<PAGE>   1
***Portions of this exhibit marked by brackets ("[ ]") have been omitted
pursuant to a request for confidential treatment. The omitted portions have
been filed separately with the Securities and Exchange Commission.***

                                                                   EXHIBIT 10.34


                                 AMENDMENT NO. 6
               TO THE TERRESTRIAL REPEATER NETWORK SYSTEM CONTRACT


THIS AMENDMENT NO. 6 TO THE TERRESTRIAL REPEATER NETWORK SYSTEM CONTRACT (the
"Amendment No. 6") is entered into on this 8th day of January 2001 (the
"Effective Date") by and between XM Satellite Radio Inc., a Delaware corporation
with its principal offices located at 1500 Eckington Place, N.E., Washington,
D.C. 20002 (hereinafter "Owner"), and LCC International, Inc., a Delaware
corporation with its principal offices located at 7925 Jones Branch Drive,
McLean, Virginia 22102 (hereinafter "Contractor").

WHEREAS, the Parties entered into and executed the Terrestrial Repeater Network
System Contract dated August 18, 1999 and several amendments thereto (hereafter
collectively referred to as the "Contract") whereby such Contract provides for
the procurement by Owner from Contractor of the engineering, design,
construction and testing of the Terrestrial Repeater Network System;

WHEREAS, the Parties have been discussing certain issues relating to the
Contract; and

WHEREAS, the Parties have reached agreement on such issues;

NOW THEREFORE, in consideration of the above premises and the mutual covenants
and agreements contained herein, and for other good and valuable consideration,
the receipt of which is hereby acknowledged, the Parties agree the Contract is
hereby amended as follows:

DEFINITIONS

1.      Unless otherwise defined herein, capitalized terms used herein shall
        have the meaning set forth in the Contract.

        (A)     "High-Power Site" means a Site with a [           ] watt
                repeater installed or mounted on the Site.

        (B)     "Supplemental Site" means a Site not subject to the revised
                Baseline Schedule (also referred to in the Contract as the
                Initial City Schedule) or liquidated damages schedule set forth
                in Table 14.1. The Supplemental Sites are currently estimated to
                be [  ] Sites. The specific Supplemental Sites will be updated
                by the Parties as required during the Term of the Contract.

SCOPE OF WORK

2.      Contractor shall complete work on the Sites identified in Schedule A as
        follows, as summarized in Schedule A (the "Required Work") and as the
        work is further described in Exhibit B (Statement of Work) and Exhibit C
        (Contract Pricing, Payments and Milestone Achievement Criteria):

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                                                                    CONFIDENTIAL


        (A)     The "Site Acquisition Sites": Approximately [   ] Sites through
                Site Acquisition (i.e., Work Units M1, RF1, RF2, RF3, AE1(a),
                AE4, SA1, SA2, SA3 and RC 1 - 6).

        (B)     The "Zoning Sites": Approximately [   ] Sites (of the above
                approximately [   ]) through Zoning (i.e., Work Units M1, RF1,
                RF2, RF3, RF4 (for Sites with repeaters installed by May 1, 2001
                only and excluding High-Power Sites), RF5 (with MCM Testing, as
                further described in paragraph 2(E) below, substituted for CW
                testing), RF6 (for Sites with repeaters installed by May 1, 2001
                only and excluding High-Power Sites), AE1(a), AE1(b), AE2(a) (as
                defined in paragraph 11(C) below), AE3, AE4, ZN1, ZN2, ZN3, SA1,
                SA2, SA3, and RC 1 - 7 (RC 7 for Sites with repeaters installed
                by May 1, 2001 only)).

        (C)     The "Construction Sites": approximately [  ]  Sites (not to
                exceed [   ] Sites) (of the above approximately [   ]) through
                Site Construction and Interim Maintenance (Work Units M1, RF1,
                RF2, RF3, RF4 (for Sites with repeaters installed by May 1, 2001
                only and excluding  High-Power Sites), RF5 (with MCM Testing
                substituted for CW testing), RF6 (for Sites with repeaters
                installed by May 1, 2001 only and excluding High-Power Sites),
                AE1(a), AE1(b), AE2(a), AE2(b) (as defined in paragraph 11(C)
                below), AE3, AE4, ZN1, ZN2, ZN3, SA1, SA2, SA3, RC 1 - 7 (RC 7
                for Sites with repeaters installed by May 1, 2001 only), SC1 and
                SC2 (for Sites with  repeaters installed by May 1, 2001 only)
                and Interim Maintenance).

        (D)     For all Zoning and Construction Sites, Owner shall purchase from
                Contractor and Contractor shall provide Satellite Receive and
                Repeater Transmit Antennas and, for High-Power Sites, Contractor
                shall also provide shelters, all in accordance with a schedule
                to be provided by Owner. For those Sites not constructed by
                Contractor, Owner shall designate where such antennas and
                shelters are to be shipped, and shall provide such other
                shipping information reasonably requested by Contractor, within
                5 Business Days of receiving Contractor's request. Owner, as a
                pre-approved Permitted Reimbursable Expense, will pay all
                shipping charges beyond normal 3 to 5 day ground delivery to the
                extent requested by Owner for Sites not constructed by
                Contractor. Contractor shall prepare for Owner's review and
                approval a forecast(s) of antenna and shelter requirements for
                all Sites except Construction Sites on a periodic basis (but no
                less frequently than monthly). Owner shall provide Contractor
                with its comments or approval within 5 Business Days of receipt
                of the forecast; otherwise, Contractor may submit the forecast
                to the relevant manufacturer as submitted by Contractor to
                Owner, which shall be deemed approved by Owner. Contractor will
                incorporate Owner's reasonable comments. Owner shall purchase
                from Contractor all such antennas and shelters ordered by
                Contractor from the relevant manufacturer pursuant to the
                approved forecast(s).


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                                                                    CONFIDENTIAL


        (E)     For all Sites, Contractor shall perform MCM testing ("MCM
                Testing") (with one and/or two satellites, as available) in
                accordance with the revised Baseline Schedules (as described in
                paragraph 25 below) (also referred to in the Contract as the
                Initial City Schedule). The scope of MCM Testing and analysis
                will be agreed to by the Parties within 30 days of the Effective
                Date of this Amendment No. 6. The Parties will work together
                cooperatively to define a scope and schedule that can be
                performed within the price set forth in paragraph 11(A) below.

3.      By way of clarification, the Construction Documents required by Work
        Unit AE2 shall be signed and sealed by a registered professional
        engineer and in sufficient detail to obtain building permits for the
        Sites. Owner shall provide Contractor with its requested corrections and
        modifications on the Construction Documents within 14 Calendar Days of
        receipt of such Construction Documents. Contractor shall make such
        requested corrections and modifications.

4.      By way of clarification, Work Unit SC1 (Substantial Completion) includes
        installation of antennas, but excludes provisioning of telco services
        (other than coordination with Global Digital Datacom Services), and Work
        Unit SC2 (Completion of Construction) includes receiving and installing
        the repeater unit.

5.      Prior to May 15, 2001, in the event additional engineering, analysis, or
        similar work is required beyond the scope agreed to above with respect
        to the Sites as identified on Schedule A, Contractor shall provide such
        additional services on the basis provided in the Contract or, if not so
        provided, on a Task Order Pricing basis.

6.      For each of the Sites identified in Schedule A, "Work Completion" is
        achieved when Contractor completes the Required Work for such Site in
        accordance with the Contract.

7.      In the event that, prior to the date hereof, Contractor has commenced
        work on any Work Unit not listed in paragraphs 2(A), 2(B) or 2(C) above
        for any Site, then Contractor shall complete the Work Units, as agreed
        to by the Parties within 21 Calendar Days of the Effective Date of this
        Amendment No. 6, and Contractor shall be paid for all Work Units
        completed, and for all unpaid work-in-progress on any Work Unit not
        completed with the payment equal to the percentage of the applicable
        Work Unit price that is equal to the percentage of the Work Unit, as
        determined by the Parties, actually completed on the applicable Work
        Unit.

8.      Where the Parties are utilizing the same contractor, subcontractor or
        vendor and conflicts arise over availability of materials or the
        scheduling of contractors, the Parties shall cooperate with each other
        to resolve the conflict to complete the work on time.


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                                                                    CONFIDENTIAL



NETWORK PERFORMANCE

9.      Contractor will remain responsible for the performance of the
        Terrestrial Repeater Network in accordance with Article 8 of the
        Contract, but performance shall be measured against the CW test criteria
        (not MCM test criteria) and, prior to any CW test, the Site(s) being
        tested shall be reconfigured for CW transmission as mutually agreed
        between by the Parties. Contractor shall perform the CW test at Owner's
        request and expense (which pricing is set forth in paragraph 23 below).
        Contractor shall not be responsible for the impact on the performance of
        the Terrestrial Repeater Network of any Sites constructed or work
        performed by vendors contracting directly with Owner, except where Owner
        can demonstrate that the Site or work involved is fully compliant with
        Contractor's design requirements.

WORK UNITS, PRICING AND PAYMENT

10.     GENERAL. As a general principle, Contractor shall be entitled to
        Milestone Payments when Milestones are completed in accordance with the
        applicable Milestone Achievement Criteria.

11.     REVISED WORK UNITS AND PRICING. The following Work Units, Work Unit
        Achievement Criteria and pricing are hereby amended as follows:

        (A)     Work Unit RF5 (City Network Acceptance) is amended to be
                completion of MCM Testing (with one or two satellites, as
                available) for a City. The price for Work Unit RF5 is the same
                as that set forth in Section 3.1 of Exhibit C of the Contract,
                i.e., [     ] for Normal-Area Sites, [    ] for Medium-Area
                Sites and [    ] for Wide-Area Sites. Payment for Work Unit RF5
                shall be earned and paid on a per City basis; that is, for each
                City, Work Unit RF5 shall be earned upon Contractor's completion
                of  MCM Testing  (with one and/or two satellites, as available)
                in such City and shall be payable per the Contract. The price
                for reconfiguring Contractor's vans, equipment and software from
                CW testing capability to MCM testing capability will be
                determined on the basis of Default Pricing.

        (B)     The pricing for Work Units RF4, RF6 and RC7 are based on Owner
                delivering repeaters and completing construction on Sites other
                than Construction Sites in accordance with a schedule to be
                agreed to by the Parties within 7 Calendar Days after the
                Effective Date of this Amendment No. 6. The Parties acknowledge
                and agree that the minimum requirements for repeater deliveries
                are [   ] available in Pilot's regional storage facilities by
                [    ] an additional [  ] so available by [   ] an additional
                [    ] so available by [    ], and an additional [  ] so
                available by [    ]. By way of clarification, Owner's failure
                to meet such schedule shall be subject to Articles 7.4
                (Excusable Delay Defined) and  7.5 (Contract Adjustments) of
                the Contract.

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                                                                    CONFIDENTIAL


(C)     Work Unit AE2 (Construction Documents and Building Permits) is
        subdivided into two Work Units as follows. Work Unit AE2(a) shall be all
        of Work Unit AE2, excluding any work related to building permits and
        shall be called "Construction Documents." The price for Work Unit AE2(a)
        shall be [    ]. Work Unit AE2(b) shall be the filing and pulling of a
        building permit and the price therefor shall be [   ] and shall be
        called "Building Permits." In the event Owner requests corrections and
        modifications in Construction Documents prior to the 14-Calendar Day
        period specified in paragraph 3 above, such corrections and
        modifications shall be made at no charge to Owner; for corrections and
        modifications requested by Owner after such 14-Calendar Day, the price
        of such requested corrections and modifications shall be determined on
        the basis of Default Pricing. The Parties will work together
        cooperatively to minimize the cost to Owner of any required corrective
        action. In addition, the Parties acknowledge and agree that, as of the
        Effective Date of this Amendment No. 6, Contractor has filed and/or
        pulled the building permits for certain Zoning Sites. Contractor shall
        provide to Owner a list of such Sites no later than January 12, 2001.
        For such Sites as identified, Owner agrees to pay Contractor the price
        for Work Unit AE2(b).

(D)     Work Unit AE3 (Final "As Built Drawings"/Construction Documents) shall
        be earned on a per Site basis as follows: (1) for Construction Sites,
        upon delivery of completed, final "As Built" drawings in accordance with
        the Contract and (2) for Zoning Sites, upon completion of Work Unit
        AE2(a) (Construction Documents).

(E)     Work Unit AE4 (Completion of Construction) shall be earned on a per Site
        basis as follows: (1) for Construction Sites, upon resolution of punch
        list items and (2) for Site Acquisition Sites and Zoning Sites, upon
        Work Completion as defined in paragraph 6 above (excluding completion of
        MCM Testing and the Required Work for Supplemental Sites). The amount
        payable for Work Unit AE4 for a Site shall equal 11% of the total amount
        payable by Owner for other AE Work Units earned by Contractor in respect
        of such Site and shall be paid the later of achieving Work Completion
        (excluding completion of MCM Testing and the Required Work for
        Supplemental Sites) for all Sites listed in Schedule A and August 1,
        2001.

(F)     Work Unit ZN3 (City Network Acceptance) shall be earned on a per Site
        basis upon Contractor achieving Work Completion as defined in paragraph
        6 above (excluding completion of MCM Testing and the Required Work for
        Supplemental Sites) and shall be paid the later of achieving Work
        Completion (excluding completion of MCM Testing and the Required Work
        for Supplemental Sites) for all Sites listed in Schedule A and August 1,
        2001.

(G)     In the event Owner fails to make repeaters available at Pilot's storage
        facilities in the quantities described in paragraph 11(B) above, and
        Work

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                                                                    CONFIDENTIAL


        Completion is delayed for any Site beyond, [       ] then Owner shall
        pay Contractor for SC2 on all remaining Sites on or before [        ].
        The price for Work Unit SC2 (excluding Sites billed on a Cost-Plus
        basis) is increased by [     ] per Site to account for subcontractor
        return visits to all such Sites requiring return visits. The Parties
        acknowledge that any pricing quoted to date on a Cost-Plus Pricing basis
        may be increased to account for additional contractor charges resulting
        from required subcontractor return visits.

12.     PROJECT MANAGEMENT: PRICE AND PAYMENT. The Project Management Fixed
        Price Amount for Project Management Services until the later of
        achieving Work Completion (excluding completion of MCM Testing and the
        Required Work for Supplemental Sites) for all Sites and [       ] is
        amended to be [       ] and shall be earned and payable as follows:

        (A)     Work Unit M1 is amended to equal a total aggregate for all Sites
                of [       ] of the Project Management Fixed Price Amount. Work
                Unit M1 shall be earned for Project Management Services and
                shall be paid at the rate of [         ] per month (up to a cap
                of ); [       ] provided,  however, to the extent Owner has paid
                in excess of [       ] as of the Effective Date of this
                Amendment No. 6, the excess will be credited to other amounts
                payable by Owner.

        (B)     The balance of the Project Management Fixed Price Amount (i.e.,
                [       ]) shall be paid in three equal installments of [      ]
                each by August 1, 2001, September 1, 2001 and September
                25, 2001, respectively. Interest shall accrue at a rate of
                [  ] per year on the [       ] balance as follows: (i) with
                respect to Project Management Services invoiced after the
                Effective Date of this Amendment No. 6, interest shall accrue
                from the date that is 30 Calendar Days after receipt of the
                invoice; and (ii) with respect to Project Management Services
                invoiced and paid prior to the Effective Date of this Amendment
                No. 6, interest shall accrue from the date such previously paid
                amounts are credited against the payment due from Owner on
                invoices received from Contractor.

        (C)     Work Unit M2 is hereby deleted.

        (D)     Project Management Services, if requested by Owner, after the
                time period set forth above shall be provided by Contractor on
                pricing and terms to be mutually agreed by the Parties.

13.     A&E PRICE FOR HIGH-POWER SITES. The total fixed price amount for A&E
        Services for those Non-Standard Sites that are High-Power Sites shall be
        as follows: for those High-Power Sites for which Contractor has
        commenced A&E Services as of the Effective Date of this Amendment No. 6,
        the price shall be [     ] and for all other High-Power Sites, the price
        shall be [     ]. Schedule A identifies all High-Power Sites and those
        High-Power Sites for which Contractor has commenced A&E


Amendment 6                             6
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                                                                    CONFIDENTIAL


        Services as of the Effective Date of this Amendment No. 6. Contractor
        shall provide Owner with a list of the High-Power Sites and the
        High-Power Sites for which A&E work has been commenced within 3 Business
        Days after the Effective Date of this Amendment No. 6. This amount shall
        be earned and paid on a per Site/per Work Unit basis and the amount
        associated with each AE Work Unit for High-Power Sites shall be the
        following:

                                   [TABLE]

        * Percentages for AE2(a) & AE2(b) shall add up to 30%.


INCENTIVES FOR TIMELY DELIVERY AND TERMINATION

14.     Paragraphs (c) and (d) of Article 7.2 (Delivery Incentives and
        Liquidated Damages) of the Contract are hereby deleted and replaced by
        the following:

               "(c) For each category set forth in Table 14.1, in the event
               Contractor fails to complete the Work Units required therein (the
               "Liquidated Damages Work") in accordance with the Contract for
               the required number of Construction Sites or [  ] or more of the
               required number of Zoning Sites, respectively, within such
               category on or before the respective dates, each as set forth in
               Table 14.1 below, Contractor shall pay Owner, as liquidated
               damages and not as a penalty, the following respective
               percentages of [         ]


Amendment 6                             7

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                                                                    CONFIDENTIAL




                                  TABLE 14.1

                                   [TABLE]

* For the avoidance of doubt, for purposes of this Table 14.1, no Site that is a
Construction Site shall be counted as a Zoning Site.

               For example, if Contractor fails to achieve the Liquidated
               Damages Work for the [  ] Construction Sites required on or
               before February 15, 2001, Contractor shall pay Owner [
                                        ].

               "(d) The total amount of liquidated damages for failure to
               achieve the Liquidated Damages Work required in Table 14.1 on or
               before the respective dates set forth therein is [         ].

               "(e) For those Sites for which Contractor fails to achieve the
               Liquidated Damages Work by the respective dates set forth in
               Table 14.1 (excluding Supplemental Sites), Contractor shall have
               a continuing obligation to achieve the Liquidated Damages Work
               for such Sites as expeditiously as possible.

               "(f) Where Contractor fails to complete the Liquidated Damages
               Work for Zoning Sites by the dates required in Table 14.1,
               Contractor will not be assessed liquidated damages for that
               period of time where Owner would have been unable to commence
               construction on the shortfall Sites due to the unavailability of
               Owner's construction contractor to begin work on those Sites.
               This relief from liquidated damages will in no event extend
               beyond [        ]."

15.     By way of clarification, Articles 7.4 (Excusable Delay) and 7.5
        (Contract Adjustments) of the Contract apply to the schedule set forth
        in Table 14.1 above; provided, however, in the case of Owner's
        responsibility to review leases provided by Contractor, (1) Owner shall
        accept or reject the lease and respond to Contractor

Amendment 6                             8

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                                                                    CONFIDENTIAL

        within 5 Business Days of being provided a lease for review, (2) in the
        event Owner fails to respond to Contractor regarding a lease for a
        Zoning Site within such 5 Business Days, Contractor shall be entitled to
        an Excusable Delay for a single Zoning Site (without regard to whether
        Owner's failure adversely impacted Contractor's ability to perform the
        Work or whether the delay could have been avoided by Contractor) and (3)
        the Contract adjustment for such Excusable Delay shall be as follows:
        for each Business Day Owner is late in responding to Contractor, an
        extension of one Business Day in the schedule for a single Zoning Site
        in the [       ] category of Zoning Sitess in Table 14.1 (except in the
        case of a materially large number of Sites for which Owner is late in
        responding on submitted leases in which case the Parties will negotiate
        an equitable adjustment to the schedule in Table 14.1 for the affected
        Sites). For example, if Owner is late by 3 Business Days in responding
        to Contractor regarding a lease, then Contractor shall be permitted an
        extension of 3 Business days in achieving the Liquidated Damages Work
        for a Site in the [       ] category of Zoning Sites in Table 14.1; all
        other Sites shall remain subject to the applicable dates in Table 14.1
        for achieving the applicable Liquidated Damages Work; that is, [  ]
        Zoning Sites shall be subject to the [            ] date in Table 14.1
        and the one remaining Site shall be subject to a revised date of [
               ] ([            ] plus 3 Business Days).

16.     With respect to each category set forth in Table 14.1, in the event
        Contractor fails to achieve for the required number of Construction
        Sites or 95% of the required number of Zoning Sites for that respective
        category the applicable Liquidated Damages Work on or before 30 Calendar
        Days after the respective date set forth therein, Owner shall have the
        right to remove, at no cost to Owner, from Contractor's scope of work
        and from the applicable category (i.e., Construction or Zoning) that
        number of Sites equal to the difference between (a) the number of Sites
        for which the Liquidated Damages Work should have been completed in
        order to achieve the required number of Sites (i.e., 100% for
        Construction Sites or 95% for Zoning Sites) set forth in Table 14.1
        above, and (b) the number of Sites for which Liquidated Damages Work was
        completed. The particular individual Sites to be removed shall be
        determined by mutual agreement of the Parties. For such removed Sites,
        Contractor shall be entitled to payment of all unpaid amounts invoiced
        hereunder for Work Units completed in accordance with this Contract and
        all unpaid amounts for Work-in-progress on any Work Unit not completed
        as of the effective date of such removal, with the payment equal to the
        percentage of the applicable Work Unit price that is equal to the
        percentage of Work Unit actually completed, as determined by the
        Parties, on the applicable Work Unit.

17.     Reserved.

VENDOR INTERFACES

18.     As part of Program Management Services, Contractor shall work
        cooperatively, to a reasonable level of support (which shall not exceed
        1 Man-Month), to provide Owner with interfaces between Contractor's work
        and the work of Owner's other

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                                                                    CONFIDENTIAL

        construction vendors at no additional charge through the later of
        achieving Work Completion (excluding completion of MCM Testing and the
        Required Work for Supplemental Sites) for all Sites and May 15, 2001.

SUSTAINING ENGINEERING

19.     Owner hereby agrees to purchase, and Contractor hereby agrees to
        provide, during the period from May 15, 2001 through December 31, 2001,
        engineering, technical advisory support, operations and maintenance and
        other technical services in accordance with a scope of work, performance
        schedule and pricing schedule to be mutually agreed by Owner and
        Contractor, which services shall average approximately [      ] per
        month and have an aggregate value of not less than [        ], to be
        invoiced monthly commencing June 2001.

20.     Reserved.

CONTRACT ADMINISTRATION

21.     INVOICE DOCUMENTATION. From and after the date hereof, all Contractor
        invoices shall identify the Milestones and Work Units completed, and the
        prices applicable thereto, and shall be accompanied by a spreadsheet
        showing, in addition to other information, the transmittal letter number
        for each Work Unit performed after September 1, 2000 and covered in the
        invoice. Within 10 Calendar Days of the receipt of an invoice for Work
        Units performed prior to September 1, 2000 and invoiced after the
        Effective Date of this Amendment No. 6, Owner will notify Contractor of
        any required deliverables for such Work Units not submitted to Owner.
        Within 10 Calendar Days of receipt of such notice, Contractor will
        provide to Owner the missing required deliverables identified in such
        notice or proof of delivery. With regard to Work Units performed after
        September 1, 2000, an invoice shall be deemed complete if accompanied by
        a copy of (a) the signed and dated transmittal letters forwarding the
        required deliverables to Owner and (b) Owner's e-mail confirmation that
        the required deliverables have been received (which confirmation Owner
        shall promptly provide to Contractor upon receipt of deliverables). With
        regard to Work Unit SC1, Contractor shall certify completion of the Work
        Unit invoiced and Owner shall process the invoice but will not pay same
        until the required report has been delivered to Owner.

SCHEDULE A

22.     All Sites are listed on draft Schedule A, which shall be finalized by
        the Parties no later than January 10, 2001, in the form and including
        all the categories set forth in draft Schedule A. Schedule A may be
        amended (including any additions, cancellations or reclassifications of
        Sites) by the Parties only by mutual agreement pursuant to e-mail
        correspondence; provided, however, that only a Vice President of
        Contractor shall be deemed an authorized representative of Contractor
        for such purposes and only a Vice President of Owner (or as otherwise
        authorized in writing


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<PAGE>   11
                                                                    CONFIDENTIAL

        by a Vice President of Owner) shall be deemed an authorized
        representative of Owner. The Parties acknowledge that any amendments to
        Schedule A shall result in an equitable adjustment to the revised
        Baseline Schedule (also referred to in the Contract as the Initial City
        Schedule), the required number of Sites set forth in Table 14.1, and
        Contract Sum. For example, the cancellation of one (1) Construction Site
        (other than a Supplemental Site) shall reduce the required number of
        Construction Sites set forth in Table 14.1 by one (1) Site.

OPTION FOR CW TESTING

23.     At any time commencing upon the Effective Date of this Amendment No. 6
        up to and including September 30, 2001, Owner may, at its option, elect
        by written notice to Contractor to purchase from Contractor those CW
        testing services described in the Contract. The price for such services
        shall be the price for Work Unit RF5 set forth in the Contract, i.e.,
        [      ] for Normal-Area Sites, [      ] for Medium-Area Sites and
        [      ] for Wide-Area Sites provided the CW testing is conducted on a
        City-wide basis and Owner requests Contractor, within 14 Calendar Days
        of completion of MCM Testing in such City, to provide CW testing for a
        City. Otherwise, the price for CW testing shall be determined on the
        basis of Default Pricing. In addition, the price for reconfiguring vans,
        equipment and software and performing antenna repointing as necessary to
        conduct CW testing shall be determined on the basis of Default Pricing.

REVISED SCHEDULES

24.     Draft revised Baseline Schedules are set forth in Schedule B. The
        Parties agree to finalize the revised Baseline Schedules no later than
        January 12, 2001. The final revised Baseline Schedules may be amended by
        the Parties only by mutual agreement pursuant to e-mail correspondence;
        provided, however, that only a Vice President of Contractor shall be
        deemed an authorized representative of Contractor for such purposes and
        only a Vice President of Owner (or as otherwise authorized in writing by
        a Vice President of Owner) shall be deemed an authorized representative
        of Owner. Each Party waives any claim to adjustment in price or schedule
        or claim for default arising from the other Party's failure to timely
        perform its obligations under the Contract, where such failure occurred
        prior to the Effective Date of this Amendment No. 6.

IMPLEMENTING CONTRACT CHANGES

25.     Article 7.1(b) of the Contract is hereby deleted and replaced with the
        following: "Contractor shall achieve Work Completion (excluding
        completion of MCM Testing and the Required Work for Supplemental Sites)
        on or before [          ] and Contractor shall perform the Work so as to
        achieve each Key Task set forth in the revised Baseline Schedule (also
        referred to in the Contract as the Initial City Schedule) in accordance
        with the schedule set forth therein."


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                                                                    CONFIDENTIAL

26.     Article 9.2(a) of the Contract is hereby deleted and replaced with the
        following: "Subject to paragraph (b) below, risk of loss to each item of
        the Work shall pass to Owner (i) for items to be incorporated in a Site
        constructed by Contractor, upon achieving Work Completion (excluding
        completion of MCM Testing) of that Site and (ii) for all other items,
        upon delivery of such item to Owner in accordance with this Contract."

27.     Article 10.1(a) of the Contract is hereby amended so that the warranty
        provided therein shall expire [          ].

28.     Article 25.2(a) of the Contract is hereby amended as follows: in the
        second sentence of such article, delete the phrase "demonstrating that
        it can achieve Acceptance of the affected City Network by the Acceptance
        Date" and replace it with the phrase "demonstrating that it can achieve
        Work Completion (excluding completion of MCM Testing and the Required
        Work for Supplemental Sites) by [          ]".

29.     Article 25.2(b) of the Contract is hereby amended as follows: delete
        "demonstrating it can achieve Acceptance of the affected City Network in
        accordance with the Acceptance Date (as may be extended pursuant to this
        Contract)" and replace it with the phrase "demonstrating that it can
        achieve Work Completion (excluding completion of MCM Testing and the
        Required Work for Supplemental Sites) by [          ]".

30.     Article 26.2 (Termination for Contractor's Default) is hereby amended as
        follows: in paragraph (1)(a), delete " (1) failure to achieve Acceptance
        for all Cities on or before the Acceptance Date, as such date may be
        adjusted in accordance with the Contract; or" and replace it with the
        following: " (1) failure to achieve Work Completion (excluding
        completion of MCM Testing and the Required Work for Supplemental Sites)
        on or before [          ]; or".

OTHER TERMS AND CONDITIONS

31.     All other terms and conditions of the Contract shall remain in full
        force and effect without modification or amendment thereto, except as
        expressly provided in this Amendment No. 6. In addition, in the event of
        any conflict between the provisions of this Amendment No. 6 and the
        Contract in effect prior to the Effective Date of this Amendment No. 6,
        the provisions of this Amendment No. 6 shall take precedence.

IN WITNESS WHEREOF this Amendment No. 6 to the Terrestrial Repeater Network
System Contract has been executed on behalf of Owner by persons authorized to
act on Owner's behalf and has also been executed on behalf of Contractor by
persons authorized to act on Contractor's behalf.

Amendment 6                             12

<PAGE>   13
                                                                    CONFIDENTIAL


LCC INTERNATIONAL, INC.                 XM SATELLITE RADIO INC.

By:_______________________              By:_______________________

PAUL O. CHELSON                         Name:  ___________________

Vice President, Deployment Services     Title: ____________________


Date:______________________             Date:_____________________


Amendment 6                             13


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                                   Schedule A
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                                   Schedule B
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