Topband: Toroidal common mode choke

[ZR]

----- Original Message ----- 
From: "Tom W8JI" <w8ji at w8ji.com>
To: <topband at 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