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Date: Wed, 11 Nov 2009 09:34:21 -0500 (EST)
From: Chris Trask <christrask@earthlink.net>
To: rsgb_lf_group@blacksheep.org, rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Ferrite characteristics
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>
> Does anyone know of a method of measuring the characteristics 
> (permeability) of ferrite cores?  I have a box of these most
> without any identification although I do have T200, 68-2T and
> T68-2s whose characteristics are known.
>
> It occurs to me that you can make a tuned circuit and measure
> resonance with a GDO when a ferrite core is inserted into the
> inductance. A graph could be made of the different resonances
> with different cores, to extrapolate the unknowns.
>
> However I think that ferrite bulk might be a problem. For example
> I guess the red T cores use the same material but would there be
> a difference between the T200 and the T68?
>

     Since some are coloured, you can reasonably assume that they are powdered iron rather than ferrite as the ferrite manufacturers, particularly Fair-Rite and Ferronics, normally don't colour code their products, though Ferroxcube does.  These two Micrometals URLs should help:

     http://www.micrometals.com/materials_index.html

     http://www.micrometals.com/materials_index.html

     Unfortunately, the tables provided by Ferroxcube do not provide the colour coding information, so you'll need to go through the individual datasheets:

     http://www.ferroxcube.com/prod/assets/sfmatgra_frnt.pdf

     The recent reply by Marco provided a reasonable approach to sorting out the permeability:

>
> just my 2 Eurocents...  wound a few (5 to 20) turns, measure
> L and take physical dimensions of the toroid, use G4FGQ's
> toroid.exe, and then play with the parameters in the program
> to find wich permeability gives the L you measured. The
> program is pretty accurate, Reg did a nice job.
>


Chris

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