Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!hodge!jdm
From: jdm@hodge.UUCP (jdm)
Newsgroups: comp.sys.ibm.pc
Subject: Eating RFI with copper foil
Keywords: RFI
Message-ID: <15763@hodge.UUCP>
Date: 17 May 89 18:45:47 GMT
Organization: Hodge Computer Research Corporation
Lines: 35


> | One way of turning a Class A into a Class B is to put conductive paint all
> | over the inside of the box; any experience with this ?

I have an old H/Z-89A that puts out RFI in bucket-loads.  The worst offender
on any computer is the keyboard.  It dosen't take a HAM operator to realize
that the foil grid pattern on the keyboard's PC board acts like an antenna
boardcasting RFI right into your face.

My solution was adhesive-backed copper foil like they use in making
stained glass.  It just so happened that there is a stained glass craft shop
near me and I found that fairly thick copper foil with adhesive 
backing can be bought in any size from large sheets to very thin strips.

I covered every interior inch of the Z-89's plastic case with copper foil.
I then connected all the foil to ground by scraping a corner of the foil,
applying flux, and soldering a copper strip between all the foil sheets.
A quick check of continuity to verify the connections finished the job.

The RFI output was decreased considerably (as demonstrated by a near by
TV set).



-- 

	jdm@hodge.cts.com [uunet zardoz]!hodge!jdm

	James D. Murray, Ethnounixologist
	Hodge Computer Research Corporation
	1588 North Batavia Street 
	Orange, California 92667  USA

	TEL: (714) 998-7750	Ask for James
	FAX: (714) 921-8038	Wait for the carrier