The URL:
http://home.earthlink.net/~w6rmk/ferrite.htm
States:
Identifying Mystery Ferrites
You've seen a big box of cheap ferrites at the surplus place. What kind of
ferrite are they? What's their properties? This question comes up all the
time, so here's some info on identification.
First, the statistical approach... Most all of the shielding ferrites you
see are Fair-Rite Type 43, or the equivalent. The permeability is around
1000 for lowish RF frequencies (<1MHz), and they become mostly resistive.
Measuring using an Antenna Analyzer (as long as it reads both R and X)
(Suggested by Scott Townley) Loop a single wire through the core. Run the
frequency up until R=X. The mix is identified by the following:
Mix 33 - around 10 MHz
Mix 43 - around 20-25 MHz
Mix 61 - around 50-70 MHz
Is there any consensus that this is a valid test procedure?
Ray, W4BYG
"The Republic can survive a fool for a president... It is less likely to
survive a multitude of fools, such as those who made him their president."
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Steve
Hunt
Sent: Sunday, April 13, 2014 4:31 AM
To: Richard (Rick) Karlquist; kz8e@wt.net; towertalk@contesting.com
Subject: Re: [TowerTalk] Measuring Ferrite
That method can work well if you simply want to distinguish between a couple
of cores with widely spaced "cross-over" frequencies; but if the core is a
complete unknown, it may not work so well. For example, take a look at the
Fair-Rite data for #31 vs #79, or #51 vs #44; you'd be hard-pressed to tell
which was which, especially when you then factor in an allowance for
manufacturing tolerance.
Steve G3TXQ
On 12/04/2014 22:25, Richard (Rick) Karlquist wrote:
> If you just want to identify what type of ferrite you have, the
> easiest thing to do is measure the frequency at which the phase of the
> impedance is 45 degrees and then compare this to the frequency where
> the epsilon' and epsilon'' curves cross over.
>
> Rick N6RK
>
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