[RFI] Filtered connectors for video cable

Jon Ogden jon.ogden@cain-forlaw.com
Thu, 25 Oct 2001 09:07:41 -0500


I didn't read you original message, but after reading it, my guess is that
regardless of what is producing the noise (the video card or the monitor
itself), the video cable is acting as the radiating element.  If it was not,
when you unplug the video cable, the noise would not go away.  But the noise
does go away when you unplug the video cable.  

If it was the monitor that was causing the problem, then also unplugging the
cable from the computer would likely make no difference.

So, if you put the video cable around a large torroid, then that should
suppress all of the junk coming out and you should be fine.



Jon Ogden
Sales Engineer
Cain-Forlaw Company
847-202-9898 (Voice)
847-202-9896 (Fax)

> -----Original Message-----
> From: Pete Smith [mailto:n4zr@contesting.com]
> Sent: Thursday, October 25, 2001 7:09 AM
> To: rfi@contesting.com
> Subject: [RFI] Filtered connectors for video cable
> In a message yesterday I mentioned that the ARRL RFI book 
> referred to these
> devices as a possible solution for RFI caused by the 
> peripheral connections
> of a computer.
> After reading that, and finding a reference to Spectrum Control, Inc.
> filtered connectors in the Mouser catalogue, I went to SCI's 
> excellent web
> site and researched the characteristics of these devices.  So 
> far as I can
> determine, none of the units they make have very much 
> attenuation at low to
> medium HF frequencies.  Their most aggressive filter has only 10 dB
> attenuation at 5 MHz, rising to 30 dB at 50 MHz.  Their 
> target seems to be
> RFI at television and V/UHF frequencies, rather than HF.
> I also received a private e-mail from a subscriber explaining 
> that video
> signals will be adversely affected by any direct filtration 
> that would have
> any useful effect at low HF.  I'm bccing him on this message, 
> and perhaps
> he'll repost that explanation for the general audience, 
> because I think it
> would be of wider interest. 
> 73, Pete N4ZR
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