I use Logitech wireless keyboard and trackball.....no cables....no problems.
73
David Harmon
K6XYZ
Sperry, OK
-----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 <rfi@contesting.com>
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
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