I personally found, with my router and computers that the computer was the
really bad end, but putting cores on both ends helped too, as there was some
low level stuff coming from the router
Sent from my phone, please excuse any mistakes
73 de KG2V
----- Reply message -----
From: "Steve" <firstname.lastname@example.org>
Subject: [RFI] Computer birdies
Date: Tue, Jun 26, 2012 2:11 pm
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.
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
> RFI mailing list
RFI mailing list
RFI mailing list