On Fri, 13 Oct 2006 19:59:38 GMT, "Dale Parfitt"
wrote:


"dave" wrote in message
...
Hi all,

Is there an easy way to test surplus toroids as to what mix they might be?
I have some here with no markings (plain black powder) and I would like to
see what frequency ranges they would be useful at. I guess I would have
to
wind up a transformer and plot the frequency response?

Dave

Plain black is likely ferrite. Wind some turns and measure the inductance.
Then resolve the turns/inductance formula for the permeability.
An Amidon or Ferrite catalog will then give you any other charactersitics
you require.
Dale W4OP

There seems to be a misconception that all iron dust cores are made by
Micrometals and often marketed under the Amidon brand name and that
all ferrite cores are made by Fair-Rite :-).

You can not assume that any colour coding system used by some
manufacturer would apply universally.

Paul OH3LWR