<PAGE>

                                                                    Exhibit 10.2

                             WESTOWER HOLDINGS LTD.
                          WESTOWER COMMUNICATIONS LTD.

                                CREDIT AGREEMENT

                                 Amendment No. 2

      This Agreement, dated as of December 17, 1998 (this "Agreement"), is among
Westower Corporation, a Washington corporation, its subsidiaries set forth on
the signature pages hereof, including Westower Holdings Ltd., a Wyoming
corporation (the "U.S. Borrower"), and Westower Communications Ltd., a British
Columbia, Canada corporation (the "Canadian Borrower") (together with the U.S.
Borrower, the "Borrowers") and BankBoston, N.A., as Agent for itself and the
other Lenders under the Credit Agreement (as defined below). The parties agree
as follows:

      7. Credit Agreement; Definitions. This Agreement amends the Credit
Agreement dated as of June 9, 1998 among the parties hereto and the Lenders (as
in effect prior to giving effect to this Agreement, the "Credit Agreement").
Terms defined in the Credit Agreement as amended hereby (the "Amended Credit
Agreement") and not otherwise defined herein are used with the meaning so
defined.

      8. Amendment of Credit Agreement. Effective upon the date hereof, Section
6.4 of the Credit Agreement is amended so that the paragraph immediately prior
to Section 6.4.1 reads in its entirety as follows:

            "6.4. Financial Statements and Reports. Each of the Company and its
      Subsidiaries shall maintain a system of accounting in which correct
      entries shall be made of all transactions in relation to their business
      and affairs in accordance with generally accepted accounting practice. The
      fiscal year of the Company and its Subsidiaries shall end on September 30
      in each year and the fiscal quarters of the Company and its Subsidiaries
      shall end on March 31, June 30, September 30 and December 31 in each
      year."

      9. Consent. Pursuant to Section 6.9.5(d) of the Credit Agreement, the
Lenders consent to the acquisition by the Company of Koch Industries, Inc.
pursuant to the Asset Purchase Agreement, to be dated on or about December 24,
1998 (the "Proposed Acquisition").

      10. Waiver. The Lenders waive the requirement that the Company deliver
certain computations, as provided in Section 6.9.5(a) of the Credit Agreement,
10 Banking Days prior to the Proposed Acquisition; provided that the Company
shall have delivered such report and computations to the Lenders prior to the
effectiveness of this Agreement.
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      11. Representation and Warranty. In order to induce the Agent to enter
into this Agreement, each of the Borrowers and the Guarantors jointly and
severally represents and warrants that, after giving effect to this Agreement,
no Default exists.

      12. General. The Amended Credit Agreement and all of the Credit Documents
are each confirmed as being in full force and effect. This Agreement, the
Amended Credit Agreement and the other Credit Documents referred to herein or
therein constitute the entire understanding of the parties with respect to the
subject matter hereof and thereof and supersede all prior and current
understandings and agreements, whether written or oral. Each of this Agreement
and the Amended Credit Agreement is a Credit Document and may be executed in any
number of counterparts, which together shall constitute one instrument, and
shall bind and inure to the benefit of the parties and their respective
successors and assigns, including as such successors and assigns all holders of
any Credit Obligation. This Agreement shall be governed by and construed in
accordance with the laws (other than the conflict of law rules) of The
Commonwealth of Massachusetts.

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      Each of the undersigned has caused this Agreement to be executed and
delivered by its duly authorized officer as an agreement under seal as of the
date first written above.

                                    WESTOWER CORPORATION


                                    By /s/ Peter Lucas
                                       -----------------------------------
                                       Title: Chief Financial officer

                                    WESTOWER HOLDINGS LTD.
                                    WESTOWER COMMUNICATIONS LTD.
                                    MJA COMMUNICATIONS CORP.
                                    NATIONAL TOWER SERVICE LTD.
                                    RALPH'S RADIO INC.
                                    WESTERN TELECOM CONSTRUCTION LTD
                                    WESTOWER COMMUNICATIONS INC.
                                    WESTOWER LEASING CANADA INC.
                                    WTC HOLDINGS INC.
                                    WTC LEASING LTD. PARTNERSHIP
                                         By 582570 ALBERTA LTD., its general
                                    partner 3479021 CANADA INC.



                                    By  /s/ Peter Lucas
                                        -----------------------------------
                                        As an authorized officer of each of the
                                        foregoing corporations


                                    BANKBOSTON, N.A.,
                                       as Agent under the Credit Agreement


                                    By  /s/ Lenny Mason
                                        -----------------------------------
                                        Title: Vice President
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                                    The foregoing amendment is approved by the
                                    Lenders signing below:

                                    PARIBAS


                                    By /s/ Salo Aizendero
                                       -----------------------------------
                                       Title: Vice President

                                    By /s/ William B Schink
                                       -----------------------------------
                                       Title: Director


                                    PARIBAS BANK OF CANADA

                                    By /s/ James Goodall
                                       -----------------------------------
                                       Title: Managing Director

                                    By /s/ William R. Jeffrey
                                       -----------------------------------
                                       Title: Director


                                    FLEET NATIONAL BANK

                                    By Tanya M. Crossley
                                       -----------------------------------
                                       Title: Vice President


                                    U.S. BANK NATIONAL ASSOCIATION

                                    By Thomas G. Gunder
                                       -----------------------------------
                                       Title: Vice President


                                    UNION BANK OF CALIFORNIA, N.A.

                                    By Michael K. McShane
                                       -----------------------------------
                                    Title: Senior Vice President