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Re: [RFI] Computer birdies

To: rfi@contesting.com
Subject: Re: [RFI] Computer birdies
From: Steve <steve65@suddenlink.net>
Date: Tue, 26 Jun 2012 14:11:09 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Thank you Jim. I happen to have a few #31 cores, 2.4in OD. At the 
computer end of the ethernet cable I began threading the cable through 
the core and made some observations along the way as I measured the 
birdie at 14015KHz on the S meter of my ICOM IC-7800:
turns 0,    S-meter reading    S 8.5
turns 1,    S-meter reading    S 8.5
turns 2,    S-meter reading    S 7.5
turns 3,    S-meter reading    S6
turns 4,    S-meter reading    S4
turns 5,    S-meter reading    S2
turns 6,    S-meter reading    S2
turns 7,    S-meter reading    S1
turns 8,    S-meter reading    no S-meter movement, barely audible

There appears to be a similar reduction in birdie level on the other 
bands. The birdies are not gone but they are now at a level I can live 
with. Wonder if I could get away from them completely by installing a 
wireless card in the Dell Inspirion?

Out of curiosity I switched the cable ends and found that putting the 8 
turns at the router raised the S-meter reading from no movement to S7. 
Evidently the computer is the source of the birdies. So I switched the 
cable back to having the 8 turns at the computer.

A second #31 core with 5 turns at the router made no discernible 
difference in either S-meter reading or to my ear.


Steve K8JQ

On 6/26/2012 10:24 AM, Jim Brown wrote:
> On 6/26/2012 7:16 AM, Steve wrote:
>> Anyone ran into this kind of thing before? Advice as to how to rid
>> myself of these unwanted signals?
> It's the Ethernet stuff related to the router. The cables are acting as
> transmitting antennas, your ham antennas are receiving the noise.  The
> solution is multi-turn ferrite chokes on each of those cables. Five
> turns on a #43 or #31 core will make a nice dent in the noise.  See
> http://audiosystemsgroup.com/RFI-Ham.pdf  for details, and for part
> numbers and vendors for suitable ferrite cores.  EVERY cable can radiate
> the noise, including the power cables, so every cable should be choked.
> 73, Jim Brown K9YC
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