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[Amps] Vacuum Variable Capacitors

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Subject: [Amps] Vacuum Variable Capacitors
From: Rob Atkinson <>
Date: Tue, 19 Mar 2024 05:09:14 -0500
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Let's forget about class C since that's a distraction.  You will
certainly have an RF v. swing well above the plate supply voltage.
Most hams who build amps and use v.v. caps for tuning just find one a
few thousand volts above the dc supply voltage and move on.  Most of
us aren't engineers; I am certainly not.  If ur supply is 2.5 or 3 KV
use a 5 or 6 KV cap.  If it's 6 KV use a 10 KV cap and so on.  If you
have a 3 KV supply and a 3 KV cap it may very well arc over.  If it's
5 KV and it arcs it likely has a leak.  Are there any 3 KV v.v. caps?
The ones I come across are all well above that, because the whole
point is to have high voltage rating and wide range in a small space.
Bread slicers that have a lot of range and voltage rating are huge.
You can get out the books and start calculating what your peak RF v.
is the way an engineer would, and I admire that, and maybe many on
this email list can do it; I lack the patience and time myself so as a
ham, I'll just find a cap a few thousand volts above dc supply, put it
in and cross my fingers, hi.  Of course that may mean spending more
money than I need to.  From a company bean counter's viewpoint, the
main point of engineers in product design is to minimize costs.


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