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Re: [RFI] ebay line filters

To: rfi@contesting.com
Subject: Re: [RFI] ebay line filters
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Mon, 15 Aug 2016 15:24:25 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Mon,8/15/2016 6:49 AM, Doug Powell wrote:
One thing you should realize about line filters is they are optimized for conducted 
line emissions coming from the product where they are built in. This means the line / 
load labeling  ‎will determine your best orientation for connection.

There's another MAJOR problem with commercial line filters -- most of the trash conducted from equipment is on the GREEN WIRE, which goes right past the filter. The specs for these filters CLAIM common mode suppression, but what they're calling common mode is voltage between neutral and ground. That's NOT what WE call common mode, and what WE call common mode is what causes most RFI -- radiation from the power conductors as a long wire antenna.

The most effective line filter for MF and HF radio is a common mode choke formed by winding multiple turns around a #31 Fair-Rite ferrite core, using the guidelines in k9yc.com/RFI-Ham.pdf for coax the same size as the power cable. See Chapter Seven the "Choke Cookbook." Also see http://nccc.cc/pdf/CQP-RFI2013-2.pdf

73, Jim K9YC

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