[Collins] Identifying BBs

[Dr. Gerald N. Johnson, electrical engineer]

Mica capacitors have a long history and are quite good. Silvered mica
are the elite of the mica family with the best Q and stability. The best
of the ceramic temperature compensating capacitors (which are not common
distributor stock) don't have quite the stability of the silver mica.
Ordinary postage stamp mica capacitors were stacks of loose foil and
mica held together with metal clips and molding in the postage stamp
sized case. Silver mica use silver paint on the mica for the electrodes
and were considered far more expensive to make and when molded in cases
the cases where colored red to signify the better quality. So dipped
silver micas are also colored red. The silver mica capacitors are the
most expensive for the value and they are good. Sometimes one comes up
with stability problems because of an air bubble in the dip, but that's
the exception, not the rule.

Silver micas generally are better than the molded micas and second to no
other type of capacitor for Q and stability. They are available from a
few vendors, including Mouser.

73, Jerry, K0CQ, Technical Advisor to the CRA
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.