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Re: [RFI] 120Hz period noise ID

To: "Leigh L Klotz, Jr." <Leigh@WA5ZNU.org>,"rfi@contesting.com" <rfi@contesting.com>
Subject: Re: [RFI] 120Hz period noise ID
From: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 30 Oct 2007 23:18:56 -0700
List-post: <mailto:rfi@contesting.com>
On Tue, 30 Oct 2007 23:04:05 -0700, Leigh L Klotz, Jr. wrote:

>I showed him a similar LV lighting system I 
>have (no dimmer though) and how it was 100% quiet with a transformer.  

The "electronic transformers" are NASTY RFI generators -- they're 
really switching power supplies.  The only fix I know of (short of 
replacing them) is to add a REALLY GOOD RF filter between them and the 
power line. The filter must go right next to the "electronic 
transformer" and the case of the filter ("ground") must have a VERY 
short bond to the case of the "electronic transformer."  The SAFETY 
GROUND must, of course, be carried through the filter, but a connection 
to EARTH is not part of the solution to the problem. The filter keeps 
the noise off the power line so that it can't radiate.

BTW -- I see you're in Palo Alto. HSC (Halted) has a great collection 
of power line filters at very low prices. The practical problem with 
all of this is that most electrical backboxes don't have room to mount 
them effectively (nor to house a transformer big enough to run the 


Jim K9YC
Santa Cruz

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