Hi Dennis,
Fixed vacuum caps seem to be extra cheap on Ebay, of
coarse you'd have to test them for value and probably
a high pot.
I will say that I've used a variety of surplus caps for
a few applications, but their makeup is/was unknown
to me.
I have some surplus door knob caps I removed from
a serious laser rebuild that I'm pretty sure would
handle the job, but again the mfgr is unmarked.
Many of the lasers I work with have substantial
numbers of high current caps, sort of a gold mine
for amp builders working "in the industry".
The value might be a non standard 882pf type of
thing, but I might be able to provide some closer
values.
Email me direct if you're seriously interested in
trying one out. I have enough of these caps now
that I can spread some out for a serious cause.
cheers
skipp
nospam4me@juno.com
--------- Forwarded message ----------
From: Dennis Ashworth <K7FL@ARRL.NET>
To: amps@contesting.com
Date: Sat, 04 Oct 2003 16:27:16 -0700
I need to insert a 1000pf of capacitance in series with my 80M vertical
to
move the resonant frequency up to the phone band. I have been using a
vacuum variable, but would like to use it in another project - and change
to a fixed capacitor. The logical choice would be a fixed 1000 pf vacuum
capacitor. Failing to locate a fixed vacuum cap, what low loss dielectric
materials should I be considering given the frequency, voltage and
current
involved. The driving impedance is 40 ohms and I run the legal limit.
Therefore, currents will be in the 6-8A range ... voltages probably less
than 500 V.
Thoughts on dielectric materials and sources would be most appreciated.
Although this is not AMP related, I suspect you folks know the answer(s).
Dennis, K7FL
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