Very true but the RF is still in the oil "dielectric" from the coax
connector to the hot end of the resistor.
Carl
KM1H
----- Original Message -----
From: "Shoppa, Tim" <[email protected]>
To: <[email protected]>; <[email protected]>; <[email protected]>;
<[email protected]>; <[email protected]>
Sent: Thursday, January 30, 2014 11:32 AM
Subject: Re: Topband: Submerging variable caps in oil as substituteforvacuum
variables
That uses the thermal properties outside a resistor, not dielectric
constant properties in a capacitor :-).
Tim N3QE
----- Original Message -----
From: ZR [mailto:[email protected]]
Sent: Thursday, January 30, 2014 11:28 AM
To: Tom W8JI <[email protected]>; HAROLD SMITH JR <[email protected]>;
Shoppa, Tim; [email protected] <[email protected]>;
[email protected] <[email protected]>
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" <[email protected]>
To: "HAROLD SMITH JR" <[email protected]>; "Shoppa, Tim"
<[email protected]>; <[email protected]>; <[email protected]>
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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