[RFI] RFI to a Home Theater System

Ed Richardson ed_richardson at shaw.ca
Fri Feb 27 11:09:11 PST 2009

Well this problem does not appear to be going away any time soon. As a recap, RFI to neighbor's Polk Audio subwoofer on all bands with any more than about 75 watts. Separation is 75-100' from antennas.

Neighbor is not very cooperative but has
granted me a small window to install some filters after he returns from a
Mexican vacation. I want to make optimal use of this time so I want to prepare
as much as possible ahead of time. I have read Jim Brown’s article as well as W1HIS’s
web article.  I have
armed myself with 100 of the 2.4”OD mix 31 rings as well as 30 of the big Clamp
on units.

 I am also
considering bringing over a Tripplite Line conditioner, that supposedly has a 75
db of common mode rejection at 1MHz on the AC line.This sub
woofer is so sensitive, that it howls when a 5 watt UHF portable is keyed up in
the same room. The engineers at Polk Audio have been able to reproduce the problem
in their lab and short of placing the amp in a Faraday cage, they have no
suggestions. (Jim Brown I have passed along your name and article to them-thanks for the offer)

What methods have others found most useful? Using binocular configurations or simple wound torroids with 10-14 turns? Are we looking at multiple fiter types to solve the problem?
In this case, the audio input to the sub is via a shielded coaxial cable (The higest quality/cost bestest in the world, Monster cable). Removing this cable from the sub does not correct/improve the problem. This makes me think that the RFI is coming in via the AC line or directly through the non shielded case.
Would differntial mode filters likely also be required?
 Any other hints
on placement of filters and the configurations you found most useful would be appreciated/


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