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Re: [RFI] GFCI

To: rfi@contesting.com
Subject: Re: [RFI] GFCI
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 17 Oct 2010 08:24:57 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
  On 10/17/2010 7:38 AM, K1TTT wrote:
> I would try swapping it with one that doesn't make the noise and see if the
> noise follows it.

Yes, I would suspect a bad GFCI, which is quite common. BUT -- there 
might also be a wiring error. Carefully check that all the colors are 
correct on every outlet, not only on that bad one. If that isn't the 
problem, replace the bad one.
> otherwise maybe some ferrites on the romex would reduce the level enough.

Yes, that might help. BUT -- you will need multiple turns through the 
ferrite to make a dent.  Study my measured data in 
http://audiosystemsgroup.com/RFI-Ham.pdf  to see what it takes to move 
the resonance of the choke to the TX frequency(ies) where you are having 
problems.

>   Or even plug in a power strip with a line filter and see
> if that reduces the signal level enough to stop the noise.

That is as likely to CAUSE a problem as to fix it. A GFCI works by 
sensing the balance between current in the black wire and the current in 
the white wire. When that difference exceeds about 5mA, it trips. That 
difference is the result of leakage current, which is due to 
capacitance. Adding a line filter will add capacitance, which will make 
the breaker more likely to trip.

73, Jim K9YC

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