[Amps] PTFE dielectricum variable cap

[TexasRF at aol.com]

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 at 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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