Exhibit 10.1
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                       FOURTH AMENDMENT TO LOAN AGREEMENT

     THIS FOURTH AMENDMENT TO LOAN AGREEMENT (the "Fourth  Amendment"),  is made
     and  entered  into  this  9th  day  of  June,  2005,  by and  among  HERLEY
     INDUSTRIES, INC. (the "Borrower"), MANUFACTURERS AND TRADERS TRUST COMPANY,
     successor  in interest to Allfirst  Bank,  and FULTON BANK (each a "Lender"
     and  collectively,  the  "Lenders")  and  MANUFACTURERS  AND TRADERS  TRUST
     COMPANY,  successor  in  interest  to  Allfirst  Bank,  as  agent  (in such
     capacity, the "Agent").

                               B A C K G R O U N D

     A.  Borrower  has  borrowed  from Lenders and desires to continue to borrow
     from Lenders in connection with the operation of its business.  On June 19,
     2002,  the parties  entered into a Loan  Agreement,  upon which monies have
     been advanced,  which was amended by an Amendment to Loan  Agreement  dated
     May 2, 2003 and a Second  Amendment to Loan Agreement  dated April 20, 2004
     and a Third Amendment to Loan Agreement dated January 28, 2005 (as amended,
     the  "Loan  Agreement").  The Loan  Agreement  is  incorporated  herein  by
     reference and made a part hereof. All capitalized terms used herein without
     definition  which are defined in the Loan Agreement shall have the meanings
     set forth therein.

     B. Borrower has requested  Lenders to amend certain  provisions of the Loan
     Agreement.

     C. The  parties  desire to enter into this  Amendment  to  effectuate  such
     amendments.

     D. Borrower has no defense,  charge,  defalcation,  claim,  plea, demand or
     set-off against the Loan Agreement or any of the Loan Documents.

     NOW,  THEREFORE,  for  valuable  consideration,  receipt of which is hereby
     acknowledged,  and intending to be legally bound hereby, the parties hereto
     covenant and agree as follows:

     1. That the above Background is incorporated herein by reference.

     2. That  Section  1.1 of the Loan  Agreement  be and  hereby is  amended by
     amending the  definitions of "Guarantor"  and  "Guarantors"  to read in its
     entirety as follows:

     "Guarantor" and "Guarantors":  one or more of HMS Investments, Inc., Herley
     Wireless Technologies, Inc., Terrasat, Inc., General Microwave Corporation,
     General Microwave Israel Corporation,  Herley-CTI,  Inc., Herley-RSS, Inc.,
     Micro Systems,  Inc., Innovative Concepts,  Inc., HMS Trading, Inc. and any
     additional U.S.-domiciled  subsidiaries which Borrower or any Guarantor has
     created or  acquired  or may  create or acquire at any time a Loan  remains
     outstanding  and  unpaid  or any  other  amount  is  owing  under  any Loan
     Document;  provided, however, the terms "Guarantor" and "Guarantors" do not
     include General Microwave Israel, Ltd and EW Simulation Technology Ltd.

     3. That Section 3.4 of the Loan  Agreement be and hereby is amended to read
     in its entirety as follows:

     3.4 Security Agreement.

     The  Agent  shall  have  received  a pledge  of and  security  interest  in
     sixty-six  percent  (66%) of the issued and  outstanding  common  shares of
     General Microwave Israel, Ltd and EW Simulation Technology Ltd.

     4. That Section 6.11 of the Loan Agreement be and hereby is amended to read
     in its entirety as follows:

     6.11 Minimum Tangible Net Worth.

     Permit the Tangible Net Worth of the Borrower,  on a consolidated basis, to
     be less  than  $90,000,000  at the time any Loan  remains  outstanding  and
     unpaid, or any other amount is owing under any Loan Document to any Lender.

     5.  That the  Borrower  reaffirms  and  restates  the  representations  and
     warranties set forth in Section 7 of the Loan Agreement, as amended by this
     Fourth Amendment, and all such representations and warranties shall be true
     and correct on the date hereof with the same force and effect as if made on
     such date, except as they may specifically refer to an earlier date(s). The
     Borrower  represents  and warrants  (which  representations  and warranties
     shall  survive  the  execution  and  delivery  hereof) to the Agent and the
     Lenders that (i) this Fourth Amendment has been duly  authorized,  executed
     and delivered and constitute a legal,  valid and binding  obligation of the
     Borrower,  and is  enforceable  in  accordance  with  its  terms;  (ii) the
     Borrower  is not in default  under the Loan  Agreement  or any of the other
     Loan  Documents,  and the  Borrower is in full  compliance  with all of the
     terms and conditions thereof;  (iii) no event exists, or is likely to exist
     in the  future,  which with the  passage  of time,  notice,  or both,  will
     constitute  a default  under the Loan  Agreement  or any of the other  Loan
     Documents;  and (iv) there  have been no  material  adverse  changes in the
     Borrower's financial condition or operations which would cause the Borrower
     to be in default under any of the financial covenants contained in the Loan
     Documents.  Borrower  shall  update  all  Schedules  as of the date of this
     Amendment.

     6.  That the terms  and  conditions,  paragraph  sections,  collateral  and
     guaranty requirements, representations and warranties of the Loan Agreement
     and Loan  Documents,  together with all  understandings  by and between the
     parties to this  Fourth  Amendment  evidenced  by  writings  of the same or
     subsequent  date not in conflict  with the above  modifications  under this
     Amendment  shall  remain in full force and effect as the  agreement  of the
     parties  relative to the Loans,  and are hereby  ratified,  reaffirmed  and
     confirmed.  Any past,  present or future  delay or failure of the Agent and
     the  Lenders  to  demand or  enforce  strict  performance  of each term and
     condition of the Loan Agreement and Loan Documents,  and any past,  present
     or future  delay or failure of the Agent or the  Lenders  to  exercise  any
     right, power or privilege shall not be deemed or construed as a waiver with
     respect to the same or any other matter, or preclude the future exercise of
     such right, power or privilege, or be construed or deemed to be a waiver of
     or acquiescence in any such default.

     7. That all  references to the Loan  Agreement,  the Loan Documents and the
     other  documents  and  instruments  delivered  pursuant to or in connection
     therewith,  as well as in writings of the same or  subsequent  date,  shall
     mean the Loan  Agreement as amended hereby and as each may in the future be
     amended, restated, supplemented or modified from time to time. Further, all
     references to Allfirst Bank in the Loan  Agreement,  the Loan Documents and
     the other documents and instruments  delivered pursuant to or in connection
     therewith  shall be deemed to have been made and to refer to  Manufacturers
     and Traders Trust  Company,  a New York banking  corporation,  successor in
     interest to Allfirst Bank.

     8.  That the  parties  hereto  shall,  at any  time,  and from time to time
     following the execution of this Fourth  Amendment,  execute and deliver all
     such  further  instruments  and  take  all such  further  action  as may be
     reasonably necessary or appropriate in order to carry out the provisions of
     this Fourth Amendment.

     IN WITNESS WHEREOF, and intending to be legally bound hereby, the Borrower,
     the Lenders and the Agent have caused this Fourth  Amendment to be executed
     by their proper corporate  officers thereunto duly authorized as of the day
     and year first above written.

ATTEST:                             HERLEY INDUSTRIES, INC.,

    /S/      Thomas V. Gilboy       By: /S/      Anello C. Garefino
- -------------------------------     --------------------------------------------
Title: Chief Financial Officer      Vice President - Finance



                                    MANUFACTURERS AND TRADERS TRUST COMPANY,
                                      successor  in interest to Allfirst  Bank,
                                      in its  capacities  as Agent and Lender

                                    By: /S/      Eric Rebert
                                    --------------------------------------------
                                    Administrative Vice President

                                    FULTON BANK

                                    By: /S/      William T. Kepler
                                    --------------------------------------------
                                    Senior Vice President