EXHIBIT 10.20


                      NON-RECOURSE SECURED PROMISSORY NOTE


     FOR VALUE RECEIVED,  MBF Capital Corp. (the "Maker") hereby promises to pay
to  the  order  of  LogiMetrics,  Inc.  or its  successors,  assigns  and  legal
representatives (the "Holder"), at its offices at 50 Orville Drive, Bohemia, New
York, or at such other  location as the Holder may designate  from time to time,
the sum of Thirty-Five  Thousand Dollars ($35,000) in lawful money of the United
States of America on July 29, 2000 (the "Maturity Date"), together with interest
thereon,  compounded annually,  at a rate of 6.07% per annum.  Interest shall be
calculated on the basis of a 360-day year for the actual number of days elapsed.

     If the date any amount is due  hereunder is not a Business  Day,  then such
amount shall be due and payable on the Business Day next succeeding the original
payment date,  together with  interest  thereon to the date of payment.  As used
herein,  "Business  Day" means any day, other than a Saturday or Sunday or other
day on which commercial banks in New York are authorized or required,  by law or
executive order, to be closed.

     If the Maker  fails to pay any amount  hereunder  when due,  whether on the
Maturity Date, upon acceleration or otherwise,  and such failure continues for a
period of five (5) days or more, interest shall thereafter accrue on any overdue
amounts at a rate of 9.07% per annum  until  paid in full.  In such  event,  the
Maker  also  shall  pay  to  the  Holder  the  reasonable  attorneys'  fees  and
disbursements and all other  out-of-pocket costs incurred by the Holder in order
to collect  amounts  due and owing under this Note or  otherwise  to enforce the
Holder's rights and remedies hereunder.

     The Maker may prepay  this Note at any time,  in whole or in part,  without
premium or penalty.  Any partial  prepayments  shall be applied first to accrued
interest  and second to the payment of  principal.  The Maker shall not have the
right to set off or otherwise  deduct from amounts payable by it hereunder,  any
amounts,  whether  liquidated or  unliquidated,  which the Holder may owe to the
Maker, which right is hereby expressly waived to the maximum extent permitted by
applicable  law.  In the event  that the Maker  sells,  transfers  or  otherwise
disposes of some or all of the  Securities  (as defined in the Pledge  Agreement
referred to below),  whether on or prior to the Maturity  Date,  the Maker shall
promptly  repay  this  Note in an  amount  equal  to the net  proceeds,  if any,
received by the Maker from such disposition.

     This Note and all amounts due hereunder  shall become  immediately  due and
payable, without demand and without notice to the Executive, upon the occurrence
of any of the following events:  (i) the sale,  transfer or other disposition by
the Maker of all of the Securities then owned by it, (ii) the  consummation of a
Company Sale (as such term is defined in the Stockholders Agreement,  dated July
29,  1997,  among the  initial  Holder of this Note and the  stockholders  party
thereto),  or (iii)  the  Maker  shall  have  applied  for or  consented  to the
appointment  of  a  custodian,   receiver,   trustee  or  liquidator,  or  other
court-appointed  fiduciary of all or a substantial part of its properties;  or a
custodian,  receiver,  trustee or liquidator or other court appointed  fiduciary
shall have been appointed with or without the consent of the Maker; or the Maker
is  generally  not  paying its debts as they  become  due by means of  available
assets or is  insolvent,  or has made a 

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general assignment for the benefit of creditors;  or the Maker files a voluntary
petition in bankruptcy,  or a petition or an answer seeking reorganization or an
arrangement  with creditors or seeking to take advantage or any insolvency  law,
or an answer admitting the material allegations of a petition in any bankruptcy,
reorganization  or insolvency  proceeding or has taken action for the purpose of
effecting  any of the  foregoing;  or if,  within  sixty  (60)  days  after  the
commencement  of any  proceeding  against the Maker seeking any  reorganization,
rehabilitation, arrangement, composition, readjustment, liquidation, dissolution
or similar  relief  under the  Federal  bankruptcy  code or similar  order under
future similar legislation, the appointment of any trustee, receiver, custodian,
liquidator,  or other  court-appointed  fiduciary  of the Maker or of all or any
substantial  part of its  properties,  such order or appointment  shall not have
been  vacated or stayed on appeal or  otherwise  or if,  within  sixty (60) days
after the expiration of any such stay, such order or appointment  shall not have
been vacated.

     This Note is the Note referred to in the Pledge  Agreement,  dated the date
hereof,  between the Maker and the initial holder of this Note and is secured by
the Securities and the other Collateral  described therein. The Pledge Agreement
grants the Holder  certain  rights with respect to the  Collateral  upon certain
defaults specified therein.

     The Holder's  sole  recourse for the payment of amounts due under this Note
shall be limited to the Collateral securing this Note. THE HOLDER SHALL NOT HAVE
THE RIGHT TO  ENFORCE  THIS NOTE  AGAINST  THE  MAKER,  OR ANY OF ITS  OFFICERS,
DIRECTORS OR SHAREHOLDERS OR ANY OTHER ASSETS OR PROPERTY OF ANY OF THEM.

     No  delay  on the  part of the  Holder  in  exercising  any  power or right
hereunder  shall  operate as a waiver of any such power or right;  nor shall any
single or partial  exercise of any power or right  preclude any other or further
exercise  of such power or right,  or the  exercise of any other power or right,
and no waiver whatsoever shall be valid unless in writing, signed by the Holder,
and then only to the  extent  expressly  set  forth  therein.  The Maker  waives
presentment,  demand for  payment,  diligence,  notice of dishonor and all other
notices or demands in  connection  with the delivery,  acceptance,  performance,
default or indorsement of this Note.

     This Note shall be binding upon the Maker and its  successors,  assigns and
legal  representatives.  This  Note  shall be  governed  by,  and  construed  in
accordance  with,  the laws of the State of New York,  without  reference to the
choice of law provisions thereof. The Maker irrevocably submits to the exclusive
jurisdiction  of the  courts  of the  State of New York  and the  United  States
District  Court for the  Southern  District  of New York for the  purpose of any
suit, action, proceeding or judgment relating to or arising out of this Note and
the transactions  contemplated  hereby.  The Maker  irrevocably  consents to the
jurisdiction of any such court in any such suit, action or proceeding and to the
laying of venue in such court. The Maker irrevocably waives any objection to the
laying of venue of any such suit,  action or  proceeding  brought in such courts
and  irrevocably  waives  any claim  that any such  suit,  action or  proceeding
brought in any such court has been brought in an inconvenient forum.

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     IN WITNESS  WHEREOF,  the Maker has caused this Note to be duly executed by
the undersigned, thereunto duly authorized, as of the date set forth below.


                                                MBF CAPITAL CORP.



                                                 By: /s/Mark B. Fisher
                                                     ___________________________
                                                     Mark B. Fisher, President


Dated:  July 29, 1997