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[Towertalk] 20 Meter J Antenna and Noise

To: <towertalk@contesting.com>
Subject: [Towertalk] 20 Meter J Antenna and Noise
From: ccc@space.mit.edu (Chuck Counselman)
Date: Sun, 20 Oct 2002 22:50:51 -0400
Bob Farkaly wrote:
>  Any advice on how to tame a Sony TV would be welcome.


1. First, install a good L-C line filter such as Corcom's two-stage 
filter, in the TV set's line cord.  It'll block both common- and 
difference-mode RFI.  If you can't wait to find one at a hamfest, 
order one (or more, incl. ones for all your ham gear) from Digi-Key.

2. A ferrite-core common-mode choke on the line cord is not so likely 
to do the job because the RFI generated by a switching p.s. is not 
common-mode.  It's primarily difference-mode, although it gets 
converted to common-mode in your household wiring because the latter 
is severely unbalanced for RF.

3. I'd still put ferrite-core common-mode chokes on all cables 
connected to the TV, including the line cord, antenna cable, cables 
to & from VCR, DVD player, etc.  However, a once-through-the-hole 
core such as you'll find at Radio Shack has too little impedance to 
do much (if any) good at 14 MHz.  Use a dozen turns on an FT-240-43 
toroid.

4. Put ferrite-core common-mode chokes on your ham antenna feedline, 
so that it doesn't conduct crap from the AC line (incl. the third 
wire) out to your antenna.

73 de Chuck, W1HIS

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