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Re: Topband: Toroidal common mode choke

To: <topband@contesting.com>
Subject: Re: Topband: Toroidal common mode choke
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Sun, 18 Nov 2012 18:58:12 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Also the difference between Mix 31 and 43 is not great and was used for decades successfully before 31 was introduced.


For a non-critical application like this almost anything would work with enough core depth and/or turns, but they are not nearly the same. There is a large difference between 43 and 31 material.

31 has an initial perm of 1500 and slopes down with increasing frequency, with a Q of unity at around 3 MHz.

43 has an initial perm of 900 and slopes down at 1 MHz, with a Q of 1 at around 15 MHz.

Both have a curie temp of around 130 C.

About half the permeability is not the same, and the Q=1 being five times higher in frequency is certainly not the same. 31, with lower Q across HF, is a significantly better suppression material.
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