Air (or epoxy -- doesn't matter as long as the relative permeability is
1) gaps between the particles will have a much greater impact on the
characteristics than the steel itself. Compared to the steel itself, the
material will have much lower permeability, much higher saturation flux
density, and much lower hysteresis. I'll bet the repeatability will be
pretty awful.

Roy Lewallen, W7EL

Tim Wescott wrote:
wrote:

Anyone have a guess as to the permeability of steel filled epoxy?

Was sort of wondering what would happen if one tried to make RF
inductor or transformer (torroid, etc) cores out of the stuff...

with care, it can even reproduce threads, so tuneable slugs might be
possible.

It's available as putty in tube form in many hardware stores, and as a
castable liquid from industrial supply catalogs - though obviously if
ordering something from a non-local supplier, it might as well be a
proper core from Amidon.

(and yes, I may go ahead and try it... soon as I get my workbench set
back up to the point where I could build something to measure the
results)

I would expect that you would have problems with loss due to hysteresis
in the steel. A good big pile of rust may be better.

I wonder: if you had your Jr. Experimenter's Chemistry set and a pile of
iron filings, what would make the best core material?