such Consolidated Net Income;

                  (iv)  any  gain or  loss  realized  upon  the  sale  or  other
         disposition of any assets of the Issuer, its consolidated  Subsidiaries
         or  any  other  Person  (including   pursuant  to  any   Sale/Leaseback
         Transaction) which is not sold or otherwise disposed of in the ordinary
         course of business and any gain or loss realized upon the sale or other
         disposition of any Capital Stock of any Person;

                  (v) any net  income  or loss of any  Unrestricted  Subsidiary,
         except  to  the  extent  distributed  to  the  Issuer  or  one  of  its
         Subsidiaries;

                  (vi)     any extraordinary gain or loss; and

                  (vii)  the  cumulative   effect  of  a  change  in  accounting
principles.

Notwithstanding the foregoing, for the purposes of Section 4.5 only, there shall
be excluded from  Consolidated Net Income any dividends,  repayments of loans or
advances or other  transfers  of assets from  Unrestricted  Subsidiaries  to the
Issuer or a Restricted  Subsidiary to the extent such

                                       5
<PAGE>   12

dividends,  repayments or transfers  increase the amount of Restricted  Payments
permitted under such covenant pursuant to clause (a)(3)(D) thereof.

                  "Consolidated  Tangible  Assets"  means,  with  respect to the
Issuer, the total consolidated  tangible assets of the Issuer and its Restricted
Subsidiaries, as shown on the most recent internal consolidated balance sheet of
the Issuer and such Restricted  Subsidiaries  calculated on a consolidated basis
in accordance with GAAP.

                  "Convertible Notes" means the Issuer's 6 3/4% Senior
Convertible Notes Due 2010.

                  "Credit  Facility"  means  any  debt  or  credit  facility  or
commercial  paper  facility  providing for revolving  credit loans,  term loans,
accounts receivable financing (including through the sale of accounts receivable
to such  lenders  or to  special  purpose  entities  formed to borrow  from such
lenders  against  such  accounts  receivable)  or letters  of  credit,  or other
non-convertible  debt securities or other form of debt financing,  in each case,
as amended,  restated,  supplemented,  extended,  modified,  renewed,  refunded,
replaced or refinanced in whole or in part from time to time, including any such
amendment, restatement, supplement, extension, modification, renewal, refunding,
replacement or refinancing  that increases the amount  borrowable  thereunder or
alters the maturity thereof.

                  "Currency  Agreement" means in respect of a Person any foreign
exchange  contract,  currency swap agreement or other similar agreement designed
to protect such Person against  fluctuations in currency values as to which such
Person is a party or a beneficiary.

                  "Default" means any event which is, or after notice or passage
of time or both would be, an Event of Default.

                  "Disqualified  Stock" means,  with respect to any Person,  any
Capital  Stock which by its terms (or by the terms of any security into which it
is  convertible  or for which it is  exchangeable)  or upon the happening of any
event (i)  matures  or is  mandatorily  redeemable  pursuant  to a sinking  fund
obligation or otherwise,  (ii) is convertible or  exchangeable  at the option of
the holder thereof for Indebtedness or Disqualified Stock or (iii) is redeemable
at the option of the  holder  thereof,  in whole or in part,  in each case on or
prior to the 91st day after the Stated Maturity of the Notes; provided, however,
that any  Capital  Stock that would not  constitute  Disqualified  Stock but for
provisions  thereof giving  holders  thereof the right to require such Person to
repurchase or redeem such Capital  Stock upon the  occurrence of an "asset sale"
or "change of control" occurring prior to the 91st day after the Stated Maturity
of the Notes  shall not  constitute  Disqualified  Stock if the "asset  sale" or
"change  of  control"  provisions  applicable  to  such  Capital  Stock  are not
materially  more favorable taken as a whole to the holders of such Capital Stock
than the provisions described under Section 4.9 and Section 4.7.

                  "EBITDA"  for any  period  means the sum of  Consolidated  Net
Income,   plus  the  following  to  the  extent  deducted  in  calculating  such
Consolidated Net Income: (a) Consolidated  Interest Expense;  (b) all income tax
expense  of  the  Issuer  and  its  consolidated  Restricted  Subsidiaries;  (c)
depreciation expense of the Issuer and its consolidated Restricted Subsidiaries;
(d)  amortization  expense  of  the  Issuer  and  its  consolidated   Restricted
Subsidiaries (excluding amortization expense attributable to a prepaid cash item
that was paid in a prior period);  (e) all

                                       6
<PAGE>   13

other  non-cash   charges  of  the  Issuer  and  its   consolidated   Restricted
Subsidiaries  (excluding  any  such  non-cash  charge  to  the  extent  that  it
represents an accrual of or reserve for cash expenditures in any future period);
and (f) any premium or penalty paid in connection with repurchasing,  redeeming,
retiring,  defeasing  or  acquiring  any  Indebtedness  prior to maturity to the
extent deducted in calculating  Consolidated  Net Income,  in each case for such
period.  Notwithstanding  the  foregoing,  the  provision for taxes based on the
income or profits of, and the depreciation and amortization and non-cash charges
of, a Restricted  Subsidiary  shall be added to the  Consolidated  Net Income to
compute  EBITDA  only to the extent  (and in the same  proportion)  that the net
income of such  Restricted  Subsidiary was included in calculating  Consolidated
Net Income and only if a corresponding  amount would be permitted at the date of
determination  to be paid  to the  Issuer  in the  form  of a  dividend  by such
Restricted  Subsidiary  without  prior  approval  (that has not been  obtained),
pursuant to the terms of its charter and all agreements, instruments, judgments,
decrees, orders, statutes, rules and governmental regulations applicable to such
Restricted Subsidiary or its stockholders, without in any event giving effect to
any restrictions or limitations permitted in Section 4.6.

                  "Equity  Offering"  means a public or private  issuance by the
Issuer of common stock of the Issuer for cash.

                  "Exchange Act" means the Securities Exchange Act of 1934, as
amended.

                  "GAAP" means generally accepted  accounting  principles in the
United States of America as in effect as of the Issue Date,  including those set
forth in (i) the opinions and pronouncements of the Accounting  Principles Board
of the American Institute of Certified Public  Accountants,  (ii) statements and
pronouncements  of the Financial  Accounting  Standards Board,  (iii) such other
statements  by such other  entity as  approved by a  significant  segment of the
accounting  profession  and (iv) the rules and  regulations of the SEC governing
the inclusion of financial statements (including pro forma financial statements)
in periodic  reports required to be filed pursuant to Section 13 of the Exchange
Act,  including  opinions and  pronouncements in staff accounting  bulletins and
similar written statements from the accounting staff of the SEC.

                  "Guarantee" means any obligation,  contingent or otherwise, of
any Person directly or indirectly  guaranteeing  any  Indebtedness of any Person
and any obligation,  direct or indirect, contingent or otherwise, of such Person
(i) to purchase or pay (or advance or supply  funds for the  purchase or payment
of) such  Indebtedness or other  obligation of such Person  (whether  arising by
virtue of partnership  arrangements,  or by agreements to keep-well, to purchase
assets,  goods,  securities or services, to take-or-pay or to maintain financial
statement  conditions  or  otherwise)  or (ii)  entered  into for the purpose of
assuring  in any other  manner the obligee of such  Indebtedness  of the payment
thereof or to protect such obligee  against loss in respect thereof (in whole or
in  part);  provided,  however,  that the term  "Guarantee"  shall  not  include
endorsements  for collection or deposit in the ordinary course of business.  The
term "Guarantee" used as a verb has a corresponding meaning.

                  "Hedging   Obligations"   of  any  Person   means  the  actual
obligations  of such Person  pursuant to any Interest Rate Agreement or Currency
Agreement.

                                       7
<PAGE>   14

                  "Holder" or "Noteholder" means the Person in whose name a Note
is registered on the Registrar's books.

                  "Incur"  means issue,  assume,  Guarantee,  incur or otherwise
become liable for; provided,  however, that any Indebtedness or Capital Stock of
a Person  existing  at the time such  Person  becomes a  Subsidiary  (whether by
merger, consolidation,  acquisition or otherwise) shall be deemed to be Incurred
by such Subsidiary at the time it becomes a Subsidiary  unless such Indebtedness
or  Capital  Stock is  repaid or  redeemed  on the date  such  Person  becomes a
Subsidiary.  The term  "Incurrence" when used as a noun shall have a correlative
meaning.

                  "Indebtedness" means, with respect to any Person on any date
of determination (without duplication):

                  (i) the  principal  in  respect  of (A)  indebtedness  of such
         Person for money  borrowed  and (B)  indebtedness  evidenced  by notes,
         debentures, bonds or other similar instruments for the payment of which
         such Person is  responsible  or liable,  including,  in each case,  any
         premium on such  indebtedness to the extent such premium has become due
         and payable;

                  (ii) all Capitalized  Lease Obligations of such Person and all
         Attributable  Debt in respect of  Sale/Leaseback  Transactions  entered
         into by such Person;

                  (iii) all  obligations of such Person issued or assumed as the
         deferred  purchase price of property,  all conditional sale obligations
         of such  Person  and all  obligations  of such  Person  under any title
         retention  agreement (but excluding  trade accounts  payable arising in
         the ordinary course of business);

                  (iv) all obligations of such Person for the  reimbursement  of
         any  obligor on any letter of credit,  banker's  acceptance  or similar
         credit  transaction  (other than obligations with respect to letters of
         credit and other  contingent  liabilities  (but only to the extent such
         contingent   liabilities  are  not  reflected  as  liabilities  on  the
         consolidated  balance sheet of such Person) securing obligations (other
         than obligations  described in clauses (i) through (iii) above) entered
         into in the  ordinary  course of  business of such Person to the extent
         such  letters  of credit  are not drawn  upon or, if and to the  extent
         drawn upon, such drawing is reimbursed no later than the tenth Business
         Day following payment on the letter of credit);

                  (v) the amount of all  obligations of such Person with respect
         to the redemption,  repayment or other  repurchase of any  Disqualified
         Stock  or,  with  respect  to  any  Subsidiary  of  such  Person,   the
         liquidation  preference  with  respect  to,  any  Preferred  Stock (but
         excluding, in each case, any accrued dividends);

                  (vi) all  obligations  of the type  referred to in clauses (i)
         through (v) above,  of other Persons and all dividends of other Persons
         for the payment of which, in either case, such Person is responsible or
         liable,  directly or  indirectly,  as obligor,  guarantor or otherwise,
         including by means of any Guarantee;

                                       8
<PAGE>   15

                  (vii) all  obligations  of the type referred to in clauses (i)
         through  (vi)  above,  of  other  Persons  secured  by any  Lien on any
         property or asset of such Person  (whether  or not such  obligation  is
         assumed by such Person),  the amount of such obligation being deemed to
         be the lesser of the value of such  property or assets or the amount of
         the obligation so secured; and

                  (viii)  to  the  extent  not   otherwise   included   in  this
         definition, Hedging Obligations of such Person.

The amount of  Indebtedness  of any Person at any date shall be the  outstanding
balance at such date of all unconditional  obligations as described above or the
accreted value thereof,  in the case of Indebtedness  issued with original issue
discount,  and the maximum  liability,  upon the  occurrence of the  contingency
giving rise to the obligation, of any contingent obligations at such date.

                  "Indebtedness  to  Adjusted  EBITDA  Ratio"  as of any date of
determination  means the ratio of (i) Consolidated  Indebtedness as of such date
to (ii) Adjusted EBITDA.

                  "Indenture" means this Indenture, as amended or supplemented
from time to time.

                  "Interest Rate Agreement" means with respect to any Person any
interest rate protection  agreement,  interest rate future  agreement,  interest
rate  option  agreement,   interest  rate  swap  agreement,  interest  rate  cap
agreement,  interest rate collar  agreement,  interest  rate hedge  agreement or
other similar  agreement or arrangement  designed to protect such Person against
fluctuations  in  interest  rates  as to  which  such  Person  is a  party  or a
beneficiary.

                  "Investment"  in any  Person  means  any  direct  or  indirect
advance,  loan (other than  advances to  customers,  lessees or licensees in the
ordinary  course of business  that are  recorded as accounts  receivable  on the
balance sheet of such Person) or other extension of credit  (including by way of
Guarantee or similar  arrangement)  or capital  contribution to (by means of any
transfer of cash or other  property  to others or any  payment  for  property or
services for the account or use of others),  or any purchase or  acquisition  of
Capital Stock,  Indebtedness or other similar instruments issued by such Person.
For purposes of the  definitions of  "Unrestricted  Subsidiary"  and "Restricted
Payment"  and  Section  4.5,  (i)   "Investment"   shall   include  the  portion
(proportionate  to the Issuer's equity interest in such  Subsidiary) of the fair
market value of the net assets of any  Subsidiary of the Issuer at the time that
such Subsidiary is designated an  Unrestricted  Subsidiary;  provided,  however,
that upon a  redesignation  of such Subsidiary as a Restricted  Subsidiary,  the
Issuer  shall be deemed  to  continue  to have a  permanent  "Investment"  in an
Unrestricted  Subsidiary  equal  to an  amount  (if  positive)  equal to (x) the
Issuer's  "Investment" in such Subsidiary at the time of such redesignation less
(y)  the  portion  (proportionate  to  the  Issuer's  equity  interest  in  such
Subsidiary) of the fair market value of the net assets of such Subsidiary at the
time that such Subsidiary is so re-designated a Restricted Subsidiary;  and (ii)
any property  transferred to or from an Unrestricted  Subsidiary shall be valued
at its  fair  market  value  at the  time of  such  transfer,  in  each  case as
determined in good faith by the Board of Directors and evidenced by a resolution
of such Board of Directors.

                  "Issue Date" means the date on which the Notes are originally
issued.

                                       9
<PAGE>   16

                  "Legal Holiday" has the meaning ascribed in Section 10.8.

                  "Lien"  means  any  mortgage,   pledge,   security   interest,
encumbrance, lien or charge of any kind (including any conditional sale or other
title retention agreement or lease in the nature thereof).

                  "Net  Available  Cash"  from an Asset  Disposition  means cash
payments  received  (including  any cash  payments  received  by way of deferred
payment of principal  pursuant to a note or installment  receivable or otherwise
and proceeds from the sale or other  disposition of any  securities  received as
consideration,   but  only  as  and  when  received,  but  excluding  any  other
consideration  received in the form of  assumption  by the  acquiring  Person of
Indebtedness  or other  obligations  relating  to such  properties  or assets or
received  in any other  non cash  form)  therefrom,  in each case net of (i) all
legal,  title,  accounting,  investment  banking  and  recording  tax  expenses,
commissions  and other  fees and  expenses  incurred,  and all  Federal,  state,
provincial,  foreign  and  local  taxes  required  to be  paid or  accrued  as a
liability  under GAAP,  as a  consequence  of such Asset  Disposition,  (ii) all
payments made on any Indebtedness which is secured by any assets subject to such
Asset  Disposition,  in  accordance  with the  terms  of any Lien  upon or other
security  arrangement of any kind with respect to such assets,  or which must by
its terms, or in order to obtain a necessary consent to such Asset  Disposition,
or by applicable law, be repaid out of the proceeds from such Asset Disposition,
(iii) all  distributions  and other  payments  required  to be made to  minority
interest  holders in Restricted  Subsidiaries  or joint  ventures as a result of
such Asset Disposition, (iv) the deduction of appropriate amounts to be provided
by the seller as a reserve,  in accordance  with GAAP,  against any  liabilities
associated with the assets disposed of in such Asset Disposition and retained by
the Issuer or any Restricted  Subsidiary after such Asset  Disposition,  and (v)
any  reserves  established  in  respect  of the  sales  price of such  asset for
post-closing  adjustments,  indemnification  purposes  or  employee  termination
expenses.

                  "Net Cash  Proceeds",  with respect to any issuance or sale of
Capital  Stock,  means  the  cash  proceeds  of such  issuance  or  sale  net of
attorneys' fees,  accountants' fees, printing costs,  underwriters' or placement
agents' fees, discounts or commissions and brokerage,  consultant and other fees
and expenses  actually incurred in connection with such issuance or sale and net
of taxes paid or payable as a result thereof.

                  "Non-Recourse Debt" means Indebtedness (i) as to which neither
the Issuer nor any  Restricted  Subsidiary  (a) provides any Guarantee or credit
support of any kind (including any undertaking,  Guarantee, indemnity, agreement
or  instrument  that  would  constitute  Indebtedness)  or  (b) is  directly  or
indirectly liable (as a guarantor or otherwise) and (ii) no default with respect
to which  (including  any  rights  that  the  holders  thereof  may have to take
enforcement  action  against an  Unrestricted  Subsidiary)  would  permit  (upon
notice,  lapse of time or both)  any  holder of any  other  Indebtedness  of the
Issuer or any  Restricted  Subsidiary  to  declare a default  under  such  other
Indebtedness  or cause the payment thereof to be accelerated or payable prior to
its stated maturity.

                  "Offering  Memorandum"  means the  Offering  Memorandum  dated
December  15,  2000  relating  to the  Initial  Notes;  provided  that after the
issuance of Exchange Notes, all
                                       10
<PAGE>   17


references  herein to "Offering  Memorandum"  shall be deemed  references to the
prospectus  contained  in the  registration  statement  relating to the Exchange
Notes.

                  "Officer" means the Chairman of the Board, the President,  the
Chief Executive Officer,  any Vice President,  the Chief Financial Officer,  the
Treasurer or the Secretary of the Issuer, as applicable.

                  "Officer's Certificate" means a certificate signed by any
Officer.

                  "Opinion of Counsel" means a written opinion that meets the
requirements of Section 10.5 hereof from Dow,  Lohnes & Albertson,  PLLC, or any
other legal counsel who is reasonably acceptable to the Trustee. The counsel may
be an employee of or counsel to the Issuer or the Trustee.

                  "Permitted  Acquisition  Indebtedness"  means  Indebtedness or
acquired  debt in an aggregate  principal  amount not to exceed $50.0 million at
any one time outstanding, incurred or assumed in connection with the acquisition
of an  entity  that is  engaged  in a  Permitted  Business  and that  becomes  a
Restricted  Subsidiary or the acquisition of any assets  constituting a business
or line of business as determined by the Board of Directors, that is a Permitted
Business or incurred by such entity or the owner of such assets and  outstanding
on the date of such acquisition.

                  "Permitted  Business"  means  any  business  conducted  by the
Issuer and its Restricted  Subsidiaries on the Issue Date and any other business
related, ancillary or complementary to any such business.

                  "Permitted  Holders"  means any or all of  Stephen  H.  Clark,
David P. Tomick,  Joe L. Finley,  Welsh,  Carson,  Anderson & Stowe, VIII, L.P.,
WCAS  Information  Partners,  L.P.,  WCAS  Capital  Partners  III,  L.P.,  their
respective general partners,  employees of Welsh, Carson, Anderson & Stowe, CIBC
WG Argosy Merchant Fund 2, L.L.C., Co-Investment Merchant Fund 3, LLC, Caravelle
Investment Fund, L.L.C., Tower Parent Corp., Whitney Equity Partners, L.P., J.H.
Whitney III, L.P.,  Whitney Strategic Partners III, L.P., J.H. Whitney Mezzanine
Fund,  L.P.,  Waller-Sutton  Media  Partners,  L.P.,  Kitty Hawk Capital Limited
Partnership,  III,  Kitty Hawk  Capital  Limited  Partnership,  IV,  Eagle Creek
Capital, L.L.C., The North Carolina Enterprise Fund, L.P., Finley Family Limited
Partnership, and their respective Affiliates.

                  "Permitted  Investment"  means an  Investment by the Issuer or
any Restricted Subsidiary in (i) the Issuer, a Restricted Subsidiary or a Person
which will, upon the making of such Investment,  become a Restricted Subsidiary;
(ii)  another  Person if as a result of such  Investment  such  other  Person is
merged  or   consolidated   with  or  into,  or  transfers  or  conveys  all  or
substantially  all  its  assets  to,  the  Issuer  or a  Restricted  Subsidiary;
provided,  however, that such Person's primary business is a Permitted Business;
(iii) Temporary Cash  Investments;  (iv) receivables  owing to the Issuer or any
Restricted Subsidiary, if created or acquired in the ordinary course of business
and payable or dischargeable in accordance with customary trade terms; provided,
however, that such trade terms may include such concessionary trade terms as the
Issuer  or  any  such  Restricted   Subsidiary   deems   reasonable   under  the
circumstances;  (v) payroll,  travel and similar  advances to cover matters that
are expected at the time of such

                                       11
<PAGE>   18

advances  ultimately to be treated as expenses for accounting  purposes and that
are made in the ordinary course of business; (vi) loans or advances to employees
made in the ordinary  course of business  consistent  with past  practice of the
Issuer or such  Restricted  Subsidiary,  but in any  event  not to  exceed  $2.0
million in the aggregate  outstanding at any one time; (vii) stock,  obligations
or securities  received in settlement of debts created in the ordinary course of
business and owing to the Issuer or any Restricted Subsidiary or in satisfaction
of judgments or pursuant to any plan of  reorganization  or similar  arrangement
upon the  bankruptcy or insolvency of a debtor;  (viii) any Person to the extent
such investment  represents the non-cash portion of the  consideration  received
for an Asset  Disposition  as permitted  pursuant to Section  4.7;  (ix) Capital
Stock  of the  Issuer  or  any  Restricted  Subsidiary  purchased,  redeemed  or
otherwise acquired or retired for value from members of the Issuer's  management
or  employees,  but in any event not to exceed $2.0  million in aggregate in any
twelve-month  period;  (x) other  Investments  in  Permitted  Businesses  not to
exceed,  at any one time outstanding  (each such Investment being measured as of
the date made and without giving effect to subsequent changes in value), the sum
of (x) $10.0 million and 10% of the Issuer's  Consolidated Tangible Assets; (xi)
any Interest Rate  Agreement or Currency  Agreement;  (xii) any  acquisition  of
assets to the extent the consideration therefor consists of Capital Stock (other
than  Disqualified  Stock) of the Issuer;  (xiii) prepaid  expenses,  negotiable
instruments  held for collection and lease,  utility and workers'  compensation,
performance and other similar deposits;  (xiv) deposits of proceeds or Qualified
Proceeds from Asset  Dispositions  with a "qualified  intermediary,"  "qualified
trustee" or similar person for purposes of  facilitating a "like-kind"  exchange
made in  accordance  with  the  applicable  provisions  of the  Code;  provided,
however,  that the making of any  Permitted  Investment  pursuant to this clause
(xiv) will not in any manner violate Section 4.7; (xv)  Investments in an amount
not to exceed the Net Cash  Proceeds or  Qualified  Proceeds of the  issuance or
sale, other than to a Subsidiary of the Issuer,  of Capital Stock of the Issuer,
other than  Disqualified  Stock,  to the extent  that such Net Cash  Proceeds or
Qualified  Proceeds  have not been  applied to make a  Restricted  Payment or to
effect other transactions pursuant to Section 4.5 or to the extent such Net Cash
Proceeds or Qualified  Proceeds  have not been used to Incur  Indebtedness;  and
(xvi)  other  Investments  not to  exceed,  at any one time  outstanding,  $75.0
million.

                  "Permitted  Liens"  means,  with  respect to any  person,  (a)
pledges  or  deposits  by  such  Person  under   worker's   compensation   laws,
unemployment  insurance laws or similar  legislation,  or good faith deposits in
connection  with  bids,  tenders,  contracts  (other  than  for the  payment  of
Indebtedness)  or leases to which such Person is a party,  or deposits to secure
public or  statutory  obligations  of such  Person or deposits or cash or United
States government bonds to secure surety or appeal bonds to which such Person is
a party, or deposits as security for contested taxes or import duties or for the
payment of rent, in each case incurred in the ordinary  course of business;  (b)
Liens  imposed  by  law,  such  as  carriers',  warehousemen's,  landlords'  and
mechanics'  Liens,  in each case for sums not yet due or being contested in good
faith by appropriate proceedings,  or judgment Liens not giving rise to an Event
of Default so long as any appropriate legal proceedings which may have been duly
initiated for the review of such judgment shall not have been finally terminated
or the period  within which such  proceedings  may be  initiated  shall not have
expired;  (c)  Liens  for  property  taxes  not yet  subject  to  penalties  for
non-payment  or  which  are  being   contested  in  good  faith  by  appropriate
proceedings;  (d) Liens in favor of issuers of surety bonds or letters of credit
issued  pursuant  to the  request of and for the  account of such  Person in the
ordinary course of its business; (e) survey exceptions,  encumbrances, easements
or reservations  of, or rights of others for,  licenses,  rights of way,

                                       12
<PAGE>   19

sewers,  electric  lines,  telegraph  and  telephone  lines  and  other  similar
purposes,  or zoning or other  restrictions  as to the use of real properties or
liens  incidental  to the  conduct  of the  business  of such  Person  or to the
ownership  of  its  properties  which  were  not  incurred  in  connection  with
Indebtedness and which do not in the aggregate  materially  adversely affect the
value of said properties or materially  impair their use in the operation of the
business of such Person;  (f) Liens securing Hedging  Obligations so long as the
related Indebtedness is, and is permitted to be under this Indenture, secured by
a Lien on the same property  securing such Hedging  Obligations;  (g) leases and
subleases of real property which do not interfere  with the ordinary  conduct of
the  business  of the Issuer or any of its  Restricted  Subsidiaries,  and Liens
securing the obligations  (other than  Indebtedness) of the Issuer or any of the
Restricted  Subsidiaries  under any such leases and subleases of real  property;
(h) Liens existing as of the date on which the Notes are  originally  issued and
Liens created by this  Indenture;  (i) Liens  created  solely for the purpose of
securing the payment of all or part of the purchase  price of assets or property
acquired or  constructed  in the ordinary  course of business  after the date on
which  the  Notes  are  originally  issued;  provided,  however,  that  (A)  the
Indebtedness  secured by such Liens shall have  otherwise  been  permitted to be
issued  under this  Indenture  and (B) such Liens shall not  encumber  any other
assets or  property  of the Issuer or any of its  Restricted  Subsidiaries;  (j)
Liens on the  assets  or  property  of a  Restricted  Subsidiary  of the  Issuer
existing  at the time such  Restricted  Subsidiary  became a  Subsidiary  of the
Issuer and not incurred as a result of (or in connection with or in anticipation
of) such Restricted  Subsidiary  becoming a Subsidiary of the Issuer;  provided,
however,  that (A) any such  Lien does not by its terms  cover any  property  or
assets after the time such Restricted Subsidiary becomes a Subsidiary which were
not covered  immediately  prior to such  transaction,  (B) the Incurrence of the
Indebtedness  secured by such Lien shall have  otherwise  been  permitted  to be
issued  under this  Indenture,  and (C) such Liens do not extend to or cover any
other  property or assets of the Issuer or any of its  Restricted  Subsidiaries;
(k) Liens  securing  Indebtedness  outstanding  under a Credit  Facility and any
other Liens securing Indebtedness  permitted under this Indenture to be Incurred
by a Restricted Subsidiary; (l) Liens extending,  renewing or replacing in whole
or in part a Lien permitted by this Indenture;  provided, however, that (A) such
Liens do not  extend  beyond  the  property  subject  to the  existing  Lien and
improvements and construction on such property and (B) the Indebtedness  secured
by the Lien may not exceed the Indebtedness  secured at the time by the existing
Lien; (m) Liens Incurred in the ordinary course of business by the Issuer or any
Restricted  Subsidiary  of the Issuer with  respect to  obligations  that do not
exceed $25.0 million at any one time  outstanding  and that (i) are not Incurred
in connection with the borrowing of money or the obtaining of advances of credit
(other than trade credit in the ordinary  course of business) and (ii) do not in
the  aggregate  materially  detract from the value of the property or materially
impair  the use  thereof  in the  operation  of  business  by the Issuer or such
Restricted  Subsidiary;  (n)  Liens  in  favor  of the  Issuer  or a  Restricted
Subsidiary;  (o) any interest in or title of a lessor to any property subject to
a Capitalized  Lease  Obligation  permitted to be Incurred under this Indenture;
(p)  Liens on the  Capital  Stock of  Unrestricted  Subsidiaries;  (q) the Liens
granted pursuant to the terms of the Security and  Subordination  Agreement,  as
amended,  modified or supplemented  from time to time,  entered into pursuant to
the terms of the  Agreement  and Plan of Merger,  dated as of February 10, 1999,
among the Issuer, SpectraSite Communications, Inc., SHI Merger Sub, Inc., Nextel
Communications,  Inc.  and  certain of its  subsidiaries;  (r) Liens,  rights of
set-off or similar  rights and  remedies  as to deposit  accounts or other funds
maintained  with a  depository  or other  financial  institution;  (s)  Liens on
property  subject to  Capitalized  Lease  Obligations  to the extent

                                       13
<PAGE>   20

the related  Capitalized  Lease  Obligation  is permitted  to be incurred  under
Section  4.3 or Section  4.4 of this  Indenture;  (t) Liens on  property  of the
Issuer  or a  Restricted  Subsidiary  at  the  time  the  Issuer  or  Restricted
Subsidiary acquired the property, including any acquisition by means of a merger
or consolidation with or into the Issuer or any Restricted Subsidiary; provided,
however,  that such Liens are not  created,  incurred  or assumed in  connection
with, or in contemplation of, such acquisition,  provided further, however, that
such  Liens  may not  extend to any other  property  owned by the  Issuer or any
Restricted  Subsidiary;  and (u)  Liens on  government  securities  that  secure
Indebtedness,  to the extent that such government  securities are purchased with
the proceeds of such Indebtedness.

                  "Person" means any individual, corporation, partnership, joint
venture,  limited liability company,  association,  joint-stock company,  trust,
unincorporated  organization,  government or any agency or political subdivision
thereof or any other entity.

                  "Preferred  Stock",  as  applied to the  Capital  Stock of any
Person,  means Capital Stock of any class or classes (however  designated) which
is  preferred  as to the payment of  dividends  or  distributions,  or as to the
distribution  of  assets  upon  any  voluntary  or  involuntary  liquidation  or
dissolution  of such Person,  over shares of Capital Stock of any other class of
such Person.

                  "Principal" of a Note means the principal of the Note plus the
premium, if any, payable on the Note which is due or overdue or is to become due
at the relevant time.

                  "Qualified  Proceeds" means assets that are used or useful in,
or Capital Stock of any Person engaged in, a Permitted Business.

                  "Refinance"   means,  in  respect  of  any  Indebtedness,   to
refinance,  extend, renew, refund, repay, prepay, redeem,  purchase,  defease or
retire,  or to issue other  Indebtedness  in exchange or  replacement  for, such
indebtedness. "Refinanced" and "Refinancing" shall have correlative meanings.

                  "Refinancing  Indebtedness" means Indebtedness that Refinances
any Indebtedness of the Issuer or any Restricted Subsidiary existing on the date
of this  Indenture  or Incurred in  compliance  with this  Indenture  (including
Indebtedness  of the  Issuer  that  Refinances  Indebtedness  of any  Restricted
Subsidiary  and  Indebtedness  of  any  Restricted  Subsidiary  that  Refinances
Indebtedness  of another  Restricted  Subsidiary)  including  Indebtedness  that
Refinances Refinancing Indebtedness; provided, however, that (i) the Refinancing
Indebtedness  has a Stated  Maturity  no earlier  than the earlier of the Stated
Maturity  of the  Notes  and  the  Stated  Maturity  of the  Indebtedness  being
Refinanced,  (ii) the Refinancing  Indebtedness  has an Average Life at the time
such  Refinancing  Indebtedness is Incurred that is equal to or greater than the
lesser of the Average Life of the Indebtedness  being Refinanced and the Average
Life of the Notes and (iii) such  Refinancing  Indebtedness  is  Incurred  in an
aggregate  principal  amount (or if issued  with  original  issue  discount,  an
aggregate  issue  price) that is equal to or less than the sum of the  aggregate
principal  amount (or if issued with  original  issue  discount,  the  aggregate
accreted value) then outstanding or committed (plus fees and expenses, including
any premium and  defeasance  costs)  under the  Indebtedness  being  Refinanced;
provided further,  however, that Refinancing  Indebtedness shall not include (x)
Indebtedness of a Subsidiary  that Refinances  Indebtedness of the Issuer or (y)

                                       14
<PAGE>   21

Indebtedness of the Issuer or a Subsidiary  that  refinances  Indebtedness of an
Unrestricted Subsidiary.

                  "Restricted  Payment" with respect to any Person means (i) the
declaration or payment of any dividends or any other  distributions  of any sort
in respect of its  Capital  Stock or similar  payment to the direct or  indirect
holders of its Capital  Stock in respect  thereof  (other than (a)  dividends or
distributions  payable  solely in its Capital  Stock  (other  than  Disqualified
Stock),  (b)  dividends  or  distributions  payable  solely  to the  Issuer or a
Restricted Subsidiary, and (c) pro rata dividends or other distributions made by
a Subsidiary that is not a Wholly Owned Subsidiary to minority  stockholders (or
owners of an equivalent  interest in the case of a Subsidiary  that is an entity
other than a corporation)),  (ii) the purchase,  redemption or other acquisition
or retirement for value of any Capital Stock of the Issuer held by any Person or
of any Capital Stock of a Restricted  Subsidiary  held by any Person (other than
the Issuer or a Restricted Subsidiary), other than the exercise by the Issuer of
any option to convert or exchange any Capital Stock into Indebtedness so long as
such  Indebtedness  is permitted to be Incurred as of the date of such  exercise
pursuant to this  Indenture,  and other than as  permitted by clause (ix) of the
definition  of  "Permitted   Investments";   (iii)  the  purchase,   repurchase,
redemption,  defeasance or other  acquisition or retirement for value,  prior to
scheduled maturity, scheduled repayment or scheduled sinking fund payment of any
Subordinated   Obligations  (other  than  the  purchase,   repurchase  or  other
acquisition of Subordinated  Obligations purchased in anticipation of satisfying
a sinking fund obligation, principal installment or final maturity, in each case
due  within  one year of the date of  acquisition);  or (iv) the  making  of any
Investment in any Person (other than a Permitted Investment).

                  "Restricted Subsidiary" means any Subsidiary of the Issuer
other than an Unrestricted Subsidiary.

                  "Sale/Leaseback  Transaction" means an arrangement relating to
property  now owned or  hereafter  acquired  whereby the Issuer or a  Restricted
Subsidiary  transfers  such  property to a Person and the Issuer or a Restricted
Subsidiary leases it from such Person.

                  "SEC" means the U.S. Securities and Exchange Commission.

                  "Secured Indebtedness" means any Indebtedness of the Issuer
secured by a Lien.

                  "Securities Act" means the Securities Act of 1933, as amended.

                  "Senior  Indebtedness"  means (i)  Indebtedness of the Issuer,
whether outstanding on the Issue Date or thereafter  Incurred,  and (ii) accrued
and unpaid interest  (including  interest accruing on or after the filing of any
petition  in  bankruptcy  or for  reorganization  relating  to the Issuer to the
extent  post-filing  interest is allowed in such  proceeding)  in respect of (A)
indebtedness of the Issuer for money borrowed and (B) indebtedness  evidenced by
notes,  debentures,  bonds or other similar instruments for the payment of which
the Issuer is responsible or liable unless,  in the case of (i) and (ii), in the
instrument  creating  or  evidencing  the same or  pursuant to which the same is
outstanding,  it is provided that such  obligations  are subordinate in right of
payment to the Notes;  provided,  however,  that Senior  Indebtedness  shall not
include (1) any  obligation of the Issuer to any  Subsidiary,  (2) any liability
for Federal,  state,  local or

                                       15
<PAGE>   22

other  taxes  owed or owing by the  Issuer,  (3) any  accounts  payable or other
liability  to  trade  creditors  arising  in the  ordinary  course  of  business
(including guarantees thereof or instruments  evidencing such liabilities),  (4)
any  Indebtedness  of the Issuer (and any accrued and unpaid interest in respect
thereof) which is subordinate or junior in any respect to any other Indebtedness
or other obligation of the Issuer, (5) that portion of any Indebtedness which at
the time of Incurrence is Incurred in violation of this Indenture.

                  "Significant  Subsidiary" means any Restricted Subsidiary that
would be a  "Significant  Subsidiary"  of the Issuer  within the meaning of Rule
1-02 under Regulation S-X promulgated by the SEC.

                  "Site  Management  Contract"  means any agreement  pursuant to
which  the  Issuer  or any of its  Restricted  Subsidiaries  has  the  right  to
substantially  control Tower Assets and the revenues  derived from the rental or
use thereof.

                  "Stated  Maturity"  means,  with respect to any security,  the
date  specified  in such  security  as the fixed  date on which the  payment  of
principal  of  such  security  is due and  payable,  including  pursuant  to any
mandatory  redemption  provision (but excluding any provision  providing for the
repurchase  of such  security  at the  option  of the  holder  thereof  upon the
happening  of any  contingency  beyond the  control of the  issuer  unless  such
contingency has occurred).

                  "Subordinated Obligation" means any Indebtedness of the Issuer
(whether  outstanding  on the  Issue  Date  or  thereafter  Incurred)  which  is
subordinate  or junior in right of  payment to the Notes  pursuant  to a written
agreement.

                  "Subsidiary" of any Person means any corporation, association,
partnership or other business  entity of which more than 50% of the total voting
power of shares  of  Capital  Stock or other  interests  (including  partnership
interests)  entitled  (without  regard to the occurrence of any  contingency) to
vote in the election of directors,  managers or trustees  thereof is at the time
owned or  controlled,  directly or  indirectly,  by (i) such  Person,  (ii) such
Person  and one or  more  Subsidiaries  of  such  Person  or  (iii)  one or more
Subsidiaries of such Person.

                  "Temporary Cash Investments"  means any of the following:  (i)
any  investment  in direct  obligations  of the United  States of America or any
agency thereof or obligations  Guaranteed by the United States of America or any
agency  thereof,  (ii)  investments in time deposit  accounts,  certificates  of
deposit  and  money  market  deposits  maturing  within  one year of the date of
acquisition  thereof issued by a bank or trust company which is organized  under
the laws of the United  States of  America,  any state  thereof  or any  foreign
country  recognized by the United States of America having capital,  surplus and
undivided  profits  aggregating  in  excess of $500.0  million  (or the  foreign
currency  equivalent  thereof)  and whose  long-term  debt is rated "A" (or such
similar  equivalent  rating)  or higher by at least  one  nationally  recognized
statistical  rating  organization  (as defined in Rule 436 under the  Securities
Act) or any money market fund sponsored by a registered  broker dealer or mutual
fund distributor,  (iii) repurchase  obligations with a term of not more than 30
days for  underlying  securities  of the types  described  in  clause  (i) above
entered  into with a bank  meeting the  qualifications  described in clause (ii)
above,  (iv)  investments in commercial  paper,  maturing not more than 270 days
after the date of acquisition,

                                       16
<PAGE>   23

issued by a corporation (other than an Affiliate of the Issuer) organized and in
existence  under the laws of the United States of America or any foreign country
recognized by the United States of America with a rating at the time as of which
any  investment  therein  is made of "P-1"  (or  higher)  according  to  Moody's
Investors  Service,  Inc. or " A-1" (or higher)  according  to Standard & Poor's
Ratings Group,  and (v) investments in 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 of America,  or by any political
subdivision or taxing  authority  thereof,  and rated at least "A" by Standard &
Poor's Ratings Group or "A" by Moody's Investors Service, Inc.

                  "TIA" means the Trust Indenture Act of 1939 (15 U.S.C. ss.ss.
77aaa-77bbbb) as in effect on the date of this Indenture.

                  "Tower  Asset  Exchange"  means any  transaction  in which the
Issuer or a  Restricted  Subsidiary  exchanges  assets for Tower Assets or Tower
Assets and cash or cash equivalents  where the fair market value (evidenced by a
resolution  of the  Board of  Directors)  of the Tower  Assets  and cash or cash
equivalents  received  by the Issuer  and its  Restricted  Subsidiaries  in such
exchange is at least equal to the fair  market  value of the assets  disposed in
such exchange.

                  "Tower  Assets" means  communication  transmission  towers and
related assets that are located on the site of a transmission tower.

                  "Tower EBITDA" means, for any period, the EBITDA of the Issuer
and its Restricted Subsidiaries for such period that is directly attributable to
site  rental  revenue,  license  or  management  fees paid to  manage,  lease or
sublease  space on  communication  sites owned,  leased or managed by the Issuer
(collectively,  "site leasing revenues"), all determined on a consolidated basis
and in accordance with GAAP.  Tower EBITDA will not include revenue derived from
the sale of assets. In allocating corporate,  general,  administrative and other
operating  expenses that are not allocated to any particular line of business in
the financial  statements of the Issuer, such expenses shall be allocated to the
Issuer's site leasing  business in proportion to the  percentage of the Issuer's
total revenues for the applicable period that were site leasing revenues.

                  "Trust  Officer"  means  any  trust  officer,  assistant  vice
president,  or  vice  president  of  the  Trustee  assigned  by the  Trustee  to
administer this Indenture.

                  "Trustee"  means  the  party  named as such in this  Indenture
until a successor replaces it and, thereafter, means such successor.

                  "2008 Notes" means the Issuer's 12% Senior Discount Notes Due
2008.

                  "2009 Notes" means the Issuer's 11 1/4% Senior  Discount Notes
Due 2009.

                  "2010  Notes" means the Issuer's 10 3/4% Senior Notes Due 2010
and the Issuer's 127/8% Senior Discount Notes Due 2010.


                  "Uniform Commercial Code" means the New York Uniform
Commercial Code as in effect from time to time.

                                       17
<PAGE>   24

                  "Unrestricted Subsidiary" means (i) SpectraSite International,
Inc. and any other  Subsidiary  of the Issuer that at the time of  determination
shall be designated an Unrestricted  Subsidiary by the Board of Directors in the
manner provided below and (ii) any Subsidiary of an Unrestricted Subsidiary. The
Board of Directors  may designate any  Subsidiary of the Issuer  (including  any
newly acquired or newly formed  Subsidiary of the Issuer) to be an  Unrestricted
Subsidiary  unless such Subsidiary or any of its  Subsidiaries  owns any Capital
Stock or  Indebtedness  of, or owns or holds any Lien on any  property  of,  the
Issuer or any other Restricted Subsidiary of the Issuer that is not a Subsidiary
of the Subsidiary to be so designated;  provided,  however,  that either (A) the
Subsidiary to be so designated has total  consolidated  assets of $1,000 or less
or (B) if such Subsidiary has consolidated assets greater than $1,000, then such
designation  would be permitted  under  Section 4.5. The Board of Directors  may
designate any Unrestricted  Subsidiary to be a Restricted Subsidiary;  provided,
however, that (a) immediately after giving effect to such designation no Default
shall have occurred and be continuing and (b) such  designation  shall be deemed
to  be  an  Incurrence  of  Indebtedness  by  a  Restricted  Subsidiary  of  any
outstanding  Indebtedness of such  Unrestricted  Subsidiary and such designation
shall only be permitted if such  Indebtedness is permitted under this Indenture.
Any such designation by the Board of Directors shall be evidenced to the Trustee
by promptly  filing with the  Trustee a copy of the  resolution  of the Board of
Directors  giving  effect  to  such  designation  and an  Officer's  Certificate
certifying that such designation complied with the foregoing provisions.

                  "U.S.  Government  Obligations"  means direct  obligations (or
certificates  representing  an ownership  interest in such  obligations)  of the
United States of America (including any agency or  instrumentality  thereof) for
the  payment of which the full faith and credit of the United  States of America
is pledged and which are not callable or redeemable at the Issuer's option.

                  "Voting  Stock" of a Person means all classes of Capital Stock
or  other  interests  (including  partnership  interests)  of such  Person  then
outstanding  and normally  entitled  (without  regard to the  occurrence  of any
contingency) to vote in the election of directors, managers, or trustee thereof.

                  "Wholly Owned Subsidiary" means a Restricted Subsidiary of the
Issuer all the Capital Stock of which (other than directors'  qualifying shares)
is owned by the Issuer or another Wholly Owned Subsidiary.





                  SECTION 1.2.  Other Definitions.

                           Term                         Defined in Section

                 "Affiliate Transaction"                       4.8
                 "Appendix"                                    2.1
                 "Authenticating Agent"                        2.2

                                       18
<PAGE>   25


                 "Bankruptcy Law"                              6.1
                 "covenant defeasance option"               8.1(b)
                 "Custodian"                                   6.1
                 "Event of Default"                            6.1
                 "legal defeasance option"                  8.1(b)
                 "Offer"                                    4.7(b)
                 "Offer Amount"                          4.7(c)(2)
                 "Offer Period"                          4.7(c)(2)
                 "Paying Agent"                                2.3
                 "Purchase Date"                         4.7(c)(1)
                 "Registrar"                                   2.3
                 "Successor Issuer"                         5.1(i)


                  SECTION 1.3.  Incorporation  by  Reference of Trust  Indenture
Act. The mandatory  provisions of the TIA are  incorporated  by reference in and
made a part of this  Indenture.  The  following  TIA  terms  have the  following
meanings:

                  "Commission" means the SEC.

                  "indenture securities" means the Notes.

                  "indenture security holder" means a Holder.

                  "indenture to be qualified" means this  Indenture.

                  "indenture trustee" or "institutional  trustee" means the
Trustee.

                  "obligor" on the indenture securities means the Issuer and any
other obligor on the indenture securities.

                  All other TIA terms used in this Indenture that are defined by
the TIA, defined by TIA reference to another statute or defined by SEC rule have
the meanings assigned to them by such definitions.

                  SECTION 1.4.  Rules of Construction.  Unless the context
otherwise requires:

                  (1)      a term has the meaning assigned to it;

                  (2) an accounting  term not otherwise  defined has the meaning
         assigned to it in accordance with GAAP;

                  (3)      "or" is not exclusive;

                  (4)      "including" means including without limitation;

                  (5) words in the singular  include the plural and words in the
plural include the singular;

                                       19
<PAGE>   26

                  (6)  unsecured   Indebtedness   shall  not  be  deemed  to  be
         subordinate or junior to Secured  Indebtedness  merely by virtue of its
         nature as unsecured Indebtedness;

                  (7) except as  otherwise  expressly  provided,  the  principal
         amount of any  noninterest  bearing or other  discount  security at any
         date shall be the  principal  amount  thereof  that would be shown on a
         balance sheet of the issuer dated such date prepared in accordance with
         GAAP;

                  (8) the principal  amount of any Preferred  Stock shall be (i)
         the maximum liquidation  preference of such Preferred Stock or (ii) the
         maximum mandatory redemption or mandatory repurchase price with respect
         to such Preferred Stock, whichever is greater; and

                  (9) except as otherwise expressly provided,  all references to
         the date the Notes were  originally  issued shall refer to the date the
         Initial Notes were originally issued.

                  SECTION  1.5.  One  Class of Notes.  The  Initial  Notes,  the
Private Exchange Notes and the Exchange Notes shall vote and consent together on
all matters as one class and none of the  Initial  Notes,  the Private  Exchange
Notes or the  Exchange  Notes  shall  have the  right  to vote or  consent  as a
separate class on any matter.

                                   ARTICLE II
                                    THE NOTES

                  SECTION 2.1. Form and Dating.  Certain provisions  relating to
the Initial  Notes,  the Private  Exchange  Notes and the Exchange Notes are set
forth in the Rule  144A/Regulation  S Appendix attached hereto (the "Appendix"),
which is hereby incorporated in and expressly made a part of this Indenture. The
Initial Notes and the Trustee's  certificate of authentication  thereof shall be
substantially  in the  form  of  Exhibit  1 to the  Appendix,  which  is  hereby
incorporated in and expressly made a part of this Indenture. The Exchange Notes,
the Private  Exchange  Notes and the  Trustee's  certificate  of  authentication
thereof  shall  be  substantially  in the form of  Exhibit  A,  which is  hereby
incorporated by reference and expressly made a part of this Indenture. The Notes
may  have  notations,  legends  or  endorsements  required  by law,  rule of any
securities  exchange  or  over-the-counter  market on which  such Notes are then
listed or quoted,  or usage,  in addition to those set forth on the Appendix and
Exhibit A. The Issuer and the Trustee  shall  approve the forms of the Notes and
any notation,  endorsement or legend on them.  Each Note shall be dated the date
of its  authentication.  The terms of the Notes  set forth in the  Appendix  and
Exhibit A are part of the terms of this Indenture and, to the extent applicable,
the Issuer and the Trustee,  by their  execution and delivery of this Indenture,
expressly agree to be bound by such terms.

                  SECTION 2.2.  Execution and Authentication.  Two Officers
shall sign the Notes for the Issuer by manual or facsimile signature.

                  If an Officer  whose  signature  is on a Note no longer  holds
that office at the time the Trustee  authenticates  the Note,  the Note shall be
valid nevertheless.

                                       20
<PAGE>   27

                  A Note shall not be valid until an authorized signatory of the
Trustee manually  authenticates the Note. The signature of the Trustee on a Note
shall  be  conclusive  evidence  that  such  Note  has  been  duly  and  validly
authenticated and issued under this Indenture.

                  The Trustee may appoint an agent (the "Authenticating  Agent")
reasonably acceptable to the Issuer to authenticate the Notes. Unless limited by
the terms of such appointment,  any such  Authenticating  Agent may authenticate
Notes  whenever  the Trustee  may do so. Each  reference  in this  Indenture  to
authentication by the Trustee includes authentication by such agent.

                  SECTION 2.3.  Registrar and Paying Agent. The Issuer shall (i)
appoint an agent (the  "Registrar") who shall maintain an office or agency where
Notes may be presented for  registration of transfer or for exchange and (ii) an
agent (the  "Paying  Agent") who shall  maintain an office or agency where Notes
may be presented for payment.  The Registrar  shall keep a register of the Notes
and  of  their  transfer  and  exchange.   The  Issuer  may  have  one  or  more
co-registrars and one or more additional paying agents.  The term "Paying Agent"
includes any such additional paying agent.

                  In the event the Issuer shall retain any Person not a party to
this Indenture as an agent hereunder, the Issuer shall enter into an appropriate
agency agreement with any Registrar, Paying Agent or co-registrar not a party to
this  Indenture,  which shall  incorporate  the terms of the TIA. The  agreement
shall implement the provisions of this Indenture that relate to such agent.  The
Issuer shall  notify the Trustee of the name and address of each such agent.  If
the Issuer fails to maintain a Registrar or Paying Agent,  the Trustee shall act
as such and shall be entitled to appropriate  compensation  therefor pursuant to
Section 7.7.  The Issuer or any of its  domestically  incorporated  Wholly Owned
Subsidiaries may act as Paying Agent.

                  The Issuer  initially  appoints the Trustee as  Registrar  and
Paying Agent for the Notes.

                  SECTION 2.4.  Paying Agent to Hold Money in Trust. By at least
11:00 a.m.  (New York City time) on the date on which any  principal or interest
on any Note is due and payable, the Issuer shall deposit with the Paying Agent a
sum  sufficient  to pay such  principal  or interest  when due. The Issuer shall
require each Paying Agent (other than the Trustee) to agree in writing that such
Paying Agent shall hold in trust for the benefit of  Noteholders  or the Trustee
all money held by such Paying  Agent for the payment of principal or interest on
the Notes and shall  notify the  Trustee of any  default by the Issuer in making
any such payment.  If the Issuer or a Subsidiary  acts as Paying Agent, it shall
segregate  the money held by it as Paying Agent and hold it as a separate  trust
fund. The Issuer at any time may require a Paying Agent (other than the Trustee)
to pay all  money  held  by it to the  Trustee  and to  account  for  any  funds
disbursed by such Paying Agent.  Upon  complying  with this Section,  the Paying
Agent (if other than the Issuer or a Subsidiary) shall have no further liability
for the money delivered to the Trustee.  Upon any bankruptcy,  reorganization or
similar proceeding with respect to the Issuer, the Trustee shall serve as Paying
Agent for the Notes.

                  SECTION 2.5.  Noteholder  Lists. The Trustee shall preserve in
as current a form as is reasonably practicable the most recent list available to
it of the names and addresses of

                                       21
<PAGE>   28

Noteholders. If the Trustee or any Paying Agent is not the Registrar, the Issuer
shall cause the Registrar to furnish to the Trustee or any such Paying Agent, in
writing at least five  Business  Days before each  interest  payment date and at
such other times as the Trustee or any such Paying Agent may request in writing,
a list in such form and as of such date as the Trustee may reasonably require of
the names and addresses of Noteholders.

                  SECTION 2.6.  [Intentionally Omitted]

                  SECTION  2.7.  Replacement  Notes.  If  a  mutilated  Note  is
surrendered  to the Trustee or if the Holder of a Note shall  provide the Issuer
and the Trustee with evidence to their satisfaction that the Note has been lost,
destroyed or  wrongfully  taken,  the Issuer  shall issue and the Trustee  shall
authenticate  a  replacement  Note if the  requirements  of Section 8-405 of the
Uniform  Commercial Code are met and the Holder  satisfies any other  reasonable
requirements  of the  Trustee.  If required  by the Trustee or the Issuer,  such
Holder shall furnish an indemnity bond  sufficient in the judgment of the Issuer
and the  Trustee to protect the  Issuer,  the  Trustee,  the Paying  Agent,  the
Registrar and any  co-registrar  from any loss which any of them may suffer if a
Note is  replaced.  The Issuer and the  Trustee  may charge the Holder for their
expenses in replacing a Note, including reasonable fees and expenses of counsel.
Every replacement Note is an additional obligation of the Issuer.

                  SECTION 2.8.  Outstanding Notes. Notes outstanding at any time
are all Notes  authenticated  by the Trustee  except for those  canceled,  those
delivered  for  cancellation  and those  described  in this  Section  2.8 as not
outstanding.  A Note does not cease to be  outstanding  because the Issuer or an
Affiliate of the Issuer holds the Note.

                  If a Note is replaced pursuant to Section 2.7, it ceases to be
outstanding unless the Trustee and the Issuer receive proof satisfactory to them
that the replaced Note is held by a bona fide purchaser.

                  If  the  Paying  Agent  segregates  and  holds  in  trust,  in
accordance  with this  Indenture,  on a redemption  date or maturity  date money
sufficient to pay all  principal and interest  payable on that date with respect
to the Notes (or portions  thereof) to be redeemed or maturing,  as the case may
be,  and the  Paying  Agent is not  prohibited  from  paying  such  money to the
Noteholders  on that date pursuant to the terms of this  Indenture,  then on and
after that date such Notes (or portions  thereof)  cease to be  outstanding  and
interest on them ceases to accrue.

                  SECTION 2.9. Temporary Notes. Until definitive Notes are ready
for  delivery,  the  Issuer  may  prepare  and the  Trustee  shall  authenticate
temporary  Notes.  Temporary  Notes  shall  be  substantially  in  the  form  of
definitive Notes but may have variations that the Issuer  considers  appropriate
for temporary Notes.  Without  unreasonable  delay, the Issuer shall prepare and
the Trustee  shall  authenticate  definitive  Notes.  After the  preparation  of
definitive Notes, the temporary Notes shall be exchangeable for definitive Notes
upon surrender of the temporary Notes at any office or agency  maintained by the
Issuer for that purpose and such exchange shall be without charge to the Holder.
Upon surrender for  cancellation of any one or more temporary  Notes, the Issuer
shall  execute,  and the  Trustee  shall  authenticate  and  deliver in exchange
therefor, one or more definitive Notes representing an equal principal amount of
Notes.  Until so

                                       22
<PAGE>   29

exchanged,  the Holder of  temporary  Notes shall in all respects be entitled to
the same benefits under this Indenture as a Holder of definitive Notes.

                  SECTION 2.10. Cancellation. The Issuer at any time may deliver
Notes to the Trustee for cancellation.  The Registrar and the Paying Agent shall
forward  to the  Trustee  for  cancellation  any Notes  surrendered  to them for
registration  of transfer or exchange or payment.  The Trustee  shall cancel and
destroy (subject to the record  retention  requirements of the Exchange Act) all
Notes  surrendered  for  registration  of  transfer  or  exchange,   payment  or
cancellation  and deliver a certificate of such destruction to the Issuer unless
the Issuer  directs the  Trustee to deliver  canceled  Notes to the Issuer.  The
Issuer  may not  issue  new  Notes to  replace  Notes it has  redeemed,  paid or
delivered to the Trustee for cancellation.

                  SECTION 2.11. Defaulted Interest.  If the Issuer defaults in a
payment of interest on the Notes, the Issuer shall pay defaulted  interest (plus
interest on such defaulted  interest to the extent lawful) at the rate specified
therefor  in the Notes in any lawful  manner.  The Issuer may pay the  defaulted
interest to the Persons who are Noteholders on a subsequent special record date.
The Issuer shall fix or cause to be fixed (or upon the Issuer's failure to do so
the Trustee  shall fix) any such  special  record  date and payment  date to the
reasonable  satisfaction of the Trustee which specified record date shall not be
less than 10 days prior to the  payment  date for such  defaulted  interest  and
shall  promptly  mail or cause to be mailed  to each  Noteholder  a notice  that
states the special  record  date,  the payment  date and the amount of defaulted
interest  to be paid.  The Issuer  shall  notify  the  Trustee in writing of the
amount of  defaulted  interest  proposed to be paid on each Note and the date of
the proposed  payment,  and at the same time the Issuer  shall  deposit with the
Trustee an amount of money equal to the aggregate  amount proposed to be paid in
respect of such defaulted  interest or shall make  arrangements  satisfactory to
the Trustee for such  deposit  prior to the date of the proposed  payment,  such
money  when so  deposited  to be held in trust  for the  benefit  of the  Person
entitled to such defaulted interest as provided in this Section 2.11.

                  SECTION 2.12.  CUSIP Numbers.  The Issuer in issuing the Notes
may use "CUSIP" numbers (if then generally in use) and, if so, the Trustee shall
use  "CUSIP"  numbers in notices of  redemption  as a  convenience  to  Holders;
provided, however, that any such notice may state that no representation is made
as to the  correctness  of such  numbers  either as  printed  on the Notes or as
contained in any notice of a redemption  and that reliance may be placed only on
the other  identification  numbers printed on the Notes, and any such redemption
shall not be affected by any defect in or omission of such numbers.

                                   ARTICLE III
                                   REDEMPTION

                  SECTION  3.1.  Notices to  Trustee.  If the  Issuer  elects to
redeem Notes  pursuant to paragraph 5 of the Notes  (Exhibit 1 to the Appendix),
it shall  notify the Trustee and the Paying  Agent in writing of the  redemption
date and the principal amount of Notes to be redeemed and the redemption price.

                  The  Issuer  shall  give each  notice to the  Trustee  and the
Paying Agent provided for in this Section at least 60 days before the redemption
date unless the Trustee and the Paying

                                       23
<PAGE>   30

Agent  consent to a shorter  period.  Such  notice  shall be  accompanied  by an
Officer's  Certificate  from the Issuer to the effect that such  redemption will
comply with the conditions  herein.  The record date relating to such redemption
shall be selected by the Issuer and set forth in the related notice given to the
Trustee and the Paying  Agent,  which record date shall be not less than 15 days
prior to the date selected for redemption by the Issuer.

                  SECTION 3.2. Selection of Notes to Be Redeemed. In the case of
any partial  redemption,  selection of the Notes for redemption  will be made by
the  Trustee in  compliance  with the  requirements  of the  principal  national
securities exchange, if any, on which the Notes are listed, or, if the Notes are
not so  listed,  on a pro rata  basis,  by lot or by such  other  method  as the
Trustee in its sole discretion shall deem to be fair and  appropriate,  although
no Note of $1,000 in original principal amount or less will be redeemed in part.
Provisions  of this  Indenture  that apply to Notes called for  redemption  also
apply to portions of Notes  called for  redemption.  Upon request of the Issuer,
the  Trustee  shall  notify the Issuer of the Notes or  portions  of Notes to be
redeemed.

                  SECTION 3.3.  Notice of  Redemption.  At least 30 days but not
more than 60 days  before a date for  redemption  of Notes,  the  Trustee at the
expense of the Issuer shall mail a notice of redemption by  first-class  mail to
each Holder of Notes to be redeemed.

                  The notice  shall  identify the Notes to be redeemed and shall
state:

                  (1)      the redemption date;

                  (2)      the redemption price;

                  (3)      the name and address of the Paying Agent;

                  (4) that Notes called for  redemption  must be  surrendered to
         the Paying  Agent to collect  the  redemption  price plus  accrued  and
         unpaid interest, if any;

                  (5)  if  fewer  than  all  the  outstanding  Notes  are  to be
         redeemed,  the  identification  and principal amounts of the particular
         Notes to be redeemed;

                  (6) that, unless the Issuer defaults in making such redemption
         payment or the Paying  Agent is  prohibited  from making  such  payment
         pursuant to the terms of this Indenture,  interest on Notes (or portion
         thereof)  called  for  redemption  ceases  to  accrue  on and after the
         redemption date;

                  (7)      the CUSIP number, if any, printed on the Notes being
redeemed; and

                  (8) that no  representation  is made as to the  correctness or
         accuracy of the CUSIP number,  if any, listed in such notice or printed
         on the Notes.

                  The  Trustee  shall  give  the  notice  of  redemption  in the
Issuer's  name and at the  Issuer's  expense.  In such event,  the Issuer  shall
provide the Trustee with the information required by this Section 3.3.

                                       24
<PAGE>   31

                  SECTION 3.4.  Effect of Notice of  Redemption.  Once notice of
redemption is mailed,  Notes called for redemption  shall become due and payable
on the redemption  date and at the redemption  price stated in the notice.  Upon
surrender to the Paying Agent,  such Notes shall be paid at the redemption price
stated  in the  notice,  plus  accrued  and  unpaid  interest,  if  any,  to the
redemption  date;  provided that the Issuer shall have  deposited the redemption
price with the Paying  Agent or the  Trustee on or before  11:00 a.m.  (New York
City time) on the date of redemption;  provided, further, that if the redemption
date is after a  regular  record  date and on or prior to the  interest  payment
date, the accrued and unpaid  interest shall be payable to the Noteholder of the
redeemed Notes registered on the relevant record date. Failure to give notice or
any  defect in the notice to any Holder  shall not  affect the  validity  of the
notice to any other Holder.

                  SECTION 3.5.  Deposit of Redemption  Price.  By at least 11:00
a.m.  (New York City time) on the date on which any  principal of or interest on
any Note is due and payable, the Issuer shall deposit with the Paying Agent (or,
if the Issuer or a Subsidiary is the Paying Agent,  shall  segregate and hold in
trust) money  sufficient to pay the  redemption  price of and accrued and unpaid
interest,  if any,  on all Notes to be redeemed on that date other than Notes or
portions  of Notes  called  for  redemption  which are owned by the  Issuer or a
Subsidiary  and have been  delivered  by the  Issuer or such  Subsidiary  to the
Trustee for cancellation.

                  If the Issuer  complies  with the preceding  paragraph,  then,
unless the Issuer defaults in the payment of such redemption price,  interest on
the Notes to be  redeemed  will  cease to  accrue  on and  after the  applicable
redemption date, whether or not such Notes are presented for payment.

                  SECTION 3.6. Notes Redeemed in Part.  Upon surrender of a Note
that is  redeemed  in part,  the Issuer  shall  execute  and the  Trustee  shall
authenticate  for the  Holder  (at the  Issuer's  expense) a new Note equal in a
principal amount to the unredeemed portion of the Note surrendered.

                                   ARTICLE IV
                                    COVENANTS

                  SECTION 4.1.  Payment of Notes.  The Issuer shall promptly pay
the  principal  of and  interest  on the Notes on the  dates  and in the  manner
provided in the Notes and in this  Indenture.  Principal  and interest  shall be
considered  paid on the date due if on or before 11:00 a.m. (New York City time)
on such date the  Trustee or the  Paying  Agent  holds  (or,  if the Issuer or a
Subsidiary is the Paying Agent,  the  segregated  account or separate trust fund
maintained  by the  Issuer  or  such  Subsidiary  pursuant  to  Section  2.4) in
accordance  with  this  Indenture  money  sufficient  to pay all  principal  and
interest  then due and the  Trustee or the Paying  Agent (or, if the Issuer or a
Subsidiary is the Paying Agent, the Issuer or such Subsidiary),  as the case may
be, is not  prohibited  from paying such money to the  Noteholders  on that date
pursuant to the terms of this Indenture.

                  The Issuer shall pay interest on overdue principal at the rate
specified  therefor  in  the  Notes,  and  it  shall  pay  interest  on  overdue
installments  of interest  at the same rate to the extent  lawful as provided in
Section 2.11.

                                       25
<PAGE>   32

                  Notwithstanding  anything to the  contrary  contained  in this
Indenture.  the Issuer or the Paying  Agent may, to the extent it is required to
do so by law,  deduct or withhold  income or other  similar taxes imposed by the
United States of America or other  domestic or foreign taxing  authorities  from
principal or interest payments hereunder.

                  SECTION 4.2. SEC Reports.  Notwithstanding that the Issuer may
not be required to remain subject to the reporting requirements of Section 13 or
15(d) of the  Exchange  Act,  the Issuer  will file with the SEC (unless the SEC
does not permit such  filing) and provide the Trustee and  Noteholders  with the
annual  reports and such  information,  documents  and other  reports  which are
specified  in Sections 13 and 15(d) of the  Exchange  Act.  The Issuer also will
comply with the other provisions of TIA ss. 314(a).

                  SECTION 4.3.  Limitation on Indebtedness.  (a) The Issuer will
not Incur, directly or indirectly,  any Indebtedness unless, on the date of such
Incurrence and after giving effect to such Incurrence and the application of the
proceeds  therefrom,  the  Indebtedness  to Adjusted  EBITDA Ratio of the Issuer
would be  equal to or less  than  7.00:1.  Accrual  of  interest,  accretion  or
amortization  of original issue discount and the payment of interest in the form
of  additional   Indebtedness  will  not  be  deemed  to  be  an  Incurrence  of
Indebtedness for purposes of this covenant.

                  (b) Notwithstanding the foregoing paragraph (a) and regardless
of the amount of outstanding  Indebtedness  of the Issuer,  the Issuer may Incur
any or all of the following  Indebtedness:  (i) Indebtedness of the Issuer owing
to and held by any  Restricted  Subsidiary;  provided,  however,  that any event
which  results in any such  Restricted  Subsidiary  ceasing  to be a  Restricted
Subsidiary  or any  subsequent  transfer  of any such  Indebtedness  (except  to
another  Restricted  Subsidiary) will be deemed, in each case, to constitute the
Incurrence of such Indebtedness by the Issuer; (ii) Indebtedness  represented by
the Notes;  (iii) Indebtedness of the Issuer outstanding on the Issue Date; (iv)
Indebtedness (including Capitalized Lease Obligations) of the Issuer Incurred to
finance the acquisition,  construction or improvement of fixed or capital assets
in an aggregate  principal  amount (together with the amount of any Indebtedness
then outstanding and Incurred  pursuant to clause (b)(vi) of Section 4.4) at any
one time  outstanding  not to exceed the greater of (x) $25.0 million and (y) an
amount equal to 7.5% of the Issuer's  Consolidated  Tangible  Assets;  provided,
that  such  Indebtedness  is  Incurred  within  180 days  after the date of such
acquisition,  construction  or  improvement  and does not exceed the fair market
value of such acquired,  constructed or improved  assets,  as determined in good
faith by the  Board of  Directors;  (v)  Refinancing  Indebtedness  Incurred  in
respect of any  Indebtedness  Incurred  pursuant to paragraph (a) or pursuant to
clause  (ii),  (iii) or this clause  (v);  (vi)  Indebtedness  (A) in respect of
performance bonds, bankers' acceptances,  letters of credit and surety or appeal
bonds provided by the Issuer in the ordinary course of its business and which do
not secure other  Indebtedness  and (B) under  Currency  Agreements and Interest
Rate Agreements  Incurred  which, at the time of Incurrence,  is in the ordinary
course of business;  provided, however, that, in the case of Currency Agreements
and Interest  Rate  Agreements,  such  Currency  Agreements  and  Interest  Rate
Agreements are directly related to Indebtedness  permitted to be Incurred by the
Issuer pursuant to this Indenture;  (vii) Indebtedness represented by Guarantees
by the Issuer of Indebtedness otherwise permitted to be Incurred by a Restricted
Subsidiary  pursuant to this Indenture;  (viii) Indebtedness of any other Person
existing  at the time  such  other  Person  is  merged  with or into the  Issuer
outstanding on or prior to the date on which such Person was

                                       26
<PAGE>   33

merged with or into the Issuer (other than  Indebtedness  Incurred in connection
with, or to provide all or any portion of the funds or credit  support  utilized
to consummate,  the  transaction or series of related  transactions  pursuant to
which such Person was merged with or into the Issuer);  provided,  however, that
on the date of such merger and after giving effect thereto either (x) the Issuer
would be permitted to incur at least $1.00 of additional  Indebtedness  pursuant
to  paragraph  (a)  of  this  Section  4.3 or  (y)  the  Issuer  would  have  an
Indebtedness  to Adjusted EBITDA Ratio  immediately  after giving effect to such
merger no greater than the  Indebtedness  to Adjusted  EBITDA Ratio  immediately
prior to such merger;  (ix) the Incurrence by the Issuer of Indebtedness  not to
exceed,  at  any  one  time  outstanding   (together  with  the  amount  of  any
Indebtedness then outstanding and Incurred pursuant to clause (b)(ix) of Section
4.4),  2.0 times the sum of 100% of the  aggregate  Net Cash Proceeds and 50% of
the non-cash  proceeds  received by the Issuer from the issue or sale of Capital
Stock (other than Disqualified  Stock) subsequent to July 1, 1999 (other than an
issuance  or sale to a  Subsidiary  of the Issuer and other than an  issuance or
sale to an employee stock ownership plan or to a trust established by the Issuer
or any of its Restricted  Subsidiaries),  less the aggregate  amount of such Net
Cash  Proceeds  used to make  Restricted  Payments  pursuant  to clause  3(B) of
paragraph  (a) of Section 4.5 or applied  pursuant to clause (i)(B) of paragraph
(b) of Section 4.5; (x) other  Indebtedness  in an  aggregate  principal  amount
outstanding at any time not to exceed $25.0 million (together with the amount of
any Indebtedness  and Preferred Stock then outstanding and Incurred  pursuant to
clause  (b)(x) of Section  4.4);  (xi)  Indebtedness  Incurred  by the  Issuer's
Subsidiaries in compliance with Section 4.4; (xii)  Indebtedness  incurred under
Credit  Facilities,  in an aggregate  principal amount  outstanding at any time,
together with the amount of any Indebtedness then outstanding and incurred under
Section 4.4(b)(i) of this Indenture, not to exceed the sum of (A) the product of
$200,000 times the number of Completed  Towers on the date of incurrence and (B)
the product of $1,000,000 times the number of Completed  Broadcast Towers on the
date of such incurrence;  provided that the amount of such Indebtedness incurred
pursuant  to this  clause (B) does not exceed  25% of the cost of  acquiring  or
constructing such Completed Broadcast Towers;  (xiii) Indebtedness  representing
the deferred  payment of the purchase  price for any entity that is engaged in a
Permitted  Business and that becomes a Restricted  Subsidiary or the acquisition
of any assets constituting a business or line of business, as determined in good
faith by the Board of Directors,  that is a Permitted Business, not to exceed at
any one time  outstanding,  together with any Indebtedness  then outstanding and
incurred pursuant to Section  4.4(b)(xi) of this Indenture,  50% of the purchase
price for the related entity or business so acquired;  provided,  however,  that
after  giving  effect  to such  acquisition  and all  Indebtedness  incurred  in
connection  therewith,  either (A) the  Issuer  would have been able to incur at
least $1.00 of additional  Indebtedness under this Section 4.3 or (B) the Issuer
would have had an Indebtedness to Adjusted EBITDA Ratio no greater than prior to
such transaction; and (xiv) Permitted Acquisition Indebtedness.

                  (c) Notwithstanding the foregoing,  the Issuer shall not Incur
any Indebtedness  pursuant to the foregoing paragraph (b) of this Section 4.3 if
the  proceeds  thereof  are used,  directly  or  indirectly,  to  Refinance  any
Subordinated  Obligations unless such new Indebtedness shall (i) be subordinated
to the Notes to at least the same extent as such Subordinated  Obligations being
Refinanced  and (ii) have a Stated  Maturity that is no earlier than the earlier
of the Stated Maturity of the Notes and the Stated Maturity of the  Subordinated
Obligations being Refinanced.

                  (d) For purposes of determining  compliance  with this Section
4.3,  (i) in the event that an item of  Indebtedness  meets the criteria of more
than one of the types of

                                       27
<PAGE>   34

Indebtedness described above, the Issuer, in its sole discretion,  will classify
(and may from time to time  reclassify)  such item of  Indebtedness  and only be
required to include the amount and type of such Indebtedness in one of the above
clauses of this Section 4.3 and (ii) an item of Indebtedness  may be divided and
classified  in more  than one of the  types of  Indebtedness  described  in this
Section 4.3.

                  SECTION 4.4. Limitation on Indebtedness and Preferred Stock of
Restricted  Subsidiaries.  (a)  The  Issuer  shall  not  permit  any  Restricted
Subsidiary to Incur, directly or indirectly, any Indebtedness or Preferred Stock
unless,  on the  date  of  such  Incurrence  and  after  giving  effect  to such
Incurrence and the application of the net proceeds  therefrom,  the Indebtedness
to Adjusted  EBITDA  Ratio of the Issuer  would be equal to or less than 7.00:1.
Accrual of interest,  accretion or  amortization  of original issue discount and
the  payment of  interest  in the form of  additional  Indebtedness  will not be
deemed to be an Incurrence of Indebtedness for purposes of this covenant.

                  (b) Notwithstanding the foregoing paragraph (a) and regardless
of the amount of outstanding  Indebtedness of the Restricted  Subsidiaries,  any
Restricted  Subsidiary may Incur any or all of the following  Indebtedness:  (i)
Indebtedness  Incurred under Credit Facilities in an aggregate  principal amount
outstanding  at any time  (together  with the  amount of any  Indebtedness  then
outstanding and incurred under clause (b)(xii) of Section 4.3) not to exceed the
sum of (x) the product of $200,000  times the number of Completed  Towers on the
date of such  Incurrence;  and (y) the product of $1,000,000 times the number of
Completed  Broadcast  Towers on the date of such  Incurrence,  provided that the
amount of such Indebtedness incurred pursuant to this clause (y) does not exceed
25% of the cost of acquiring or constructing  such Completed  Broadcast  Towers;
(ii)  Indebtedness or Preferred Stock of a Restricted  Subsidiary  issued to and
held by the  Issuer or a  Restricted  Subsidiary;  provided,  however,  that any
subsequent  issuance or transfer of any Capital  Stock which results in any such
Restricted  Subsidiary  ceasing to be a Restricted  Subsidiary or any subsequent
transfer of such  Indebtedness or Preferred Stock (other than to the Issuer or a
Restricted  Subsidiary)  shall  be  deemed,  in each  case,  to  constitute  the
Incurrence of such Indebtedness or Preferred Stock by the issuer thereof;  (iii)
Indebtedness  or  Preferred  Stock  of  a  Restricted  Subsidiary  Incurred  and
outstanding  on or prior to the date on which  such  Restricted  Subsidiary  was
acquired by the Issuer and  Indebtedness  or Preferred Stock of an entity merged
into a Restricted  Subsidiary  (other  than,  in either  case,  Indebtedness  or
Preferred Stock Incurred in connection with, or to provide all or any portion of
the funds or credit support utilized to consummate, the transaction or series of
related  transactions  pursuant  to which such  Restricted  Subsidiary  became a
Restricted  Subsidiary  or was  acquired by the Issuer or such entity was merged
into such Restricted  Subsidiary);  provided,  however, that on the date of such
acquisition  or merger and after giving  effect  thereto,  either (x) the Issuer
would have been  permitted  to incur at least $1.00 of  additional  Indebtedness
pursuant to  paragraph  (a) of Section  4.3 or (y) the Issuer  would have had an
Indebtedness  to Adjusted EBITDA Ratio  immediately  after giving effect to such
merger or acquisition no greater than the  Indebtedness to Adjusted EBITDA Ratio
immediately  prior to such  transaction;  (iv)  Indebtedness  or Preferred Stock
outstanding on the Issue Date; (v) Refinancing  Indebtedness Incurred in respect
of  Indebtedness  or Preferred  Stock  referred to in paragraph  (a) above or in
clauses (iii) or (iv) of this paragraph or this clause (v);  provided,  however,
that  Indebtedness  of the Issuer may not be refinanced  pursuant to this clause
(v); (vi) Indebtedness  (including  Capitalized Lease Obligations) Incurred by a
Subsidiary to finance the  acquisition,  construction

                                       28

<PAGE>   35

or improvement of fixed or capital  assets in an aggregate  principal  amount at
any one time outstanding (together with the amount then outstanding and Incurred
pursuant  to clause  (b)(iv)  of Section  4.3) not to exceed the  greater of (x)
$25.0  million  and (y) an  amount  equal to 7.5% of the  Issuer's  Consolidated
Tangible Assets;  provided,  that such  Indebtedness is Incurred within 180 days
after the date of such  acquisition,  construction  or improvement  and does not
exceed the fair market value of such acquired,  constructed or improved  assets,
as determined in good faith by the Board of Directors; (vii) Indebtedness (A) in
respect of performance bonds, bankers' acceptances, letters of credit and surety
or appeal bonds provided in the ordinary course of its business and which do not
secure  other  Indebtedness  and (B)  Incurred  under  Currency  Agreements  and
Interest Rate Agreements  which,  at the time of Incurrence,  is in the ordinary
course of business;  provided, however, that, in the case of Currency Agreements
and Interest  Rate  Agreements,  such  Currency  Agreements  and  Interest  Rate
Agreements  are  directly  related  to  Indebtedness  permitted  to be  Incurred
pursuant to this Indenture;  (viii) Indebtedness represented by Guarantees, by a
Subsidiary,  of Indebtedness otherwise permitted to be Incurred by the Issuer or
a Subsidiary  pursuant to this  Indenture;  provided that any  Subsidiary  which
guarantees  the 2008 Notes,  the 2009 Notes,  the 2010 Notes or the  Convertible
Notes will  guarantee the Notes,  in each case on  substantially  similar terms;
(ix) the Incurrence of Indebtedness  not to exceed,  at any one time outstanding
(together  with the amount of any  Indebtedness  then  outstanding  and Incurred
pursuant to clause (b)(ix) of Section 4.3), 2.0 times (A) the sum of 100% of the
aggregate  Net Cash  Proceeds and 50% of the non-cash  proceeds  received by the
Issuer from the issue or sale of Capital Stock (other than  Disqualified  Stock)
subsequent to July 1, 1999, other than an issuance or sale to a Subsidiary or to
an employee stock ownership plan or to a trust  established by the Issuer or any
Restricted  Subsidiary,  less (B) the amount of such Net Cash  Proceeds  used to
make Restricted Payments pursuant to clause 3(B) of paragraph (a) of Section 4.5
or applied  pursuant to clause (i)(B) of paragraph (b) of Section 4.5; (x) other
Indebtedness and Preferred Stock in an aggregate  principal  and/or  liquidation
amount  outstanding  at any time not to exceed $25.0 million (less the amount of
any  Indebtedness  then  outstanding  and Incurred  pursuant to clause (b)(x) of
Section  4.3);  (xi)  Indebtedness  representing  the  deferred  payment  of the
purchase  price for any entity that is engaged in a Permitted  Business and that
becomes a Restricted  Subsidiary or the acquisition of any assets constituting a
business  or line of  business,  as  determined  in good  faith by the  Board of
Directors,  that  is a  Permitted  Business,  not  to  exceed  at any  one  time
outstanding,  together  with any  Indebtedness  then  outstanding  and  incurred
pursuant to Section  4.3(b)(xiii) of this  Indenture,  50% of the purchase price
for the related entity or business so acquired;  provided,  however,  that after
giving effect to such  acquisition and all  Indebtedness  incurred in connection
therewith, either (A) the Issuer would have been able to incur at least $1.00 of
additional  Indebtedness  under  Section 4.3 or (B) the Issuer would have had an
Indebtedness to Adjusted EBITDA Ratio no greater than prior to such transaction;
and (xii) Permitted Acquisition Indebtedness.

                  (c) For purposes of determining  compliance  with this Section
4.4,  (i) in the event that an item of  Indebtedness  meets the criteria of more
than one of the types of Indebtedness  described above, the Issuer,  in its sole
discretion,  will classify (and may from time to time  reclassify)  such item of
Indebtedness  and  only be  required  to  include  the  amount  and type of such
Indebtedness in one of the above clauses of this Section 4.4 and (ii) an item of
Indebtedness  may be  divided  and  classified  in more than one of the types of
Indebtedness described in this Section 4.4

                                       29
<PAGE>   36

                  (d) The Issuer will not permit any Unrestricted  Subsidiary to
Incur any Indebtedness other than Non-Recourse Debt.

                  SECTION 4.5. Limitation on Restricted Payments. (a) The Issuer
will not make and will not permit any Restricted  Subsidiary to make directly or
indirectly,  any Restricted Payment if at the time the Issuer or such Restricted
Subsidiary makes such Restricted Payment: (1) a Default or Event of Default will
have occurred and be  continuing  (or would result  therefrom);  (2) except with
respect to making an  Investment,  the Issuer  could not incur at least $1.00 of
additional Indebtedness under paragraph (a) of Section 4.3; or (3) the aggregate
amount of such Restricted Payment and all other Restricted  Payments (the amount
so expended,  if other than in cash, to be determined in good faith by the Board
of  Directors,  whose  determination  will be evidenced by a resolution  of such
Board of Directors)  declared or made  subsequent to the Issue Date would exceed
the sum of: (A) (x) the aggregate  EBITDA (or, in the event such EBITDA shall be
a deficit,  minus such deficit)  accrued  subsequent to July 1, 1999 to the most
recent date for which financial information is available to the Issuer, taken as
one accounting period, (y) less 1.4 times Consolidated  Interest Expense for the
same period; (B) (x) 100% of the aggregate Net Cash Proceeds (less the aggregate
amount of such Net Cash Proceeds used to Incur  Indebtedness  pursuant to clause
(b)(ix) of Section  4.3 and  clause  (b)(ix) of Section  4.4) and (y) 70% of the
GAAP  purchase  accounting  valuation  of  Qualified  Proceeds  (with  each such
valuation  calculated  as of the sale  date of the  Capital  Stock  received  as
consideration  therefor),  in each case received by the Issuer from the issue or
sale of Capital Stock (other than Disqualified Stock) subsequent to July 1, 1999
(other than an issuance or sale to a Subsidiary  of the Issuer and other than an
issuance or sale to an employee stock  ownership plan or to a trust  established
by the Issuer or any of its  Restricted  Subsidiaries);  (C) the amount by which
Indebtedness  of the Issuer is reduced on the  Issuer's  balance  sheet upon the
conversion  or exchange  (other than by a Restricted  Subsidiary)  subsequent to
March 15, 2000 of any Indebtedness of the Issuer convertible or exchangeable for
Capital Stock (other than Disqualified  Stock) of the Issuer (less the amount of
any cash,  or the fair value of any other  property,  distributed  by the Issuer
upon such conversion or exchange); (D) an amount equal to the sum of (i) the net
reduction in Investments in Unrestricted  Subsidiaries resulting from dividends,
repayments  of loans or advances or other  transfers  of assets to the Issuer or
any Restricted  Subsidiary from  Unrestricted  Subsidiaries and (ii) the portion
(proportionate  to the Issuer's equity interest in such  Subsidiary) of the fair
market value of the net assets of an  Unrestricted  Subsidiary  at the time such
Unrestricted  Subsidiary is designated a Restricted Subsidiary;  provided,  that
the foregoing sum shall not exceed, in the case of any Unrestricted  Subsidiary,
the  amount of  Investments  previously  made by the  Issuer  or any  Restricted
Subsidiary  in such  Unrestricted  Subsidiary,  which amount was included in the
calculation   of  the  amount  of   Restricted   Payments;   (E)  dividends  and
distributions  received  by  the  Issuer  subsequent  to  March  15,  2000  from
Unrestricted  Subsidiaries,  to the extent such dividends and  distributions are
not otherwise included in calculating EBITDA; and (F) Net Cash Proceeds received
by the  Issuer  subsequent  to March  15,  2000  from  Investments  that are not
Permitted  Investments,  to the extent not  otherwise  included  in  calculating
EBITDA.

                  (b) The  provisions  of the  foregoing  paragraph  (a) of this
Section 4.5 will not prohibit: (i) any purchase, redemption, defeasance or other
acquisition of Capital Stock of the Issuer or Subordinated  Obligations  made by
exchange for, or out of the net proceeds of the  substantially  concurrent  sale
of,  Capital Stock of the Issuer (other than  Disqualified  Stock and

                                       30
<PAGE>   37

other than  Capital  Stock  issued or sold to a  Subsidiary  of the Issuer or an
employee stock ownership plan or to a trust  established by the Issuer or any of
its  Subsidiaries);  provided,  however,  that  (A) such  purchase,  redemption,
defeasance  or other  acquisition  will be  excluded in the  calculation  of the
amount of  Restricted  Payments  and (B) to the extent  applied  toward any such
purchase,  redemption,  defeasance or other  acquisition,  the Net Cash Proceeds
from such sale will be excluded  from  clause  (3)(B) of  paragraph  (a) of this
Section 4.5,  clause  (b)(ix) of Section 4.3 and clause  (b)(ix) of Section 4.4;
(ii) any purchase,  redemption,  defeasance or other acquisition of Subordinated
Obligations   made  by  exchange  for,  or  out  of  the  net  proceeds  of  the
substantially  concurrent  sale  of,  Subordinated  Obligations  of the  Issuer;
provided,  however,  that (A) the principal amount of such new Indebtedness does
not  exceed  the  principal  amount  of the  Subordinated  Obligations  being so
redeemed,  repurchased,  acquired  or retired  for value (plus the amount of any
premium  required  to be paid under the terms of the  instrument  governing  the
Subordinated Obligations being so redeemed,  repurchased,  acquired or retired),
(B) such new  Indebtedness  is  subordinated  to the  Notes at least to the same
extent as such  Subordinated  Obligations  so  purchased,  exchanged,  redeemed,
repurchased,  acquired or retired  for value,  (C) such new  Indebtedness  has a
final  scheduled  maturity  date later than the  earlier of the final  scheduled
maturity date of the Subordinated  Obligations  being so redeemed,  repurchased,
acquired or retired and the final scheduled maturity date of the Notes, (D) such
new  Indebtedness has an Average Life equal to or greater than the lesser of the
Average Life of the Indebtedness being so redeemed,  repurchased,  acquired,  or
retired,  and the Average Life of the Notes,  and (E) any purchase,  redemption,
defeasance or other  acquisition  made  pursuant to this clause  (b)(ii) will be
excluded  in the  calculation  of  the  amount  of  Restricted  Payments;  (iii)
dividends paid within 60 days after the date of  declaration  thereof if at such
date of  declaration  such  dividend  would have  complied  with this  covenant;
provided,  however,  that the amount of such  dividend  will be  included in the
calculation  of the  amount  of  Restricted  Payments;  and  (iv)  purchases  of
outstanding  shares of the Issuer's  capital  stock from former  employees in an
amount not to exceed $5.0 million in the aggregate; provided, however, that such
purchases  will be  included  in the  calculation  of the  amount of  Restricted
Payments;  provided,  however, that, at the time of, and after giving effect to,
any  Restricted  Payment  permitted by clauses (i), (ii) and (iv), no Default or
Event of Default shall have occurred and be continuing.

                  (c) The amount of any Investment shall be measured on the date
made and shall not give effect to subsequent changes in value.

                  SECTION 4.6.  Limitation on Restrictions on Distributions from
Restricted Subsidiaries. The Issuer will not, and will not permit any Restricted
Subsidiary to, create or otherwise cause or permit to exist or become  effective
any  consensual  encumbrance  or  restriction  on the ability of any  Restricted
Subsidiary to (i) pay dividends or make any other  distributions  on its Capital
Stock to the Issuer or a Restricted  Subsidiary or pay any Indebtedness or other
obligation owed to the Issuer,  (ii) make any loans or advances to the Issuer or
(iii)  transfer  any of its  property or assets to the Issuer or any  Restricted
Subsidiary,  except:  (1) any  encumbrance or  restriction  pursuant to a Credit
Facility or any  agreement in effect at or entered  into on the Issue Date;  (2)
any encumbrance or restriction with respect to a Restricted  Subsidiary pursuant
to an agreement relating to any Indebtedness or Capital Stock Incurred or issued
by such  Restricted  Subsidiary on or prior to the date on which such Restricted
Subsidiary  was  acquired by the Issuer or a Restricted  Subsidiary  (other than
Indebtedness  or Capital Stock  Incurred or issued as  consideration  for, or to
provide any portion of the funds or credit  support  utilized to consummate

                                       31
<PAGE>   38

the  transaction  or series  of  related  transactions  pursuant  to which  such
Restricted  Subsidiary  became a  Subsidiary  or was acquired by the Issuer or a
Restricted  Subsidiary)  and  outstanding on such date;  (3) any  encumbrance or
restriction  pursuant to an agreement  effecting a Refinancing  of  Indebtedness
Incurred  pursuant  to an  agreement  referred  to in clause  (1) or (2) of this
Section 4.6 or contained in any amendment to an agreement  referred to in clause
(1) or (2) of this Section 4.6;  provided,  however,  that the  encumbrances and
restrictions  with respect to such Restricted  Subsidiary  contained in any such
refinancing agreement or amendment taken as a whole are no less favorable to the
Noteholders  than  the  encumbrances  and  restrictions  with  respect  to  such
Restricted Subsidiary contained in such predecessor  agreements as determined in
good  faith by the  Board of  Directors;  (4) in the case of clause  (iii),  any
encumbrance or restriction  that restricts in a customary manner the subletting,
assignment  or  transfer  of any  property  or asset that is subject to a lease,
license or other contract or such lease, license or other such contract;  (5) in
the case of clause (iii), contained in security agreements or mortgages securing
Indebtedness  of a  Restricted  Subsidiary  to the extent  such  encumbrance  or
restrictions  restrict  the transfer of the  property  subject to such  security
agreements  or  mortgages;  (6) any  restriction  with  respect to a  Restricted
Subsidiary  imposed  pursuant  to an  agreement  entered  into  for the  sale or
disposition  of all or  substantially  all the  Capital  Stock or assets of such
Restricted  Subsidiary  pending  the  closing of such sale or  disposition;  (7)
customary  provisions  with respect to the disposition or distribution of assets
or property in joint venture and other similar agreements;  and (8) restrictions
on cash or other  deposits or net worth  imposed by  customers  under  contracts
entered into in the  ordinary  course of  business;  provided  that the Board of
Directors  in good  faith  determines  that  such  restrictions  will not have a
material adverse impact on the Issuer's ability to make payments on the Notes.

                  SECTION  4.7.  Limitation  on Sale of  Assets  and  Subsidiary
Stock.  (a) The Issuer will not, and will not permit any  Restricted  Subsidiary
to,  directly or  indirectly,  consummate any Asset  Disposition  unless (i) the
Issuer or such Restricted Subsidiary receives  consideration at the time of such
Asset  Disposition at least equal to the fair market value  (including as to the
value of all non cash  consideration),  as determined in good faith by the Board
of Directors of the shares and assets subject to such Asset Disposition and (ii)
except in the case of a Tower Asset Exchange,  at least 75% of the consideration
thereof  received by the Issuer or such Restricted  Subsidiary is in the form of
cash or cash equivalents.

                  Within 365 days after the  receipt of any Net  Available  Cash
from an Asset Disposition,  the Issuer or the applicable  Restricted  Subsidiary
may apply such Net  Available  Cash to: (A)  prepay,  repay,  redeem or purchase
Indebtedness  (other  than  Disqualified  Stock)  of  a  Restricted   Subsidiary
(provided,  that the applicable  Restricted  Subsidiary also may prepay,  repay,
redeem or purchase its own outstanding  Indebtedness) or Senior Indebtedness (in
each case other than  Indebtedness  owed to the  Issuer or an  Affiliate  of the
Issuer);  (B) make an offer with respect to the 2008 Notes,  the 2009 Notes, the
2010 Notes or the  Convertible  Notes to the extent  required in the  indentures
governing  the 2008 Notes,  the 2009 Notes,  the 2010 Notes and the  Convertible
Notes,  respectively;  (C) acquire all or substantially  all of the assets of an
entity  engaged in a Permitted  Business;  (D) acquire Voting Stock of an entity
engaged in a Permitted  Business  from a Person that is not a Subsidiary  of the
Issuer;  provided,  that (x) after  giving  effect  thereto,  the  Issuer or its
Restricted  Subsidiary  owns a  majority  of such  Voting  Stock  and  (y)  such
acquisition  is otherwise  made in accordance  with this  Indenture,  including,
without  limitation,  Section 4.5; or (E) make a capital  expenditure or acquire
other long-term assets that are used or

                                       32
<PAGE>   39

useful  in a  Permitted  Business.  To the  extent  of the  balance  of such Net
Available Cash after  application in accordance  with clauses (A), (B), (C), (D)
or (E), the Issuer shall make an Offer (as defined in Section 4.7(b)) to Holders
of the Notes to purchase  Notes  pursuant to and subject to the  conditions  set
forth in paragraph (b) of this Section 4.7.

                  Notwithstanding the foregoing  provisions,  the Issuer and its
Restricted Subsidiaries shall not be required to apply any Net Available Cash in
accordance  herewith  except to the extent that the aggregate Net Available Cash
from all  Asset  Dispositions  which are not  applied  in  accordance  with this
covenant  exceeds $10.0  million.  Pending  application  of Net  Available  Cash
pursuant  to this  covenant,  such  Net  Available  Cash  shall be  invested  in
Permitted Investments.

                  For the purposes of this Section  4.7(a),  the  following  are
deemed to be cash: (x) the assumption by the transferee of  Indebtedness  of the
Issuer (other than Disqualified  Stock of the Issuer and other than Indebtedness
that is subordinated to the Notes) or Indebtedness of any Restricted  Subsidiary
and the release of the Issuer or such  Restricted  Subsidiary from all liability
on such Indebtedness in connection with such Asset  Disposition;  (y) securities
received by the Issuer or any Restricted Subsidiary from the transferee that are
converted by the Issuer or such  Restricted  Subsidiary into cash within 20 days
of the applicable  Asset  Disposition (to the extent of the cash received);  and
(z) any liabilities  (as shown on the Issuer's or such  Restricted  Subsidiary's
most recent  balance sheet) of the Issuer or any  Restricted  Subsidiary  (other
than contingent liabilities and liabilities that are by their terms subordinated
to the Notes or any guarantee thereof) that are assumed by the transferee of any
such assets pursuant to a customary  novation agreement that releases the Issuer
or any such Restricted Subsidiary from further liability.

                  (b) In the event of an Asset  Disposition  that  requires  the
purchase of Notes pursuant to paragraph (a) of this Section 4.7, the Issuer will
be required to purchase  Notes  tendered  pursuant to an offer by the Issuer for
the Notes (the "Offer") at a purchase price of 100% of their principal amount as
of the date of purchase  (without  premium) plus accrued and unpaid  interest to
the date of purchase in accordance with the procedures  (including  prorating in
the event of  oversubscription)  set forth in this  Indenture.  If the aggregate
purchase  price of Notes  tendered  pursuant  to the  Offer is less than the Net
Available  Cash  allotted to the  purchase of the Notes,  the Issuer may use any
remaining  Net  Available  Cash for general  corporate  purposes  not  otherwise
prohibited by this Indenture.  If the aggregate purchase price of Notes tendered
pursuant to the Offer is greater  than the Net  Available  Cash  allotted to the
purchase of the Notes,  the Trustee will select the Notes to be purchased on the
basis set forth in paragraph  (c) of this Section 4.7.  Upon  completion  of any
required  Offer to the holders of the Notes,  the amount of Net  Available  Cash
will be reset at zero.  The Issuer  shall not be  required  to make an Offer for
Notes pursuant to this Section 4.7 if the Net Available Cash available  therefor
(after  application  of the  proceeds  as provided  in the second  paragraph  of
Section  4.7(a)) are less than $10.0 million for all Asset  Dispositions  (which
lesser amounts shall be carried  forward for purposes of determining  whether an
Offer is required  with respect to the Net  Available  Cash from any  subsequent
Asset Disposition).

                  (c) (1)  Promptly,  and in any event  within 30 days after the
Issuer  becomes  obligated  to make an Offer,  the Issuer  shall be obligated to
deliver to the Trustee and send,  by

                                       33
<PAGE>   40

first-class  mail to each  Holder,  at the  address  appearing  in the  security
register,  a written  notice stating that the Holder may elect to have his Notes
purchased by the Issuer either in whole or in part (subject to  prorationing  as
hereinafter  described  in the event the Offer is  oversubscribed)  in  integral
multiples of $1,000 of principal amount,  at the applicable  purchase price. The
notice shall specify a purchase date not less than 30 days nor more than 60 days
after the date of such  notice  (the  "Purchase  Date")  and shall  contain  all
instructions and materials necessary to tender Notes pursuant to the Offer.

                  (2) Not later  than the date upon which  written  notice of an
Offer is delivered to the Trustee as provided below, the Issuer shall deliver to
the  Trustee  an  Officer's  Certificate  as to (i) the amount of the Offer (the
"Offer  Amount"),  (ii) the  allocation of the Net Available Cash from the Asset
Dispositions pursuant to which such Offer is being made and (iii) the compliance
of such allocation with the provisions of Section 4.7(a). Upon the expiration of
the period for which the Offer  remains  open (the "Offer  Period"),  the Issuer
shall  deliver to the Trustee  for  cancellation  the Notes or portions  thereof
which have been properly  tendered to and are to be accepted by the Issuer.  Not
later than 11:00 a.m.  (New York City  time) on the  Purchase  Date,  the Issuer
shall  irrevocably  deposit  with the Trustee or with a paying agent (or, if the
Issuer is acting as Paying Agent, segregate and hold in trust) an amount in cash
sufficient  to pay the Offer  Amount  for all Notes  properly  tendered  to, not
withdrawn from and accepted by the Issuer.  The Trustee  shall,  on the Purchase
Date,  mail or  deliver  payment to each  tendering  Holder in the amount of the
purchase price.

                  (3) Holders electing to have a Note purchased will be required
to  surrender  the Note,  together  with all  necessary  endorsements  and other
appropriate materials duly completed,  to the Issuer at the address specified in
the notice at least three Business Days prior to the Purchase Date. Holders will
be entitled to withdraw their election in whole or in part if the Trustee or the
Issuer  receives not later than one  Business Day prior to the Purchase  Date, a
facsimile  transmission  or letter  setting  forth the name of the  Holder,  the
principal  amount of the Note (which shall be $1,000 in  principal  amount or an
integral multiple  thereof) which was delivered for purchase by the Holder,  the
aggregate  principal  amount of such Note (if any) that  remains  subject to the
original notice of the Offer and that has been or will be delivered for purchase
by the Issuer and a statement  that such Holder is  withdrawing  his election to
have such Note purchased. If at the expiration of the Offer Period the aggregate
principal amount of Notes  surrendered by Holders exceeds the Offer Amount,  the
Trustee shall select the Notes to be purchased in accordance with the provisions
of  Section  3.2 (with  such  adjustments  as may be deemed  appropriate  by the
Trustee so that only securities in denominations of $1,000 principal  amount, or
integral  multiples  thereof,  shall be  purchased).  Holders  whose  Notes  are
purchased only in part will be issued new Notes equal in principal amount to the
unpurchased portion of the Notes surrendered.

                  (4) A Note shall be deemed to have been  accepted for purchase
at the time the Trustee, directly or through an agent, mails or delivers payment
therefor to the surrendering Holder.

                  (d) The Issuer will comply, to the extent applicable, with the
requirements of Section 14(e) of the Exchange Act and any other  securities laws
or  regulations  in connection  with the  repurchase  of Notes  pursuant to this
covenant.  To  the  extent  that  the  provisions  of  any

                                       34
<PAGE>   41

securities laws or regulations  conflict with  provisions of this covenant,  the
Issuer will comply with the applicable  securities laws and regulations and will
not be deemed to have  breached its  obligations  under this  covenant by virtue
thereof.

                  (e) The  provisions of this Section 4.7 shall not apply to any
transaction that is permitted under the provisions of Section 5.1.

                  SECTION 4.8.  Limitation on Transactions with Affiliates.  (a)
The Issuer will not, and will not permit any Restricted  Subsidiary to, directly
or indirectly,  enter into or conduct any  transaction or series of transactions
(including  the  purchase,  sale,  lease or exchange of any  property,  employee
compensation arrangements or the rendering of any service) with any Affiliate of
the  Issuer  (an  "Affiliate   Transaction")   unless  (i)  the  terms  of  such
transaction,  taken as a whole,  are no less  favorable  to the  Issuer  or such
Restricted Subsidiary,  as the case may be, than those that could be obtained at
the time of such  transaction in arm's-length  dealings with a Person who is not
such an  Affiliate;  (ii) in the event such  Affiliate  Transaction  involves an
aggregate  amount in excess of $5.0 million,  the terms of such  transaction are
set forth in writing  and shall have been  approved by a majority of the members
of the Board of Directors having no personal stake in such Affiliate Transaction
(and such majority  determines  that such  Affiliate  Transaction  satisfies the
criteria in clause (i) above) and (iii) in the event such Affiliate  Transaction
involves an aggregate amount in excess of $10.0 million, the Issuer has received
a written opinion from a nationally  recognized  independent  investment banking
firm that such  Affiliate  Transaction  is fair to the Issuer and its Restricted
Subsidiaries from a financial point of view.

                  (b) The  provisions of paragraph (a) of this Section 4.8 shall
not prohibit (i) any Restricted Payment permitted to be made pursuant to Section
4.5, (ii) any issuance of  securities,  or other  payments,  awards or grants in
cash,  securities  or  otherwise  pursuant  to, or the  funding  of,  employment
arrangements,  stock options and stock  ownership plans approved by the Board of
Directors,  or any  arrangements  relating  thereto,  (iii)  the  grant of stock
options or similar  rights to employees and directors of the Issuer  pursuant to
plans approved by the Board of Directors, (iv) loans or advances to employees in
the ordinary  course of business in  accordance  with the past  practices of the
Issuer or its  Restricted  Subsidiaries,  (v) the payment of reasonable  fees to
directors of the Issuer and its Restricted Subsidiaries who are not employees of
the Issuer or its  Restricted  Subsidiaries,  (vi) any  transaction  between the
Issuer and a Restricted Subsidiary or between Restricted Subsidiaries, (vii) the
issuance or sale of any Capital  Stock  (other than  Disqualified  Stock) of the
Issuer,  (viii)  any  transaction  consummated  pursuant  to  the  terms  of any
agreement  described in the Issuer's  Form 10-K for the year ended  December 31,
1999 or Forms 10-Q or Forms 8-K filed  prior to the Issue  Date,  including  the
exhibits and  documents  included by  reference  therein,  giving  effect to any
subsequent  supplements,  amendments,  modifications or alterations thereof that
are approved by the  disinterested  members of the Board of Directors,  (ix) any
transaction  in the  ordinary  course  of  business  between  the  Issuer or any
Restricted   Subsidiary  and  any  Affiliate  of  the  Issuer  relating  to  the
acquisition,  management,  construction,  leasing or licensing of Tower  Assets,
provided, however, that such transaction is on terms that are no less favorable,
taken as a whole, to the Issuer or the relevant Restricted Subsidiary than those
that could have been obtained in a comparable  transaction by the Issuer or such
Restricted  Subsidiary  with an unrelated  Person or is otherwise on terms that,
taken as a whole,  the  Issuer  has  determined  to be fair to the Issuer or the
relevant Restricted

                                       35
<PAGE>   42

Subsidiary) and (x) any transaction  between the Issuer or any of its Restricted
Subsidiaries  and any of its Affiliates  involving  ordinary  course  investment
banking, commercial banking or related activities.

                  SECTION 4.9.  Change of Control.  (a) Upon the occurrence of a
Change of Control,  each Holder  shall have the right to require that the Issuer
repurchase  all or any part of such Holder's  Notes at a purchase  price in cash
equal to 101% of the principal amount thereof as of the date of repurchase, plus
accrued and unpaid  interest,  if any, to the date of repurchase,  in accordance
with the terms contemplated in Section 4.9(b).

                  (b) Within 30 days following any Change of Control, the Issuer
shall mail a notice to each Holder at its registered  address with a copy to the
Trustee stating:

                           (1) that a Change of Control  has  occurred  and that
                  such  Holder has the right to require  the Issuer to  purchase
                  such  Holder's  Notes in  denominations  of  $1,000  principal
                  amount or any integral multiple thereof at a purchase price in
                  cash equal to 101% of the principal  amount  thereof as of the
                  date of repurchase,  plus accrued and unpaid interest, if any,
                  to the date of repurchase;

                           (2) the  circumstances  and relevant facts  regarding
                  such Change of Control (including  information with respect to
                  pro forma  historical  income,  cash  flow and  capitalization
                  after giving effect to such Change of Control);

                           (3) the  repurchase  date (which  shall be no earlier
                  than 30 days nor later than 60 days from the date such  notice
                  is mailed); and

                           (4)  the  instructions   determined  by  the  Issuer,
                  consistent with this Section 4.9, that a Holder must follow in
                  order to have its Notes purchased by the Issuer.

                  (c) Holders electing to have a Note purchased will be required
to  surrender  the Note,  together  with all  necessary  endorsements  and other
appropriate materials duly completed,  to the Issuer at the address specified in
the notice at least three Business Days prior to the purchase date. Holders will
be entitled to withdraw their election if the Trustee or the Issuer receives not
later than one Business Day prior to the purchase date, a facsimile transmission
or letter setting forth the name of the Holder, the principal amount of the Note
which was  delivered  for  purchase  by the  Holder as to which  such  notice of
withdrawal is being  submitted and a statement  that such Holder is  withdrawing
his election to have such Note purchased.

                  (d) On the purchase  date,  all Notes  purchased by the Issuer
under this Section 4.9 shall be delivered to the Trustee for  cancellation,  and
the Issuer shall pay the purchase price, including premium, if any, plus accrued
and unpaid interest, if any, to the Holders entitled thereto.

                  (e) The Issuer will comply, to the extent applicable, with the
requirements of Section 14(e) of the Exchange Act and any other  securities laws
or  regulations  in connection  with the  repurchase  of Notes  pursuant to this
Section  4.9.  To the  extent  that the  provisions  of any  securities  laws or
regulations conflict with provisions of this Section 4.9, the Issuer will

                                       36
<PAGE>   43

comply  with the  applicable  securities  laws and  regulations  and will not be
deemed  to have  breached  its  obligations  under  this  Section  4.9 by virtue
thereof.
                  (f) The Issuer will not be required to make an offer  pursuant
to this Section 4.9 upon a Change of Control if a third party, in the manner, at
the times and otherwise in compliance  with the  requirements  set forth in this
Indenture  applicable to a Change of Control made by the Issuer,  makes an offer
to purchase and  purchases all Notes  validly  tendered and not withdrawn  under
such offer.

                  (g) Notwithstanding the occurrence of a Change of Control, the
Issuer shall not be obligated to repurchase  the Notes or otherwise  comply with
this Section 4.9 if the Issuer has  irrevocably  elected to redeem all the Notes
in accordance with Article III; provided that the Issuer does not default in its
redemption obligations pursuant to such election.

                  SECTION 4.10.  Limitation on Sale or Issuance of Capital Stock
of  Restricted  Subsidiaries.  The Issuer (i) will not,  and will not permit any
Restricted Subsidiary to, transfer,  convey, sell, lease or otherwise dispose of
any Capital Stock of any Restricted  Subsidiary to any Person (other than to the
Issuer or a Wholly Owned  Subsidiary),  and (ii) will not permit any  Restricted
Subsidiary  to  issue  any of its  Capital  Stock  (other  than,  to the  extent
necessary  or  mandated  by  applicable   law,   shares  of  its  Capital  Stock
constituting  directors' qualifying shares or the ownership by foreign nationals
of Capital Stock of any  Restricted  Subsidiary) to any Person other than to the
Issuer or a Subsidiary  unless in either case (a) the  Issuer's  and  Restricted
Subsidiary's  minority equity interest in such Person after giving effect to any
such  disposition,  would be permitted  under  Section 4.5; and (b) the net cash
proceeds from such transfer,  conveyance,  sale, lease or other  disposition are
applied in accordance with Section 4.7.

                  SECTION 4.11.  Limitation  on Liens.  The Issuer will not, and
will not permit any Restricted Subsidiary to, directly or indirectly,  create or
permit to exist any Lien on any of its  property  or assets  (including  Capital
Stock),  whether  owned on the Issue Date or thereafter  acquired,  securing any
obligation,  other than  Permitted  Liens,  unless  contemporaneously  therewith
effective  provision is made to secure the Notes equally and ratably with (or on
a senior basis to, in the case of Subordinated  Obligations) such obligation for
so long as such obligation is so secured.

                  SECTION 4.12. Limitation on Sale/Leaseback  Transactions.  The
Issuer will not, and will not permit any  Restricted  Subsidiary  to, enter into
any  Sale/Leaseback  Transaction  with  respect to any  property  unless (i) the
Issuer or such Restricted Subsidiary would be entitled to (A) Incur Indebtedness
in an  amount  equal  to the  Attributable  Indebtedness  with  respect  to such
Sale/Leaseback Transaction pursuant to Section 4.3 and (B) create a Lien on such
property  securing such  Attributable  Indebtedness  without equally and ratably
securing the Notes pursuant to Section 4.11, (ii) the net cash proceeds received
by  the  Issuer  or  any   Restricted   Subsidiary  in   connection   with  such
Sale/Leaseback  Transaction  are at least equal to the fair value (as determined
in good faith by the Board of Directors) of such property and (iii) the transfer
of such property is permitted by, and the Issuer or such  Restricted  Subsidiary
applies the proceeds of such transaction in compliance with, Section 4.7.

                                       37
<PAGE>   44


                  SECTION 4.13.  Compliance  with Laws. The Issuer shall comply,
and  shall  cause  each of its  Restricted  Subsidiaries  to  comply,  with  all
applicable statutes, rules,  regulations,  orders and restrictions of the United
States  of  America,   all  states  and  municipalities   thereof,  and  of  any
governmental department, commission, board, regulatory authority, bureau, agency
and  instrumentality  of the  foregoing,  in  respect  of the  conduct  of their
respective businesses and the ownership of their respective  properties,  except
for such noncompliances as are not in the aggregate  reasonably likely to have a
material  adverse effect on the financial  condition or results of operations of
the Issuer and its Subsidiaries, taken as a whole.

                  SECTION 4.14. Compliance Certificate. The Issuer shall deliver
to the  Trustee  within 120 days after the end of each fiscal year of the Issuer
an  Officer's  Certificate  signed by the  chief  executive  officer,  the chief
financial officer or the chief accounting  officer stating that in the course of
the performance by the signer of his duties as an Officer of the Issuer he would
normally  have  knowledge  of any Default or Event of Default and whether or not
the signers  know of any Default or Event of Default that  occurred  during such
period.  If he does,  the  certificate  shall  describe  the Default or Event of
Default,  its status and what  action the Issuer is taking or  proposes  to take
with respect thereto. The Issuer also shall comply with TIA ss. 314(a)(4).

                  SECTION 4.15.  Further  Instruments  and Acts. Upon reasonable
request of the  Trustee,  the Issuer  will  execute  and  deliver  such  further
instruments and do such further acts as may be reasonably necessary or proper to
carry out more effectively the purpose of this Indenture.

                  SECTION  4.16.  Maintenance  of Office or  Agency.  The Issuer
shall maintain the office or agency required under Section 2.3. The Issuer shall
give prior written notice to the Trustee of the location,  and any change in the
location,  of such  office or agency.  If at any time the  Issuer  shall fail to
maintain any such required office or agency or shall fail to furnish the Trustee
with the address thereof,  such presentations,  surrenders,  notices and demands
may be made or served at the address of the Trustee set forth in Section 10.2.

                  SECTION  4.17.  Corporate   Existence.   Except  as  otherwise
permitted by Article V and Section 4.9, the Issuer shall do or cause to be done,
at its own cost and expense,  all things  necessary to preserve and keep in full
force and effect its  corporate  existence  and the  corporate,  partnership  or
limited liability  company existence of each of its Significant  Subsidiaries in
accordance with the respective  organizational documents of each such Subsidiary
and the material rights (charter and statutory) and franchises of the Issuer and
each such Subsidiary;  provided,  however, that the Issuer shall not be required
to preserve,  with respect to itself,  any material right or franchise and, with
respect to any of its Significant  Subsidiaries,  any such  existence,  material
right or  franchise,  if the Board of  Directors  shall  determine in good faith
(such   determination  to  be  evidenced  by  a  board  resolution),   that  the
preservation  thereof is no longer  desirable  in the conduct of the business of
the Issuer and the Subsidiaries, taken as a whole.

                  SECTION 4.18.  Payment of Taxes and Other  Claims.  The Issuer
shall pay or discharge or cause to be paid or discharged,  before the same shall
become delinquent,  (i) all material taxes, assessments and governmental charges
(including withholding taxes and any

                                       38
<PAGE>   45

penalties,  interest and additions to taxes) levied or imposed upon it or any of
its  Restricted  Subsidiaries  or  properties  of it or any  of  its  Restricted
Subsidiaries and (ii) all lawful claims for labor,  materials and supplies that,
if  unpaid,  might by law  become a Lien upon the  property  of it or any of its
Restricted Subsidiaries; provided, however, that the Issue shall not be required
to pay or discharge or cause to be paid or discharged any such tax,  assessment,
charge or claim whose amount,  applicability  or validity is being  contested in
good  faith  by  appropriate  proceedings  properly  instituted  and  diligently
conducted for which adequate  reserves,  to the extent required under GAAP, have
been taken.

                  SECTION 4.19. Maintenance of Properties and Insurance. (a) The
Issuer shall, and shall cause each of its Significant  Subsidiaries to, maintain
its material properties in good working order and condition (subject to ordinary
wear and tear)  and make or cause to be made all  necessary  repairs,  renewals,
replacements,  additions,  betterments  and  improvements  thereto and  actively
conduct  and carry on its  business,  all as in the  reasonable  judgment of the
Issuer  is  necessary  so  that  the  business  carried  on by  Issuer  and  its
Significant  Subsidiaries may be actively  conducted;  provided,  however,  that
nothing in this Section 4.19 shall prevent the Issuer or any of its Subsidiaries
from  discontinuing  the operation and maintenance of any of its properties,  if
such  discontinuance  is,  in the  good  faith  judgment  of the  Issuer  or the
Subsidiary,  as the case may be,  desirable  in the conduct of their  respective
businesses and is not disadvantageous in any material respect to the Holders.

                  (b) The  Issuer  shall  provide or cause to be  provided,  for
itself  and  each  of  its  Significant   Subsidiaries,   insurance   (including
appropriate  self-insurance)  against  loss or damage of the kinds that,  in the
good faith judgment of the Issuer,  are adequate and appropriate for the conduct
of the business of the Issuer and such  Subsidiaries in a prudent  manner,  with
reputable  insurers or with the government of the United States of America,  any
state  thereof or any agency or  instrumentality  of such  governments,  in such
amounts,  with such deductibles,  and by such methods as shall be customary,  in
the good faith judgment of the Issuer,  for companies  similarly situated in the
industry.

                                    ARTICLE V
                                SUCCESSOR ISSUER

                  SECTION 5.1. When the Issuer May Merge or Transfer Assets. The
Issuer will not consolidate  with or merge with or into, or convey,  transfer or
lease, in one transaction or a series of transactions,  all or substantially all
its assets to, any Person, unless:

                  (i)  the  resulting,   surviving  or  transferee  Person  (the
         "Successor  Issuer") will be a Person  organized and existing under the
         laws of the United States of America, any State thereof or the District
         of Columbia and the Successor Issuer (if not the Issuer) will expressly
         assume,  by  supplemental  indenture,  executed  and  delivered  to the
         Trustee,  in form  satisfactory to the Trustee,  all the obligations of
         the Issuer under the Notes and this Indenture;

                  (ii) immediately  after giving effect to such transaction on a
         pro forma  basis  (and  treating  any  Indebtedness  which  becomes  an
         obligation of the Successor  Issuer or any  Restricted  Subsidiary as a
         result of such  transaction  as having been  Incurred by the

                                       39
<PAGE>   46

         Successor Issuer or such Restricted  Subsidiary at the time of such
         transaction), no Default or Event of Default will have occurred and be
         continuing;

                  (iii)  except (A) in the case of a merger of the Issuer into a
         Wholly  Owned  Subsidiary,  (B) a merger  entered  into  solely for the
         purpose of reincorporating the Issuer in another  jurisdiction or (C) a
         merger  the Issuer  enters  into  solely  for the  purpose of forming a
         holding  company to hold all of the  outstanding  capital  stock of the
         Issuer,  immediately  after giving effect to such  transaction on a pro
         forma basis as if such transaction had occurred at the beginning of the
         applicable four quarter  period,  the Issuer or the Person formed by or
         surviving any such  consolidation or merger (if other than the Issuer),
         or to which such conveyance, transfer, lease or other disposition shall
         have been made,  either (x) would have been permitted to incur at least
         $1.00 of additional Indebtedness under Section 4.3(a) or (y) would have
         had an Indebtedness to Adjusted EBITDA Ratio  immediately  after giving
         effect to such consolidation,  merger,  conveyance,  transfer, lease or
         other  disposition no greater than the  Indebtedness to Adjusted EBITDA
         Ratio immediately prior to such transaction; and

                  (iv)  the  Issuer  will  have  delivered  to  the  Trustee  an
         Officer's Certificate and an Opinion of Counsel, each stating that such
         consolidation,  merger or transfer and such supplemental  indenture (if
         any) comply with this Indenture, as set forth in this Indenture.

                  The Successor  Issuer will succeed to, and be substituted for,
and may exercise every right and power of, the Issuer under this Indenture,  but
the predecessor Issuer in the case of a conveyance, transfer or lease of all its
assets or  substantially  all its assets will be released  from the  obligations
under this Indenture and the Notes,  including without limitation the obligation
to pay the principal of and interest on the Notes.

                                   ARTICLE VI
                              DEFAULTS AND REMEDIES

                  SECTION 6.1.  Events of Default.  An "Event of Default" occurs
if:

                  (1) the Issuer defaults in any payment of interest on any Note
         when the same becomes due and payable, and such default continues for a
         period of 30 days;

                  (2) the Issuer defaults in the payment of the principal of any
         Note when the same becomes due and payable at its Stated Maturity, upon
         optional  or  mandatory  redemption,  upon  required  repurchase,  upon
         declaration or otherwise;

                  (3) the  Issuer  fails to comply  with its  obligations  under
Article V;

                  (4) the Issuer  fails to comply with Section  4.2,  4.3,  4.4,
         4.5, 4.6, 4.7,  4.8, 4.9,  4.10,  4.11 or 4.12 (other than a failure to
         purchase  Notes when  required  pursuant to Section  4.7 or 4.9,  which
         failure shall  constitute an Event of Default under Section 6.1(2)) and
         such failure continues for 30 days after the notice specified below;

                                       40
<PAGE>   47

                  (5) the Issuer fails to comply with any of its  agreements  in
         the Notes or this Indenture  (other than those referred to in (1), (2),
         (3) or (4)  above)  and such  failure  continues  for 60 days after the
         notice specified below;

                  (6) the  Issuer or any  Significant  Subsidiary  of the Issuer
         fails  to pay any  Indebtedness  within  any  applicable  grace  period
         provided in such Indebtedness  after final maturity or the acceleration
         of any such Indebtedness by the holders thereof because of a default if
         the total amount of such  Indebtedness  unpaid or  accelerated  exceeds
         $10.0 million or its foreign currency equivalent at the time;

                  (7) the  Issuer  or a  Significant  Subsidiary  of the  Issuer
         pursuant to or within the meaning of any Bankruptcy Law:

                           (A)      commences a voluntary case;

                           (B)  consents  to the  entry of an order  for  relief
                  against it in an involuntary case in which it is the debtor;

                           (C) consents to the  appointment of a Custodian of it
                  or for any substantial part of its property; or

                           (D)      makes a general assignment for the benefit
of its creditors;

                  or takes any comparable action under any foreign laws relating
to insolvency;

                  (8)      a court of competent jurisdiction enters an order or
decree under any Bankruptcy Law that:

                           (A)      is for relief against the Issuer or any
Significant Subsidiary of the Issuer in an involuntary case;

                           (B)  appoints  a  Custodian  of  the  Issuer  or  any
                  Significant  Subsidiary  or for  any  substantial  part of its
                  property of the Issuer or any Significant Subsidiary; or

                           (C)  orders  the  winding  up or  liquidation  of the
                  Issuer or any Significant Subsidiary of the Issuer

         (or any  similar  relief is  granted  under any  foreign  laws) and the
         order, decree or relief remains unstayed and in effect for 90 days; or

                  (9) any final  judgment  or decree for the payment of money in
         excess of $10.0  million  (net of any amounts  with  respect to which a
         creditworthy insurance company has acknowledged full liability (subject
         to any  deductible  amounts of less than $10.0  million  required to be
         paid by the  Issuer  or the  Significant  Subsidiary  of the  Issuer in
         accordance with the applicable  insurance  policy)) is rendered against
         the Issuer or any  Significant  Subsidiary of the Issuer and either (A)
         an enforcement  proceeding has been commenced by any creditor upon such
         judgment or decree or (B) such  judgment or decree  remains

                                       41
<PAGE>   48

         unpaid and outstanding  for a period of 60 days following such judgment
         and is not discharged, waived or stayed within 10 days after notice.

                  The foregoing will constitute  Events of Default  whatever the
reason for any such Event of Default and whether it is voluntary or  involuntary
or is effected by operation of law or pursuant to any judgment,  decree or order
of any  court  or any  order,  rule  or  regulation  of  any  administrative  or
governmental body.

                  The term  "Bankruptcy Law" means Title 11, United States Code,
or any  similar  Federal  or  state  law for the  relief  of  debtors.  The term
"Custodian"  means any receiver,  trustee,  assignee,  liquidator,  custodian or
similar official under any Bankruptcy Law.

                  A Default under clause (4), (5) and (9) of this Section 6.1 is
not an Event of Default until the Trustee by notice to the Issuer or the Holders
of at least 25% in aggregate principal amount of the outstanding Notes by notice
to the Issuer  give  notice of the  Default  and the  Issuer  does not cure such
Default  within the time  specified in said clause (4), (5) or (9) after receipt
of such notice. Such notice must specify the Default, demand that it be remedied
and state that such notice is a "Notice of Default".

                  The Issuer shall deliver to the Trustee,  within 30 days after
it obtains knowledge of the occurrence thereof, written notice in the form of an
Officer's  Certificate  of any Event of Default under clause (6) of this Section
6.1 and any event  which  with the  giving of notice or the lapse of time  would
become an Event of Default  under clause (4), (5) or (9) of this Section 6.1 and
what action the Issuer is taking or proposes to take with respect thereto.

                  SECTION 6.2. Acceleration.  If an Event of Default (other than
an Event of  Default  specified  in  Section  6.1(7) or (8) with  respect to the
Issuer)  occurs and is continuing,  the Trustee by notice to the Issuer,  or the
Holders of at least 25% in aggregate  principal amount of the outstanding  Notes
by notice to the Issuer,  may declare the  principal  amount of, and accrued but
unpaid interest on all the Notes to be due and payable. Upon such a declaration,
such principal amount and interest shall be due and payable  immediately.  If an
Event of Default  specified in Section  6.1(7) or (8) with respect to the Issuer
occurs and is continuing,  the principal  amount of, and accrued interest on all
the Notes shall ipso facto become and be immediately due and payable without any
declaration or other act on the part of the Trustee or any Holders.  The Holders
of a majority in aggregate  principal amount of the outstanding  Notes by notice
to  the  Trustee  may  rescind  an  acceleration  and  its  consequences  if the
rescission  would not  conflict  with any judgment or decree and if all existing
Events of Default have been cured or waived  except  nonpayment  of principal or
interest that has become due solely because of acceleration  and the Trustee has
been paid all  amounts due to it  pursuant  to Section  7.7. No such  rescission
shall affect any subsequent Default or impair any right consequent thereto.

                  SECTION 6.3. Other Remedies. If an Event of Default occurs and
is  continuing,  the  Trustee  may pursue any  available  remedy to collect  the
payment  of  principal  amount of or  interest  on the Notes or to  enforce  the
performance of any provision of the Notes or this Indenture.

                                       42
<PAGE>   49

                  The  Trustee  may  maintain a  proceeding  even if it does not
possess any of the Notes or does not produce  any of them in the  proceeding.  A
delay or omission by the Trustee or any  Noteholder in  exercising  any right or
remedy accruing upon an Event of Default shall not impair the right or remedy or
constitute  a waiver of or  acquiescence  in the Event of Default.  No remedy is
exclusive  of any other  remedy.  All  available  remedies  are,  to the  extent
permitted by law, cumulative.

                  SECTION  6.4.  Waiver  of  Past  Defaults.  The  Holders  of a
majority in aggregate  principal  amount of the Notes then outstanding by notice
to the  Trustee  may waive any past or  existing  Default  and its  consequences
except (i) a Default in the payment of the principal of or interest on a Note or
(ii) a Default in  respect  of a  provision  that  under  Section  9.2 cannot be
amended  without  the  consent of each  Noteholder  affected.  When a Default is
waived,  it is deemed cured, and any Event of Default arising therefrom shall be
deemed to have been cured,  but no such waiver shall extend to any subsequent or
other Default or impair any consequent right.

                  SECTION 6.5. Control by Majority. Upon provision of reasonable
indemnity to the Trustee  satisfactory to the Trustee, the Holders of a majority
in aggregate principal amount of the Notes then outstanding may direct the time,
method and place of conducting any  proceeding  for any remedy  available to the
Trustee or of exercising any trust or power  conferred on the Trustee.  However,
the  Trustee,  which may rely on opinions  of counsel,  may refuse to follow any
direction  that conflicts with law or this Indenture or, subject to Section 7.1,
that the  Trustee  determines  is  unduly  prejudicial  to the  rights  of other
Noteholders  or would  involve  the  Trustee in  personal  liability;  provided,
however, that the Trustee may take any other action deemed proper by the Trustee
that is not inconsistent with such direction.

                  SECTION 6.6.  Limitation on Suits.  A Holder may not pursue
any remedy with respect to this Indenture or the Notes unless:

                  (i)      the Holder gives to the Trustee previous written
notice stating that an Event of Default is continuing;

                  (ii) the Holders of at least 25% in aggregate principal amount
         of the Notes then  outstanding make a written request to the Trustee to
         pursue the remedy;

                  (iii) such Holder or Holders  offer to the Trustee  reasonable
         security or indemnity against any loss, liability or expense;

                  (iv) the Trustee  does not comply  with the request  within 60
         days  after  receipt  of the  request  and the  offer  of  security  or
         indemnity; and

                  (v) the Holders of a majority in aggregate principal amount of
         the  Notes  then  outstanding  do not  give  the  Trustee  a  direction
         inconsistent with such request within such 60-day period.

                  A  Noteholder  may not use this  Indenture  to  prejudice  the
rights of another  Noteholder or to obtain a preference or priority over another
Noteholder.

                                       43
<PAGE>   50

                  SECTION   6.7.   Rights  of  Holders   to   Receive   Payment.
Notwithstanding  any other provision of this Indenture,  the right of any Holder
to receive payment of the principal  amount of and interest on the Notes held by
such Holder,  on or after the respective due dates expressed in the Notes, or to
bring suit for the  enforcement of any such payment on or after such  respective
dates, shall not be impaired or affected without the consent of such Holder.

                  SECTION  6.8.  Collection  Suit by  Trustee.  If an  Event  of
Default specified in Section 6.1(1) or (2) occurs and is continuing, the Trustee
may recover  judgment in its own name and as trustee of an express trust against
the Issuer for the whole amount then due and owing  (together  with  interest on
any unpaid  interest  to the extent  lawful)  and the  amounts  provided  for in
Section 7.7.

                  SECTION 6.9. Trustee May File Proofs of Claim. The Trustee may
file such proofs of claim and other  papers or  documents as may be necessary or
advisable in order to have the claims of the Trustee and the Noteholders allowed
in any  judicial  proceedings  relative  to the  Issuer,  its  creditors  or its
property and shall be entitled and empowered to collect,  receive and distribute
any money or other  securities or property  payable or  deliverable  on any such
claims and to distribute the same, and,  unless  prohibited by law or applicable
regulations,  may vote on behalf of the Holders in any  election of a trustee in
bankruptcy or other Person performing  similar  functions,  and any Custodian in
any such  judicial  proceeding  is  hereby  authorized  by each  Holder  to make
payments to the Trustee and, in the event that the Trustee  shall consent to the
making of such  payments  directly  to the  Holders,  to pay to the  Trustee any
amount  due it for the  reasonable  compensation,  expenses,  disbursements  and
advances of the Trustee,  its agents and its counsel,  and any other amounts due
the Trustee under Section 7.7.

                  SECTION 6.10.  Priorities.  If the Trustee collects any money
or property pursuant to this Article VI, it shall pay out the money or property
in the following order:

                  FIRST:  to the Trustee for amounts due under Section 7.7;

                  SECOND:  to Noteholders for amounts due and unpaid on the
          Notes for principal and interest, ratably, without preference or
          priority of any kind, according to the amounts due and payable on the
          Notes for principal amount and interest, respectively; and

                  THIRD:  to the Issuer or to such party as a court of competent
          jurisdiction shall direct.

                  The Trustee  may fix a record  date and  payment  date for any
payment to  Noteholders  pursuant to this Section  6.10. At least 15 days before
such record  date,  the Issuer shall mail to each  Noteholder  and the Trustee a
notice that states the record date, the payment date and amount to be paid.

                  SECTION  6.11.  Undertaking  for  Costs.  In any  suit for the
enforcement  of any right or remedy under this  Indenture or in any suit against
the  Trustee for any action  taken or omitted by it as  Trustee,  a court in its
discretion  may  require  the  filing  by any party  litigant  in the suit of an
undertaking  to pay the costs of the suit,  and the court in its  discretion may
assess  reasonable  costs,  including  reasonable  attorneys' fees and expenses,
against any party litigant in the suit, having due regard to the merits and good
faith of the claims or defenses  made by the

                                       44
<PAGE>   51

party  litigant.  This Section  6.11 does not apply to a suit by the Trustee,  a
suit by a Holder  pursuant  to Section 6.7 or a suit by Holders of more than 10%
in aggregate principal amount of the outstanding Notes.

                  SECTION 6.12. Waiver of Stay or Extension Laws. The Issuer (to
the extent it may lawfully do so) shall not at any time insist  upon,  or plead,
or in any manner  whatsoever claim or take the benefit or advantage of, any stay
or extension law wherever enacted,  now or at any time hereafter in force, which
may affect the covenants or the  performance of this  Indenture;  and the Issuer
(to the extent that it may lawfully do so) hereby  expressly  waives all benefit
or  advantage  of any such  law,  and  shall not  hinder,  delay or  impede  the
execution  of any power  herein  granted to the  Trustee,  but shall  suffer and
permit the execution of every such power as though no such law had been enacted.

                                   ARTICLE VII
                                     TRUSTEE

                  SECTION 7.1. Duties of Trustee. (a) If an Event of Default has
occurred and is  continuing,  the Trustee  shall  exercise the rights and powers
vested  in it by this  Indenture  and use the same  degree  of care and skill in
their exercise as a prudent Person would exercise or use under the circumstances
in the conduct of such Person's own affairs.

                  (b)      Except during the continuance of an Event of Default:

                  (i) the  Trustee  undertakes  to perform  such duties and only
         such duties as are specifically set forth in this Indenture and the TIA
         and no  implied  covenants  or  obligations  shall  be read  into  this
         Indenture against the Trustee; and

                  (ii) in the absence of bad faith on its part,  the Trustee may
         conclusively   rely,  as  to  the  truth  of  the  statements  and  the
         correctness of the opinions  expressed  therein,  upon  certificates or
         opinions furnished to the Trustee and conforming to the requirements of
         this  Indenture.  However,  in the  case of any  such  certificates  or
         opinions which by any provision hereof are specifically  required to be
         furnished to the Trustee,  the Trustee shall  examine the  certificates
         and  opinions  to  determine   whether  or  not  they  conform  to  the
         requirements of this Indenture.

                  (c) The Trustee may not be relieved from liability for its own
negligent  action,  its  own  negligent  failure  to  act  or  its  own  willful
misconduct, except that:

                  (i)      this paragraph does not limit the effect of paragraph
(b) of this Section 7.1;

                  (ii) the Trustee shall not be liable for any error of judgment
         made in good  faith by a Trust  Officer  unless it is  proved  that the
         Trustee was negligent in ascertaining the pertinent facts; and

                  (iii) the  Trustee  shall not be liable  with  respect  to any
         action  it takes or omits to take in good  faith in  accordance  with a
         direction received by it pursuant to Section 6.5.

                                       45
<PAGE>   52

                  (d)  Whether  or not  therein  expressly  so  provided,  every
provision of this Indenture that in any way relates to the Trustee is subject to
paragraphs (a), (b) and (c) of this Section 7.1.

                  (e) Money held in trust by the Trustee need not be  segregated
from other funds except to the extent required by law.

                  (f) No provision of this  Indenture  shall require the Trustee
to expend or risk its own funds or otherwise  incur  financial  liability in the
performance  of any of its duties  hereunder  or in the  exercise  of any of its
rights or powers, if it shall have reasonable  grounds to believe that repayment
of such  funds or  adequate  indemnity  against  such risk or  liability  is not
reasonably assured to it.

                  (g) Every provision of this Indenture  relating to the conduct
or affecting  the  liability of or affording  protection to the Trustee shall be
subject to the provisions of this Section 7.1 and to the provisions of the TIA.

                  SECTION 7.2. Rights of Trustee. (a) The Trustee may rely upon,
and shall be fully  protected  from acting or  refraining  from  acting,  on any
document  believed by it to be genuine and to have been signed or  presented  by
the proper person. The Trustee need not investigate any fact or matter stated in
the document.

                  (b) Before the Trustee acts or refrains  from  acting,  it may
request an Officer's  Certificate  or an Opinion of Counsel or both. The Trustee
shall not be liable  for any  action it takes or omits to take in good  faith in
reliance on the Officer's Certificate or Opinion of Counsel.

                  (c) The  Trustee  may act  through  agents  and  shall  not be
responsible  for the  misconduct or negligence of any agent  appointed  with due
care.

                  (d) The Trustee shall not be liable for any action it takes or
omits to take in good faith  which it believes  to be  authorized  or within its
rights  or  powers;  provided,  however,  that the  Trustee's  conduct  does not
constitute willful misconduct or negligence.

                  (e) The Trustee may consult with counsel of its selection, and
the advice or opinion of counsel with respect to legal matters  relating to this
Indenture and the Notes shall be full and complete  authorization and protection
from  liability  in respect  to any action  taken,  omitted  or  suffered  by it
hereunder  in good  faith and in  accordance  with the advice or opinion of such
counsel.

                  (f) The Trustee  shall be under no  obligation to exercise any
of the  rights  or powers  vested  in it by this  Indenture  at the  request  or
direction of any of the Holders pursuant to this Indenture,  unless such Holders
shall have offered to the Trustee  reasonable  security or indemnity against the
costs, expenses and liabilities which might be incurred by it in compliance with
such request or direction.

                  (g) The Trustee  shall not be charged  with  knowledge  of any
Default or Event of Default with respect to the Notes unless  either (1) a Trust
Officer  shall have actual  knowledge

                                       46
<PAGE>   53

of such  Default or Event of Default or (2)  written  notice of such  Default or
Event of Default  shall  have been given to the  Trustee by the Issuer or by any
Holder of the Notes.

                  SECTION 7.3. Individual Rights of Trustee.  The Trustee in its
individual  or any other  capacity  may become the owner or pledgee of Notes and
may otherwise  deal with the Issuer or its respective  Affiliates  with the same
rights  it would  have if it were not  Trustee.  Any  Paying  Agent,  Registrar,
co-registrar or co-paying agent may do the same with like rights.  However,  the
Trustee must comply with Sections 7.10 and 7.11.

                  SECTION 7.4.  Trustee's  Disclaimer.  The Trustee shall not be
responsible  for and makes no  representation  as to the validity or adequacy of
this Indenture or the Notes, it shall not be accountable for the Issuer's use of
the proceeds from the Notes,  and it shall not be responsible  for any statement
of the Issuer in this Indenture or in any document issued in connection with the
sale of the  Notes or in the  Notes  other  than the  Trustee's  certificate  of
authentication.

                  SECTION 7.5.  Notice of Defaults.  If a Default or an Event of
Default occurs and is continuing and if it is known to the Trustee,  the Trustee
must mail to each Noteholder notice of the Default within the earlier of 90 days
after it  occurs  or 30 days  after it is known to a Trust  Officer  or  written
notice of it is  received  by the  Trustee.  Except in the case of a Default  in
payment of principal of,  premium (if any) or interest on any Note,  the Trustee
may withhold  notice if and so long as a committee of its Trust Officers in good
faith  determines  that  withholding  notice is not opposed to the  interests of
Noteholders.

                  SECTION  7.6.  Reports by Trustee to  Holders.  As promptly as
practicable  after each January 15 beginning  with the January 15 following  the
date of this  Indenture,  and in any event  prior to March 15 in each year,  the
Trustee, if applicable, shall mail to each Noteholder a brief report dated as of
such January 15 that complies with TIA ss. 313(a). The Trustee also shall comply
with TIA ss. 313(b).  The Trustee shall promptly deliver to the Issuer a copy of
any report it delivers to Holders pursuant to this Section 7.6.

                  A  copy  of  each  report  at  the  time  of  its  mailing  to
Noteholders  shall be filed by the Trustee with the SEC and each stock  exchange
(if any) on which the Notes are listed. The Issuer agrees to notify promptly the
Trustee  whenever  the Notes  become  listed on any  stock  exchange  and of any
delisting thereof.

                  SECTION 7.7. Compensation and Indemnity.  The Issuer shall pay
to the  Trustee  from time to time such  compensation  for its  services  as the
Issuer and the Trustee  shall from time to time agree in writing.  The Trustee's
compensation  shall not be limited by any law on compensation of a trustee of an
express  trust.  The Issuer  shall  reimburse  the Trustee  upon request for all
reasonable fees and expenses, including out-of-pocket expenses, incurred or made
by it in connection  with the  performance  of its duties  hereunder,  including
costs of collection,  in addition to such compensation for its services,  except
any such  expense,  disbursement  or advance  as may arise from its  negligence,
willful misconduct or bad faith, unless the Trustee shall have complied with the
applicable standard of care required by the TIA. Such expenses shall include the
reasonable  compensation  and  expenses,   disbursements  and  advances  of  the
Trustee's agents,  counsel,  accountants and experts.  The Trustee shall provide
the Issuer

                                       47
<PAGE>   54

reasonable  notice of any  expenditure  not in the ordinary  course of business;
provided that prior approval by the Issuer of any such expenditure  shall not be
a requirement for the making of such  expenditure nor for  reimbursement  by the
Issuer  thereof.  The  Issuer  shall  indemnify  each  of the  Trustee  and  any
predecessor  Trustees (and their respective officers,  directors,  employees and
agents) against any and all loss, damage, claim, liability or expense (including
reasonable  attorneys'  fees and expenses)  (other than taxes  applicable to the
Trustee's  compensation  hereunder)  incurred  by  it  in  connection  with  the
acceptance or  administration  of this trust and the  performance  of its duties
hereunder.  The Trustee shall notify the Issuer  promptly of any claim for which
it may seek indemnity.  Failure by the Trustee to so notify the Issuer shall not
relieve the Issuer of its  obligations  hereunder.  The Issuer  shall defend the
claim and the Trustee  may have  separate  counsel,  and the Issuer will pay the
reasonable fees and expenses of such counsel.  The Issuer need not reimburse any
expense or  indemnify  against any loss,  liability  or expense  incurred by the
Trustee through the Trustee's own willful  misconduct,  negligence or bad faith,
unless the Trustee  shall have  complied  with the  applicable  standard of care
required by the TIA.

                  To secure the  Issuer's  payment  obligations  in this Section
7.7,  the Trustee  shall have a lien prior to the Notes on all money or property
held or collected by the Trustee  other than money or property  held in trust to
pay principal of and interest on particular Notes.

                  The Issuer's payment obligations  pursuant to this Section 7.7
shall  survive the  resignation  or removal of the Trustee and discharge of this
Indenture.  When the Trustee  incurs  expenses after the occurrence of a Default
specified in Section 6.1(7) or (8) with respect to the Issuer,  the expenses are
intended to constitute  expenses of  administration  under the  Bankruptcy  Law,
provided,  however, that this shall not affect the Trustee's rights as set forth
in the preceding paragraph or Section 6.10.

                  SECTION 7.8. Replacement of Trustee. The Trustee may resign at
any time with 30 days'  notice to the  Issuer.  The  Holders  of a  majority  in
principal amount of the Notes then  outstanding,  may remove the Trustee with 30
days notice to the Trustee and the Issuer and may appoint a successor Trustee.
The Issuer shall remove the Trustee if:

                  (i)       the Trustee fails to comply with Section 7.10;

                  (ii)     the Trustee is adjudged bankrupt or insolvent;

                  (iii) a receiver or other public  officer  takes charge of the
Trustee or its property; or

                  (iv) the Trustee otherwise becomes incapable of acting.

                  If the  Trustee  resigns,  is  removed by the Issuer or by the
Holders of a majority in  principal  amount of the Notes and such Holders do not
reasonably  promptly appoint a successor Trustee,  or if a vacancy exists in the
office of Trustee  for any reason (the  Trustee in such event being  referred to
herein as the retiring  Trustee),  the Issuer shall promptly appoint a successor
Trustee.

                  A successor Trustee shall deliver a written  acceptance of its
appointment to the retiring Trustee and to the Issuer. Thereupon the resignation
or removal of the retiring  Trustee

                                       48
<PAGE>   55

shall become  effective,  and the  successor  Trustee shall have all the rights,
powers and duties of the Trustee under this  Indenture.  The  successor  Trustee
shall mail a notice of its succession to Noteholders. The retiring Trustee shall
promptly  transfer all property held by it as Trustee to the successor  Trustee,
subject to the lien provided for in Section 7.7.

                  If a successor  Trustee  does not take  office  within 30 days
after the retiring  Trustee resigns or is removed,  the retiring  Trustee or the
Holders  of 10% in  principal  amount  of the Notes  may  petition  any court of
competent jurisdiction for the appointment of a successor Trustee.

                  If  the  Trustee  fails  to  comply  with  Section  7.10,  any
Noteholder may petition any court of competent  jurisdiction  for the removal of
the Trustee and the appointment of a successor Trustee.

                  SECTION  7.9.  Successor  Trustee  by Merger.  If the  Trustee
consolidates  with,  merges or converts into, or transfers all or  substantially
all its corporate  trust business or assets to,  another  corporation or banking
association,  the  resulting,  surviving or transferee  corporation  without any
further act shall be the successor Trustee, provided that such corporation shall
be eligible under this Article VII and TIA ss. 3.10(a).

                  In case at the time such  successor or  successors  by merger,
conversion or  consolidation  to the Trustee shall succeed to the trusts created
by this  Indenture  any of the  Notes  shall  have  been  authenticated  but not
delivered,  any such  successor  to the  Trustee  may adopt the  certificate  of
authentication   of  any  predecessor   trustee,   and  deliver  such  Notes  so
authenticated;  and in case at that  time any of the  Notes  shall not have been
authenticated,  any successor to the Trustee may authenticate  such Notes either
in the name of any predecessor  hereunder or in the name of the successor to the
Trustee; and in all such cases such certificates shall have the full force which
it is anywhere in the Notes or in this Indenture  provided that the  certificate
of the Trustee shall have.

                  SECTION 7.10. Eligibility; Disqualification. The Trustee shall
at all times satisfy the requirements of TIA ss. 310(a).  The Trustee shall have
a combined capital and surplus of at least  $50,000,000 as set forth in its most
recent published  annual report of condition.  The Trustee shall comply with TIA
ss. 310(b);  provided,  however, that there shall be excluded from the operation
of TIA ss. 310(b)(1) any indenture or indentures under which other securities or
certificates of interest or  participation in other securities of the Issuer are
outstanding if the requirements for such exclusion set forth in TIA ss.
310(b)(1) are met.

                  SECTION  7.11.   Preferential  Collection  of  Claims  Against
Issuer.  The Trustee  shall comply with TIA ss.  311(a),  excluding any creditor
relationship listed in TIA ss.311(b). A Trustee who has resigned or been removed
shall be subject to TIA ss. 311(a) to the extent indicated.

                                  ARTICLE VIII
                       DISCHARGE OF INDENTURE; DEFEASANCE

                  SECTION 8.1. Discharge of Liability on Notes; Defeasance.  (a)
When (i) the Issuer  delivers to the Trustee all  outstanding  Notes (other than
Notes replaced pursuant

                                       49
<PAGE>   56

to Section 2.7) for  cancellation or (ii) all outstanding  Notes have become due
and  payable,  whether at  maturity or as a result of the mailing of a notice of
redemption  pursuant  to Article  III  hereof or the Notes  will  become due and
payable at their Stated  Maturity  within 91 days, or the Notes are to be called
for redemption within 91 days under arrangements satisfactory to the Trustee for
the  giving of notice  of  redemption  by the  Trustee  in the name,  and at the
expense,  of the  Issuer,  and,  in each case of this  clause  (ii),  the Issuer
irrevocably deposits or causes to be deposited with the Trustee funds sufficient
to pay at maturity or upon redemption all outstanding Notes,  including interest
thereon to maturity or such redemption date (other than Notes replaced  pursuant
to Section  2.7),  and if in either case the Issuer pays all other sums  payable
hereunder by the Issuer,  then this Indenture shall,  subject to Section 8.1(c),
cease to be of further effect.  The Trustee shall  acknowledge  satisfaction and
discharge of this Indenture on demand of the Issuer  accompanied by an Officer's
Certificate  and an  Opinion  of Counsel  from the  Issuer  that all  conditions
precedent  provided  herein for relating to  satisfaction  and discharge of this
Indenture have been complied with and at the cost and expense of the Issuer.

                  (b) Subject to Sections 8.1(c) and 8.2, the Issuer at any time
may  terminate  (i) all of its  obligations  under the Notes and this  Indenture
("legal  defeasance  option") or (ii) its  obligations  under Sections 4.2, 4.3,
4.4, 4.5, 4.6, 4.7, 4.8, 4.9,  4.10,  4.11,  4.12,  4.14,  4.18 and 4.19 and the
operation of Sections  6.1(6),  6.1(7) (but only with  respect to a  Significant
Subsidiary),  6.1(8) (but only with respect to a Significant Subsidiary), 6.1(9)
and 5.1(iii) ("covenant  defeasance option").  The Issuer may exercise its legal
defeasance option  notwithstanding its prior exercise of its covenant defeasance
option.

                  If the Issuer exercises its legal defeasance  option,  payment
of the Notes  may not be  accelerated  because  of an Event of  Default.  If the
Issuer exercises its covenant defeasance option, payment of the Notes may not be
accelerated because of an Event of Default specified in Section 6.1(4),  6.1(5),
6.1(6), 6.1(7) (but only with respect to a Significant Subsidiary),  6.1(8) (but
only with respect to a Significant  Subsidiary),  6.1(9),  6.1(10) or because of
the failure of the Issuer to comply with Section 5.1(iii).

                  Upon  satisfaction of the conditions set forth herein and upon
request of the Issuer, the Trustee shall acknowledge in writing the discharge of
those obligations that the Issuer terminates.

                  (c)  Notwithstanding  clauses (a) and (b) above,  the Issuer's
obligations in Sections 2.3, 2.4, 2.5, 2.7, 4.1, 4.13,  4.15,  4.16,  4.17, 7.7,
7.8,  8.4,  8.5 and 8.6 shall  survive  until the Notes  have been paid in full.
Thereafter, the Issuer's obligations in Sections 7.7, 8.4 and 8.5 shall survive.

                  SECTION 8.2.  Conditions to Defeasance.  The Issuer may
exercise its legal defeasance option or its covenant defeasance option only if:

                  (i) the Issuer irrevocably  deposits or causes to be deposited
         in trust with the Trustee money or U.S.  Government  Obligations  which
         through the  scheduled  payment of  principal  and  interest in respect
         thereof in accordance  with their terms will provide cash at such times
         and in such amounts as will be sufficient to pay principal and interest
         when

                                       50
<PAGE>   57

         due on all  outstanding  Notes (except Notes replaced  pursuant to
         Section 2.7) to maturity or redemption, as the case may be;

                  (ii) the Issuer  delivers to the Trustee a certificate  from a
         nationally recognized firm of independent  accountants expressing their
         opinion  that the  payments  of  principal  and  interest  when due and
         without reinvestment on the deposited U.S. Government  Obligations plus
         any deposited money without  investment will provide cash at such times
         and in such amounts as will be sufficient to pay principal and interest
         when due on all  outstanding  Notes (except Notes replaced  pursuant to
         Section 2.7) to maturity or redemption, as the case may be;

                  (iii) 91 days pass  after the  deposit  is made and during the
         91-day  period  no  Default  specified  in  Section  6.1(7) or (8) with
         respect  to the Issuer  occurs  which is  continuing  at the end of the
         period;

                  (iv) the deposit does not constitute a default under any other
         material agreement binding on the Issuer;

                  (v) the Issuer  delivers  to the Trustee an Opinion of Counsel
         to the  effect  that the  trust  resulting  from the  deposit  does not
         constitute,  or is qualified as, a regulated  investment  company under
         the Investment Company Act of 1940;

                  (vi) in the case of the legal  defeasance  option,  the Issuer
         shall have delivered to the Trustee an Opinion of Counsel  stating that
         (i) the Issuer has received  from, or there has been  published by, the
         Internal  Revenue  Service  a  ruling,  or (ii)  since the date of this
         Indenture there has been a change in the applicable  federal income tax
         law, in either case to the effect that,  and based thereon such Opinion
         of Counsel  shall  confirm  that,  the  Noteholders  will not recognize
         income,  gain or loss for  federal  income tax  purposes as a result of
         such deposit and  defeasance  and will be subject to federal income tax
         on the same amounts,  in the same manner and at the same times as would
         have been the case if such deposit and defeasance had not occurred;

                  (vii)  in the  case of the  covenant  defeasance  option,  the
         Issuer shall have delivered to the Trustee an Opinion of Counsel to the
         effect that the Noteholders will not recognize income, gain or loss for
         federal income tax purposes as a result of such covenant defeasance and
         will be subject to federal  income tax on the same  amounts  and in the
         same  manner  and at the same times as would have been the case if such
         deposit and covenant defeasance had not occurred; and

                  (viii)  the  Issuer  delivers  to  the  Trustee  an  Officer's
         Certificate and an Opinion of Counsel, each stating that all conditions
         precedent to the defeasance and discharge of the Notes as  contemplated
         by this Article VIII have been complied with.

                  Before or after a deposit,  the  Issuer may make  arrangements
satisfactory  to the  Trustee  for the  redemption  of Notes at a future date in
accordance with Article III.

                  SECTION 8.3.  Application  of Trust Money.  The Trustee  shall
hold in trust money or U.S. Government Obligations deposited with it pursuant to
this Article VIII.  It shall

                                       51
<PAGE>   58

apply the deposited money and the money from U.S. Government  Obligations either
directly  or through  the  Paying  Agent as the  Trustee  may  determine  and in
accordance  with this  Indenture  to the payment of principal of and interest on
the Notes.

                  SECTION 8.4.  Repayment to Issuer.  The Trustee and the Paying
Agent shall  promptly  turn over to the Issuer upon  request any excess money or
securities held by them at any time.

                  Subject to any applicable  abandoned property law, the Trustee
and the Paying Agent shall pay to the Issuer upon written request any money held
by them for the payment of principal or interest that remains  unclaimed for one
year after such  principal  and  interest  have  become  due and  payable,  and,
thereafter,  Noteholders  entitled  to the  money  must look to the  Issuer  for
payment as general creditors.

                  SECTION 8.5. Indemnity for Government Obligations.  The Issuer
shall pay and shall  indemnify the Trustee  against any tax, fee or other charge
imposed on or assessed  against  deposited  U.S.  Government  Obligations or the
principal and interest received on such U.S.  Government  Obligations other than
any such tax, fee or other charge which by law is for the account of the Holders
of the defeased Notes; provided that the Trustee shall be entitled to charge any
such tax, fee or other charge to such Holder's account.

                  SECTION 8.6. Reinstatement.  If the Trustee or Paying Agent is
unable to apply any money or U.S. Government Obligations in accordance with this
Article  VIII by  reason of any  legal  proceeding  or by reason of any order or
judgment  of any  court or  governmental  authority  enjoining,  restraining  or
otherwise  prohibiting such  application,  the Issuer's  obligations  under this
Indenture and the Notes shall be revived and reinstated as though no deposit had
occurred  pursuant to this Article VIII until such time as the Trustee or Paying
Agent is permitted  to apply all such money or U.S.  Government  Obligations  in
accordance with this Article VIII;  provided,  however,  that, (a) if the Issuer
has made any payment of  interest on or  principal  of any Notes  following  the
reinstatement of their obligations, the Issuer shall be subrogated to the rights
of the  Holders  of such Notes to receive  such  payment  from the money or U.S.
Government  Obligations  held by the  Trustee  or Paying  Agent  and (b)  unless
otherwise required by any legal proceeding or any order or judgment of any court
or  governmental  authority,  the Trustee or Paying  Agent shall return all such
money and U.S.  Government  Obligations to the Issuer promptly after receiving a
written  request  therefor at any time,  if such  reinstatement  of the Issuer's
obligations has occurred and continues to be in effect.

                                   ARTICLE IX
                                   AMENDMENTS

                  SECTION 9.1.  Without Consent of Holders.  The Issuer and the
Trustee may amend this Indenture or the Notes without notice to or consent of
any Noteholder:

                  (i)      to cure any ambiguity, omission, defect or
inconsistency;

                  (ii)     to comply with Article V;

                                       52
<PAGE>   59

                  (iii) to provide for uncertificated Notes in addition to or in
         place of certificated Notes (provided, however, that the uncertificated
         Notes are issued in registered  form for purposes of Section  163(f) of
         the  Code or in a manner  such  that the  uncertificated  Notes  are as
         described in Section 163(f)(2)(B) of the Code);

                  (iv)     to add Guarantees with respect to the Notes;

                  (v)      to secure the Notes;

                  (vi) to add to the  covenants of the Issuer for the benefit of
         the  Noteholders  or to surrender  any right or power herein  conferred
         upon the Issuer;

                  (vii) to make any  change  that  does not,  in the good  faith
         opinion of the Board of Directors,  materially and adversely affect the
         rights of any Noteholder; and

                  (viii)  to  comply  with  any   requirements  of  the  SEC  in
         connection with qualifying this Indenture under the TIA.

                  After an amendment  under this Section 9.1 becomes  effective,
the Issuer shall mail to Noteholders a notice briefly describing such amendment.
The failure to give such notice to all Noteholders, or any defect therein, shall
not impair or affect the validity of an amendment under this Section 9.1.

                  SECTION  9.2.  With  Consent  of  Holders.  The Issuer and the
Trustee may amend this  Indenture or the Notes without  notice to any Noteholder
but with the written  consent of the Holders of at least a majority in principal
amount of the Notes then outstanding  (including consents obtained in connection
with a tender offer or exchange for Notes). However, without the consent of each
Noteholder of an outstanding Note affected, an amendment may not:

                  (i)      reduce the amount of Notes whose Holders must consent
          to an amendment;

                  (ii)     reduce the rate of or extend the time for payment of
          interest on any Note;

                  (iii) reduce the principal of or extend the Stated Maturity of
          any Note;

                  (iv) reduce the premium  payable  upon the  redemption  of any
         Note or change the time at which any Note may be redeemed in accordance
         with Article III;

                  (v) make any Note  payable in money  other than that stated in
          the Note;

                  (vi)  impair  the right of any  Holder to  receive  payment of
         principal  of and interest on such  Holder's  Notes on or after the due
         dates therefor or to institute suit for the  enforcement of any payment
         on or with respect to such Holder's Notes; or

                  (vii) make any change in this second sentence of Section 9.2.

                                       53
<PAGE>   60

                  It shall not be necessary for the consent of the Holders under
this Section 9.2 to approve the particular form of any proposed  amendment,  but
it shall be sufficient if such consent approves the substance thereof.

                  After an amendment  under this Section 9.2 becomes  effective,
the Issuer shall mail to Noteholders a notice briefly describing such amendment.
The failure to give such notice to all Noteholders, or any defect therein, shall
not impair or affect the validity of an amendment under this Section 9.2.

                  SECTION 9.3.  Compliance with Trust Indenture Act.  Every
amendment to this Indenture or the Notes shall comply with the TIA as then in
effect.

                  SECTION 9.4.  Revocation and Effect of Consents and Waivers. A
consent to an  amendment or a waiver by a Holder of a Note shall bind the Holder
and every  subsequent  Holder of that Note or portion of the Note that evidences
the same debt as the consenting  Holder's Note,  even if notation of the consent
or  waiver  is not  made on the  Note.  After an  amendment  or  waiver  becomes
effective, it shall bind every Noteholder.

                  The Issuer may,  but shall not be  obligated  to, fix a record
date for the  purpose of  determining  the  Noteholders  entitled  to give their
consent or take any other action  described above or required or permitted to be
taken   pursuant  to  this   Indenture.   If  a  record  date  is  fixed,   then
notwithstanding  the  immediately  preceding  paragraph,  those Persons who were
Noteholders  at such record date (or their duly  designated  proxies),  and only
those  Persons,  shall be entitled to give such consent or to revoke any consent
previously  given or to take  any  such  action,  whether  or not  such  Persons
continue to be Holders after such record date. No such consent shall be valid or
effective for more than 120 days after such record date.

                  SECTION 9.5. Notation on or Exchange of Notes. If an amendment
changes  the terms of a Note,  the Trustee may require the Holder of the Note to
deliver it to the Trustee.  The Trustee may place an appropriate notation on the
Note regarding the changed terms and return it to the Holder. Alternatively,  if
the Issuer or the  Trustee so  determine,  the Issuer in  exchange  for the Note
shall issue and the Trustee  shall  authenticate  a new Note that  reflects  the
changed terms.  Failure to make the appropriate  notation or to issue a new Note
shall not affect the validity of such amendment.

                  SECTION 9.6.  Trustee to Sign  Amendments.  The Trustee  shall
sign any amendment  authorized pursuant to this Article IX if the amendment does
not  materially  and  adversely  affect  the  rights,  duties,   liabilities  or
immunities of the Trustee.  If it does, the Trustee may but need not sign it. In
signing  such  amendment  the Trustee  shall be  entitled  to receive  indemnity
reasonably  satisfactory  to it and to  receive,  and  (subject to Section 7. 1)
shall be fully protected in relying upon, in addition to the documents  required
by Section 10.4, an Officer's Certificate and an Opinion of Counsel stating that
such amendment complies with the provisions of this Article IX.

                  SECTION 9.7.  Payment for Consent.  Neither the Issuer nor any
affiliate of the Issuer shall,  directly or indirectly,  pay or cause to be paid
any consideration,  whether by way of interest, fee or otherwise,  to any Holder
for, or as an inducement to any consent, waiver or

                                       54
<PAGE>   61

amendment  of any of the  terms or  provisions  of this  Indenture  or the Notes
unless such  consideration is offered to be paid to all Holders that so consent,
waive or agree to amend in the time  frame set forth in  solicitation  documents
relating to such consent, waiver or agreement;  provided,  however, that Holders
who do not consent, waive or agree to amend this Indenture in the time frame set
forth in such solicitation  documents shall not be entitled to any consideration
offered for timely consent, waiver or amendment,  even if the consent, waiver or
amendment is agreed to by sufficient Holders to approve such consent,  waiver or
amendment to this Indenture.

                                    ARTICLE X
                                  MISCELLANEOUS

                  SECTION 10.1.  Trust Indenture Act Controls.  If any provision
of this Indenture limits, qualifies or conflicts with another provision which is
required to be included in this Indenture by the TIA, the provision  required by
the TIA shall control.

                  SECTION 10.2. Notices. Any notice or communication shall be in
writing and delivered in person,  transmitted by facsimile machine, or mailed by
first-class  mail or  overnight  air  courier  guaranteeing  next  day  delivery
addressed as follows:

                  if to the Issuer:

                           SpectraSite Holdings, Inc.
                           100 Regency Forest Drive, Suite 400
                           Cary, North Carolina  27511

                           Attention:  Chief Financial Officer

                  if to the Trustee:

                           United States Trust Company of New York
                           114 West 47th Street, 25th Floor
                           New York, New York  10036-1532

                           Attention:  Corporate Trust Administration

                  The  Issuer  or  the  Trustee  by  notice  to the  others  may
designate   additional  or  different   addresses  for  subsequent   notices  or
communications.

                  Any notice or  communication  mailed to a Noteholder  shall be
mailed to the  Noteholder  at the  Noteholder's  address  as it  appears  on the
registration books of the Registrar and shall be sufficiently given if so mailed
within the time prescribed.

                  Failure to mail a notice or  communication  to a Noteholder or
any  defect  in it shall  not  affect  its  sufficiency  with  respect  to other
Noteholders. Except for a notice to the Trustee, which is deemed given only when
received,  and except as otherwise  provided in this  Indenture,  if a notice or
communication is mailed in the manner provided above, it is duly given,  whether
or not the addressee receives it

                                       55
<PAGE>   62

                  SECTION  10.3.  Communication  by Holders with Other  Holders.
Noteholders  may communicate  pursuant to TIA ss. 312(b) with other  Noteholders
with respect to their rights under this Indenture or the Notes. The Issuer,  the
Trustee, the Registrar and anyone else shall have the protection of TIA ss.
312(c).

                  SECTION  10.4.   Certificate  and  Opinion  as  to  Conditions
Precedent.  Upon any request or application by the Issuer to the Trustee to take
or refrain from taking any action under this Indenture, the Issuer shall furnish
to the Trustee:

                  (i) an Officer's  Certificate in form and substance reasonably
         satisfactory to the Trustee stating that, in the opinion of the signer,
         all  conditions  precedent,  if any,  provided  for in  this  Indenture
         relating to the proposed action have been complied with; and

                  (ii) an Opinion of  Counsel in form and  substance  reasonably
         satisfactory  to the  Trustee  stating  that,  in the  opinion  of such
         counsel, all such conditions precedent have been complied with.

                  SECTION 10.5.  Statements  Required in Certificate or Opinion.
Each  certificate  or opinion  with  respect to  compliance  with a covenant  or
condition provided for in this Indenture shall include:

                  (i)      a statement that the individual making such
         certificate or opinion has read such covenant or condition;

                  (ii) a brief  statement  as to the  nature  and  scope  of the
         examination  or  investigation  upon which the  statements  or opinions
         contained in such certificate or opinion are based;

                  (iii) a statement that, in the opinion of such individual,  he
         has made such  examination or  investigation  as is necessary to enable
         him to express an informed  opinion as to whether or not such  covenant
         or condition has been complied with; and

                  (iv) a statement  as to whether or not, in the opinion of such
         individual, such covenant or condition has been complied with.

                  SECTION 10.6. When Notes Disregarded.  In determining  whether
the Holders of the  required  principal  amount of Notes have  concurred  in any
direction,  waiver  or  consent,  Notes  owned by the  Issuer  or by any  Person
directly or indirectly  controlling or controlled by or under direct or indirect
common  control  with the  Issuer  shall be  disregarded  and  deemed  not to be
outstanding,  except that,  for the purpose of  determining  whether the Trustee
shall be protected  in relying on any such  direction,  waiver or consent,  only
Notes  which a Trust  Officer  of the  Trustee  knows  are so owned  shall be so
disregarded.  Also, subject to the foregoing, only Notes outstanding at the time
shall be considered in any such determination.

                  SECTION 10.7.  Rules by Trustee,  Paying Agent and  Registrar.
The  Trustee  may  make  reasonable  rules  for  action  by or at a  meeting  of
Noteholders.  The Registrar and the Paying Agent may make  reasonable  rules for
their functions.

                                       56
<PAGE>   63

                  SECTION 10.8. Legal Holidays. A "Legal Holiday" is a Saturday,
a Sunday or a day on which banking  institutions  are not required to be open in
the State of New York.  If a payment date is a Legal  Holiday,  payment shall be
made on the next  succeeding  day that is not a Legal  Holiday,  and no interest
shall accrue on such payment for the intervening  period. If a regular date is a
Legal Holiday, the record date shall not be affected.

                  SECTION  10.9.  Governing  Law.  THIS  INDENTURE AND THE NOTES
SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF
NEW YORK BUT WITHOUT GIVING EFFECT TO APPLICABLE  PRINCIPLES OF CONFLICTS OF LAW
TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER  JURISDICTION WOULD BE
REQUIRED THEREBY.

                  SECTION  10.10.  No  Recourse  Against  Others.  No  director,
officer,  employee,  incorporator or stockholder of the Issuer,  as such,  shall
have any  liability  for any  obligations  of the Issuer  under the Notes,  this
Indenture  or for any  claim  based  on,  in  respect  of,  or by reason of such
obligations or their  creation.  Each Holder of Notes by accepting a Note waives
and  releases  all such  liability.  This  waiver  and  release  are part of the
consideration for issuance of the Notes.

                  SECTION 10.11.  Successors.  All agreements of the Issuer in
this Indenture and the Notes shall bind its successors.  All agreements of the
Trustee in this Indenture shall bind its successors.

                  SECTION 10.12.  Multiple Originals.  The parties may sign any
number of copies of this Indenture.  Each signed copy shall be an original, but
all of them together represent the same agreement.  One signed copy is enough to
prove this Indenture.

                  SECTION 10.13.  Variable Provisions.  The Issuer initially
appoints the Trustee as Paying Agent and Registrar and custodian with respect to
any Global Notes.

                  SECTION 10.14.  Qualification  of Indenture.  The Issuer shall
qualify this Indenture under the TIA in accordance with the terms and conditions
of the  Registration  Rights  Agreement (as defined in the Appendix  hereto) and
shall pay all reasonable costs and expenses  (including  attorneys' fees for the
Issuer,  the  Trustee  and  the  Holders)  incurred  in  connection   therewith,
including,  but not limited to,  costs and  expenses  of  qualification  of this
Indenture  and the Notes.  The Trustee  shall be  entitled  to receive  from the
Issuer  any  such   Officer's   Certificates,   Opinions  of  Counsel  or  other
documentation  as  it  may  reasonably  request  in  connection  with  any  such
qualification of this Indenture under the TIA.

                  SECTION  10.15.  Table of  Contents;  Headings.  The  table of
contents,  cross-  reference  sheet and headings of the Articles and Sections of
this  Indenture have been inserted for  convenience  of reference  only, are not
intended to be  considered a part hereof and shall not modify or restrict any of
the terms or provision hereof.

                  SECTION  10.16.  Severability.  In case any  provision in this
Indenture  or in the Notes shall be invalid,  illegal or  unenforceable,  in any
respect for any reason,  the validity,  legality and  enforceability of any such
provision in every other  respect and of the remaining  provisions  shall not in
any way be affected or impaired thereby.

                                       57

<PAGE>   64



                  IN WITNESS WHEREOF,  the parties have caused this Indenture to
be duly executed as of the date first written above.

                                                     SPECTRASITE HOLDINGS, INC.


                                          By: /s/ David P. Tomick
                                             -----------------------------------
                                              Name:     David P. Tomick
                                              Title:    Chief Financial Officer


                                                UNITED STATES TRUST COMPANY OF
                                                NEW YORK, as Trustee


                                          By: /s/ Annette L. Kos
                                             -----------------------------------
                                              Name:     Annette L. Kos
                                              Title:    Assistant Vice President





                                       58

<PAGE>   65





                                                 RULE 144A/REGULATION S APPENDIX

                              INSTITUTIONAL BUYERS
            PURSUANT TO RULE 144A AND TO CERTAIN PERSONS IN OFFSHORE
                    TRANSACTIONS IN RELIANCE ON REGULATION S.

                      PROVISIONS RELATING TO INITIAL NOTES,
                    PRIVATE EXCHANGE NOTES AND EXCHANGE NOTES

1.       Definitions.

                  1.1.     Definitions.  For the purposes of this Appendix the
following terms shall have the meanings indicated below:

                  "Depositary" means The Depository Trust Company,  its nominees
and their respective successors and assigns.

                  "Exchange Notes" means the 12 1/2% Senior Notes due 2010 to be
issued pursuant to this Indenture in connection with a Registered Exchange Offer
pursuant to the Registration Rights Agreement.

                  "Initial Purchaser" means CIBC World Markets Corp.

                  "Initial  Notes"  means  the 12 1/2%  Senior  Notes  due 2010,
issued under this Indenture on or about the date hereof

                  "Notes" means the Initial  Notes,  the Exchange  Notes and the
Private Exchange Notes, treated as a single class.

                  "Notes Custodian" means the custodian with respect to a Global
Note (as appointed by the Depositary), or any successor person thereto and shall
initially be the Trustee.

                  "Private Exchange" means the offer by the Issuer,  pursuant to
the  Registration  Rights  Agreement,  to the  Initial  Purchaser  to issue 'and
deliver to the Initial Purchaser,  in exchange for the Initial Notes held by the
Initial  Purchaser  as  part  of its  initial  distribution,  a  like  aggregate
principal amount of Private Exchange Notes.

                  "Private  Exchange  Notes"  means the 12 1/2% Senior Notes due
2010, if any, to be issued  pursuant to this Indenture to the Initial  Purchaser
in a Private Exchange.

                  "Purchase   Agreement"  means  the  Purchase  Agreement  dated
December 15, 2000, between the Issuer and the Initial Purchaser.

                  "QIB" means a "qualified institutional buyer" as defined in
Rule 144A.

                  "Registered  Exchange  Offer"  means the offer by the  Issuer,
pursuant to the  Registration  Rights  Agreement,  to certain Holders of Initial
Notes, to issue and deliver to such

                                       59
<PAGE>   66

Holders,  in exchange for the Initial Notes,
a like  aggregate  principal  amount  of  Exchange  Notes  registered  under the
Securities Act.

                  "Registration  Rights Agreement" means the Registration Rights
Agreement  dated as of  December  20,  2000  between  the Issuer and the Initial
Purchaser.

                  "Regulation S" means Regulation S under the Securities Act.

                  "Rule 144A" means Rule 144A under the Securities Act.

                  "Securities Act" means the Securities Act of 1933, as amended.

                  "Shelf   Registration   Statement"   means  the   registration
statement issued by the Issuer, in connection with the offer and sale of Initial
Notes or Private  Exchange  Notes,  pursuant  to  Section 2 of the  Registration
Rights Agreement.

                  "Transfer  Restricted  Notes"  means  Notes  that  bear or are
required to bear the legend set forth in Section 2.3(b) hereof.

                  1.2.     Other Definitions


                                                                   Defined
                Term                                             in Section
                "Agent Members".........................           2.1(b)
                "Global Note"...........................           2.1(a)

2      The Notes.

                  2.1. Form and Dating.  The Initial Notes are being offered and
sold by the Issuer pursuant to the Purchase Agreement.

                  (a) Global  Notes.  Initial Notes offered and sold to a QIB in
reliance on Rule 144A or in reliance on  Regulation  S, in each case as provided
in the Purchase Agreement,  shall be issued initially in the form of one or more
permanent  global Notes in definitive,  fully  registered form without  interest
coupons with the global securities  legend and restricted  securities legend set
forth in Exhibit I hereto (each, a "Global  Note"),  which shall be deposited on
behalf of the  purchasers  of the Initial  Notes  represented  thereby  with the
Trustee as custodian  for the  Depositary  (or with such other  custodian as the
Depositary  may  direct),  and  registered  in the name of the  Depositary  or a
nominee of the Depositary,  duly executed by the Issuer and authenticated by the
Trustee as hereinafter  provided.  The aggregate  principal amount of the Global
Notes may from time to time be increased or decreased by adjustments made on the
records  of the  Trustee  and  the  Depositary  or its  nominee  as  hereinafter
provided.

                  (b)      Book-Entry Provisions.  This Section 2. 1 (b) shall
apply only to a Global Note deposited with or on behalf of the Depositary.

                                       60
<PAGE>   67

                  The Issuer shall execute and the Trustee shall,  in accordance
with this Section 2.1 (b), authenticate and deliver initially one or more Global
Notes that (i) shall be registered in the name of the Depositary for such Global
Note or Global Notes or in the name of the nominee of such  Depositary  and (ii)
shall be  delivered  by the  Trustee  to such  Depositary  or  pursuant  to such
Depositary's   instructions  or  held  by  the  Trustee  as  custodian  for  the
Depositary.

                  Members  of,  or  participants  in,  the  Depositary   ("Agent
Members")  shall have no rights under this  Indenture with respect to any Global
Note held on their behalf by the  Depositary  or by the Trustee as the custodian
of the  Depositary or under such Global Note,  and the Depositary may be treated
by the  Issuer,  the  Trustee  and any agent of the Issuer or the Trustee as the
absolute owner of such Global Note for all purposes whatsoever.  Notwithstanding
the foregoing, nothing herein shall prevent the Issuer, the Trustee or any agent
of the Issuer or the Trustee  from giving  effect to any written  certification,
proxy or other  authorization  furnished by the Depositary or impair, as between
the Depositary and its Agent  Members,  the operation of customary  practices of
such Depositary governing the exercise of the rights of a holder of a beneficial
interest in any Global Note.

                  (c) Certificated  Notes.  Except as provided in Section 2.1 or
Section 2.3 or 2.4,  owners of beneficial  interests in Global Notes will not be
entitled to receive physical delivery of certificated Notes.

                  2.2.  Authentication.   The  Trustee  shall  authenticate  and
deliver:  (1) Initial Notes for original issue in an aggregate  principal amount
of U.S.  $200,000,000 and (2) Exchange Notes or Private Exchange Notes for issue
only  in a  Registered  Exchange  Offer  or a  Private  Exchange,  respectively,
pursuant to the Registration  Rights  Agreement,  for a like principal amount of
Initial  Notes,  in each case upon a written  order of the Issuer  signed by two
Officers  or by an Officer and either an  Assistant  Treasurer  or an  Assistant
Secretary of the Issuer.  Such order shall specify the amount of the Notes to be
authenticated  and the  date on  which  the  original  issue  of  Notes is to be
authenticated  and whether the Notes are to be Initial Notes,  Exchange Notes or
Private Exchange Notes. The aggregate  principal amount of Notes  outstanding at
any time may not exceed U.S.  $200,000,000  except as provided in Section 2.7 of
this Indenture.

                  2.3.     Transfer and Exchange.

                  (a) Transfer and  Exchange of Global  Notes.  (i) The transfer
and exchange of Global Notes or beneficial  interests  therein shall be effected
through the Depositary,  in accordance with this Indenture (including applicable
restrictions  on transfer set forth  herein,  if any) and the  procedures of the
Depositary  therefor.  A transferor  of a  beneficial  interest in a Global Note
shall  deliver to the  Registrar a written  order given in  accordance  with the
Depositary's procedures containing information regarding the participant account
of the Depositary to be credited with a beneficial  interest in the Global Note.
The  Registrar  shall,  in  accordance  with  such  instructions   instruct  the
Depositary to credit to the account of the Person specified in such instructions
a beneficial  interest in the Global Note and to debit the account of the Person
making  the  transfer  of the  beneficial  interest  in the  Global  Note  being
transferred.

                  (ii)  Notwithstanding  any other  provisions  of this Appendix
(other than the  provisions  set forth in Section 2.4), a Global Note may not be
transferred  as a whole except

                                       61
<PAGE>   68

by  the  Depositary  to a  nominee  of the  Depositary  or by a  nominee  of the
Depositary  to the  Depositary  of another  nominee of the  Depositary or by the
Depositary  or any such nominee to a successor  Depositary  or a nominee of such
successor Depositary.

                  (iii) In the event that a Global Note is  exchanged  for Notes
in  definitive  registered  form  pursuant  to Section  2.4 of this  Appendix or
Section 2.9 of this Indenture prior to the consummation of a Registered Exchange
Offer or the  effectiveness  of a Shelf  Registration  Statement with respect to
such Notes,  such Notes may be exchanged only in accordance with such procedures
as are  substantially  consistent  with  the  provisions  of  this  Section  2.3
(including  the  certification  requirements  set  forth on the  reverse  of the
Initial Notes  intended to ensure that such  transfers  comply with Rule 144A or
Regulation S, as the case may be) and such other  procedures as may from time to
time be adopted by the Issuer.

                  (b)  Legend.   (i)  Except  as  permitted  by  the   following
paragraphs  (ii),  (iii) and (iv), each Note  certificate  evidencing the Global
Notes (and all Notes  issued in exchange  therefor or in  substitution  thereof)
shall bear a legend in substantially the following form:

                  "THIS NOTE HAS NOT BEEN REGISTERED  UNDER THE U.S.  SECURITIES
         ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND,  ACCORDINGLY,  MAY
         NOT BE  OFFERED  OR SOLD  WITHIN  THE  UNITED  STATES OR TO, OR FOR THE
         ACCOUNT  OR  BENEFIT  OF,  U.S.  PERSONS,  EXCEPT  AS SET  FORTH IN THE
         FOLLOWING   SENTENCE.   BY  ITS  ACQUISITION  HEREOF,  THE  HOLDER  (1)
         REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL BUYER" (AS DEFINED
         IN RULE 144A UNDER THE SECURITIES ACT), OR (B) IT IS AN  "INSTITUTIONAL
         ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(A)(1),  (2), (3) OR (7) OR
         REGULATION D UNDER THE SECURITIES  ACT) (AN  "INSTITUTIONAL  ACCREDITED
         INVESTOR") OR (C) IT IS NOT A U.S. PERSON AND IS ACQUIRING THIS NOTE IN
         AN OFFSHORE  TRANSACTION  IN  COMPLIANCE  WITH  REGULATION  S UNDER THE
         SECURITIES  ACT,  (2)  AGREES  THAT IT WILL  NOT  RESELL  OR  OTHERWISE
         TRANSFER THIS NOTE EXCEPT (A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF,
         (B) TO A QUALIFIED  INSTITUTIONAL  BUYER IN  COMPLIANCE  WITH RULE 144A
         UNDER  THE  SECURITIES   ACT,  (C)  INSIDE  THE  UNITED  STATES  TO  AN
         INSTITUTIONAL   ACCREDITED  INVESTOR  THAT,  PRIOR  TO  SUCH  TRANSFER,
         FURNISHES   TO  THE  TRUSTEE  A  SIGNED   LETTER   CONTAINING   CERTAIN
         REPRESENTATIONS AND AGREEMENTS RELATING TO THE RESTRICTIONS ON TRANSFER
         OF THIS  NOTE  (THE  FORM OF  WHICH  LETTER  CAN BE  OBTAINED  FROM THE
         TRUSTEE) AND, IF SUCH TRANSFER IS IN RESPECT OF AN AGGREGATE  PRINCIPAL
         AMOUNT  OF NOTES AT THE TIME OF  TRANSFER  OF LESS  THAN  $100,000,  AN
         OPINION OF COUNSEL  ACCEPTABLE  TO THE COMPANY THAT SUCH TRANSFER IS IN
         COMPLIANCE WITH THE SECURITIES ACT, (D) OUTSIDE THE UNITED STATES IN AN
         OFFSHORE  TRANSACTION IN COMPLIANCE WITH RULE 904 OF REGULATION S UNDER
         THE  SECURITIES  ACT  OR  (E)  PURSUANT  TO AN  EFFECTIVE  REGISTRATION
         STATEMENT  UNDER THE SECURITIES ACT AND (3) AGREES THAT IT WILL DELIVER
         TO EACH PERSON TO WHOM THIS NOTE IS TRANSFERRED A NOTICE  SUBSTANTIALLY
         TO THE EFFECT OF THIS

                                       62
<PAGE>   69

         LEGEND.  IN CONNECTION  WITH ANY TRANSFER OF THIS NOTE,  THE  HOLDER
         MUST  CHECK  THE  APPROPRIATE  BOX SET FORTH ON THE REVERSE HEREOF
         RELATING TO THE MANNER OF SUCH TRANSFER AND SUBMIT THIS CERTIFICATE  TO
         THE  TRUSTEE.   IF  THE  PROPOSED   TRANSFEREE  IS  AN INSTITUTIONAL
         ACCREDITED  INVESTOR,  THE  HOLDER  MUST,  PRIOR TO SUCH TRANSFER,
         FURNISH TO THE TRUSTEE AND THE COMPANY SUCH  CERTIFICATIONS, LEGAL
         OPINIONS OR OTHER  INFORMATION  AS EITHER OF THEM MAY REASONABLY
         REQUIRE TO CONFIRM  THAT SUCH  TRANSFER  IS BEING MADE  PURSUANT  TO AN
         EXEMPTION  FROM, OR IN A TRANSACTION  NOT SUBJECT TO, THE  REGISTRATION
         REQUIREMENTS OF THE SECURITIES ACT. AS USED HEREIN, THE TERMS "OFFSHORE
         TRANSACTION," "UNITED STATES" AND "U.S. PERSON" HAVE THE MEANINGS GIVEN
         TO THEM BY  REGULATION  S  UNDER  THE  SECURITIES  ACT.  THE  INDENTURE
         CONTAINS A PROVISION  REQUIRING  THE TRUSTEE TO REFUSE TO REGISTER  ANY
         TRANSFER OF THIS NOTE IN VIOLATION OF THE FOREGOING RESTRICTIONS."

                  (ii) Upon any sale or transfer of a Transfer  Restricted  Note
(including any Transfer  Restricted Note  represented by a Global Note) pursuant
to Rule 144 under the  Securities  Act, in the case of any  Transfer  Restricted
Note that is represented by a Global Note, the Registrar shall permit the Holder
thereof to exchange such Transfer  Restricted Note for a certificated  Note that
does not bear the legend set forth  above and  rescind  any  restriction  on the
transfer of such Transfer Restricted Note, if the Holder certifies in writing to
the  Registrar  that its request for such  exchange was made in reliance on Rule
144 (such certification to be in the form set forth on the reverse of the Note).

                  (iii) After a transfer of any  Initial  Securities  or Private
Exchange  Securities during the period of the effectiveness of and pursuant to a
Shelf Registration  Statement with respect to such Initial Securities or Private
Exchange Securities,  as the case may be, all requirements pertaining to legends
on such Initial  Securities or such Private  Exchange Notes will cease to apply,
but the requirements requiring such Initial Notes or such Private Exchange Notes
issued to certain  Holders be issued in global form will continue to apply,  and
Initial Notes or Private  Exchange Notes in global form without  legends will be
available  to the  transferee  of the  Holder of such  Initial  Notes or Private
Exchange  Notes upon  exchange of such  transferring  Holder's  Initial Notes or
Private  Exchange Notes or directions to transfer such Holder's  interest in the
Global Note, as applicable.

                  (iv) Upon the consummation of a Registered Exchange Offer with
respect to the Initial Notes pursuant to which Holders of such Initial Notes are
offered  Exchange  Notes in exchange for their Initial Notes,  all  requirements
pertaining to such Initial Notes that Initial Notes issued to certain Holders be
issued in global form will  continue  to apply and Initial  Notes in global form
with the  restricted  securities  legend set forth in  Exhibit 1 hereto  will be
available to Holders of such Initial  Notes that do not exchange  their  Initial
Notes,  and  Exchange  Notes in global form without the  restriction  securities
legend will be  available to Holders that  exchange  such Initial  Notes in such
Registered Exchange Offer.

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<PAGE>   70

                  (v) Upon the  consummation of a Private  Exchange with respect
to the Initial Notes pursuant to which Holders of such Initial Notes are offered
Private  Exchange  Notes in exchange for their Initial Notes,  all  requirements
pertaining to such Initial Notes that Initial Notes issued to certain Holders be
issued in global form will still  apply,  and Private  Exchange  Notes in global
form with the restricted securities legend set forth in Exhibit 1 hereto will be
available to Holders that exchange such Initial Notes in such Private Exchange.

                  (c) Cancellation or Adjustment of Global Note. At such time as
all  beneficial  interests  in a Global  Note have  either  been  exchanged  for
certificated Notes, redeemed, repurchased or canceled, such Global Note shall be
returned to the  Depositary  for  cancellation  or retained  and canceled by the
Trustee. At any time prior to such cancellation, if any beneficial interest in a
Global Note is  exchanged  for  certificated  Notes,  redeemed,  repurchased  or
canceled, the principal amount of Notes represented by such Global Note shall be
reduced and an adjustment  shall be made on the books and records of the Trustee
(if it is then the Notes  Custodian  for such Global  Note) with respect to such
Global Note, by the Trustee or the Notes Custodian, to reflect such reduction.

                  (d)  Obligations  with Respect to Transfers  and  Exchanges of
Notes. (i) To permit registrations of transfers and exchanges,  the Issuer shall
execute and the Trustee shall  authenticate  certificated Notes and Global Notes
at  the  Registrar's  or  any  co-registrar's  request,  subject  to  terms  and
conditions of this Indenture.

                  (ii) No service charge shall be made for any  registration  of
transfer or exchange,  but the Issuer may require payment of a sum sufficient to
cover any transfer tax,  assessments,  or similar governmental charge payable in
connection therewith (other than any such transfer taxes, assessments or similar
governmental  charge payable upon exchange or transfer pursuant to Sections 3.6,
4.7, 4.9 and Section 9.5 of this Indenture).

                  (iii) The Registrar or any co-registrar  shall not be required
to register the transfer of or exchange of (a) any  certificated  Note  selected
for  redemption in whole or in part  pursuant to Article III of this  Indenture,
except the unredeemed  portion of any certificated  Note being redeemed in part,
or (b) any Note for a period  beginning 15 Business Days before the mailing of a
notice of an offer to  repurchase  or redeem Notes or 15 Business Days before an
interest payment date.

                  (iv)  Prior  to  the  due  presentation  for  registration  of
transfer of any Note, the Issuer,  the Trustee,  the Paying Agent, the Registrar
or any  co-registrar  may deem and  treat  the  person  in whose  name a Note is
registered  as the  absolute  owner of such Note for the  purpose  of  receiving
payment of  principal  of and  interest on such Note and for all other  purposes
whatsoever,  whether or not such Note is overdue,  and none of the  Issuer,  the
Trustee,  the Paying Agent, the Registrar or any co-registrar  shall be affected
by notice to the contrary.

                  (v) All Notes issued on any  transfer or exchange  pursuant to
the terms of this  Indenture  shall evidence the same debt and shall be entitled
to the same benefits  under this  Indenture as the Notes  surrendered  upon such
transfer or exchange.

                                       64
<PAGE>   71

                  (e) No  Obligation  of the  Trustee  or the  Issuer.  (i)  The
Trustee  and the  Issuer  shall  have no  responsibility  or  obligation  to any
beneficial  owner of a  Global  Note,  a  member  of,  or a  participant  in the
Depositary  or other  Person with  respect to the accuracy of the records of the
Depositary or its nominee or of any participant or member thereof,  with respect
to any  ownership  interest in the Notes or with  respect to the delivery to any
participant,   member,   beneficial  owner  or  other  Person  (other  than  the
Depositary) of any notice (including any notice of redemption) or the payment of
any amount,  under or with respect to such Notes. All notices and communications
to be given to the  Holders  and all  payments  to be made to Holders  under the
Notes shall be given or made only to or upon the order of the registered Holders
(which shall be the Depositary or its nominee in the case of a Global Note). The
rights of beneficial  owners in any Global Note shall be exercised  only through
the Depositary subject to the applicable rules and procedures of the Depositary.
The Trustee and the Issuer may rely and shall be fully protected in relying upon
information   furnished  by  the   Depositary   with  respect  to  its  members,
participants and any beneficial owners.

                  (ii) The Trustee and the Issuer  shall have no  obligation  or
duty to monitor,  determine or inquire as to compliance with any restrictions on
transfer  imposed under this  Indenture or under  applicable law with respect to
any transfer of any interest in any Note  (including  any  transfers  between or
among Depositary participants,  members or beneficial owners in any Global Note)
other than to require delivery of such  certificates and other  documentation or
evidence  as are  expressly  required  by,  and to do so if and  when  expressly
required by, the terms of this  Indenture,  and to examine the same to determine
substantial compliance as to form with the express requirements hereof.

                  2.4.  Certificated Notes. (a) A Global Note deposited with the
Depositary  or with the  Trustee as  custodian  for the  Depositary  pursuant to
Section 2.1 shall be transferred to the beneficial owners thereof in the form of
certificated  Notes in an  aggregate  principal  amount  equal to the  principal
amount of such Global  Note,  in exchange  for such  Global  Note,  only if such
transfer  complies with Section 2.3 and (i) the  Depositary  notifies the Issuer
that it is unwilling or unable to continue as Depositary for such Global Note or
if at any time such Depositary ceases to be a "clearing agency" registered under
the  Exchange  Act and a successor  depositary  is not  appointed  by the Issuer
within 90 days of such  notice,  or (ii) an Event of Default has occurred and is
continuing or (iii) the Issuer, in its sole discretion,  notifies the Trustee in
writing  that it elects to cause the issuance of  certificated  Notes under this
Indenture.

                  (b) Any Global  Note that is  transferable  to the  beneficial
owners  thereof  pursuant to this Section shall be surrendered by the Depositary
to the  Trustee,  to be so  transferred,  in whole or from time to time in part,
without  charge,  and the Trustee  shall  authenticate  and  deliver,  upon such
transfer  of each  portion of such Global  Note,  an equal  aggregate  principal
amount of certificated Initial Notes of authorized denominations. Any portion of
a  Global  Note  transferred   pursuant  to  this  Section  shall  be  executed,
authenticated  and  delivered  only in  denominations  of  $1,000  any  integral
multiple  thereof and registered in such names as the  Depositary  shall direct.
Any  certificated  Initial  Note  delivered  in exchange  for an interest in the
Global Note shall,  except as  otherwise  provided by Section  2.3(d),  bear the
restricted securities legend set forth in Exhibit 1 hereto.

                                       65
<PAGE>   72

                  (c)  Subject  to  the  provisions  of  Section   2.4(b),   the
registered Holder of a Global Note may grant proxies and otherwise authorize any
Person,  including  Agent  Members and Persons that may hold  interests  through
Agent Members,  to take any action which a Holder is entitled to take under this
Indenture or the Notes.

                  (d)  In  the  event  of the  occurrence  of any of the  events
specified in Section  2.4(a),  the Issuer will  promptly  make  available to the
Trustee  a  reasonable  supply  of  certificated  Notes  in  definitive,   fully
registered form without interest coupons.

                                       66

<PAGE>   73




                                                                       EXHIBIT 1
                                                       TO RULE 144A/REGULATION S
                                                                        APPENDIX


                         [FORM OF FACE OF INITIAL NOTE]

                              [Global Notes Legend]


                  UNLESS  THIS   CERTIFICATE   IS  PRESENTED  BY  AN  AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION  ("DTC"),
NEW YORK,  NEW YORK,  TO THE ISSUER OR ITS AGENT FOR  REGISTRATION  OF TRANSFER,
EXCHANGE OR PAYMENT,  AND ANY  CERTIFICATE  ISSUED IS  REGISTERED IN THE NAME OF
CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF
DTC  (AND ANY  PAYMENT  IS MADE TO CEDE & CO.,  OR TO SUCH  OTHER  ENTITY  AS IS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER
USE HEREOF FOR VALUE OR  OTHERWISE  BY OR TO ANY PERSON IS WRONGFUL  INASMUCH AS
THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

                  TRANSFERS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFERS IN
WHOLE,  BUT NOT IN PART,  TO NOMINEES  OF DTC OR TO A SUCCESSOR  THEREOF OR SUCH
SUCCESSOR'S  NOMINEES,  AND  TRANSFERS  OF PORTIONS OF THIS GLOBAL NOTE SHALL BE
LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE  RESTRICTIONS  SET FORTH IN THE
INDENTURE REFERRED TO ON THE REVERSE HEREOF.

                         [Restricted Securities Legend]


                  THIS NOTE HAS NOT BEEN  REGISTERED  UNDER THE U.S.  SECURITIES
ACT OF 1933, AS AMENDED (THE "SECURITIES  ACT"),  AND,  ACCORDINGLY,  MAY NOT BE
OFFERED OR SOLD  WITHIN THE UNITED  STATES OR TO, OR FOR THE  ACCOUNT OR BENEFIT
OF,  U.S.  PERSONS,  EXCEPT  AS SET  FORTH  IN THE  FOLLOWING  SENTENCE.  BY ITS
ACQUISITION  HEREOF,  THE  HOLDER  (1)  REPRESENTS  THAT (A) IT IS A  "QUALIFIED
INSTITUTIONAL  BUYER" (AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT), OR (B)
IT IS AN "INSTITUTIONAL ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(A)(1), (2),
(3) OR (7)  OR  REGULATION  D  UNDER  THE  SECURITIES  ACT)  (AN  "INSTITUTIONAL
ACCREDITED  INVESTOR") OR (C) IT IS NOT A U.S. PERSON AND IS ACQUIRING THIS NOTE
IN AN OFFSHORE  TRANSACTION IN COMPLIANCE WITH REGULATION S UNDER THE SECURITIES
ACT, (2) AGREES THAT IT WILL NOT RESELL OR OTHERWISE  TRANSFER  THIS NOTE EXCEPT
(A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF,  (B) TO A QUALIFIED  INSTITUTIONAL
BUYER IN  COMPLIANCE  WITH RULE 144A UNDER THE  SECURITIES  ACT,  (C) INSIDE THE
UNITED  STATES  TO AN  INSTITUTIONAL  ACCREDITED  INVESTOR  THAT,  PRIOR TO SUCH
TRANSFER,
                                       67
<PAGE>   74

FURNISHES TO THE TRUSTEE A SIGNED LETTER CONTAINING CERTAIN  REPRESENTATIONS AND
AGREEMENTS  RELATING TO THE  RESTRICTIONS  ON TRANSFER OF THIS NOTE (THE FORM OF
WHICH  LETTER CAN BE OBTAINED  FROM THE  TRUSTEE)  AND,  IF SUCH  TRANSFER IS IN
RESPECT OF AN  AGGREGATE  PRINCIPAL  AMOUNT OF NOTES AT THE TIME OF  TRANSFER OF
LESS THAN  $100,000,  AN OPINION OF COUNSEL  ACCEPTABLE TO THE COMPANY THAT SUCH
TRANSFER IS IN COMPLIANCE WITH THE SECURITIES ACT, (D) OUTSIDE THE UNITED STATES
IN AN OFFSHORE TRANSACTION IN COMPLIANCE WITH RULE 904 OF REGULATION S UNDER THE
SECURITIES ACT OR (E) PURSUANT TO AN EFFECTIVE  REGISTRATION STATEMENT UNDER THE
SECURITIES  ACT AND (3) AGREES THAT IT WILL  DELIVER TO EACH PERSON TO WHOM THIS
NOTE IS  TRANSFERRED  A NOTICE  SUBSTANTIALLY  TO THE EFFECT OF THIS LEGEND.  IN
CONNECTION WITH ANY TRANSFER OF THIS NOTE, THE HOLDER MUST CHECK THE APPROPRIATE
BOX SET FORTH ON THE REVERSE HEREOF  RELATING TO THE MANNER OF SUCH TRANSFER AND
SUBMIT  THIS  CERTIFICATE  TO THE  TRUSTEE.  IF THE  PROPOSED  TRANSFEREE  IS AN
INSTITUTIONAL  ACCREDITED  INVESTOR,  THE HOLDER MUST,  PRIOR TO SUCH  TRANSFER,
FURNISH TO THE TRUSTEE AND THE COMPANY SUCH  CERTIFICATIONS,  LEGAL  OPINIONS OR
OTHER INFORMATION AS EITHER OF THEM MAY REASONABLY  REQUIRE TO CONFIRM THAT SUCH
TRANSFER IS BEING MADE PURSUANT TO AN EXEMPTION  FROM,  OR IN A TRANSACTION  NOT
SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT. AS USED HEREIN,
THE TERMS "OFFSHORE  TRANSACTION,"  "UNITED  STATES" AND "U.S.  PERSON" HAVE THE
MEANINGS GIVEN TO THEM BY REGULATION S UNDER THE  SECURITIES  ACT. THE INDENTURE
CONTAINS A PROVISION REQUIRING THE TRUSTEE TO REFUSE TO REGISTER ANY TRANSFER OF
THIS NOTE IN VIOLATION OF THE FOREGOING RESTRICTIONS.

                                       68


<PAGE>   75



                           SPECTRASITE HOLDINGS, INC.


No. 1    Principal Amount  $100,000,000

CUSIP NO. 84760TAM2

                          12 1/2% Senior Note due 2010

                  SpectraSite Holdings,  Inc., a Delaware corporation,  promises
to pay to __________,  or registered  assigns,  the principal sum of ONE HUNDRED
MILLION Dollars on November 15, 2010.

                  Interest Payment Dates: May 15 and November 15.

                  Record Dates: May 1 and November 1.

                  Additional  provisions of this Note are set forth on the other
side of this Note.

                                       69

<PAGE>   76





Dated:                                  SPECTRASITE HOLDINGS, INC.

                                           By:
                                             ---------------------------



                                           By:
                                             ---------------------------

TRUSTEE'S CERTIFICATE OF
AUTHENTICATION

This is one of the Notes referred to in the Indenture.

UNITED STATES TRUST COMPANY OF NEW YORK
   as Trustee

By:
   ----------------------------
                     Authorized Signatory

                                       70

<PAGE>   77



                           SPECTRASITE HOLDINGS, INC.


No. 2    Principal Amount  $99,900,000

CUSIP NO. 84760TAM2

                          12 1/2% Senior Note due 2010

                  SpectraSite Holdings,  Inc., a Delaware corporation,  promises
to pay to __________,  or registered  assigns,  the principal sum of NINETY NINE
MILLION NINE HUNDRED THOUSAND Dollars on November 15, 2010.

                  Interest Payment Dates: May 15 and November 15.

                  Record Dates: May 1 and November 1.

                  Additional  provisions of this Note are set forth on the other
side of this Note.


                                       71
<PAGE>   78





Dated:                                     SPECTRASITE HOLDINGS, INC.

                                                By:
                                                   --------------------------



                                                By:

                                                   --------------------------
TRUSTEE'S CERTIFICATE OF
AUTHENTICATION

This is one of the Notes referred to in the Indenture.

UNITED STATES TRUST COMPANY OF NEW YORK
   as Trustee

By:
   -------------------------
                   Authorized Signatory

                                       72

<PAGE>   79



                           SPECTRASITE HOLDINGS, INC.


No. 3    Principal Amount  $100,000

CUSIP NO. U84561AE6

                          12 1/2% Senior Note due 2010

                  SpectraSite Holdings,  Inc., a Delaware corporation,  promises
to pay to __________,  or registered  assigns,  the principal sum of ONE HUNDRED
THOUSAND Dollars on November 15, 2010.

                  Interest Payment Dates: May 15 and November 15.

                  Record Dates: May 1 and November 1.

                  Additional  provisions of this Note are set forth on the other
side of this Note.


                                       73
<PAGE>   80





Dated:                                 SPECTRASITE HOLDINGS, INC.

                                               By:
                                                  ---------------------------



                                               By:
                                                  ---------------------------

TRUSTEE'S CERTIFICATE OF
AUTHENTICATION

This is one of the Notes referred to in the Indenture.

UNITED STATES TRUST COMPANY OF NEW YORK
   as Trustee

By:
   -------------------------------
       Authorized Signatory


                                       74

<PAGE>   81



                     [FORM OF REVERSE SIDE OF INITIAL NOTE]

                                (Reverse of Note)

                          12 1/2% Senior Note due 2010


1.       Interest

                  SpectraSite  Holdings,  Inc.,  a  Delaware  corporation  (such
corporation,  and its  successors  and assigns under the  Indenture  hereinafter
referred to, being herein called the "Issuer"),  promises to pay interest on the
principal  amount  of this  Note at the rate per annum  shown  above;  provided,
however,  that if a Registration  Default (as defined in the Registration Rights
Agreement)  occurs,  additional cash interest will accrue on this Note at a rate
of 0.50% per annum from and  including  the date on which any such  Registration
Default shall occur to but excluding the date on which all Registration Defaults
have been cured,  calculated on the principal amount of this Note as of the date
on which such interest is payable; provided, however, that in no event shall the
aggregate  amount of such  additional  interest  exceed  0.50% per  annum.  Such
interest is payable in addition to any other interest  payable from time to time
with  respect to this Note.  The Trustee  will not be deemed to have notice of a
Registration  Default  until  it  shall  have  received  actual  notice  of such
Registration Default.

                  The Notes will accrete interest at a rate of 12 1/2% per annum
from the Issue Date, payable  semi-annually  commencing May 15, 2001, to Holders
of  record at the  close of  business  on the May 1 or  November  1  immediately
preceding the interest  payment date of May 15 and November 15 of each year. The
Issuer shall pay interest on overdue  principal at 1% per annum in excess of the
rate borne by the Notes to the extent  lawful.  Interest will be computed on the
basis of a 360-day year of twelve 30-day months.

2.       Method of Payment

                  By at least  11:00  a.m.  (New York City  time) on the date on
which any  principal of or interest on any Note is due and  payable,  the Issuer
shall irrevocably  deposit with the Trustee or the Paying Agent money sufficient
to pay such  principal  and/or  interest.  The Issuer will pay interest  (except
defaulted  interest) to the Persons who are  registered  Holders of Notes at the
close of business on the May 1 or November 1 next preceding the interest payment
date even if Notes are cancelled,  repurchased or redeemed after the record date
and on or before the interest  payment date.  Holders must surrender  Notes to a
Paying Agent to collect  principal  payments.  The Issuer will pay principal and
interest  in money of the  United  States  that at the time of  payment is legal
tender for  payment of public and  private  debts.  However,  the Issuer may pay
principal and interest by check  payable in such money.  It may mail an interest
check to a Holder's registered address.

3.       Paying Agent and Registrar

                  Initially, United States Trust Company of New York, a national
banking association (the "Trustee"), will act as Paying Agent and Registrar. The
Issuer  may  appoint  and

                                       75
<PAGE>   82

change  any  Paying  Agent,  Registrar  or  co-registrar  without  notice to any
Noteholder.  The Issuer or any of its  domestically  incorporated  Wholly  Owned
Subsidiaries may act as Paying Agent.
4.       Indenture

                  The Issuer  issued the Notes  under an  Indenture  dated as of
December  20,  2000 (as it may be amended or  supplemented  from time to time in
accordance with the terms thereof, the "Indenture"),  between the Issuer and the
Trustee.  The terms of the Notes include those stated in the Indenture and those
made part of the  Indenture by reference to the Trust  Indenture Act of 1939, as
amended  (15  U.S.C.  ss.ss.  77aaa-77bbbb)  as in  effect  on the  date  of the
Indenture (the "TIA"). Capitalized terms used herein and not defined herein have
the meanings  ascribed  thereto in the  Indenture.  The Notes are subject to all
such terms,  and  Noteholders  are referred to the  Indenture  and the TIA for a
statement of those terms.

                  The Notes  are  unsecured  senior  obligations  of the  Issuer
limited to $200,000,000  aggregate  principal  amount (subject to Section 2.7 of
the Indenture), all of which are being offered on the Issue Date.

                  This  Note  is one of the  Initial  Notes  referred  to in the
Indenture.  The Notes include the Initial Notes and any Private  Exchange  Notes
and  Exchange  Notes issued in exchange  for the Initial  Notes  pursuant to the
Indenture and the Registration Rights Agreement. The Initial Notes., the Private
Exchange  Notes  and the  Exchange  Notes  are  treated  as a  single  class  of
securities under the Indenture. The Indenture imposes certain limitations on the
Incurrence of  Indebtedness by the Issuer and its Restricted  Subsidiaries,  the
payment of dividends and other  distributions on the Capital Stock of the Issuer
and its Restricted Subsidiaries,  the purchase or redemption of Capital Stock of
the Issuer and Capital Stock of such Restricted Subsidiaries,  certain purchases
or redemptions of Subordinated  Obligations,  the sale or transfer of assets and
Capital Stock of Restricted Subsidiaries,  the issuance or sale of Capital Stock
of Restricted  Subsidiaries,  the investments of the Issuer and its Subsidiaries
and transactions with Affiliates.  In addition, the Indenture limits the ability
of the Issuer and its  Restricted  Subsidiaries  to restrict  distributions  and
dividends from Restricted Subsidiaries.

5.       Redemption

                  Except as set forth in the following paragraph, the Notes will
not be  redeemable  at the  option of the Issuer  prior to  November  15,  2005.
Thereafter, the Notes will be redeemable, at the Issuer's option, in whole or in
part,  at any time or from time to time,  upon not less than 30 nor more than 60
days'  prior  notice  mailed by  first-class  mail to each  Holder's  registered
address,  at the following  redemption  prices (expressed as a percentage of the
principal amount),  plus accrued and unpaid interest,  if any, on such principal
amount to the redemption  date (subject to the right of Holders of record on the
relevant record date to receive  interest due on the relevant  interest  payment
date), if redeemed  during the 12-month period  commencing on November 15 of the
years set forth below:

                                       76
<PAGE>   83



                 Period                               Redemption Price

                 2005.................................        106.250%
                 2006.................................        104.167%
                 2007.................................        102.083%
                 2008 and thereafter..................        100.000%

                  In  addition,  at any  time  and  from  time to time  prior to
November  15,  2003,  the Issuer may  redeem in the  aggregate  up to 35% of the
aggregate  principal amount of the Notes with the proceeds of one or more Equity
Offerings,  at a redemption  price  (expressed  as a percentage of the principal
amount  thereof) of 112.5%  plus  accrued  and unpaid  interest,  if any, to the
redemption  date  (subject  to the right of  Holders  of record on the  relevant
record date to receive  interest due on the  relevant  interest  payment  date);
provided,  however,  that at least 65% of the aggregate  principal amount of the
Notes must remain  outstanding after each such redemption  (excluding Notes held
by the Issuer or any of its Subsidiaries); provided further that such redemption
shall occur within 90 days of the date of closing of such Equity Offering.

6.       Notice of Redemption

                  Notice of  redemption  will be mailed at least 30 days but not
more than 60 days before the redemption date by first-class  mail to each Holder
of Notes to be redeemed at his registered  address.  Notes in  denominations  of
principal  amount  larger  than $1,000 may be redeemed in part but only in whole
multiples of $1,000.  If money  sufficient  to pay the  redemption  price of and
accrued and unpaid interest on all Notes (or portions thereof) to be redeemed on
the  redemption  date is  deposited  with  the  Paying  Agent on or  before  the
redemption  date and certain other  conditions are satisfied,  on and after such
date interest  ceases to accrue on such Notes (or such portions  thereof) called
for redemption.

7.       Put Provisions

                  Upon a Change of  Control,  any  Holder of Notes will have the
right to cause  the  Issuer to  repurchase  all or any part of the Notes of such
Holder at a repurchase price equal to 101% of the principal amount thereof as of
the date of repurchase, plus accrued and unpaid interest, if any, to the date of
repurchase as provided in, and subject to the terms of, the Indenture.

8.       Registration Rights

                  The Issuer is party to a Registration Rights Agreement,  dated
as of  December  20,  2000,  between  the Issuer and CIBC  World  Markets  Corp.
pursuant  to  which it is  obligated  to pay  Additional  Interest  (as  defined
therein)  upon the  occurrence  of certain  Registration  Defaults  (as  defined
therein).

9.       Denominations; Transfer; Exchange

                  The  Notes  are  in   registered   form  without   coupons  in
denominations  of principal  amount of $1,000 and whole  multiples of $1,000.  A
Holder  may  register,  transfer  or  exchange  Notes  in  accordance  with  the
Indenture.  The Registrar may require a Holder,  among other things,  to furnish
appropriate  endorsements  or transfer  documents  and to pay any taxes and fees

                                       77
<PAGE>   84

required by law or permitted by the  Indenture.  The Registrar need not register
the transfer of or exchange (i) any Notes  selected for redemption  (except,  in
the case of a Note to be  redeemed  in part,  the  portion of the Note not to be
redeemed) for a period beginning 15 business days before a selection of Notes to
be  redeemed  and ending on the date of such  selection  or (ii) any Notes for a
period  beginning 15 business days before an interest payment date and ending on
such interest payment date.

10.      Persons Deemed Owners

                  The registered holder of this Note may be treated as the owner
of it for all purposes.

11.      Unclaimed Money

                  If money for the  payment of  principal  or  interest  remains
unclaimed for one year after the date of payment of principal and interest,  the
Trustee or Paying  Agent  shall pay the money back to the Issuer at its  request
unless an  abandoned  property law  designates  another  Person.  After any such
payment,  Holders  entitled to the money must look only to the Issuer and not to
the Trustee for payment.

12.      Defeasance

                  Subject to certain conditions set forth in the Indenture,  the
Issuer at any time may terminate some or all of its obligations  under the Notes
and the  Indenture  if the  Issuer  deposits  with  the  Trustee  money  or U.S.
Government Obligations for the payment of principal of and interest on the Notes
to redemption or maturity, as the case may be.

13.      Amendment, Waiver

                  Subject to certain exceptions set forth in the Indenture,  (i)
the  Indenture  or the Notes may be  amended  with the  written  consent  of the
Holders of at least a majority in principal amount of the outstanding  Notes and
(ii) any  default or  noncompliance  with any  provision  may be waived with the
written  consent  of the  Holders  of a  majority  in  principal  amount  of the
outstanding  Notes.  Subject to certain  exceptions  set forth in the Indenture,
without the consent of any Noteholder,  the Issuer and the Trustee may amend the
Indenture or the Notes to cure any ambiguity, omission, defect or inconsistency,
or to comply with Article V of the Indenture,  or to provide for  uncertificated
Notes in addition to or in place of  certificated  Notes,  or to add  guarantees
with respect to the Notes or to secure the Notes, or to add additional covenants
of or surrender rights and powers conferred on the Issuer, or to make any change
that does not materially and adversely  affect the rights of any Noteholder,  or
to  comply  with  any  request  of the SEC in  connection  with  qualifying  the
Indenture under the Act.

14.      Defaults and Remedies

                  Under the Indenture,  Events of Default  include (i) a default
in any payment of interest on any Note when due,  continued for 30 days,  (ii) a
default in the payment of principal of any Note when due at its Stated Maturity,
upon  optional  or  mandatory   redemption,   upon  required  repurchase,   upon
declaration  or  otherwise,  (iii) the  failure by the Issuer to comply with its

                                       78
<PAGE>   85

obligations under Article V of the Indenture,  (iv) the failure by the Issuer to
comply for 30 days after notice with any of its obligations  under the covenants
described  under Section 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9,  4.10,  4.11 or
4.12 of the  Indenture (in each case,  other than a failure to purchase  Notes),
(v) the failure by the Issuer to comply for 60 days after  notice with its other
agreements  contained  in the  Indenture,  (vi) the failure by the Issuer or any
Significant  Subsidiary  of  the  Issuer  to pay  any  Indebtedness  within  any
applicable  grace period after final  maturity or the  acceleration  of any such
Indebtedness  by the holders thereof because of a default if the total amount of
such  Indebtedness  unpaid or  accelerated  exceeds $10.0 million or its foreign
currency  equivalent,   (vii)  certain  events  of  bankruptcy,   insolvency  or
reorganization  of the  Issuer or any  Significant  Subsidiary  of the Issuer or
(viii) any final  judgment or decree for the payment of money in excess of $10.0
million  (net of any  amounts  with  respect to which a  creditworthy  insurance
company has acknowledged  full liability  (subject to any deductible  amounts of
less than $10.0  million  required  to be paid by the Issuer or the  Significant
Subsidiary of the Issuer in accordance with the applicable insurance policy)) is
rendered  against  the Issuer or any  Significant  Subsidiary  of the Issuer and
either (A) an  enforcement  proceeding  has been  commenced by any creditor upon
such  judgment  or decree or (B) such  judgment  or decree  remains  unpaid  and
outstanding  for a  period  of 60  days  following  such  judgment  and  is  not
discharged, waived or stayed within 10 days after notice. If an Event of Default
occurs  and is  continuing,  the  Trustee  or the  Holders  of at  least  25% in
aggregate  principal amount of the Notes may declare all the Notes to be due and
payable  immediately.  Certain  events of bankruptcy or insolvency are Events of
Default  which will result in the Notes being due and payable  immediately  upon
the occurrence of such Events of Default.

                  Noteholders  may not enforce the Indenture or the Notes except
as provided in the Indenture. The Trustee may refuse to enforce the Indenture or
the Notes  unless it  receives  reasonable  indemnity  or  security.  Subject to
certain limitations,  Holders of a majority in principal amount of the Notes may
direct the  Trustee  in its  exercise  of any trust or power.  The  Trustee  may
withhold from Noteholders  notice of any continuing  Default or Event of Default
(except a Default or Event of Default in payment of principal or interest) if it
determines that withholding notice is not opposed to their interest.

15.      Trustee Dealings with the Issuer

                  Subject to certain limitations set forth in the Indenture, the
Trustee under the Indenture, in its individual or any other capacity, may become
the  owner  or  pledgee  of  Notes  and may  otherwise  deal  with  and  collect
obligations  owed to it by the Issuer or its  Affiliates  and may otherwise deal
with the Issuer or its Affiliates  with the same rights it would have if it were
not Trustee.

16.      No Recourse Against Others

                  No director, officer, employee, incorporator or stockholder of
the Issuer,  as such, shall have any liability for any obligations of the Issuer
under the Notes,  the  Indenture or for any claim based on, in respect of, or by
reason of such obligations or their creation.  Each Holder of Notes by accepting
a Note waives and releases all such liability.  This waiver and release are part
of the consideration for issuance of the Notes.

                                       79
<PAGE>   86

17.      Authentication

                  This Note shall not be valid until an authorized  signatory of
the Trustee (or an authenticating agent acting on its behalf) manually signs the
certificate of authentication on the other side of this Note.

18.      Abbreviations

                  Customary   abbreviations  may  be  used  in  the  name  of  a
Noteholder  or an  assignee,  such  as TEN COM  (=tenants  in  common),  TEN ENT
(=tenants by the entirety),  JT TEN (=joint  tenants with rights of survivorship
and not as tenants in common),  CUST  (=custodian) and U/G/M/A (=Uniform Gift to
Minors Act).

19.      CUSIP Numbers

                  Pursuant to a  recommendation  promulgated by the Committee on
Uniform Security Identification  Procedures, the Issuer has caused CUSIP numbers
to be printed on the Notes and has directed the Trustee to use CUSIP  numbers in
notices of redemption as a convenience to Noteholders. No representation is made
as to the  accuracy  of such  numbers  either  as  printed  on the  Notes  or as
contained  in any notice of  redemption  and  reliance may be placed only on the
other identification numbers placed thereon.

20.      GOVERNING LAW

                  THIS NOTE SHALL BE GOVERNED BY, AND  CONSTRUED  IN  ACCORDANCE
WITH,  THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT GIVING EFFECT TO APPLICABLE
PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF
ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

                  The Issuer will furnish to any Noteholder upon written request
and without charge to the Noteholder a copy of the Indenture which has in it the
text of this Note in larger type. Requests may be made to: SpectraSite Holdings,
Inc.,  100  Regency  Forest  Drive,  Suite  400,  Cary,  North  Carolina  27511,
Attention: Chief Financial Officer.

                                       80

<PAGE>   87



                                 ASSIGNMENT FORM

                  To assign this Note, fill in the form below:


I or we assign and transfer this Note to:




(Print or type assignee's name, address and zip code)

(Insert assignee's soc. sec. or tax I.D. No.)

and irrevocably appoint
agent to transfer this Note on the books of the Issuer. The agent may substitute
another to act for him.

Date:               Your Signature:__________________
                    Sign exactly as your name appears on the other side
                    of this Note.

Signature Guarantee:
                           (Signature  must be guaranteed by a participant  in a
                           recognized  Signature  Guarantee Medallion Program or
                           other   signature    guarantor   program   reasonably
                           acceptable to the Trustee)

In  connection  with any  transfer or exchange of any of the Notes  evidenced by
this  certificate  occurring prior to the date that is two years after the later
of the date of  original  issuance  of such Notes and the last date,  if any, on
which such Notes were owned by the Issuer or any  Affiliate  of the Issuer,  the
undersigned confirms that such Notes are being transferred:

CHECK ONE BOX BELOW:

[  ]     (1)      to the Issuer; or

[  ]     (2)      pursuant to an effective registration statement under the
                  Securities Act of 1933; or

[  ]     (3)      inside  the  United  States to a "qualified  institutional
                  buyer" (as  defined in Rule 144A under the  Securities  Act of
                  1933) that purchases for its own account or for the account of
                  a qualified  institutional  buyer to whom notice is given that
                  such  transfer is being made in reliance on Rule 144A, in each
                  case  pursuant to and in  compliance  with Rule 144A under the
                  Securities Act of 1933; or

[ ]      (4)      outside the United  States in an  offshore  transaction
                  within the meaning of Regulation S under the Securities Act in
                  compliance with Rule 904 under the Securities Act of 1933.

                                       81
<PAGE>   88

Unless one of the boxes is checked,  the Trustee  will refuse to register any of
the Notes evidenced by this certificate in the name of any Person other than the
registered holder thereof;  provided,  however,  that if box (4) is checked, the
Trustee may require,  prior to registering any such transfer of the Notes,  such
legal  opinions,   certifications  and  other  information  as  the  Issuer  has
reasonably  requested to confirm that such transfer is being made pursuant to an
exemption  from,  or  in  a  transaction   not  subject  to,  the   registration
requirements  of the Securities  Act of 1933, as amended,  such as the exemption
provided by Rule 144 under such Act.

Date:                     Your Signature:  ___________________
                          Sign exactly as your name appears on the other side
                          of this Note.

Signature Guarantee:
                           (Signature  must be guaranteed by a participant  in a
                           recognized  Signature  Guarantee Medallion Program or
                           other   signature    guarantor   program   reasonably
                           acceptable to the Trustee)

                                       82


<PAGE>   89



              TO BE COMPLETED BY PURCHASER IF (3) ABOVE IS CHECKED.


                  The undersigned  represents and warrants that it is purchasing
this Note for its own account or an account  with  respect to which it exercises
sole  investment  discretion  and that it and any such  account is a  "qualified
institutional buyer" within the meaning of Rule 144A under the Securities Act of
1933, as amended,  and is aware that the sale to it is being made in reliance on
Rule 144A and acknowledges  that it has received such information  regarding the
Issuer as the undersigned has requested  pursuant to Rule 144A or has determined
not to request  such  information  and that it is aware that the  transferor  is
relying upon the undersigned's  foregoing  representations in order to claim the
exemption from registration provided by Rule 144A.

Date:                   Your Signature:_______________
                        NOTICE:  To be executed by an
                        executive officer

                       OPTION OF HOLDER TO ELECT PURCHASE

                  If you want to elect to have this Note purchased by the Issuer
pursuant to Section 4.7 or 4.9 of the Indenture, check the appropriate box:

                  Section 4.7       [    ]

                  Section 4.9       [    ]

                  If you want to elect to have only part of this Note  purchased
by the Issuer pursuant to Section 4.7 or 4.9 of the Indenture,  state the amount
you elect to have purchased (must be integral multiple of $1,000):
$
 -----------------

                                       83
<PAGE>   90



                        [TO BE ATTACHED TO GLOBAL NOTES]


                SCHEDULE OF INCREASES OR DECREASES IN GLOBAL NOTE

    The following increases or decreases in this Global Note have been made:
<TABLE>
<S>                        <C>                    <C>                      <C>                      <C>


Date of Exchange           Amount of decrease in    Amount of increase in   Principal Amount         Signature of
                           Principal Amount of      Principal Amount of     of this Global Note      authorized
                           this Global Note         this Global Note        following such           officer of Trustee or
                                                                            decrease or increase     Notes Custodian



</TABLE>

                                       84
<PAGE>   91




                                                                       EXHIBIT A

                         [FORM OF FACE OF EXCHANGE NOTE
                           [OR PRIVATE EXCHANGE NOTE]]

1

2



                           SPECTRASITE HOLDINGS, INC.

No.__    Principal Amount $________________

CUSIP NO.__________

                          12 1/2% Senior Note Due 2010

                  SpectraSite Holdings,  Inc., a Delaware corporation,  promises
to  pay  to  _____________,   or  registered  assigns,   the  principal  sum  of
__________________ Dollars on November 15, 2010.

                  Interest Payment Dates: May 15 and November 15.

                  Record Dates: May 1 and November 1.

                  Additional  provisions of this Note are set forth on the other
side of this Note.


--------
1        1[If the  Security  is to be  issued  in  global  form  add the  Global
         Securities  Legend from Exhibit 1 to Appendix A and the attachment from
         such  Exhibit  1  captioned  "[TO BE  ATTACHED  TO  GLOBAL  SECURITIES]
         SCHEDULE OF INCREASES OR DECREASES IN GLOBAL SECURITY".]

2        2[If the Security is a Private  Exchange  Security  issued in a Private
         Exchange  to an  Initial  Purchaser  holding  an unsold  portion of its
         initial allotment,  add the Restricted Securities Legend from Exhibit 1
         to Appendix A and replace the Assignment  Form included in such Exhibit
         1.]
                                       85

<PAGE>   92





Dated:                                      SPECTRASITE HOLDINGS, INC.

                                                 By:
                                                    --------------------------


                                                 By:
                                                    --------------------------

TRUSTEE'S CERTIFICATE OF
AUTHENTICATION

This is one of the Notes referred to in the Indenture.

UNITED STATES TRUST COMPANY OF NEW YORK
  as Trustee

By:  _________________________
            Authorized Signatory

                                       86

<PAGE>   93



                     [FORM OF REVERSE SIDE OF EXCHANGE NOTE
                           [OR PRIVATE EXCHANGE NOTE]]


                          12 1/2% Senior Note due 2010

1.       Interest

                  SpectraSite  Holdings,  Inc.,  a  Delaware  corporation  (such
corporation,  and its  successors  and assigns under the  Indenture  hereinafter
referred to, being herein called the "Issuer"),  promises to pay interest on the
principal  amount  of this Note at the rate per annum  shown  above[;  provided,
however,  that if a Registration  Default (as defined in the Registration Rights
Agreement)  occurs,  additional cash interest will accrue on this Note at a rate
of 0.50% per annum from and  including  the date on which any such  Registration
Default shall occur to but excluding the date on which all Registration Defaults
have been cured,  calculated on the principal amount of this Note as of the date
on which such interest is payable; provided, however, that in no event shall the
aggregate  amount of such  additional  interest  exceed  0.50% per  annum.  Such
interest is payable in addition to any other interest  payable from time to time
with  respect to this Note.  The Trustee  will not be deemed to have notice of a
Registration  Default  until  it  shall  have  received  actual  notice  of such
Registration Default].

                  The Notes will  accrue  interest at a rate of 12 1/2% from the
Issue Date, payable semi-annually  commencing May 15, 2001, to Holders of record
at the close of business on the May 1 or November 1  immediately  preceding  the
interest payment date of May 1 and November 1 of each year. The Issuer shall pay
interest on overdue principal at 1% per annum in excess of the rate borne by the
Notes to the extent lawful.  Interest will be computed on the basis of a 360-day
year of twelve 30-day months.

2.       Method of Payment

                  By at least  11:00  a.m.  (New York City  time) on the date on
which any  principal of or interest on any Note is due and  payable,  the Issuer
shall irrevocably  deposit with the Trustee or the Paying Agent money sufficient
to pay such  principal  and/or  interest.  The Issuer will pay interest  (except
defaulted  interest) to the Persons who are  registered  Holders of Notes at the
close of business on the May 1 or November 1 next preceding the interest payment
date even if Notes are cancelled,  repurchased or redeemed after the record date
and on or before the interest  payment date.  Holders must surrender  Notes to a
Paying Agent to collect  principal  payments.  The Issuer will pay principal and
interest  in money of the  United  States  that at the time of  payment is legal
tender for  payment of public and  private  debts.  However,  the Issuer may pay
principal and interest by check  payable in such money.  It may mail an interest
an interest check to a Holder's registered address.

3.       Paying Agent and Registrar

                  Initially, United States Trust Company of New York, a national
banking association (the "Trustee"), will act as Paying Agent and Registrar. The
Issuer  may  appoint  and change any Paying  Agent,  Registrar  or  co-registrar
without  notice  to any  Noteholder.  The  Issuer  or  any  of its  domestically
incorporated Wholly Owned Subsidiaries may act as Paying Agent.

                                       87
<PAGE>   94

4.       Indenture

                  The Issuer  issued the Notes  under an  Indenture  dated as of
December  20,  2000 (as it may be amended or  supplemented  from time to time in
accordance with the terms thereof, the "Indenture"),  between the Issuer and the
Trustee.  The terms of the Notes include those stated in the Indenture and those
made part of the  Indenture by reference to the Trust  Indenture Act of 1939, as
amended  (15  U.S.C.  ss.ss.  77aaa-77bbbb)  as in  effect  on the  date  of the
Indenture (the "TIA"). Capitalized terms used herein and not defined herein have
the meanings  ascribed  thereto in the  Indenture.  The Notes are subject to all
such terms,  and  Noteholders  are referred to the  Indenture  and the TIA for a
statement of those terms.

                  The Notes  are  unsecured  senior  obligations  of the  Issuer
limited to $200,000,000  aggregate  principal  amount (subject to Section 2.7 of
the Indenture), all of which are being offered on the Issue Date.

                  This  Note is one of the  Exchange  Notes  referred  to in the
Indenture.  The Notes include the Initial Notes and any Private  Exchange  Notes
and  Exchange  Notes issued in exchange  for the Initial  Notes  pursuant to the
Indenture and the Registration Rights Agreement.  The Initial Notes, the Private
Exchange  Notes  and the  Exchange  Notes  are  treated  as a  single  class  of
securities under the Indenture. The Indenture imposes certain limitations on the
Incurrence of  Indebtedness by the Issuer and its Restricted  Subsidiaries,  the
payment of dividends and other  distributions on the Capital Stock of the Issuer
and its Restricted Subsidiaries,  the purchase or redemption of Capital Stock of
the Issuer and Capital Stock of such Restricted Subsidiaries,  certain purchases
or redemptions of Subordinated  Obligations,  the sale or transfer of assets and
Capital Stock of Restricted Subsidiaries,  the issuance or sale of Capital Stock
of Restricted  Subsidiaries,  the investments of the Issuer and its Subsidiaries
and transactions with Affiliates.  In addition, the Indenture limits the ability
of the Issuer and its  Restricted  Subsidiaries  to restrict  distributions  and
dividends from Restricted Subsidiaries.

5.       Redemption

                  Except as set forth in the following paragraph, the Notes will
not be  redeemable  at the  option of the Issuer  prior to  November  15,  2005.
Thereafter, the Notes will be redeemable, at the Issuer's option, in whole or in
part,  at any time or from time to time,  upon not less than 30 nor more than 60
days'  prior  notice  mailed by  first-class  mail to each  Holder's  registered
address,  at the following  redemption  prices (expressed as a percentage of the
principal amount),  plus accrued and unpaid interest,  if any, on such principal
amount to the redemption  date (subject to the right of Holders of record on the
relevant record date to receive  interest due on the relevant  interest  payment
date), if redeemed  during the 12-month period  commencing on November 15 of the
years set forth below:


                  Period                              Redemption Price
                  ------                              ----------------
                  2005...............................         106.250%
                  2006...............................         104.167%
                  2007...............................         102.083%
                  2008 and thereafter................         100.000%

                                       88
<PAGE>   95

                  In  addition,  at any  time  and  from  time to time  prior to
November  15,  2003,  the Issuer may  redeem in the  aggregate  up to 35% of the
aggregate  principal amount of the Notes with the proceeds of one or more Equity
Offerings,  at a redemption  price  (expressed  as a percentage of the principal
amount  thereof) of 112.5%  plus  accrued  and unpaid  interest,  if any, to the
redemption  date  (subject  to the right of  Holders  of record on the  relevant
record date to receive  interest due on the  relevant  interest  payment  date);
provided,  however,  that at least 65% of the aggregate  principal amount of the
Notes must remain  outstanding after each such redemption  (excluding Notes held
by the  Issuer  or  any  of  its  Subsidiaries);  provided  further,  that  such
redemption  shall  occur  within 90 days of the date of closing  of such  Equity
Offering.

6.        Notice of Redemption

                  Notice of  redemption  will be mailed at least 30 days but not
more than 60 days before the redemption date by first-class  mail to each Holder
of Notes to be redeemed at his registered  address.  Notes in  denominations  of
principal  amount  larger  than $1,000 may be redeemed in part but only in whole
multiples of $1,000.  If money  sufficient  to pay the  redemption  price of and
accrued and unpaid interest on all Notes (or portions thereof) to be redeemed on
the  redemption  date is  deposited  with  the  Paying  Agent on or  before  the
redemption  date and certain other  conditions are satisfied,  on and after such
date interest  ceases to accrue on such Notes (or such portions  thereof) called
for redemption.

7.        Put Provisions

                  Upon a Change of  Control,  any  Holder of Notes will have the
right to cause  the  Issuer to  repurchase  all or any part of the Notes of such
Holder at a repurchase price equal to 101% of the principal amount thereof as of
the date of repurchase, plus accrued and unpaid interest, if any, to the date of
repurchase as provided in, and subject to the terms of, the Indenture.

8.        Denominations, Transfer, Exchange

                  The  Notes  are  in   registered   form  without   coupons  in
denominations  of principal  amount of $1,000 and whole  multiples of $1,000.  A
Holder  may  register,  transfer  or  exchange  Notes  in  accordance  with  the
Indenture.  The Registrar may require a Holder,  among other things,  to furnish
appropriate  endorsements  or transfer  documents  and to pay any taxes and fees
required by law or permitted by the  Indenture.  The Registrar need not register
the transfer of or exchange (i) any Notes  selected for redemption  (except,  in
the case of a Note to be  redeemed  in part,  the  portion of the Note not to be
redeemed) for a period beginning 15 business days before a selection of Notes to
be  redeemed  and ending on the date of such  selection  or (ii) any Notes for a
period  beginning 15 business days before an interest payment date and ending on
such interest payment date.

9.        Persons Deemed Owners

                  The registered holder of this Note may be treated as the owner
of it for all purposes.

                                       89
<PAGE>   96

10.       Unclaimed Money

                  If money for the  payment of  principal  or  interest  remains
unclaimed for one year after the date of payment of principal and interest,  the
Trustee or Paying  Agent  shall pay the money back to the Issuer at its  request
unless an  abandoned  property law  designates  another  Person.  After any such
payment,  Holders  entitled to the money must look only to the Issuer and not to
the Trustee for payment.

11.       Defeasance

                  Subject to certain conditions set forth in the Indenture,  the
Issuer at any time may terminate some or all of its obligations  under the Notes
and the  Indenture  if the  Issuer  deposits  with  the  Trustee  money  or U.S.
Government Obligations for the payment of principal of and interest on the Notes
to redemption or maturity, as the case may be.

12.       Amendment, Waiver

                  Subject to certain exceptions set forth in the Indenture,  (i)
the  Indenture  or the Notes may be  amended  with the  written  consent  of the
Holders of at least a majority in principal amount of the outstanding  Notes and
(ii) any  default or  noncompliance  with any  provision  may be waived with the
written  consent  of the  Holders  of a  majority  in  principal  amount  of the
outstanding  Notes.  Subject to certain  exceptions  set forth in the Indenture,
without the consent of any Noteholder,  the Issuer and the Trustee may amend the
Indenture or the Notes to cure any ambiguity, omission, defect or inconsistency,
or to comply with Article V of the Indenture,  or to provide for  uncertificated
Notes in addition to or in place of  certificated  Notes,  or to add  guarantees
with respect to the Notes or to secure the Notes, or to add additional covenants
of or surrender rights and powers conferred on the Issuer, or to make any change
that does not materially and adversely  affect the rights of any Noteholder,  or
to  comply  with  any  request  of the SEC in  connection  with  qualifying  the
Indenture under the Act.

13.       Defaults and Remedies

                  Under the Indenture,  Events of Default  include (i) a default
in any payment of interest on any Note when due,  continued for 30 days,  (ii) a
default in the payment of principal of any Note when due at its Stated Maturity,
upon  optional  or  mandatory   redemption,   upon  required  repurchase,   upon
declaration  or  otherwise,  (iii) the  failure by the Issuer to comply with its
obligations under Article V of the Indenture,  (iv) the failure by the Issuer to
comply for 30 days after notice with any of its obligations  under the covenants
described  under Section 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9,  4.10,  4.11 or
4.12 of the  Indenture (in each case,  other than a failure to purchase  Notes),
(v) the failure by the Issuer to comply for 60 days after  notice with its other
agreements  contained  in the  Indenture,  (vi) the failure by the Issuer or any
Significant  Subsidiary  of  the  Issuer  to pay  any  Indebtedness  within  any
applicable  grace period after final  maturity or the  acceleration  of any such
Indebtedness  by the holders thereof because of a default if the total amount of
such  Indebtedness  unpaid or  accelerated  exceeds $10.0 million or its foreign
currency  equivalent,   (vii)  certain  events  of  bankruptcy,   insolvency  or
reorganization  of the  Issuer or any  Significant  Subsidiary  of the Issuer or
(viii) any final  judgment or decree for the payment of money in excess of $10.0
million  (net of any  amounts  with  respect to which a  creditworthy

                                       90
<PAGE>   97

insurance  company has  acknowledged  full liability  (subject to any deductible
amounts  of less than  $10.0  million  required  to be paid by the Issuer or the
Significant Subsidiary of the Issuer in accordance with the applicable insurance
policy)) is rendered  against the Issuer or any  Significant  Subsidiary  of the
Issuer  and either  (A) an  enforcement  proceeding  has been  commenced  by any
creditor  upon such  judgment or decree or (B) such  judgment or decree  remains
unpaid and  outstanding  for a period of 60 days  following such judgment and is
not  discharged,  waived or stayed within 10 days after  notice.  If an Event of
Default occurs and is continuing,  the Trustee or the Holders of at least 25% in
aggregate  principal amount of the Notes may declare all the Notes to be due and
payable  immediately.  Certain  events of bankruptcy or insolvency are Events of
Default  which will result in the Notes being due and payable  immediately  upon
the occurrence of such Events of Default.

                  Noteholders  may not enforce the Indenture or the Notes except
as provided in the Indenture. The Trustee may refuse to enforce the Indenture or
the Notes  unless it  receives  reasonable  indemnity  or  security.  Subject to
certain limitations,  Holders of a majority in principal amount of the Notes may
direct the  Trustee  in its  exercise  of any trust or power.  The  Trustee  may
withhold from Noteholders  notice of any continuing  Default or Event of Default
(except a Default or Event of Default in payment of Principal or interest) if it
determines that withholding notice is not opposed to their interest.

14.       Trustee Dealings with the Issuer

                  Subject to certain limitations set forth in the Indenture, the
Trustee under the Indenture, in its individual or any other capacity, may become
the  owner  or  pledgee  of  Notes  and may  otherwise  deal  with  and  collect
obligations  owed to it by the Issuer or its  Affiliates  and may otherwise deal
with the Issuer or its Affiliates  with the same rights it would have if it were
not Trustee.

15.       No Recourse Against Others

                  No director, officer, employee, incorporator or stockholder of
the Issuer,  as such, shall have any liability for any obligations of the Issuer
under the Notes,  the  Indenture or for any claim based on, in respect of, or by
reason of such obligations or their creation.  Each Holder of Notes by accepting
a Note waives and releases all such liability.  This waiver and release are part
of the consideration for issuance of the Notes.

16.       Authentication

                  This Note shall not be valid until an authorized  signatory of
the Trustee (or an authenticating agent acting on its behalf) manually signs the
certificate of authentication on the other side of this Note.

17.       Abbreviations

                  Customary   abbreviations  may  be  used  in  the  name  of  a
Noteholder  or an  assignee,  such  as TEN COM  (=tenants  in  common),  TEN ENT
(=tenants by the entirety),  JT TEN (=joint  tenants with rights of survivorship
and not as tenants in common),  CUST  (=custodian) and U/G/M/A (=Uniform Gift to
Minors Act).

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18.       CUSIP Numbers

                  Pursuant to a  recommendation  promulgated by the Committee on
Uniform Security  Identification  Procedures the Issuer has caused CUSIP numbers
to be printed on the Notes and has directed the Trustee to use CUSIP  numbers in
notices of redemption as a convenience to Noteholders. No representation is made
as to the  accuracy  of such  numbers  either  as  printed  on the  Notes  or as
contained  in any notice of  redemption  and  reliance may be placed only on the
other identification numbers placed thereon.

19.       GOVERNING LAW

                  THIS NOTE SHALL BE GOVERNED BY, AND  CONSTRUED  IN  ACCORDANCE
WITH,  THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT GIVING EFFECT TO APPLICABLE
PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF
ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

               The Issuer will furnish to any  Noteholder  upon written  request
and without charge to the Noteholder a copy of the Indenture which has in it the
text of this Note in larger type. Requests may be made to: SpectraSite Holdings,
Inc.,  100  Regency  Forest  Drive,  Suite  400,  Cary,  North  Carolina  27511,
Attention: Chief Financial Officer.

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                                 ASSIGNMENT FORM

                                  To assign  this  Note, fill in the form below:

I or we assign and transfer this Note to:




(Print or type assignee's name, address and zip code)

(Insert assignee's soc. sec. or tax I.D. No.)

and irrevocably appoint
agent to transfer this Note on the books of the Issuer. The agent may substitute
another to act for him.

Date:                            Your

                                 Signature:____________________
                                 Sign   exactly  as
                                 your name  appears
                                 on the other  side
                                 of this Note.

                           Signature Guarantee:      _________________________
                           (Signature  must be guaranteed by a participant  in a
                           recognized  Signature  Guarantee Medallion Program or
                           other   signature    guarantor   program   reasonably
                           acceptable to the Trustee)

                                        OPTION-OF-HOLDER TO ELECT PURCHASE

                  If you want to elect to have this Note purchased by the Issuer
pursuant to Section 4.7 or 4.9 of the Indenture, check the appropriate box:

                  Section 4.7       [   ]

                  Section 4.9       [   ]

                  If you want to elect to have only part of this Note  purchased
by the Issuer pursuant to Section 4.7 or 4.9 of the Indenture,  state the amount
you elect to have purchased (must be integral multiple of $1,000):
$ -------------------------

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