EXHIBIT 10.10


                          SUBSTITUTE NEGOTIABLE SECURED
                       SENIOR SUBORDINATED PROMISSORY NOTE


$____________
                                                       Final Maturity Date:
                                                       July 1, 2000

FOR VALUE RECEIVED, LogiMetrics, Inc., a Delaware corporation, and mmTech, Inc.,
a New Jersey  corporation  (collectively,  the  "Makers"),  hereby  jointly  and
severally promise to pay to the order of [NAME OF HOLDER], or his successors and
assigns (the  "Holder"),  at [ADDRESS],  or at such other location as the Holder
may  designate  from  time to  time,  the sum of  [DOLLAR  AMOUNT]  ($________),
together with interest  thereon from September 7, 1999 to and including the date
of repayment at the rate of 13% per annum,  in lawful money of the United States
of  America on or before  July 1, 2000,  or on demand at any time upon or during
the continuance of an Event of Default as defined in the Security  Agreement (as
defined  below),  with or without demand as provided in the Security  Agreement.
The  obligations  of the Makers are joint and several and the Holder may proceed
to collect the full  amount owed  hereunder  from  either  Maker  whether or not
proceeding against the other.

          If the Holder  fails to pay any amount  hereunder  when due,  interest
shall  thereafter  accrue  on such  overdue  amount at the rate of 16% per annum
until paid in full.  Interest  hereunder  shall be  calculated on the basis of a
360-day year for the actual number of days elapsed.

          The  Makers  may  prepay  this Note at any time,  in whole or in part,
without  premium or penalty.  The Makers  shall  prepay this Note in full within
five (5) Business Days after the  consummation of (i) any public or private sale
by either Maker of its debt or equity securities or securities  convertible into
or exchangeable  for its debt or equity  securities,  (ii) any permanent loan or
other credit  facility  obtained by either Maker from a bank or other  financial
institution,  or (iii) any sale by either Maker of all or  substantially  all of
its assets to a third party which results, in each such case, in net proceeds to
the Makers  (after all related  fees and  expenses)  of at least  Three  Million
Dollars ($3,000,000).  As used herein,  "Business Day" means a day, other than a
Saturday or Sunday,  on which commercial banks in New York City are open for the
general transaction of business.

          The Makers 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. All payments received shall be
applied,  first, to the costs of collection,  second,  to unpaid  interest,  and
third, to principal.

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

<PAGE>

          This  Note is a  replacement  and  substitute  Note  for  the  several
Negotiable Secured Senior  Subordinated  Promissory Notes (the "Original Notes")
made payable by Makers to Holder, evidencing loans advanced by Holder to Makers,
made between August 27, 1999 and September 23, 1999, in the aggregate  principal
amount of this Note, which loans are and shall remain secured by and pursuant to
the Second Amended and Restated  Security  Agreement,  Intercreditor  Agreement,
Waiver and Consent  dated on or about August 31, 1999, as amended on December 2,
1999 and February 17, 2000,  and as the same may  hereafter be further  amended,
restated,  supplemented or modified (the "Security Agreement") among the makers,
Cramer  Rosenthal  McGlynn,  LLC, as Agent,  and the other parties  thereto,  as
amended from time to time.  This Note is issued in connection with the extension
by the Holder of the maturity date of the loans from the original  maturity date
of March 7, 2000 to the new  maturity  date set forth above.  The Makers  hereby
acknowledge  that the Original Notes have been delivered to Makers and have been
cancelled and, by its acceptance of this Note in  substitution  for the Original
Notes,  the Holder  agrees to the extension of the maturity date of the loans to
July 1, 2000.

          This Note shall be  binding  upon each  Maker and its  successors  and
assigns.  This Note shall be governed by, and construed in accordance  with, the
internal  laws of the  State of New York  pursuant  to  Section  15-1402  of the
General  Obligations Law of such state.  Each 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.  Service of process in connection with any such suit, action or proceeding
may be served on the Makers  anywhere in the world by any method  authorized  by
law. Each 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.
Each 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.

          No modification, alteration, waiver or change of any of the provisions
hereof  shall be  effective  unless in writing  and signed by each Maker and the
Holder and, then, only to the extent set forth in such writing.

ATTEST:                                     LOGIMETRICS, INC.



_____________________                       _____________________________
Name:                                       By: Norman M. Phipps
                                            Title: President


ATTEST:                                     MMTECH, INC.



_____________________                       _____________________________
Name:                                       By: Charles S. Brand
                                            Title: President

Dated as of:  March 7, 2000