[Elecraft] HELP! Permeability of Ferrite Cores...

[Jim Brown]

On Fri, 12 Sep 2008 11:15:22 -0700, Dave G. wrote:

>Can nyone provide me with the permeability number for the T37-2 and 
the 
>FT37-43 cores???

I also suggest that you study the material on ferrites in 
http://audiosystemsgroup.com/RFI-Ham.pdf  

The discussion of ferrites in this tutorial is considerably more 
advanced than what's on the Amidon site or in ARRL publications, and 
should give you a much better understanding of ferrites, how they work, 
and how to use them. Tne most important thing to understand is that 
permeability of ferrites is not a single number -- it varies (a LOT) 
with frequency. The commonly published number is the LOW FREQUENCY 
permeability. The second most important thing to realize is that 
ferrites are pure inductors ONLY at low frequencies. As frequency 
increases, resistance and capacitance become increasingly important, 
and at high frequencies R and C dominate (to the extent that there's no 
L!). When we use ferrites to wind coils for transceivers, we mostly 
care about L. When we use ferrites to suppress RFI, we only want R. 

Most (all?) ferrite cores sold to hams by Amidon and others are 
actually made by Fair-Rite, a very good US company based in NY State. 
They publish an excellent catalog that includes extensive data on all 
of their products. 

http://www.fair-rite.com/newfair/index.htm

73,

Jim Brown K9YC