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Re: [Amps] Triband balun

To: amps@contesting.com
Subject: Re: [Amps] Triband balun
From: donroden@hiwaay.net
Date: Tue, 18 Mar 2014 14:58:55 -0500
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REACTANCE

Don W4DNR




Quoting Jim Brown <jim@audiosystemsgroup.com>:

On 3/18/2014 8:49 AM, Gary Smith wrote:
I'm going to try the 10 rolls of coax again, this time alone.

Contrary to popular mythology, a coil of coax is NOT an effective common mode choke, because it is inductive. An effective common mode choke must have a large value of resistance at the frequency of interest. Only a multiple turns wound through suitable ferrite cores to form a low Q parallel resonant circuit are effective, and a LARGE value of parallel resistance is needed both for power handling and for noise suppression.

See the "Cookbook" in k9yc.com/RFI-Ham.pdf for specific bands and combinations of bands. 4-5 turns of RG-213-size coax through 5 #31 or #43 Fair-Rite cores covers 20-10M effectively.

73, Jim K9YC


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