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                                                                     Exhibit 4.4

                                                                  EXECUTION COPY

         AMENDMENT NO. 2, dated as of January 15, 2001 ("Amendment No 2"), among
Acterna Corporation, a Delaware corporation (the "Company"), Clayton, Dubilier &
Rice Fund V Limited Partnership, a Cayman Islands limited partnership ("Fund V")
and Clayton, Dubilier & Rice Fund VI Limited Partnership, a Cayman Islands
limited partnership ("Fund VI"), to the Registration Rights Agreement, dated as
of May 21, 1998 (the "Registration Rights Agreement"), among the Company, Fund V
and the other parties thereto, and as previously amended by Amendment No. 1,
dated as of May 23, 2000, among the Company, Fund V and Fund VI. Capitalized
terms used herein without definition have the meanings given to them in the
Registration Rights Agreement.

         WHEREAS, in order to obtain additional liquidity for general corporate
purposes, Acterna LLC, a Delaware limited liability company wholly-owned and
controlled by the Company ("Acterna LLC"), and the Company entered into an
Investment Agreement, dated as of December 27, 2001 (the "Investment
Agreement"), with Fund VI, under which Acterna LLC issued and sold to Fund VI
$75,000,000 aggregate principal amount of its 12% Senior Secured Convertible
Notes Due 2007 (the "Notes");

         WHEREAS, the Investment Agreement and the Notes provide for the
issuance by the Company of warrants (the "Warrants") to purchase Common Stock to
the holders of any Notes repurchased or redeemed by Acterna LLC prior to their
stated maturity; and

         WHEREAS, the Company, Fund V and Fund VI desire to amend the
Registration Rights Agreement to provide registration rights to Fund VI in
respect of the shares of Common Stock issuable upon conversion of the Notes or
upon exercise of the Warrants.

         NOW, THEREFORE, in consideration of the premises and the mutual
promises and agreements herein made, the receipt and sufficiency of which is
hereby acknowledged, the parties hereto agree as follows:

         1. Amendment to Section 2. The definition of "Registrable Securities"
in Section 2 of the Registration Rights Agreement is hereby amended to read in
its entirety as follows:

                  "Registrable Securities": (a) The Common Stock (i) received by
                  Fund V, the Manager and the Trusts as a result of the Merger,
                  (ii) issued to each of Fund V and Fund VI pursuant to the Fund
                  Stock Subscription Agreements, (iii) issued to Fund VI (or any
                  permitted transferee) upon conversion of any of the Company's
                  12% Senior Secured Convertible Notes Due 2007 (the "Notes")
                  issued pursuant to that certain Investment Agreement, dated as
                  of December 27, 2001 (the "Investment Agreement"), between the
                  Company, Acterna LLC and Fund VI, (iv) issued to Fund VI (or
                  any permitted transferee) upon exercise of any warrants to
                  purchase Common Stock received by Fund VI (or its transferee)
                  pursuant to the Investment Agreement or the Notes or (v)
                  issued to Individual Investors pursuant to a stock
                  subscription agreement or other agreement that provides that
                  such


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                  Common Stock shall be Registrable Securities, (b) any shares
                  of Common Stock issued pursuant to the terms of, and under the
                  circumstances set forth in, Section 4, and (c) any securities
                  issued or issuable with respect to any Common Stock referred
                  to in the foregoing clauses (w) upon any conversion or
                  exchange thereof, (x) by way of stock dividend or stock split,
                  (y) in connection with a combination of shares,
                  recapitalization, merger, consolidation or other
                  reorganization or (z) otherwise, in all cases subject to the
                  last paragraph of Section 3.3. As to any particular
                  Registrable Securities, once issued such securities shall
                  cease to be Registrable Securities when (A) a registration
                  statement (other than a Special Registration pursuant to which
                  such securities were issued by the Company) with respect to
                  the sale of such securities shall have become effective under
                  the Securities Act and such securities shall have been
                  disposed of in accordance with such registration statement,
                  (B) such securities shall have been distributed to the public
                  in reliance upon Rule 144, (C) such securities shall have been
                  otherwise transferred, new certificates for such securities
                  not bearing a legend restricting further transfer shall have
                  been delivered by the Company and subsequent disposition of
                  such securities shall not require registration or
                  qualification of such securities under the Securities Act or
                  any similar state law then in force, or (D) such securities
                  shall have ceased to be outstanding.

         2. Amendment to Section 4.4. The address of the Company set forth in
Section 4.4 of the Registration Rights Agreement is hereby amended as follows:

                   Acterna Corporation
                   20410 Observation Drive
                   Germantown, Maryland  20876
                   Attention:  General Counsel

         3. Confirmation of Registration Rights Agreement. Other than as
expressly modified pursuant to this Amendment, all provisions of the
Registration Rights Agreement remain unmodified and in full force and effect.

         4. Miscellaneous. This Amendment shall be governed by and construed in
accordance with the internal laws of the State of New York without giving effect
to any choice or conflict of law provision or rule to the extent such provision
or rule would require or permit the application of the laws of any jurisdiction
other than the State of New York. This Amendment may be executed in one or more
counterparts, each of which shall be deemed an original and all of which shall
together constitute one and the same instrument and shall bind and inure to the
benefit of the parties and their respective successors and assigns.

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                  IN WITNESS WHEREOF, each of the undersigned has executed this
Amendment as of the date first written above.

                              ACTERNA CORPORATION


                              By:______________________________
                                  Name:
                                  Title:


                              CLAYTON, DUBILIER & RICE
                                 FUND V LIMITED PARTNERSHIP

                              By:     CD&R Associates V Limited Partnership,
                                        the general partner

                              By:     CD&R Investment Associates II, Inc.,
                                        its managing general partner



                              By:______________________________
                                  Name:
                                  Title:


                              CLAYTON, DUBILIER & RICE
                                 FUND VI LIMITED PARTNERSHIP

                              By:     CD&R Associates VI Limited Partnership,
                                        the general partner

                              By:     CD&R Investment Associates VI, Inc.,
                                        its managing general partner



                              By:______________________________
                                 Name:
                                 Title:

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