Page 10 of K9YC's Noise Suppression Manual suggest 7 turns on a
0431177081 Snap-on for 80/160. I think 7 turns will fit in
there. I've got an HDMI cable with 5 turns, and it looks like I
could jam two more turns in there. How about trying a USB Hub,
with one of those chokes between the hub and the computer?
Dave Hachadorian, K6LL
Yuma, Arizona
-----Original Message-----
From: Pete Smith N4ZR
Sent: Monday, March 13, 2017 4:31 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
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