Document:

EXHIBIT 4.15

                            CERTIFICATE OF AMENDMENT
                                       OF
                           CERTIFICATE OF DESIGNATION
                                       OF
         SERIES A 12% CUMULATIVE CONVERTIBLE REDEEMABLE PREFERRED STOCK
                              OF LOGIMETRICS, INC.

          LogiMetrics,  Inc., a  corporation  organized  and existing  under the
General  Corporation  Law of the State of  Delaware  (the  "Corporation"),  does
hereby certify that:

          The following amendments to the Certificate of Designation of Series A
12% Cumulative Convertible Redeemable Preferred Stock ("Preferred Stock") of the
Corporation  ("Certificate of Designation") were duly adopted in accordance with
the  provisions  of Section 242 of the General  Corporation  Law of the State of
Delaware:

          1. Section 2 of the  Certificate  of  Designation is hereby amended to
read in its entirety as follows:

          "2.  Dividends.  The  holders of shares of  Preferred  Stock  shall be
entitled  to receive,  but only when and as declared by the Board of  Directors,
dividends  in an amount  equal to twelve  percent  (12%) of the Stated Value per
share per annum,  payable quarterly on such dates in each year as shall be fixed
by the Board of Directors. Such dividends shall be payable, at the option of the
Board of  Directors,  either in cash or in shares of Common Stock having a "Fair
Market Value" (as defined  below) on the date of  declaration  equal to the cash
dividend otherwise payable.  As used herein,  "Fair Market Value" on any date of
determination  means the  average of the last sale price per share of the Common
Stock for ten trading days  immediately  preceding  such date as reported by any
national  securities  exchange  on which  the  Common  Stock is then  listed  or
admitted  for trading or as reported  by the Nasdaq  Stock  Market if the Common
Stock is not then listed or  admitted  for  trading on any  national  securities
exchange,  or the average of the  closing bid and asked  prices per share of the
Common  Stock  for the ten  trading  days  immediately  preceding  such  date as
reported  on the OTC  Bulletin  Board  or any  similar  successor  service  then
publishing quotations on the Common Stock if the Common Stock is not then listed
or admitted for trading on any national  securities  exchange or included on the
Nasdaq Stock Market,  or as  determined in good faith by the Company's  Board of
Directors  in the event that the Common Stock is not then listed or admitted for
trading on any  national  securities  exchange or  included on the Nasdaq  Stock
Market  and  quotations  on the  Common  Stock  are  not  then  being  regularly
published."

          2. Section 8 of the  Certificate  of  Designation is hereby amended to
read in its entirety as follows:

          "8. Voting rights of preferred.  Except as expressly  provided by law,
the  Preferred  Stock  shall  have no  right to vote on any  question  or in any
proceeding or to be  represented  at or to receive  notice of any meeting of the
stockholders."

          IN WITNESS WHEREOF,  the Corporation has caused this certificate to be
executed  and  attested  by its  duly  authorized  officers,  this  30th  day of
November, 1999.

                                             LOGIMETRICS, INC.

                                              By:______________________________
                                                 Norman M. Phipps, President and
                                                 Chief Operating Officer

ATTEST:

__________________________
Erik S. Kruger, SecretaryCERTAIN PORTIONS OF THIS EXHIBIT HAVE BEEN OMITTED BASED UPON A REQUEST
   FOR CONFIDENTIAL TREATMENT. THE OMITTED PORTIONS OF THIS EXHIBIT HAVE
        BEEN SEPARATELY FILED WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                  EXHIBIT 10.1

                          Signal Technology Corporation
                               222 Rosewood Drive
                                Danvers, MA 01923

                                February 17, 2000

LogiMetrics, Inc.
50 Orville Drive
Bohemia, NY 11716

Gentlemen:

          Signal Technology Corporation,  a Delaware corporation ("Signal"),  is
interested in making an offer to LogiMetrics,  Inc., a Delaware corporation (the
"Company"),  of the following proposed transaction terms (the "Terms"),  whereby
Signal would  acquire the Company by the merger of a  newly-formed  wholly-owned
subsidiary of Signal into the Company in a transaction intended to be a tax-free
reorganization  under Section 368(a)(1)(A) of the Internal Revenue Code, as more
fully described below ("the Merger").

          1. (a) Subject to the completion of the "due diligence"  investigation
contemplated  by Section 7 hereof,  as the merger  consideration,  Signal  would
issue (i) shares of Signal  common  stock,  $.01 par value (the  "Signal  Common
Stock"),  and (ii) shares of SWG Equity (as defined in paragraph (b) below). The
number of shares of Signal  Common Stock to be issued would,  immediately  after
the issuance  thereof,  be equal to  [confidential  portion has been omitted and
filed  separately with the Securities and Exchange  Commission] of the aggregate
of the number of then issued and  outstanding  shares of Signal Common Stock and
the  number of shares  of Signal  Common  Stock  then  subject  to vested  stock
options.  The  number  of shares  of SWG  Equity to be issued  would be equal to
[confidential  portion has been omitted and filed separately with the Securities
and Exchange Commission] of the SWG Equity, calculated prior to any distribution
to Signal  stockholders  and prior to the sale of SWG Equity to the public in an
initial  public  offering (the "SWG IPO").  (The Signal Common Stock and the SWG
Equity to be issued in connection with the Merger are hereinafter referred to as
the  "Merger  Consideration.")  The  parties  understand  that the  certificates
representing  the SWG Equity  portion of the Merger  Consideration  would not be
issued and would not be tradable  until the SWG IPO.  In the event that,  during
the period  between  the signing of this Letter of Intent and the closing of the
Merger,  Signal grants  options to purchase  shares of Signal Common Stock which
vest  immediately  upon  grant,  or  Signal  issues  any  securities  which  are
convertible into shares of Signal Common Stock, the Company shall be entitled to
anti-dilution  protection.  The  transaction  would close as soon as practicable
after  receipt of any required  director,  stockholder  and bank  approvals  and
regulatory approvals,  including Hart-Scott-Rodino approval (if applicable). The
transaction is contingent upon the conversion of the Company's  indebtedness for
borrowed  money (other than that owed to North Fork Bank and as may be set forth
on Schedule I hereto) into Company common stock at or prior to the acquisition.

          (b) It is the  mutual  intention  of Signal and the  Company  that the
assets owned by mmTech, Inc., a New Jersey corporation ("mmTech"), the Company's
wholly-owned  subsidiary,  shall become part of the Signal Wireless Group. It is
also the mutual  intention  of Signal and the Company  that the Signal  Wireless
Group shall be employed as a separate  vehicle  (such new company to be referred
to  hereinafter  as "SWG") to  enhance  the value of that  business,  through an
offering by Signal of a "tracking"  security to reflect the SWG  business  (such
tracking  security is herein referred to as "SWG Equity").  Signal would use its
commercially  reasonable efforts to consummate the SWG IPO as soon as reasonably
practicable,  given  market  conditions.  It is Signal's  intention to issue SWG
Equity  only in such  circumstances  and to such  parties as would  benefit  SWG
directly. The parties agree that if the SWG IPO has not occurred by the later of
December 31, 2001 or eighteen (18) months following the Merger, at the option of
either  Signal or the  holders of a majority  of the SWG Equity  issuable to the
Company's former  shareholders (the "Majority Company Holders"),  all of the SWG
Equity shall be exchanged for shares of Signal Common Stock. Such exchange shall
be based on the  respective  fair market  values of both the Signal Common Stock
and the SWG Equity,  as  determined  by an  investment  banking firm selected by
Signal  (subject to approval by the Majority  Company  Holders,  which  approval
shall not be unreasonably withheld or delayed).

<PAGE>

          (c) As conditions to the  finalization of the percentages set forth in
paragraph (a) above prior to execution of the Agreement referred to in Section 5
below,  both the Company and Signal shall have completed  their  respective "due
diligence" investigation and valuation of the other's assets that will be a part
of SWG and each shall have received  from its  respective  financial  advisor an
opinion that such transaction is fair to its stockholders from a financial point
of view. In the event that,  based on such  investigations  and valuations,  the
percentages  are  adjusted  in a manner  adverse to the  Company and the Company
therefore   terminates  its  discussions   with  Signal  regarding  the  Merger,
thereafter  the Company  shall not be obligated to pay the Break-Up Fee referred
to in Section 10(b) hereof.  The Company and Signal agree that,  for purposes of
the  valuation  of the  Company's  assets  referred  to in the second  preceding
sentence,  the $2,000,000 loan from Signal to the Company referred to in Section
6(a) hereof shall be ignored.  The parties will attempt to keep such  $2,000,000
loan from being a liability of SWG or from otherwise burdening SWG.

          2.  The  Merger   Consideration  would  be  reduced  for  all  Company
liabilities assumed by Signal, other than current liabilities,  indebtedness for
borrowed money owed to North Fork Bank, and other  indebtedness  and obligations
specifically  assumed by it.  The  parties  agree that the Merger  Consideration
shall not be reduced by either (i) the aggregate  amount,  up to $1,000,000,  of
loans from certain of the Company's existing lenders referred to in Section 6(a)
hereof or (ii)  twenty-five  percent  (25%) of the  indebtedness  (not to exceed
$250,000)  currently  owed by the  Company  to Charles  Brand,  such loans to be
assumed and paid off by Signal at the closing of the Merger. To the extent that,
as of the  closing  date,  the net  assets  of the  Company,  as  determined  in
accordance  with  Schedule II attached  hereto,  exceed or are less than the net
assets of the Company set forth on such  Schedule II, there would be an increase
or decrease,  as the case may be, in the Merger Consideration to be paid. At the
closing of the Merger,  the Company's  assets and mmTech's  assets shall be free
and clear of all liens and  encumbrances,  except to the  extent  such liens and
encumbrances secure indebtedness assumed by Signal.

          3. Signal will be required to register the Signal Common Stock and the
SWG Equity issued in connection with the transaction  contemplated  hereby under
the Securities  Act of 1933, as amended.  Signal shall apply for listing of such
Signal  Common  Stock  on the  American  Stock  Exchange  (or  on  the  National
Association of Securities  Dealers,  Inc.  National Market System, if the Signal
Common Stock is then traded on that exchange).  Signal and the Company shall use
commercially  reasonable  efforts to prepare  and file with the  Securities  and
Exchange Commission a registration statement on Form S-4 within thirty (30) days
after signing the definitive  agreements  referred to in Section 5 below. During
the one hundred eight (180) day period following the closing date, the Company's
principal  stockholders  owning  approximately 80% of the Company's equity shall
not be permitted to sell, in the  aggregate,  more than five percent (5%) of the
total number of shares of Signal Common Stock issued to such stockholders in the
transaction.

          4. Prior to the closing of the  Merger,  Signal's  Board of  Directors
shall  increase  the size of the Board by one (1)  director,  for the purpose of
electing to the Board a nominee of Cramer Rosenthal McGlynn,  LLC ("CRM"),  such
nominee to be acceptable to Signal's  Board.  The parties agree that, so long as
CRM and its  affiliates  own in the  aggregate at least five percent (5%) of the
Signal Common Stock issued in connection with the Merger,  CRM shall be entitled
to have a nominee on Signal's Board.

          5. The Company  understands  that Signal will  instruct its counsel to
prepare an Agreement and Plan of Reorganization (the "Agreement") and such other
agreements and documentation as shall be necessary or appropriate to reflect the
Terms.  Such definitive  agreements shall contemplate and be contingent upon the
receipt by Signal of audited  consolidated  financial  statements of the Company
for its  fiscal  years  ended  June 30,  1998 and  June 30,  1999 and  unaudited
financial statements for the fiscal quarters ended September 30 and December 31,
1999,  and, if possible in light of the  closing  date,  for the fiscal  quarter
ended March 31, 2000,  and shall  contain  terms,  conditions,  representations,
warranties  and  covenants  as are  customary  in  transactions  of  this  type,
consistent with the Terms, including the following:

          (a) an adjustment to the Merger  Consideration  to the extent to which
the net assets of the  Company  exceed or are less than the net assets  shown on
Schedule II hereto;

          (b) the Company shall make  representations,  warranties and covenants
reasonable to the transaction, which will expire one year after the closing date
(the "Survival Period");

<PAGE>

          (c) the Company  shall provide  normal and  customary  indemnification
(through an escrow of a portion of the Merger  Consideration)  by the  Company's
stockholders  for any breach of  representation,  warranty  or  covenant  by the
Company and for all liabilities  not  specifically  assumed by Signal,  provided
that, except for certain standard exceptions (the "Standard  Exceptions"),  such
as with  respect  to  authority,  capitalization,  title,  taxes,  environmental
liabilities,  ERISA  liabilities and other  identified  claims and  liabilities,
there will be no such  indemnification  for claims  unless the total exceeds the
value of one and one-half  percent  (1-1/2%) of the Merger  Consideration,  and,
provided further,  that there shall be no indemnification  for amounts in excess
of seven and one-half percent (7-1/2%) of the value of the Merger  Consideration
(unless Signal discovers  something during its due diligence  investigation that
causes it to  reasonably  believe  that such amount is  materially  inadequate),
which indemnity shall be secured by a post-closing  escrow of seven and one-half
percent  (7-1/2%)  of  the  Merger   Consideration,   which  shall  be  released
immediately  after the Survival  Period  except for shares  necessary to provide
security  for claims  previously  made (for  purposes  of the  escrow,  (i) with
respect  to shares of Signal  Common  Stock  taken  from the  escrow  during the
Survival  Period,  the Signal  Common  Stock shall be deemed to have a value per
share equal to the average  closing  price of Signal  Common  Stock for the five
trading days  immediately  preceding the date that the shares are taken from the
escrow to satisfy such claim),  and (ii) with respect to shares of Signal Common
Stock  retained  in the  escrow at the end of the  Survival  Period  to  provide
security for claims  previously made, the Signal Common Stock shall be deemed to
have a value per share equal to the average closing price of Signal Common Stock
for the five trading  days  immediately  preceding  the last day of the Survival
Period);

          (d) mutually acceptable  employment agreements between Signal and each
of Norman Phipps and Charles Brand;

          (e)  non-compete  agreements from the following  individuals,  for the
specified  durations  commencing on the closing  date,  wherever the Company has
done  business:  Norm Phipps for two years;  Charles  Brand for five years;  and
certain  key  engineers  for two years,  with each of such key  engineers  to be
granted, after the closing of the Merger, an option to purchase shares of Signal
Common Stock,  in such form and for such number of shares of Signal Common Stock
as Signal customarily grants to similarly situated Signal employees; and

          (f) an exclusivity  agreement from the Company,  in substantially  the
form set forth in Section 10(a)(i) hereof,  with a so-called  "fiduciary out" in
the event that the Company receives from a third party a superior  proposal with
respect to the  Company  and/or its  subsidiaries,  and the  Company's  Board of
Directors determines in good faith (based on the advice of outside counsel) that
its fiduciary  duties  require it to consider such  proposal;  provided that the
Company shall pay to Signal the amount of $800,000 as  reimbursement of Signal's
expenses and as liquidated damages (a "Break-Up Fee") in the event that it shall
consummate an  Acquisition  Transaction  (as defined below in Section  10(a)(i))
with a third  party  within  twelve  months  thereafter,  such  Break-Up  Fee to
supersede and extinguish the Company's  obligations with respect to the Break-Up
Fee referred to in Section 10(b) hereof and to be paid within three (3) business
days  after the  consummation  of the  transaction  with such third  party.  The
parties  agree  that  in the  event  they  do  not  consummate  the  transaction
contemplated hereby based on the fact that the conditions  precedent to Signal's
obligations under the definitive agreements are not satisfied,  through no fault
or  failure  on the  part of the  Company,  Signal  shall  waive  the  Company's
obligation to pay the Break-Up Fee under this Section 5(f), and such  obligation
shall terminate.

          6. (a) In  consideration  of the parties  entering into this Letter of
Intent,  Signal is committing to loan to the Company  $2,000,000.  $1,000,000 of
the loan will be advanced  forthwith  upon  completion of Signal's due diligence
examination  of the  Company's  New York  Business  (as defined in Section  6(b)
below),  and the  balance of the loan will be advanced  in  accordance  with the
schedule  set forth on Schedule III hereto.  In  connection  with the loan,  the
parties agree to execute and deliver the forms of Loan  Agreement and Promissory
Note attached hereto, as well as the other agreements and documents  referred to
therein.  The  parties  agree  that the loan by  Signal is  contingent  upon the
Company's  borrowing from certain of its existing  lenders  amounts equal in the
aggregate to $1,000,000,  of which $610,000 has been advanced since  December 2,
1999.  The  remaining  $390,000  of such loans  shall be  disbursed  as follows:
$50,000  at the  time  Signal  loans  its  first  $1,000,000,  and  the  balance
thereafter at the rate of $34,000 for every $100,000 loaned by Signal, with such
disbursements to be made simultaneously with Signal's disbursements.

          (b) Upon execution of this Letter of Intent,  as an  accommodation  to
the Company,  Signal is agreeing that, upon  disbursing the first  $1,000,000 of
the Signal  loans  referred to in Section  6(a)  hereof,  it shall take over the
responsibility  of running the  Company's  "New York  Business,"  which shall be
defined for these purposes as the business located at 50 Orville Drive, Bohemia,
New York 11706,  pursuant to a Management  Agreement in the form attached hereto
and the other agreements and documents referred to therein.

<PAGE>

          7.  Signal  anticipates  being  able to  conduct  the  necessary  "due
diligence"  investigation  and to execute and deliver  definitive  agreements by
such date as is 45 days  from the date of this  Letter of  Intent.  During  this
period, the Company shall provide Signal with reasonable access to the books and
records of the Company and its subsidiaries and other information  regarding the
Company and its subsidiaries.

          8.  Both   Signal  and  the  Company   agree  to   maintain   complete
confidentiality  (except as may be  necessary  to disclose  to their  respective
Boards of Directors,  advisors and bankers) of the proposed  transaction and any
terms,  conditions or other facts related to it, unless  required by law to make
disclosure;  provided  that any press  release  or  announcement  made  shall be
mutually  agreed upon by the  parties.  Signal and the Company  acknowledge  and
agree  that  they  are  also  bound  by  the   obligations   set  forth  in  the
Confidentiality  Agreement  between  Signal and the Company  dated  December 14,
1999.

          9. Between now and the closing,  the Company will conduct its business
in the normal and  ordinary  course and,  among other  things,  will pay no cash
dividends and will not purchase or redeem any of its outstanding securities.

          10. (a) In  consideration  of Signal's  devotion of its  resources  in
conducting  its due  diligence  investigation  and  having its  counsel  prepare
definitive  agreements,  and for other  valid  consideration,  the  receipt  and
adequacy of which are hereby acknowledged, the Company agrees that from the date
hereof until such date as is 45 days from the date of this Letter of Intent (the
"Exclusivity Period"):

          (i)  neither  it  nor  any  of  its  officers,  directors,  employees,
representatives  or agents,  including without  limitation  investment  bankers,
attorneys and accountants,  shall directly or indirectly  solicit or initiate or
participate in any discussions or negotiations  with, or provide any information
to, any corporation,  partnership,  person, or other entity or group (other than
Signal and its designees) concerning any offer or proposal,  with respect to the
Company  or any of its  subsidiaries,  for any  merger,  tender  offer,  sale of
substantial  assets,  sale of shares of capital stock or debt securities,  joint
venture,  long term  leasing of assets  (other  than in the  ordinary  course of
business)  or any  similar  transaction  related  to the  Company  or any of its
subsidiaries (each such transaction, an "Acquisition Transaction"); and

          (ii) it will  promptly  (and in no event  later  than 24  hours  after
receipt)  communicate  to  Signal  the terms of any such  proposal,  discussion,
negotiation or inquiry  relating to the Company or any of its  subsidiaries  and
the  identity  of  the  party  making  or  having  such  proposal,   discussion,
negotiation or inquiry that it may receive in respect of any such proposal.

<PAGE>

          (b) The Company  agrees  that in the event the  Company  enters into a
letter of intent or similar  agreement  with a third  party  with  respect to an
Acquisition  Transaction  at any time during the period  commencing  on the date
which is 46 days  following  the date of this  Letter of Intent  and  continuing
through and  including  such date which is 120 days from the date of this Letter
of Intent,  the Company  will pay to Signal the amount of $800,000 as a Break-Up
Fee. The Company  shall pay this  Break-Up  Fee within  three (3) business  days
after the execution of such letter of intent or  agreement.  As noted in Section
5(f) above,  the Company's  obligation to pay such Break-Up Fee shall  terminate
upon the  execution  by Signal and the Company of  definitive  agreements  which
include the exclusivity and Break-Up Fee provisions  referred to in such Section
5(f).

          (c) Notwithstanding any provision herein to the contrary, in the event
that (i) Signal  informs the Company in writing,  at any time during the 120-day
period  following  the date  hereof,  that  Signal  is no longer  interested  in
pursuing a transaction hereunder, or (ii) Signal informs the Company at any time
that Signal will not agree in the Agreement to assume and pay the loans referred
to in  clauses  (i) and (ii) of  Section 2  hereof,  and the  Company  therefore
terminates in writing its discussions with Signal regarding the Merger and three
(3) days shall have expired  without Signal  notifying the Company in writing of
its willingness to so assume and pay such loans, then the Exclusivity Period, if
not already expired, and the related obligations of the Company shall expire and
the Company shall not be obligated to pay to Signal the Break-Up Fee referred to
in paragraph (b) immediately above.

          11. It is understood  that this letter merely  constitutes a statement
of mutual intentions with respect to the transactions  contemplated herein, does
not contain a resolution of all matters upon which agreement must be reached for
the consummation of those  transactions  and,  therefore,  does not constitute a
binding agreement with respect thereto.  A binding agreement with respect to the
transaction  will result only from the  execution of the  definitive  agreements
referred to in Section 5 above.  Notwithstanding  the two  preceding  sentences,
upon  execution and delivery of this letter by both parties,  Sections 6 through
12 of this letter  shall be legally  binding  upon and  enforceable  against the
parties.  Either of the parties  shall be  entitled to seek legal and  equitable
relief for any breach of any legally binding provision.

          12.  This  letter  of  intent  shall  be  construed  and  enforced  in
accordance with the laws of The Commonwealth of Massachusetts.

                         [Signatures on Following Page]

          Please  indicate your agreement with the terms hereof by executing and
delivering a copy of this letter to the undersigned.

                                             Very truly yours,

                                             Signal Technology Corporation

                                             By:/s/George E. Lombard
                                                ________________________________
                                                George E. Lombard, Chairman and
                                                Chief Executive Officer

                                             Agreed and Assented:

                                             LogiMetrics, Inc.

                                             By: /s/Norman M. Phipps
                                                 _______________________________
                                                 Norman M. Phipps, President

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