On 6/16/21 4:07 PM, Jim Brown wrote:
On 6/16/2021 2:39 PM, Dan Maguire wrote:
I never found an actual datasheet for Amidon type 31. A link to a
page showing the u'/u'' plots, not just physical dimensions, would be
much appreciated. Amidon has not responded to email requests.
Amidon is not a manufacturer, they are a distributor/reseller, and
they've been selling stuff at VERY high markups (like $15 for a part
that costs them less than $3) for years, having invented part numbers
like 240-xx. The manufacturer of the parts identified with Fair-Rite
mix numbers is Fair-Rite, an old line US company. Many manufacturers
make mixes similar to their #43 and their #61. The chemical recipes
for some of these materials is a closely guarded secret. The
properties of #31 is quite special compared to other MnZn materials.
Many years ago there was a ham named Amidon. Long SK.
Here's what I know...
Bill Amidon, in North Hollywood, literally in his garage (the Otsego st
address is in a residential area), bought wholesale and repackaged for
ham and entertainment industry use in little envelopes. He published a
giant tissue paper datasheet that you unfolded like a map. A fairly
steep markup as I recall, but back then, the mfrs only sold substantial
quantities (100s) - I think Palomar Electronics did the same sort of thing.
He sold out quite a while ago, I'm thinking the 80s - The company got
into the magnetic recording head business (that may also have been part
of Bill Amidon's business) and moved down into the South Bay (Torrance
or somewhere like that) to be close to Ampex and similar suppliers. They
grew, and then split into the "recording head" and the "ferrite
components" businesses - the recording head business long ago collapsed
(not just for them). I honestly don't know why they even still sell in
small retail quantities. Amidon Associates was founded in 1990, and I
think that's roughly the time of the split up.
Fair-Rite was owned by a husband and wife team, and I met them in
2004-5 at an IEEE EMC conference where I was presenting a paper. She
was the EE, he was the ChemE. They retired a few years later, but last
I heard, the company is still owned by the family. Don't know if
they're still alive.
73, Jim K9YC
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