[Amps] PTFE dielectricum variable cap

[DF3KV]

That will work pretty well.
The loading capacitor in the Tentec Titan 425 is made that way.
There is also a relatively small 3nF unit available in The Netherlands which
I bought them for amplifier projects with Pi-L in favour of a vacuum
variable (too slow on band change).
I already hi pot tested them to 5KV DC without problems.

http://www.elektrodump.nl/data/Content/Images/IMG_0223_01.jpg

http://www.elektrodump.nl/data/html/temp.html?51


73
Peter



-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of pc5m, Carel
Sent: Montag, 15. März 2010 21:36
To: amps at contesting.com
Subject: [Amps] PTFE dielectricum variable cap

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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