

Article 13619 of rec.ham-radio:
Path: philabs!philmtl!uunet!ginosko!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!att!cbnewsc!parnass
>From: [email-masked] (Bob Parnass, AJ9S)
Newsgroups: rec.ham-radio
Subject: Old article on curing MX-5000 microprocessor RFI
Keywords: scanner, RFI, interference, conductive spray
Message-ID: <[email-masked]>
Date: 23 Aug 89 20:33:26 GMT
Organization: AT&T Bell Laboratories
Lines: 49
Posted: Wed Aug 23 16:33:26 1989

x
   I found at least one old article about  the  RFI  problem
   (microprocessor  noise)  in  the Regency MX-5000 scanner.
   It was entitled "Curing the RFI Problem  in  the  Regency
   MX-5000,"  written  by Dave Buda, WA2RYC, and appeared in
   8/84 Monitoring Times.

   Portions of that article follow:

    "As anyone who has used the new Regency  MX-5000  knows,
   there's  a good amount of interference radiating from its
   internal workings....The problem disappeared as  soon  as
   an outside antenna was connected to the unit."

    "...I decided to make a simple modification that  proved
   to  be  a  great help in eliminating 95% of the radiation
   problem."

    "I contacted Miller-Stephenson" (Danbury, CT 06810)  and
   obtained  a  couple of cans of the RFI-conductive Coating
   Spray.  The MS-485 spays has an attenuation of 78 dB at 1
   MHz  and  44 dB at 1000 MHz with a surface resistivity of
   2.9 ohms per square inch."

    "The manufacturer recommends  you  apply  several  light
   coats to obtain 1.5 to 2 mil coating."

    "I removed the top and bottom covers and the front panel
   as  well.   After  carefully masking the outside of these
   covers I proceeded to spray the inside of the covers  and
   panels with about 4 thin coats as recommended."

    "The spray  dries  quickly  so  the  whole  modification
   shouldn't take more than a half hour."

    "When I replaced the covers, I simply  added  star  lock
   washers  between  the metal chassis and the outer covers.
   This allowed for good contact  to  ground  for  the  now-
   shielded plastic case."

    "The modification was a success.  As soon  as  I  turned
   the unit on again, the RFI problem had disappeared.  Bir-
   dies were almost nonexistent and I was on my way to scan-
   ning again..."

-- 
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Bob Parnass, AJ9S - AT&T Bell Laboratories - att!ihuxz!parnass (312)979-5414