[600MRG] Ferrite cores

[Rudy Severns]

Following up on my earlier comments on ferrite cores for 600m.  I went to
the www.mouser.com web page and checked out the availability of cores.  I
also went back through the Fair-Rite catalog reading the material
descriptions to jog this old memory.

A few comments:

1) The type 31 material is MnZn but it's primarily for EMI suppression.
The range of core sizes is limited and I wouldn't recommend it for 
transformers and
inductors anyway.

2) I looked over the Fair-Rite MnZn materials and it appears to me that the
77 material is really the most appropriate for 600m.  Fortunately Mouser 
(and
I'm sure other suppliers) has a great selection of toroids in stock.  One is 
4" in
diameter by an 1" thick!  Of course those are $40 a pop.  The smaller ones
are much cheaper.

3) Fair-Rite also has EE, EI, EER, etc cores in 78 material as well as some 
new material, 95 and 98, which I haven't had a chance to evaluate.

4) For an inductor with a ferrite core you will need to use an air gap.  The 
EE, EI, UU, etc cores make this easy and Fair-Rite has applications 
information on AL and gap lengths.

5) The ARRL used to sell a very nice book by Doug DeMaw "Ferromagnetic-Core 
Design & Application Handbook".  I don't think it's for sale anymore but if 
you can get your hands a copy grab it!  If I put together a monograph for 
600m magnetics I would shamelessly plagiarize DeMaw!

6) Besides Fair-Rite, TDK also has a large line of ferrite cores although I 
haven't looked at the material characteristics for years so no 
recommendations.  Mouser sells some TDK cores.

What this discussion has done is to prompt me dredge up things I haven't 
thought about for years which is kind of fun.  I'll have to give some 
thought to some guidelines at least.

GL and 73, Rudy