<PAGE>
 
                                                                    EXHIBIT 10.2


                         CAPITAL CONTRIBUTION AGREEMENT

     CAPITAL CONTRIBUTION AGREEMENT, dated as of September 18, 1998, made by
each of Omnipoint Corporation, a Delaware corporation ("Omnipoint"), and D&E
                                                        ---------           
Communications, Inc., a Pennsylvania corporation ("D&E"), in favor of
                                                   ---               
D&E/Omnipoint Wireless Joint Venture, L.P., a Delaware limited partnership (the
"Borrower"), and in favor of the Lenders (the "Lenders") from time to time
 --------                                      -------                    
parties to the Loan Agreement (as defined below) and Northern Telecom Inc., as
administrative agent (together with its successors as such administrative agent,
the "Administrative Agent") for the Lenders.
     --------------------                   

     PRELIMINARY STATEMENTS:

     (1) The Lenders and the Administrative Agent have entered into a Loan
Agreement dated as of September 18, 1998 with the Borrower (as amended or
otherwise modified from time to time, the "Loan Agreement", the terms defined
therein and not otherwise defined herein being used herein as therein defined).
Each of Omnipoint and D&E will derive substantial direct and indirect benefit
from the transactions contemplated by the Loan Agreement.

     (2) It is a condition precedent to the making of Advances by the Lenders
under the Loan Agreement that each of Omnipoint and D&E shall have executed and
delivered this Agreement.

     NOW, THEREFORE, in consideration of the premises and in order to induce the
Lenders to make Advances under the Loan Agreement, each of Omnipoint and D&E
agrees as follows:

     SECTION 1.  Obligation to Contribute Funds.  Omnipoint and D&E shall
                 ------------------------------                          
jointly and severally pay, or shall cause one of their Subsidiaries (other than
the Borrower or any of its Subsidiaries) (such other Subsidiaries, being "Other
                                                                          -----
Subsidiaries") to pay, to the Borrower (except as otherwise provided herein)
------------                                                                
immediately upon written request by

          (a)  the Borrower, or

          (b) if an Event of Default shall have occurred and be continuing, the
     Administrative Agent,

cash in U.S. dollars in the amount specified in such request; provided that the
aggregate amount of cash required to paid to the Borrower by Omnipoint, D&E or
any Other Subsidiary pursuant to any such request as of any date of
determination shall not exceed the greater of zero and the following amount (the
"Maximum Amount"):
 --------------   
<PAGE>
 
               (1)  the sum of (I) $50,000,000, plus (II) the aggregate amount
               of all dividends and other distributions by the Borrower in
               respect of its Stock and payments of interest and principal owing
               by the Borrower and its Subsidiaries to Omnipoint, D&E and their
               Other Subsidiaries (other than the Borrower and its Subsidiaries)
               on or before such date, plus (III) the aggregate amount of all
               cash payments made to D&E or Omnipoint pursuant to Section 4(c)
               of the Master Services Agreements,

                    minus

               (2)   the greater of

                    (I)  zero, and

                    (II) the aggregate amount of all cash equity contributions 
               to the Borrower and Subordinated Debt excluding, however,
               cumulative amounts advanced to Borrower to meet financial
               covenants pursuant to Section 6.14(A)(a), (b), (c) and (d), of
                                     ------------------------------------
               the Loan Agreement. 

Omnipoint or any other Subsidiary shall make payment of funds hereunder through
additional capital or other contributions in respect of the owners' equity of
the Borrower; provided that

          (x) to the extent such purchases or contributions are prohibited under
     agreements binding on Omnipoint or D&E or both on the date hereof (the
     "Conflicting Agreements"), such of Omnipoint, D&E or both which are party
     -----------------------                                                  
     to such Conflicting Agreements shall make payment hereunder through the
     lending of funds to the Borrower by way of Subordinated Debt;

          (y) if any such payment made as such a loan may at a later time be
     made as an equity contribution to the Borrower without violating such
     Conflicting Agreements, such loan shall be converted to an equity
     contribution to the Borrower; and

          (z) each of Omnipoint and D&E shall use its best efforts to take such
     action as will permit any such loan to be converted to such an equity
     contribution.
 
     SECTION 2.  Taxes. Etc.  (a)  Omnipoint and D&E, jointly and severally,
                 ----------                                                 
will pay any present or future stamp or other taxes, charges or similar levies
(collectively, "Taxes"), including any interest and penalties, which arise from
                -----                                                          
any payment made hereunder or from the execution, delivery or registration of,
or otherwise with respect to, this Agreement.

                                      -2-
<PAGE>
 
          (b) Omnipoint and D&E, jointly and severally, will indemnify the
Administrative Agent and each Lender for the full amount of Taxes (including,
without limitation, any Taxes imposed by any jurisdiction on amounts payable
under this Section) paid by the Administrative Agent or such Lender and any
liability (including penalties, interest and expenses) arising therefrom or with
respect thereto, whether or not such Taxes were correctly or legally asserted.
This indemnification shall be made within 30 days from the date the
Administrative Agent or such Lender (as the case may be) makes written demand
therefor.

     SECTION 3.  Obligation Absolute.  Each of Omnipoint and D&E will perform
                 -------------------                                         
its obligations under this Agreement regardless of any law, regulation or order
now or hereafter in effect in any jurisdiction affecting any of the terms of the
Notes, the Loan Agreement, the other Loan Documents or any other document
related thereto or the rights of the Administrative Agent or the Lenders with
respect thereto.  The obligations of each of Omnipoint and D&E under this
Agreement are independent of the Loan Agreement, the Notes and the other Loan
Documents, and a separate action or actions may be brought and prosecuted
against either of Omnipoint or D&E or both to enforce this Agreement,
irrespective of whether any action is brought against the other of Omnipoint or
D&E or the Borrower or whether Omnipoint or D&E or the Borrower is joined in any
such action or actions.  The obligations of each of Omnipoint and D&E under this
Agreement are joint and several and shall be absolute and unconditional
irrespective of:

          (i) any lack of validity or enforceability of the Loan Agreement, the
     Notes, any other Loan Document or any other agreement or instrument
     relating thereto or any collateral therefor;

          (ii) any change in the time, manner or place of payment of, or in any
     other term of, the Notes, the Loan Agreement, any other Loan Document, or
     any other amendment or waiver of or any consent to departure from the Loan
     Agreement, the Notes or any other Loan Document, including, without
     limitation, any increase in the Notes or the obligations of the Borrower
     under the Loan Agreement resulting from the extension of additional credit
     to the Borrower or any of its Subsidiaries or otherwise;

          (iii) any taking, exchange, release or non-perfection of any
     collateral, or any taking, release or amendment or waiver of or consent to
     departure from any guaranty, the Notes, the Loan Agreement or any other
     Loan Document;

          (iv) any manner of application of collateral, or proceeds thereof, to
     all or any of the obligations evidenced by the Loan Agreement, the Notes or
     any other Loan Document, or any manner of sale or other disposition of any
     collateral for all or any of the obligations evidenced by the Loan
     Agreement, the Notes or any other Loan Document or any other assets of the
     Borrower or any of its Subsidiaries;

                                      -3-
<PAGE>
 
          (v) any charge, restructuring or termination of the corporate or
     partnership structure or existence of the Borrower or any of its
     Subsidiaries; or

          (vi)  any other circumstances which might otherwise constitute a
     defense available to, or a discharge of, the Borrower or a surety.

This Agreement shall continue to be effective or be reinstated, as the case may
be, if at any time any payment of any of the Notes is rescinded or must
otherwise be returned by the Administrative Agent or any Lender upon the
insolvency, bankruptcy or reorganization of the Borrower or otherwise, all as
though such payment had not been made.

     SECTION 4.  Waiver.  Each of Omnipoint and D&E waives promptness,
                 ------                                               
diligence, notice of acceptance and any other notice with respect to the Loan
Agreement, the Notes, the other Loan Documents and this Agreement and any
requirement that the Administrative Agent or any Lender protect, secure, perfect
or insure any security interest or lien or any property subject thereto or
exhaust any right or take any action against the Borrower or any other person or
entity or any collateral.

     SECTION 5.  Separate Undertaking.  Without limiting the generality of any
                 --------------------                                         
of the foregoing provisions of this Agreement, each of Omnipoint and D&E
irrevocably waives, to the full extent permitted by applicable law and for the
benefit of, and as a separate undertaking with, the Lenders and the
Administrative Agent, any defense to the performance of this Agreement which may
be available to either of Omnipoint or D&E or both as a consequence of this
Agreement being rejected or otherwise not assumed by the Borrower or any trustee
or other similar official for the Borrower or for any substantial part of the
property of the Borrower, or as a consequence of this Agreement being otherwise
terminated or modified, in any proceeding seeking to adjudicate the Borrower a
bankrupt or insolvent, or seeking liquidation, winding up,  reorganization,
arrangement, adjustment, protection, relief or composition of the Borrower or
the debts of the Borrower under any law relating to bankruptcy, insolvency or
reorganization or relief of debtors, whether such rejection, non-assumption,
termination or modification be by reason of this Agreement being held to be an
executory contract or by reason of any other circumstance.  If this Agreement
shall be so rejected or otherwise not assumed, or so terminated or modified,
each of Omnipoint and D&E promises for the benefit of, and as a separate
undertaking with, the Lenders and the Administrative Agent, unconditionally,
jointly and severally, to pay to the Administrative Agent an amount equal to
each payment which would otherwise be payable by Omnipoint or D&E under or in
connection with this Agreement if this Agreement were not so rejected or
otherwise not assumed or were otherwise not so terminated or modified, such
amount to be payable to the Administrative Agent, at its account specified in
the Loan Agreement for the payment of amounts owing by the Borrower thereunder
(or otherwise in accordance with the instructions of the Administrative Agent),
as and when such payment would otherwise be payable hereunder and such amount to
be applied as such payment would 

                                      -4-
<PAGE>
 
otherwise be applied under Section 2.07 of the Loan Agreement.
                           ------------       

     SECTION 6.  Representations and Warranties of Omnipoint.  Omnipoint
                 -------------------------------------------            
represents and warrants as follows:

          (a) Omnipoint is a corporation duly organized, validly existing and in
     good standing under the laws of the State of Delaware.

          (b) The execution, delivery and performance by Omnipoint of this
     Agreement, and the consummation of the transactions contemplated hereby,
     are within Omnipoint's corporate powers, have been duly authorized by all
     necessary corporate action, and do not contravene (i) Omnipoint's charter
     or by-laws or (ii) any law or any contractual restriction binding on or
     affecting Omnipoint.

          (c) No authorization or approval or other action by, and no notice to
     or filing with any governmental authority or regulatory body or any other
     third party is required for the due execution, delivery and performance by
     Omnipoint of this Agreement.

          (d) This Agreement has been duly executed and delivered by Omnipoint.
     This Agreement is the legal, valid and binding obligation of Omnipoint
     enforceable against Omnipoint in accordance with its terms.

          (e) There are no conditions precedent to the effectiveness of this
     Agreement that have not been satisfied or waived.

          (f) Omnipoint has, independently and without reliance upon the
     Administrative Agent or any Lender and based on documents and information
     as it has deemed appropriate, made its own credit analysis and decision to
     enter into this Agreement.

     SECTION 7.  Representations and Warranties of D&E.  D&E represents and
                 -------------------------------------                     
warrants as follows:

          (a) D&E is a corporation duly organized, validly existing and in good
     standing under the laws of the Commonwealth of Pennsylvania.

          (b) The execution, delivery and performance by D&E of this Agreement,
     and the consummation of the transactions contemplated hereby, are within
     D&E's corporate powers, have been duly authorized by all necessary
     corporate action, and do not contravene (i) D&E's charter or by-laws or
     (ii) any law or any contractual restriction binding on or affecting D&E.

          (c) No authorization or approval or other action by, and no notice to
     or 

                                      -5-
<PAGE>
 
     filing with any governmental authority or regulatory body or any other
     third party is required for the due execution, delivery and performance by
     D&E of this Agreement.

          (d) This Agreement has been duly executed and delivered by D&E.  This
     Agreement is the legal, valid and binding obligation of D&E enforceable
     against D&E in accordance with its terms.

          (e) There are no conditions precedent to the effectiveness of this
     Agreement that have not been satisfied or waived.

          (f) D&E has, independently and without reliance upon the
     Administrative Agent or any Lender and based on documents and information
     as it has deemed appropriate, made its own credit analysis and decision to
     enter into this Agreement.

     SECTION 8.  Other Agreements.  Each of Omnipoint and D&E will make its
                 ----------------                                          
senior officers available for discussions with potential purchasers of
assignments of or participations in loans made by or commitments of Northern
Telecom Inc. under the Loan Agreement and any loan agreement with Northern
Telecom Inc. regarding vendor-financing loans and commitments primarily in
respect of the Network (as defined in the Loan Agreement), and otherwise
cooperate in the syndication of such loans and commitments at such times and
with such frequency as the Administrative Agent may reasonably request, provided
                                                                        --------
that the Administrative Agent shall use its best efforts to prevent unreasonable
----                                                                            
interference with or disruption of Omnipoint's and D&E's business on account of
the foregoing.

     SECTION 9.  Amendments, Etc.  No amendment or waiver of any provision of
                 ---------------                                             
this Agreement, and no consent to any departure by Omnipoint or D&E or both
herefrom, shall in any event be effective unless the same shall be in writing
and signed by the Borrower, the Administrative Agent and the Required Lenders
(provided that no amendment, waiver or consent shall, unless in writing and
signed by all the Lenders, (a) limit the liability of Omnipoint or D&E or both
hereunder, or (b) change the number of Lenders required to take any action
hereunder), and then such waiver or consent shall be effective only in the
specific instance and for the specific purpose for which given.

     SECTION 10.  Expenses.  Each of Omnipoint and D&E will, jointly and
                  --------                                              
severally, upon demand pay to the Borrower and the Administrative Agent,
respectively, the amount of any and all expenses, including the fees and
expenses of their respective counsel and of any experts and agents, which the
Borrower and the Administrative Agent or the Lenders, as the case may be, may
incur in connection with (a) the exercise or enforcement of any of their
respective rights hereunder or (b) the failure by Omnipoint or D&E or both to
perform or observe any of the provisions hereof.

                                      -6-
<PAGE>
 
     SECTION 11.  Addresses for Notices.  All notices and other communications
                  ---------------------                                       
provided for hereunder shall be in writing (including telecopy communication)
and mailed, telecopied, or delivered if to Omnipoint, at its address at 3
Bethesda Metro Center, Suite 400, Bethesda, Maryland 20814, Attention: Bradley
Sparks (fax no. (301) 951-2580), if to D&E, at its address at
________________________, Attention: __________________ (fax no. ___________),
and if to the Borrower, the Administrative Agent or any Lender, at its address
specified in the Loan Agreement, or, as to any party at such other address as
shall be designated by such party in a written notice to the other parties.  All
such notices and other communications shall, when mailed, be effective when
deposited in the mails or, when telecopied, when transmitted by telecopy,
respectively.

     SECTION 12.  No Waiver; Remedies.  No failure on the part of the Borrower,
                  -------------------                                          
the Administrative Agent or any Lender to exercise, and no delay in exercising,
any right hereunder shall operate as a waiver thereof; nor shall any single or
partial exercise of any right hereunder preclude any other or further exercise
thereof or the exercise of any other right.  The remedies herein provided are
cumulative and not exclusive of any remedies provided by law.

     SECTION 13.  Continuing Agreement; Assignments under Loan Agreement. This
                  ------------------------------------------------------      
Agreement is a continuing agreement and shall

          (a) remain in full force and effect until the later of

               (i) the payment in full of the Notes and all other amounts
          payable under the Loan Agreement, the other Loan Documents or this
          Agreement, and

               (ii)  the expiration or termination of the Commitments;

          (b) be binding upon Omnipoint, D&E, and their respective successors
     and assigns; and

          (c) inure to the benefit of and be enforceable by the Borrower, the
     Lenders, the Administrative Agent and their respective successors,
     transferees and assigns.

Without limiting the generality of the foregoing clause (c), any Lender may
assign or otherwise transfer all or any portion of its rights and obligations
under the Loan Agreement and this Agreement  (including, without limitation, all
or any portion of its Commitment, the Advances owing to it and any Note held by
it) to any other person or entity, and such other person or entity shall
thereupon become vested with all the rights in respect thereof granted to such
Lender herein or otherwise, subject, however, to the provisions of Article XI
                                                                   ----------
(concerning the Administrative Agent) of the Loan Agreement.

                                      -7-
<PAGE>
 
     SECTION 14.  Execution in Counterparts.  This Agreement may be executed in
                  -------------------------                                    
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed shall be deemed to be an original
and all of which when taken together shall constitute one and the same
agreement.  Delivery of an executed counterpart of a signature page to this
Agreement by telecopier shall be effective as delivery of a manually executed
counterpart of this Agreement.

     SECTION 15.  Governing Law.  This Agreement shall be governed by, and
                  -------------                                           
construed in accordance with, the laws of the State of New York.

     SECTION 16.  Consent to Jurisdiction.  Each of Omnipoint and D&E
                  -----------------------                            
irrevocably

          (a) submits to the jurisdiction of any New York state or federal court
     sitting in New York City in any action or proceeding arising out of or
     relating to this Agreement;

          (b) agrees that all claims in respect of such action or proceeding may
     be heard and determined in such New York state court or in such federal
     court;

          (c) waives, to the fullest extent that it may effectively do so, the
     defense of an inconvenient forum to the maintenance of such action or
     proceeding;

          (d) consents to the service of any and all process in any such action
     or proceeding by the mailing of copies of such process to such Borrower at
     its address specified in Section 9; and
                              ---------     

          (e) agrees that a final judgment in any such action or proceeding
     shall be conclusive and may be enforced in other jurisdictions by suit on
     the judgment or in any other manner provided by law.

Nothing in this Section 16 shall affect the right of the Administrative Agent,
                ----------                                                    
any Lender or the Borrower to serve legal process in any other manner permitted
by law or affect the right of the Administrative Agent or any Lender to bring
any action or proceeding against Omnipoint or its property in the courts of
other jurisdictions.

     SECTION 17.  Waiver of Jury Trial.  Each of Omnipoint, D&E and, by their
                  --------------------                                       
acceptance hereof, the Borrower and the Administrative Agent (on behalf of
itself and the Lenders), irrevocably waives all right to trial by jury in any
action, proceeding or counterclaim (whether based on contract, tort or
otherwise) arising out of or relating to this Agreement or the actions of the
Administrative Agent, any Lender or the Borrower in the negotiation,
administration, performance or enforcement thereof.

                                      -8-
<PAGE>
 
     IN WITNESS WHEREOF, each of Omnipoint and D&E has caused this Agreement to
be duly executed and delivered by its officer thereunto duly authorized as of
the date first above written.

                              OMNIPOINT CORPORATION


                              By:   /s/ Bradley E. Sparks
                                    ----------------------------
                                    Name:  Bradley E. Sparks
                                    Title: Vice President

                              D&E COMMUNICATIONS, INC.


                              By:   /s/ Donald R. Kaufmann
                                    ----------------------------
                                    Name:  Donald R. Kaufmann
                                    Title: Vice President
The foregoing Agreement is
accepted and agreed to as of the
date first-above written:

D&E/OMNIPOINT WIRELESS JOINT
VENTURE, L.P.


By:  /s/ Robert L. Quaranta
     -------------------------------
     Name:  Robert L. Quaranta
     Title: Chief Executive Officer



NORTHERN TELECOM INC., as Administrative Agent
for itself and on behalf of the Lenders


By:  /s/ Michael W. McCorkle
     -------------------------------
     Name:  Michael W. McCorkle
     Title: Director, Customer Finance - North America

                                      -9-