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Re: [RFI] Good guess as to type of ferrite?

To: rfi@contesting.com
Subject: Re: [RFI] Good guess as to type of ferrite?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 17 Dec 2013 23:20:28 -0800
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On 12/17/2013 9:48 PM, David Cole wrote:
They mostly use Mix43 on monitors...

Or a mix with a similar spec by another mfr. As has been noted, Part 15 compliance essentially starts at 30 MHz. OTOH, a single turn on #43 (one pass through the core) is predominantly inductive below about 75 MHz.

As noted in my RFI tutorial, resistive choking Z is the most useful, because it cannot be resonated by the antenna behavior of the line it's choking. This was known at least as far back as the 1950s -- when researching for my AES paper on the topic, I found applications advice from that time frame making that clear -- but somehow that knowledge died with the retirement of the RFI practitioners of that era. By the time I found those references, I had already come to that conclusion on my own.

73, Jim K9YC

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