FW: [RFI] Spray Shielding?

Hare, Ed, W1RFI Hare, Ed, W1RFI" <w1rfi@arrl.org
Mon, 12 Jun 2000 16:02:08 -0400

I received a personal inquiry I am reposting with permission.

Ed Hare, W1RFI
ARRL Laboratory Supervisor
225 Main St
Newington, CT 06111
Tel: 860-594-0318
FAX: 860-594-0259
Internet: w1rfi@arrl.org
ARRL Web: http://www.arrl.org
ARRL Technical Information Service: http://www.arrl.org/tis/

-----Original Message-----
From: Terry Dunlap [mailto:kk6t@joneslumber.com] 
Sent: Monday, June 12, 2000 3:49 PM
To: Hare, Ed, W1RFI
Subject: RE: [RFI] Spray Shielding?

Hi Ed,

I have toroids on both the cables coming out of the monitor and these
help but certainly don't cure the problem.

And sure, go ahead and post my question to the reflector.

73 de Terry KK6T

At 03:36 PM 6/12/2000 -0400, you wrote:

>Generally, yes, one would have to ensure that the shielding material is
>connected to the chassis ground.

>BTW, in my enthusiasm to answer the question, I didn't mention what one
>other fellow did; try the more conventional cures first.  Many times, the
>monitor or computer circuitry is not radiating directly, but is radiating
>through the interconnecting wires.  Using ferrite material on the external
>wiring would be a logical first step.  Palomar
>http://www.arrl.org/cgi-bin/tisfind?patt=Palomar+Engineers or
>http://www.palomar-engineers.com/ sells suitable ferrite materials.
>Generally, for upper HF and VHF, either a toroidal core or several of the
>clamp-on or split-bead ferrites will work well; for lower HF, you usually
>need to use a toroidal core to get enough inductance.
>If you do resort to shielding spray, keep two things in mind. First, some
>equipment may have a "live" chassis and in spraying the case, if you bring
>that chassis ground outside the equipment, you may create a shock hazard.
>Remember also that it is paint, and if the surface is not clean, it can
>flake off later, probably causing damage.
>For general info on computer RFI, see
>BTW, this is a good question; do you mind if I share it on the reflector? 
>Ed Hare, W1RFI
>ARRL Laboratory Supervisor
>225 Main St
>Newington, CT 06111
>Tel: 860-594-0318
>FAX: 860-594-0259
>Internet: w1rfi@arrl.org
>ARRL Web: http://www.arrl.org
>ARRL Technical Information Service: http://www.arrl.org/tis/

>-----Original Message-----
>From: Terry Dunlap [mailto:kk6t@joneslumber.com]
>Sent: Monday, June 12, 2000 1:58 PM
>To: Hare, Ed, W1RFI
>Subject: RE: [RFI] Spray Shielding?
>When you use these shielding products, do you need to somehow ground
>73 de Terry KK6T

FAQ on WWW:               http://www.contesting.com/FAQ/rfi
Submissions:              rfi@contesting.com
Administrative requests:  rfi-REQUEST@contesting.com
Questions:                owner-rfi@contesting.com