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                                                                     Exhibit 4.7

                               FIFTH AMENDMENT TO
                     COMMON STOCK PURCHASE WARRANT AGREEMENT
                              AND JOINDER AGREEMENT

          This Fifth Amendment to Common Stock Purchase Warrant Agreement and
Joinder Agreement, dated as of October 18, 2002, is between MURDOCK
COMMUNICATIONS CORPORATION, an Iowa corporation (the "Company") and
COMPUTERSHARE TRUST COMPANY, INC., as Warrant Agent (the "Warrant Agent").

                                    RECITALS

          A. The Company has entered into a Common Stock Purchase Warrant
Agreement dated as of October 21, 1996, as amended (the "Agreement"), with U.S.
Bank National Association, formerly known as Firstar Trust Company, as warrant
agent (the "Former Warrant Agent"), with respect to 920,000 Common Stock
Purchase Warrants (the "Warrants") issued by the Company on October 21, 1996.

          B. Pursuant to Section 10(f) of the Agreement, the Former Warrant
Agent resigned as warrant agent effective July 9, 2002. Pursuant to Section
10(f) of the Agreement, the Company desires to appoint the Warrant Agent as the
new warrant agent to act on behalf of the Company, and the Warrant Agent is
willing to so act, in connection with the issuance, registration, transfer and
exchange of certificates representing the Warrants and the exercise of the
Warrants.

          C. The Company and the Warrant Agent deem it desirable to amend the
Agreement to extend the "Warrant Expiration Date" from October 21, 2002 to
October 21, 2003.

          D. Pursuant to Section 10 of the Agreement, the Company and the
Warrant Agent may by supplemental agreement make any changes or corrections in
the Agreement that they may deem necessary or desirable and which do not
adversely affect the interests of the holders of Warrant Certificates

                                   AGREEMENTS

          In consideration of the foregoing and the mutual covenants and
agreements contained herein and in the Agreement, and intending to be

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legally bound hereby, the Warrant Agent and the Company hereby agree as follows:

          1. Joinder of the Warrant Agent. The Warrant Agent hereby accepts its
appointment to act as agent for the Company as provided in the Agreement. The
Warrant Agent agrees to the terms and conditions of the Agreement and
acknowledges that, by the execution hereof by the Warrant Agent and the Company,
the Warrant Agent shall be bound by the Agreement as the "Warrant Agent"
thereunder.

          2. Amendment of Section 1(i). The definition of "Warrant Expiration
Date" in Section 1(i) of the Agreement is hereby amended to read in its entirety
as follows:

               "Warrant Expiration Date" shall mean 5 p.m. (Central Time) on
               October 21, 2003, or if such date shall in the State of Wisconsin
               be a holiday or a day on which banks are authorized to close,
               then 5 p.m. (Central Time) on the next following day which in the
               State of Wisconsin is not a holiday or a day on which banks are
               authorized to close. Unless exercised during the Warrant Exercise
               Period, the Warrants will automatically expire. The Warrants may
               be called for redemption and the expiration date herefor
               accelerated, on the terms and conditions set forth in sections
               4(b) and 4(c) of this Agreement. If so called for redemption,
               Warrant Certificate holders shall have a period of at least 30
               days after the date of the call notice within which to exercise
               the Warrants. However, Warrant Certificate holders will receive
               the redemption price only if such certificates are surrendered to
               the Corporate Office within the redemption period (as defined
               below).

          3. Full Force and Effect. All remaining provisions of the Agreement
remain unchanged and in full force and effect.

          4. Governing Law. This Amendment shall be governed by and construed in
accordance with the laws of the State of Wisconsin. Section headings in this
Amendment appear for convenience of reference only and shall not be used in any
interpretation of this Amendment.

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          5. Binding Effect. This Amendment shall be binding upon and inure to
the benefit of the Company, the Warrant Agent and their respective successors
and assigns, and the Registered Holders from time to time of Warrant
Certificates or any of them. Nothing in this Amendment shall be construed to
confer any right, remedy or claim upon any other person.

          6. Counterparts. This Amendment may be executed in counterparts, which
taken together shall constitute a single document.

     IN WITNESS WHEREOF, the Warrant Agent and the Company have caused this
Amendment to be executed as of the date first written above by their respective
officers thereunto duly authorized.

                                            MURDOCK COMMUNICATIONS CORPORATION


                                            BY  /s/ Eugene I. Davis
                                               ---------------------------------
                                                    Eugene I. Davis
                                                    Chief Executive Officer


                                            COMPUTERSHARE TRUST COMPANY, INC.


                                            BY  /s/
                                               ---------------------------------
                                                    Authorized Officer

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