SF6 is sulphur hexaflouride. It's a dielectric gas, not an oil. For everyone thinking about oil there is also silicone oil available. I have no idea if its better or worse for rf though -- like Tom said, dielectric oils aren't usually specified for rf performance.
-Bill Sent from my iPhone On Feb 2, 2014, at 8:16 AM, "Tom W8JI" <w...@w8ji.com> wrote: > The major issue with dielectrics is dissipation factor at 2 MHz, which > affects losses and Q. Dissipation factor is not published all the time. I > can't find dissipation factor for mineral oil. > > > > ----- Original Message ----- From: "Bill Wichers" <bi...@waveform.net> > To: "Tom W8JI" <w...@w8ji.com> > Cc: "HAROLD SMITH JR" <w0ri...@sbcglobal.net>; "Shoppa, Tim" > <tsho...@wmata.com>; <n...@contesting.com>; <topband@contesting.com> > Sent: Saturday, February 01, 2014 4:05 PM > Subject: Re: Topband: Submerging variable caps in oil as substituteforvacuum > variables > > > 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" <w...@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. >> >> >> _________________ >> Topband Reflector Archives - http://www.contesting.com/_topband > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2014.0.4259 / Virus Database: 3684/7051 - Release Date: 02/01/14 > > _________________ Topband Reflector Archives - http://www.contesting.com/_topband