----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: <topband@contesting.com>
Sent: Sunday, November 18, 2012 6:58 PM
Subject: Re: Topband: Toroidal common mode choke
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.
On paper I agree but what about real world? Topbanders seemed to do quite
well with the old 43 mix and the resultant lower impedance.
How much is good enough?
I havent changed any of the 43 material in the house since they removed the
noise from each consumer device; some have been in place for over 30 years
going back to the prior QTH. As new stuff is added I use 31 mix, seems to
work the same.
Carl
KM1H
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