Topband: Submerging variable caps in oil as substitute forvacuum variables

[Bill Wichers]

I was reading this thread and all the concerns about oil in the capacitor. Has anyone ever thought about trying SF6 as a dielectric? It's commonly used in high voltage (hundreds of kilovolts) switchgear by utilities. 

Just a thought, more curiosity than anything else. 

-Bill

Sent from my iPhon

On Jan 30, 2014, at 5:32 AM, "Tom W8JI" <w8ji at w8ji.com> wrote:

> Still I am intrigued by the thought of a remote tuning capacitor via hydraulic tubing :-). The capacitor plates could be as simple as two concentric cylinder conductors with appropriate spacers. I betcha crud collecting on the top of the oil would set voltage limit.>>>
> 
> I would be as concerned, or more concerned, with the dissipation factor of the oil at short wave frequencies.
> 
> The thing that worries me is I cannot recall every seeing a single good high-Q oil-dielectric capacitor above power line and audio frequencies. As a matter of fact, many years ago I tried to use a surplus 20-40kV oil capacitor from Fair Radio as a plate blocking capacitor, and it overheated so badly it exploded.
> 
> I looked for HF data on mineral oil as a dielectric and couldn't find anything. That would be my main concern. I guess I could stick mineral oil between the plates of a capacitor and see what happens to Q.
> 
> 
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