Pete.
I ran into a similar issue.
It was not the individual USB devices, but rather the USB provider (the PC
board with the USB plugs which allowed the USB cables to be plugged in). It
appeared in my case that each USB cable that was plugged in acted as an antenna
and radiated like crazy.
My solution was to get rid of the that computer and replaced it with a quiet
one.
73
Chet VE3CFK
________________________________
From: RFI <rfi-bounces@contesting.com> on behalf of Wes Attaway (N5WA)
<wesattaway@bellsouth.net>
Sent: March 13, 2017 10:11 AM
To: 'Pete Smith N4ZR'; 'RFI List'
Subject: Re: [RFI] USB qrm - what to do?
Pete ... does every device add noise, or is it a specific device? Maybe you
have done this, but you didn't specify this in your post. I would unplug
them (and/or turn them off) one at a time, and then plug them back in one at
a time. You might find out that there is only one item that is the major
culprit.
-------------------
Wes Attaway (N5WA)
(318) 393-3289 - Shreveport, LA
Computer/Cellphone Forensics
AttawayForensics.com
-------------------
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Pete Smith N4ZR
Sent: Monday, March 13, 2017 6:32 AM
To: RFI List
Subject: [RFI] USB qrm - what to do?
My shack computer has 6 different USB devices attached. When I
disconnect all but the keyboard, it cuts the background noise level on
160M by a whopping 25 dB, from S9+18 down to S8 (as monitored by HDSDR
and my QS1R, calibrated by an Elecraft XG3).
What is to be done? It doesn't seemvery feasible to wind each usb cable
on a small type 31 toroid and get enough attenuation . Available
snap-ons all seem to roll off dramatically below 25 MHz. Can a common
mode filter be built using discrete components that will have decent
attenuation at 160 M? Or, maybe, is such a filter available
commercially? I have Googled and reviewed K9YC's tutorial but found
nothing directly apposite.
Thanks for any ideas!
--
73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|