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
|