MERRIMAC INDUSTRIES, INC.
                               41 FAIRFIELD PLACE
                         WEST CALDWELL, NEW JERSEY 07006

February 1, 2002

Ericsson Microelectronics, A.B.
675 Jarvis Drive
Morgan Hill, California 95037
Attention: Mr. Thomas Moller
           Vice President and General Manager

Ericsson Holding International, B.V.
Rijen, Netherlands
Attention: Mr. Thomas Moller

Gentlemen:

Our companies entered into a letter agreement of April 7, 2000 (hereinafter
"Letter Agreement") which set forth an exclusivity arrangement for goods and
services by Merrimac in favor of Ericsson. With this letter we shall more
clearly (i) define the meaning of terms used in that Letter Agreement and (ii)
clarify the intended scope of the exclusivity arrangement set forth in the
Letter Agreement.

1. Meaning of Multi-Mix(TM). As used in the April 7, 2000 Letter Agreement
between Ericsson Microelectronics, A.B. and Merrimac Industries, Inc., the term
"Multi-Mix(TM)" means one or more Fluoropolymer Composite substrate layers
fusion bonded into a homogeneous dielectric subassembly having at least one
embedded active radio frequency ("RF") power transistor and processes of making
that subassembly as claimed in U.S. Patent No. 6,099,677. As used in this
definition of Multi-Mix(TM), the term "Fluoropolymer Composite" means a
composition which contains polytetrafluoroethylene, glass fibers and ceramic
particles.

2. Amendment to Section 1, subsection (a). Subsection (a) of Section 1 of the
Letter Agreement, is hereby amended as follows:

         (1) By revising the first parenthetical expression of the introductory
         paragraph to read as follows;

         "(and similar Multi-Mix(TM) type products, if developed or acquired by
         Merrimac for Ericsson during the term of this letter agreement and
         designated by Ericsson hereafter as "Products for Ericsson"))

                                       1


         (2) By adding at the end of the introductory paragraph the sentences:

"For purposes of clarity, (1) the phase "wireless base station applications" as
used in this letter agreement shall not be construed as extending to anything
other than cellular bases stations, which operate within a frequency range of
eight hundred megahertz (800 MHz) to two thousand one hundred and seventy
megahertz (2170 MHz), for (a) analog cellular telephones for narrow band
advanced mobile phone systems and (2) digital cellular telephones for the
following systems:

         o    time division multiple access, (TDMA, IS-54, IS-136)

         o    code division multiple access ("CDMA", IS-95),

         o    wideband CDMA International Mobile Telecommunications
              2000/Universal Mobile Telecommunications System ("IMT2000/UMTS").

         o    global system for mobile communications ("GSM"), and

         o    personal digital cellular ("PDC")

as an example, wireless base station applications" does not cover cordless
handset base stations which operate below the frequency of eight hundred
megahertz (800 MHz) or above the frequency range of two thousand one hundred and
seventy megahertz (2170 MHz) or cellular handsets regardless of their frequency
range of operation and (2) the phrase "other applications that would compete
with any product now or hereafter sold or developed for sale by Ericsson" shall
not be construed as extending to anything other than the cellular base stations
listed in (1) above. For example, "other applications" does not cover cordless
handset base stations which operate below the frequency of eight hundred
megahertz (800 MHz) or above the frequency range of two thousand one hundred and
seventy megahertz (2170 MHz) or cellular handsets regardless of their frequency
range of operation.

3. Amendment to Section 1, subsection (b). Subsection (b) of Section 1 of the
Letter Agreement, is hereby amended as follows:

         (1) By revising the first parenthetical expression of the introductory
         paragraph to read as follows:

"(and similar Multi-Mix(TM) type products, if developed or acquired by Merrimac
for Ericsson during the term of this letter agreement and designated by Ericsson
hereafter as "Products for Ericsson")).


                                       2


Please indicate your acceptance of this letter by countersigning one copy of the
letter and returning it to me at the above address.

Sincerely yours,


Merrimac Industries, Inc.

/s/ Mason N. Carter
- -------------------------
Mason N. Carter
Chairman and Chief Executive Officer


Agreed and Accepted:


Ericsson Microelectronics, A.B.


/s/ Thomas Moller
- -------------------------
Thomas Moller
Vice President and General Manager



Ericsson Holding International, B.V.

/s/ Thomas Moller
- -------------------------
Thomas Moller

                                       3