EXHIBIT 10.21

                                PLEDGE AGREEMENT


     PLEDGE  AGREEMENT,  dated as of July 29,  1997,  by and between MBF Capital
Corp. (the "Borrower") and LogiMetrics, Inc. (the "Company").

                              W I T N E S S E T H:

     WHEREAS, the Borrower has purchased from the Company Series G Warrants (the
"Warrants")  exercisable  into 500,000  shares (the  "Shares") of the  Company's
Common Stock, par value $.01 per share ("Common Stock"); and

     WHEREAS,  in  connection  with such  purchase the Company has loaned to the
Borrower the sum of $35,000; such loan being evidenced by a non-recourse secured
promissory  note (the  "Note") in the  principal  amount of $35,000  made by the
Borrower in favor of the Company; and

     WHEREAS,  the loan to the  Borrower  is to be  secured  by a pledge  by the
Borrower  to the  Company  of the  Warrants  and the Shares  (collectively,  the
"Securities") and the other Collateral referenced herein; and

     WHEREAS,  the  parties  hereto  desire  to set  forth  the  terms of and to
evidence  the  Borrower's  grant to the  Company of a security  interest  in the
Collateral.

     NOW, THEREFORE,  in consideration of the mutual covenants herein contained,
and for other good and valuable  consideration,  the receipt and  sufficiency of
which is hereby  acknowledged,  the Borrower  hereby  agrees with the Company as
follows:

     Section 1.  Definitions.  The following terms, when used in this Agreement,
shall have the following  meanings (such definitions to be equally applicable to
the singular and plural forms thereof):

     "Default" means the failure to make any payment of principal of or interest
on, or any other amounts due under, the Note when due, whether at maturity, upon
acceleration or otherwise.

     "Distributions" means all stock dividends, liquidating dividends, shares of
stock  resulting  from  the  exercise  of the  Warrants,  or any  stock  splits,
reclassifications, warrants, options, non-cash dividends and other distributions
on or with  respect to the  Securities,  whether  similar or  dissimilar  to the
foregoing, but shall not include Dividends.

     "Dividends" means regular dividends declared with respect to the Shares.

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     "Liabilities" means the Note, and all amounts becoming due thereunder,  and
all other  payment  obligations  of the Borrower  hereunder or thereunder or any
instrument executed pursuant hereto or thereto.

     Section 2. Grant of  Security  Interest.  As  security  for  payment of all
Liabilities,  the Borrower hereby pledges, assigns and transfers to the Company,
and  grants  to the  Company  a  continuing  security  interest  in and to,  the
Securities,  together with all Dividends and  Distributions,  interest and other
payments and rights with respect  thereto,  together  with all proceeds  thereof
(collectively,  the  "Collateral").  The Borrower further  pledges,  assigns and
transfers  to the  Company,  and  grants to the  Company a  continuing  security
interest in and to, and agrees to duly endorse to the order of the Company,  any
additional  Collateral,  together  will all proceeds  thereof,  delivered by the
Borrower to the Company for the  purposes of pledge  under this  Agreement.  Any
Collateral  delivered  by the  Borrower  to the  Company  may be endorsed by the
Company,  in its own  name or in the  name of the  Borrower,  on  behalf  of the
Borrower to the order of the Company.

     Section 3. Stock Powers,  Endorsements,  Etc. The Borrower shall, from time
to time, upon request of the Company,  promptly  execute such  endorsements  and
deliver to the Company such stock powers and similar documents,  satisfactory in
form and substance to the Company, with respect to the Collateral as the Company
may  reasonably  request  and  shall,  from time to time,  upon  request  of the
Company,  promptly transfer any securities which are part of the Collateral into
the  name  of  any  nominee  designated  by the  Company  on  the  books  of the
corporation or other entity issuing such securities; provided, however, that the
Company  shall not be entitled to effect or demand a transfer of the  Collateral
into the name of the Company or the Company's nominee without the consent of the
Borrower unless and until a Default shall have occurred.

     Section 4. Certain  Other  Agreements  Regarding  Collateral.  The Borrower
shall deliver (properly endorsed where necessary) to the Company:

     (a) after a Default  shall have occurred and be  continuing,  promptly upon
receipt thereof by the Borrower and without any request therefor by the Company,
all Dividends and  Distributions,  and other proceeds of the Collateral,  all of
which shall be held by the Company as additional Collateral; and

     (b) at any time after a Default  shall  have  occurred  and be  continuing,
promptly  upon  request of the  Company,  such  consents  or  proxies  and other
documents  as may be necessary to allow the Company to exercise any voting power
or other  right  with  respect to any  securities  included  in the  Collateral;
provided,  however, that unless a Default shall have occurred and be continuing,
the Borrower shall be entitled:

          (i) to exercise, as the Borrower shall deem appropriate, all voting or
     other powers with respect to securities  pledged  hereunder  (including but
     not limited to the Shares);

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          (ii) to exercise any right of  conversion  or exercise with respect to
     securities pledged hereunder; and

          (iii) to receive and retain for the Borrower's own account any and all
     Dividends paid in cash.

     Section 5. Actions Upon Default. Whenever a Default shall have occurred and
be continuing, the Company may exercise from time to time any and all rights and
remedies  available to it under applicable law, including but not limited to all
rights of a secured  party  available to it under the Uniform  Commercial  Code.
Without limiting the above, the Company may from time to time, whether before or
after any of the Liabilities shall become due and payable, but only if a Default
shall have  occurred,  without  notice to the  Borrower,  take any or all of the
following actions:

     (a) transfer all or any part of the Collateral into the name of the Company
or its nominee; and

     (b)  execute  (in the name,  place and  stead of the  Borrower)  any or all
endorsements,  assignments,  stock powers and other instruments of conveyance or
transfer with respect to all or any of the Collateral.

     The Borrower  understands that compliance with the Federal securities laws,
applicable blue sky or other state  securities laws or similar laws analogous in
purpose or effect may strictly limit the course of conduct of the Company if the
Company were to attempt to dispose of all or any part of the  Collateral and may
also limit the extent to which or the manner in which any subsequent  transferee
of the Collateral may dispose of the same. Accordingly, the Borrower agrees that
IF ANY  COLLATERAL IS SOLD AT ANY PUBLIC OR PRIVATE SALE,  THE COMPANY MAY ELECT
TO SELL ONLY TO A BUYER WHO WILL GIVE FURTHER  ASSURANCES,  SATISFACTORY IN FORM
AND SUBSTANCE TO THE COMPANY, RESPECTING COMPLIANCE WITH THE REQUIREMENTS OF THE
SECURITIES ACT OF 1933, AS AMENDED,  AND ANY AND ALL APPLICABLE STATE SECURITIES
LAWS;  AND A SALE  SUBJECT  TO  SUCH  CONDITION  SHALL  BE  DEEMED  COMMERCIALLY
REASONABLE.  The  Company  shall  have the  right to bid  upon or  purchase  the
Securities, or any other part of the Collateral, or all of the foregoing, at any
such sale,  less any and all amounts owing to the Company by the Borrower  under
the  Note,  this  Agreement  or  otherwise,   and  that  any  such  purchase  is
commercially reasonable.

     Section 6.  Application of Moneys.  Any moneys received by the Company upon
payment  to it of  any  Collateral  held  by it or as  proceeds  of  any  of the
Collateral  may be applied by the Company  first to the payment of any  expenses
incurred by it in connection with the Collateral, including, without limitation,
reasonable attorneys' fees and legal expenses,  and all other amounts payable to
the Company by the  Borrower,  and any balance of such moneys so received by the
Company may be applied to all  Liabilities of the Borrower  (including,  without
limitation,  the principal  amount of the Note  outstanding  whether or not such
principal  amount is at that time due and payable) in such order of  application
as the Company in its sole discretion 

<PAGE>

may determine.  Any amounts  remaining  after payment of the  Liabilities may be
applied  by the  Company  to the  payment  of any and all other  amounts  owing,
whether or not then due,  to the Company  from the  Borrower  and any  remaining
balance thereafter shall be paid to the Borrower.

     Section 7. Release of Collateral.  Upon the indefeasible payment in full of
the Liabilities,  the Company shall, upon the request of the Borrower,  promptly
reassign and redeliver to the Borrower the  Collateral  which has not been sold,
disposed  of,  retained or applied by the Company in  accordance  with the terms
hereof,  together with such endorsements,  stock powers and similar documents as
the Borrower may reasonably  request.  Such reassignment and redelivery shall be
without warranty by or recourse to the Company,  except as to the absence of any
prior assignments by the Company of its interest in the Collateral. In the event
that the Borrower  proposes to sell,  transfer or otherwise  dispose of all or a
portion of the Securities,  upon the request of the Borrower,  the Company shall
release from its security  interest  the  Securities  to be sold by the Borrower
and, at the sole  expense of the  Borrower,  shall  deliver such  Securities  as
directed by the  Borrower,  free and clear of any security  interest  hereunder,
upon receipt from or on behalf of the Borrower of the net proceeds of such sale,
transfer  or  other  disposition  in cash in next day or  immediately  available
funds. In the event that the Borrower  proposes to exercise the all or a portion
of the  Warrants,  upon the request of the  Borrower,  the Company shall release
from its security  interest the Warrants to be exercised by the Borrower and, at
the sole expense of the Borrower, shall deliver such Warrants as directed by the
Borrower,  free and clear of any security interest hereunder,  upon receipt from
or on behalf of the Borrower of the Shares  issuable  upon such  exercise or, in
the  event of the  simultaneous  sale,  transfer  or other  disposition  of such
Shares, the net proceeds of such sale,  transfer or other disposition in cash in
next day or immediately available funds.

     Section 8. Non-Recourse Nature of Liabilities.  The Company's sole recourse
for the payment of the Liabilities  shall be limited to the Collateral  securing
the  Note.  THE  COMPANY  SHALL NOT HAVE THE RIGHT TO  ENFORCE  THE  LIABILITIES
AGAINST THE BORROWER OR ANY OF THE BORROWER'S OTHER ASSETS OR PROPERTY.

     Section 9. Miscellaneous.

     (a) To the fullest extent permitted by applicable law, this Agreement shall
continue to be  effective or be  reinstated,  as the case may be, if at any time
any amount received by the Company in respect of the Liabilities is rescinded or
must  otherwise  be restored or returned by the Company upon the  insolvency  or
bankruptcy of the Borrower or upon the appointment of any receiver,  intervenor,
conservator,  trustee or similar  official for the  Borrower or any  substantial
part of his assets, or otherwise, all as though such payments had not been made.

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     (b) No remedy  herein  conferred  is intended to be  exclusive of any other
remedy herein  conferred or otherwise  available to the Company,  but every such
remedy  shall be  cumulative  and in  addition  to  every  other  remedy  herein
conferred,  or conferred on the Company by any other  agreement or instrument or
now or hereafter existing at law, in equity or by statute.

     (c) Any provision of this Agreement which is prohibited or unenforceable in
any jurisdiction,  shall, as to such jurisdiction,  be ineffective to the extent
of such  prohibition  or  unenforceability  without  invalidating  the remaining
provisions  hereof,  and  any  such  prohibition  or   unenforceability  in  any
jurisdiction shall not invalidate or render  unenforceable such provision in any
other jurisdiction.

     (d) Except as otherwise  expressly provided herein, no term or provision of
this Agreement may be amended, waived, discharged or terminated orally, but only
by an instrument in writing signed by the parties.

     (e)  THIS  AGREEMENT  AND  ALL  RIGHTS  HEREUNDER  SHALL  BE  CONSTRUED  IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE OF NEW YORK WITHOUT GIVING
EFFECT TO THE CONFLICTS OF LAWS PROVISIONS THEREOF. THE BORROWER HEREBY CONSENTS
AND  SUBMITS TO THE  EXCLUSIVE  JURISDICTION  OF THE  FEDERAL  AND STATE  COURTS
LOCATED  IN  THE  STATE  OF NEW  YORK  HAVING  SUBJECT  MATTER  JURISDICTION  IN
CONNECTION  WITH ANY AND ALL DISPUTES  ARISING OUT OF OR IN CONNECTION WITH THIS
AGREEMENT, THE NOTE OR THE TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY. FURTHER,
THE BORROWER  HEREBY CONSENTS AND AGREES THAT SERVICE OF PROCESS BY THE COMPANY,
OR ANY  PARTY  ACTING  ON BEHALF OF THE  COMPANY,  SHALL BE DEEMED  VALIDLY  AND
PROPERLY  EFFECTED  AGAINST  THE  BORROWER  UPON THE  MAILING  OF A COPY OF SUCH
PROCESS BY CERTIFIED MAIL,  POSTAGE PREPAID,  TO THE BORROWER AT ITS ADDRESS SET
FORTH ABOVE.

     (f) No course of  dealing  and no delay on the part of any party  hereto in
exercising any right, power, or remedy conferred by this Agreement shall operate
as a waiver  thereof or  otherwise  prejudice  such party's  rights,  powers and
remedies hereunder or in connection  herewith.  No single or partial exercise of
any power or remedy  conferred  by this  Agreement  shall  preclude any other or
further exercise thereof or the exercise of any other right, power or remedy.

     (g) This  Agreement  shall inure to the benefit of and be binding  upon the
parties   hereto   and   their   respective   successors,   assigns   and  legal
representatives.

     (h) This Agreement  constitutes the entire agreement among the parties with
respect to the matters covered hereby and supersedes all previous written,  oral
or implied agreements and understandings  among the parties with respect to such
matters.

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     (i) All notices or other  communications  required or  permitted  hereunder
shall be in writing and shall be delivered  personally,  by facsimile or sent by
certified,  registered or express air mail, postage prepaid, and shall be deemed
given which so delivered  personally,  or by facsimile,  or if mailed, five days
after the date of mailing, as follows:

             If to the Company:        50 Orville Drive
                                       Bohemia, New York 11716
                                       Telephone:        (516) 784-4110
                                       Facsimile:        (516) 784-4132
                                       Attention:        Chief Borrower Officer


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             If to the Borrower:       12 East 49th Street
                                       35th Floor
                                       New York, New York 10017
                                       Telephone:        (212) 339-2861
                                       Facsimile:        (212) 339-2834
                                       Attention:        President

or at such other  addresses  as shall be furnished in writing to the other party
hereto.

     (j) The headings in this  Agreement are for reference  purposes  only,  and
shall not in any way affect the meaning or interpretation

     (k) This  Agreement  may be executed in one or more  counterparts,  each of
which shall be deemed an original  agreement,  but all of which  together  shall
constitute one and the same instrument.


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     IN WITNESS WHEREOF, the parties have duly executed this Agreement as of the
date first written above.

                                              MBF CAPITAL CORP.



                                              By:/s/Mark B. Fisher
                                                 _______________________________
                                                 Name: Mark B. Fisher
                                                 Title: President



                                              LOGIMETRICS, INC.



                                              By:/s/Norman M. Phipps
                                                 _______________________________
                                                 Name: Norman M. Phipps
                                                 Title: President