That uses the thermal properties outside a resistor, not dielectric constant
properties in a capacitor :-).
Tim N3QE
----- Original Message -----
From: ZR [mailto:zr@jeremy.mv.com]
Sent: Thursday, January 30, 2014 11:28 AM
To: Tom W8JI <w8ji@w8ji.com>; HAROLD SMITH JR <w0rihps@sbcglobal.net>; Shoppa,
Tim; n4zr@contesting.com <n4zr@contesting.com>; topband@contesting.com
<topband@contesting.com>
Subject: Re: Topband: Submerging variable caps in oil as substituteforvacuum
variables
The large Bird dummy loads use oil up into the low microwave region.
Carl
KM1H
----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: "HAROLD SMITH JR" <w0rihps@sbcglobal.net>; "Shoppa, Tim"
<tshoppa@wmata.com>; <n4zr@contesting.com>; <topband@contesting.com>
Sent: Thursday, January 30, 2014 5:32 AM
Subject: Re: Topband: Submerging variable caps in oil as substituteforvacuum
variables
> 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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