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Re: [RFI] USB qrm - what to do?

To: "'Pete Smith N4ZR'" <n4zr@comcast.net>, "'RFI List'" <rfi@contesting.com>
Subject: Re: [RFI] USB qrm - what to do?
From: "David Harmon" <k6xyz@sbcglobal.net>
Date: Mon, 13 Mar 2017 08:31:49 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
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
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

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