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                                  EXHIBIT 5.1
 
                  [LETTERHEAD HELLER EHRMAN WHITE & MCAULIFFE]
 
                                                                   July 10, 1996
 
REMEC, Inc.
9404 Chesapeake Drive
San Diego, California 92123
 
                       Registration Statement of Form S-4
 
Ladies and Gentlemen:
 
   
     We have acted as counsel to REMEC, Inc., a California corporation (the
"Company"), in connection with the Registration Statement on Form S-4
(Registration No. 333-05343) filed with the Securities and Exchange Commission
on June 6, 1996 (the "Registration Statement") for the purpose of registering
under the Securities Act of 1933, as amended , 1,081,486 shares of the Company's
Common Stock, par value $.01 per share (the "Shares"), to be issued in
connection with the proposed merger (the "Merger") of REMEC Acquisition
Corporation, a California corporation and wholly-owned subsidiary of the
Company, with and into Magnum Microwave Corporation ("Magnum") pursuant to an
Agreement and Plan of Reorganization and Merger dated May 16, 1996 (the
"Agreement") and related Merger Agreement among Magnum, the Company and REMEC
Acquisition Corporation.
    
 
     In connection with this opinion, we have assumed the authenticity of all
records, documents and instruments submitted to us as originals, the genuineness
of all signatures, the legal capacity of natural persons and the conformity to
the originals of all the records, documents and instruments submitted to us as
copies. We have based our opinion upon our review of the following records,
documents, instruments and certificates:
 
          (a) The Restated Articles of Incorporation of the Company certified by
     the Secretary of State of the State of California as of July 8, 1996, and
     certified to us by an officer of the Company as being complete and in full
     force and effect as of the date of this opinion;
 
          (b) The Bylaws of the Company certified to us by an officer of the
     Company as being complete and in full force and effect as of the date of
     this opinion;
 
          (c) A Certificate of the Secretary of the Company: (i) certifying that
     copies of all records of proceedings and actions of the Board of Directors
     of the Company, including any committee thereof, relating to the Merger
     have been provided to us; and (ii) certifying as to certain factual
     matters;
 
          (d) The Registration Statement;
 
          (e) The Agreement;
 
          (f) Merger Agreement included as exhibit 2.1 to the Registration
     Statement; and
 
          (g) A Certificate of Wells Fargo Bank, Transfer Agent to the Company,
     to the effect that, as of July 9, 1996, there were 7,813,523 shares of
     Common Stock issued and outstanding.
 
     This opinion is limited to the laws of the State of California, and we
disclaim any opinion as to the laws of any other jurisdiction. We further
disclaim any opinion as to any other statute, rule, regulation, ordinance, order
or other promulgation of any other jurisdiction or any regional or local
governmental body or as to any related judicial or administrative opinion.
 
     Based upon the foregoing and our examination of such questions of law as we
have deemed necessary or appropriate for the purpose of this opinion, and
assuming that: (i) the Registration Statement becomes and remains effective
during the period when the Shares are offered and sold; (ii) the currently
unissued Shares to be sold by the Company are issued, delivered and paid for in
accordance with the terms of the Registration Statement, the Agreement and the
Merger Agreement; (iii) the Merger Agreement is executed in the form
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contained in exhibit 2.1 to the Registration Statement; (iv) the shareholders of
Magnum approve the Merger; and (v) all applicable securities laws are complied
with, it is our opinion that the Shares, when issued by the Company, will be
legally issued, fully paid and nonassessable.
 
     This opinion is rendered to you in connection with the Registration
Statement and is solely for your benefit. This opinion may not be relied upon by
you for any other purpose, or relied upon by any other person, firm, corporation
or other entity for any purpose, without our prior written consent. We disclaim
any obligation to advise you of any developments that come to our attention
after the date of this opinion.
 
     We hereby consent to the filing of this opinion as an exhibit to, and our
being named under the heading "Legal Matters" in, the Registration Statement.
 
                                          Very truly yours,
 
                                          /s/ HELLER EHRMAN WHITE & MCAULIFFE