From: Roy Lewallen on Fri, Dec 2 2005 4:20 pm

wrote:

Since Bill Amidon sold his business to another company, the "new"
Amidon company has been reselling another company's toroidal core
forms.
. . .

I didn't know that anyone else but Micrometals made powdered iron cores
suitable for RF.

I have a few left-over Arnold Magnetics powdered-iron toroidal
cores that were used by RCA Corporation back in the 70s. For
the high end of HF for maximum Q.

Must have been a pot full of powdered iron core makers during
WW2. I still have some screw-in "slugs" which were sold under
"surplus" in 1948 at H & H Electronics in Rockford, IL. Their
Qs peak at around the bottom of HF. The old AN/PRC-6 Handy-
Talky of Korean War time had little powdered iron slugs for
preset tuning...and it covered low VHF. Collins Radio used
them quite a bit in the now-famous R-390 series of receivers
(besides as permeability-tuned master oscillator).

I'd say that the ham magazine editors didn't get around to
playing much with powdered-iron cores in the last half-century
so not much was stated about them. Few hams had Q Meters at
their disposal (way too expensive) and toroidal coil winding
is a picky thing done by hand. Folks in the RF industry knew
about them long ago.

Amidon never manufactured their own cores. They used to carry
Micrometals powdered iron and Fair-Rite ferrite cores, with a few other
ferrite cores from Magnetics and other manufacturers. Whose cores are
they selling now?

Bill Amidon set up a small packaging business as a sideline
to working at NBC Western Hq in Burbank, CA, many years ago.
He included data from Micrometals and Fair-Rite in those
packages as they applied to the kit. Good deal for the average
hobbyist. Micrometals turns out toroid cores almost like
Krispy Kreme makes donuts in each shop...and they don't make
real money selling in singles or very small quantities. A
reseller/packager like Amidon could make some profit. It
served the more serious home-builder very well, no minimum
quantities and rare Q curve info was included.

At www.amidoncorp.com you can find a line card on PDF as well as
in HTML at that page. The PDF didn't want to download this night
for me...:-) Amidon stocks/distributes Micrometals, Fair-Rite,
Philips/Ferroxcube, Arnold, Ferronics, Chang Sung, American Cores
& Electronics (located in China near Hong Kong), Associated
Components, Coiltronics/Cooper, NEC/Tokin, Coilcraft, Mag-Layers,
AEM, Magnetics Inc.

"Amidon Associates" (the old label for the plastic envelope kits)
is now described as a custom winder of coils under the Amidon
Corporation umbrella.

As to getting toroidal cores in small quantities, I found that
www.partsandkits.com was quite good. Dieter Gentzow, W8DIZ,
has that in Florida. Genuine Micrometals cores from what I
could tell were in my order. Good prices, quick service.