----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <amps@contesting.com>
Sent: Friday, August 26, 2011 2:58 PM
Subject: Re: [Amps] Ferrite toroids
> On 8/26/2011 5:33 AM, Carl wrote:
>> Its not 100% but close
>> enough since ferrites have a wide production tolerance.
>
> DANGER, WILL ROBINSON! Ferrite materials have VERY different
> characteristics as a function of frequency. This simple-minded sort of
> procedure only tells you about the low frequency behavior of the core --
> that is, well below the self resonance of the core with the conductor
> passing through it. A much more sophisticated approach is needed to
> understand the characteristics at HF and VHF.
Danger yourself. Ive yet to find an unknown ferrite that cant be tested with
simple methods to get a ballpark indication. Then its a simple matter of
reading the various catalogs to ID with a reasonable certainty.
And of course you neglected (or was it selective amnesia) to read the rest
of my post which included using a signal generator.
> Anyone wanting to characterize a ferrite material would do well to first
> study my tutorial and then the Fair-Rite catalog. Fair-Rite is
> certainly not the only company making ferrites, but they are by far the
> dominant one in North America, and their catalog provides 100 times the
> information of all the other manufacturers combined. You can actually
> LEARN a lot from studying their catalog. Virtually all ferrite materials
> commonly sold to hams are made by Fair-Rite.
I do agree about the Fair-Rite catalog; Ive been following it for almost 30
years. Its the first place Id suggest if one is interested in RF ferrites.
> 73, Jim Brown K9YC
Carl
KM1H
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