Carel, dielectric losses in PTFE are many times lower than the dielectric
material in ceramic capacitors. Your idea should work just fine
electrically. Your challenge will be the mechanical design to keep the PTFE in
place. I
suppose you could use circular shaped insulators so that their position
makes no difference in operation.
Please do let us all know how your novel idea works out.
73,
Gerald K5GW
In a message dated 3/15/2010 3:36:46 P.M. Central Daylight Time,
pc5m@xs4all.nl writes:
Hi, I would like to get the opinion of this group on constructing a
homemade
variable 500 pF/1nF capacitor for my new 160mtrs amp. To get sizes down I
am
considering using 1mm (40 mill) thick teflon sheet material as dielectric
(10 times or so capacitance increase when comparing with air construction).
So a sandwich of several stator-PTFE-rotor-PTFE-stator-etc, etc. Capacitor
stress will be around 5KV and 20 Amps of RF current.
Did google a bit,but no hits.should this be attainable ? I think losses of
PTFE are well enough at 2 MHz to cause any heating or change in Eps
R/capacitance and 40 mill will provide enough rigidness and stability ?
Thanks, Carel
p.s. Yes, of course I do know that vacuum capacitors do exists ...
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