Re: [RFI] Solar panel RFI

[Jim Brown <jim@audiosystemsgroup.com>]

Exactly right! I hadn't seen any of this, but independently arrived at 
the same methods I just posted.
The method depending on dimensions requires integral calculus for cores 
of non-cylindrical shapes (like most clamp-ons) if Ae and le values are 
not known.
73, Jim K9YC

On 2/20/2022 11:04 AM, David Eckhardt wrote:
> FairRite has an excellent presentation on determining ferrite toroid
> material.  All that's required is some method of measuring both the
> physical dimensions of the toroid (a ruler or calipers) and the inductance
> at low frequency (100 to 300 kHz) of 10 or so turns of wire on the toroid.
>    This and many additional "goodies" can be accessed at the following URL
> (scroll down for the ferrite material determination tutorial):
>
>             https://www.fair-rite.com/videos-presentations/
>
> I've used this quite successfully over the last year.  It's golden in
> determining unknown toroids bought at a hamfest.  Also, the distinction
> between 31 (general low frequency) and 43 (generally high frequency)
> material is easy.  43 material consists of NiZn and has an extremely high
> bulk resistivity - above the reach of most DMMs.  31 material consists of
> MnZn and exhibits relatively low bulk resistivity - easily measured by any
> good DMM.  Other than that, refer to the online FairRite video.
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