Dear Osten,
"Doorknob" capacitors are manufactured in various "flavors"
and have various applications both in HV-DC and in RF
service.
The numbers HT-50, HT-58, HT-57, HT-59 are all common
to RF service, however, the Temperature Coefficient and
KVaR rating as well as tolerance varies.
Depending upon the application, i.e., Coupling, Padding,
De-Coupling, etc., the Type is important.
Type NPO top the list, with Type N750 right behind.
The HEC company publishes several catalogues of RF
and DC capacitors with excellent guidelines and tables for
RF current, voltage, etc.
For instance, mica doorknobs are plentiful, buit they are useful
under 1MHz. only. Many amateurs use HV rated (read:
No KVaR rating), doorknobs for bypass service and are
playing with firecrackers in their amplifiers.
For a moderately sized amplifier, using HT-57's with N750
ratings makes sense, especiallly when RF currents are expected
in tank circuitry. These devices can carry a couple of amperes
at amateur frequencies, and can be paralleled (except in
DC Blocker service where resonance comes into play) to
provide enough capacitiance.
Hal Mandel
W4HBM
> Are the "door-knob" capacitors sold by RF-parts usable
> as padding capacitors for 160 meters, meaning do these
> manage rather high currents?
>
> 73 de Osten SM5DQC sm5dqc@areteadsl.se
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