Paul Keinanen wrote:
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.


Magnetic materials do not have a universal colour code like resistors.
Their properties are much more complex, including shape and size, and
the magnetic properties also depend very much on the ingredients and the
processing. Rather like bread, no two products are exactly the same, and
it's hard work for manufacturers to maintain consistent quality even in
the same material.

If someone has good reason to believe that the cores were made in the
USA, then they may well be identifiable from the Micrometals, Amidon or
Fair-Rite catalogs. Unless it's a custom shape, the exact dimensions are
often the best clue about which company's catalogue to look in. Then a
few electrical tests should help to identify one of that company's
standard mixes.

On the other hand, cores from other manufacturers and other parts of the
world could be almost anything! The only thing you know for sure is that
they are NOT made from any "US standard" mix, so they're going to need a
separate drawer or bag of their own.

Living in Europe, I have given up buying surplus cores "just in case"
they might be useful, because they have almost all been a waste of money
and storage space. After wasting time trying to measure and classify
them, they have always turned out to be the wrong material or the wrong
size for what I needed. As a result of that experience, I now keep
almost no stocks of magnetic cores of any kind.

Instead, I keep the money in my pocket, and then buy exactly the right
ones for each project, as and when they are needed.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek