On Fri, 23 Jan 2004 14:13:09 -0000, "Graham"
wrote:

I am trying to make some high value toroids, about 1mH. I have a commercial
one using a half inch core with about 20turns on it to give 3.3mH. Does
anyone know what the core material/description is or an UK source please?
The normal ones such as T37-2s etc only give a few uH.

I got some from Bardwells that were about 20mm dia and when
close-wound all round with one layer of 0.7mm enamel wire came out at
exactly 1mH (which was handy since that was the objective!). Give them
a try. They do mail order and are very reasonable.
--

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