[Amps] PTFE dielectricum variable cap

[Dr. David Kirkby]

pc5m, Carel wrote:
> 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. 


I'd double-check the relative permittivity of PTFE - I don't think it is as high 
  as 10. I don't say this reference can be trusted, but

http://www.microwaves101.com/encyclopedia/permittivity.cfm

says it's 2.2. It is certainly closer to 2 than 10 - that I am sure of.

Dave