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Re: [TowerTalk] RFI WITH MY NEIGHBOR...HELP!

To: "Tower" <towertalk@contesting.com>
Subject: Re: [TowerTalk] RFI WITH MY NEIGHBOR...HELP!
From: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 28 Dec 2008 13:03:46 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
The On Sun, 28 Dec 2008 20:39:43 -0000, Jim Hargrave wrote:

>Tony,

>I would first replace the DVD cable with one that each line has individual
>shields. You might want to go with individual cables. Normally single cables
>are shielded. If you have a three wire Siamese cable, I'm surprised it would
>not be shielded.

You would be barking up the wrong tree!  This is not a shielding problem, it 
is likely to be a pin 1 problem. One or more cables in the neighbor's system 
is acting as a receive antenna and coupling your RF into some part of the 
audio system that is detecting it. The most practical solution is usually to 
block the antenna current with a common mode choke, or to divert it away from 
the entertainment system. 

The other VERY common coupling mode is the loudspeaker wiring, which couples 
RF into the output stage. All output stages use negative feedback to reduce 
distortion and noise. Any RF present on the output wiring is coupled by that 
feedback network back to the input, where it is detected. This coupling can 
also be fixed with a common mode choke. It can also usually be fixed by 
replacing parallel wire speaker cable (glorified zip cord) with twisted pair.

See http://audiosystemsgroup.com/RFI-Ham.pdf for more detailed explanation and 
advice on this. 

73,

Jim Brown K9YC




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