[RFI] Filtered connectors for video cable

Turner, Robert D. Jr Robert.Turner@ibx.com
Fri, 26 Oct 2001 07:26:37 -0400

I've had some success in moving the interference to a different frequency by
changing the monitor's refresh rate via Windows software configuration.


 -----Original Message-----
From: 	Pete Smith [mailto:n4zr@contesting.com] 
Sent:	Thursday, October 25, 2001 2:34 PM
To:	rfi@contesting.com
Subject:	Re: [RFI] Filtered connectors for video cable

Hi Dale [WA9ENA] -- thank you for all the very good info.  I just
discovered that my new portable shortwave RX has an external antenna jack,
so I will use that and make myself a sniffer as you suggest.

I suspect the video cable chiefly because when I disconnect the video cable
from the back of the computer the noise goes away totally.  When I power
down the monitor, there is little to no change.  Someone suggested, though,
that the video card might automagically stop sending video in the
disconnected state, so you couldn't know for sure.  Does that make sense?

Because of the way my wife has her desk arranged, the PC is 2x6' video
cables from her monitor.  I suppose that poor video cable shielding could
account for a lot of this noise radiation.  There isn't much slack in the
cable -- would it make any sense to get yet another 6' cable and plan on
winding most of its length on a series of toroids to try to get some common
mode attenuation -- or would a leaky shield thereafter defeat the purpose?
Do you know of a maker of better-shielded video cables, short of TEMPEST or
MILSPEC stuff?

I have a new video card on the way - she had wanted one anyway - and
hopefully that will be a quick and dirty solution.  Think I'll build up the
sniffer anyhow...

Thanks again, Dale.

73, Pete N4ZR

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