[RFI] toroids

[Michael Tope]

Yes and no, Tom. You can wind a known number of turns on each
toroid and then measure the inductance with an impedance analyzer
like the MFJ-259B. From the physical dimensions of the toroid
(cross section area, Ae and average circumference, Le) and the
inductance measurement, you can calculate the initial permeability
of the material. This will tell you which materials the sample
is probably NOT. It may not, however, tell you exactly which material
the sample IS, since there are a number of materials available with
similar initial permeability. You also have to be careful about what
frequency you use for the measurement as low frequency materials
(like type 77) will start to look very resistive at higher frequencies,
and higher frequency materials (like type 61) may not provide enough
inductive reactance at low frequencies to generate an accurate
reading on the impedance meter (in this case you add more turns
to the test inductor or raise the test frequency).

If you interested I can provide more details.

73 de Mike,
W4EF..................................................................
---- Original Message -----
From: "Tom Horton" <k5iid at sbcglobal.net>
To: <RFI at contesting.com>
Sent: Saturday, August 14, 2004 8:59 PM
Subject: [RFI] toroids


> I have quite a few miscellaneous toroid cores.
> Is there any way to determine what the mix is
> in them?
> I know, it's a silly question, but I get sillier the older I get.
> Thanks, 73, Tom K5IID
>
>
> Tom Horton  K5IID
>  Hillsboro, TX
>
>
>  USA-CA All Counties 661---DXCC---5 BAND DXCC
>  WPX HONOR ROLL---5 BAND WAC---WAZ
>
>  Finally back home in Texas after all these years!
>
> "E" sorter for the ARRL W5 QSL bureau
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