Minicircuits coats their cores with "Parylene". The cores are conductive
like FairRite73 and are in fact probably similar material. A long time
ago, a batch of uncoated cores managed to find their way into a bunch
of ASK-1 mixers. We had a special application at HP where we put a DC
bias on one of the windings. Most users do NOT do this. These
defective mixers caused a devil of a problem because they didn't
just fail outright. They would get noisy when DC was applied
and eventually short out the DC. It took us 6 months to get MCL
to admit the problem.
What I learned from this is that you should not wind ordinary
enameled wire on conductive cores even if it seems to be OK
at first. It may be a time bomb.
Rick N6RK
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