Topband
[Top] [All Lists]

Re: Topband: Submerging variable caps in oil as substituteforvacuum vari

To: "'zr@jeremy.mv.com'" <zr@jeremy.mv.com>, "'w8ji@w8ji.com'" <w8ji@w8ji.com>, "'w0rihps@sbcglobal.net'" <w0rihps@sbcglobal.net>, "'n4zr@contesting.com'" <n4zr@contesting.com>, "'topband@contesting.com'" <topband@contesting.com>
Subject: Re: Topband: Submerging variable caps in oil as substituteforvacuum variables
From: "Shoppa, Tim" <tshoppa@wmata.com>
Date: Thu, 30 Jan 2014 16:32:56 +0000
List-post: <topband@contesting.com">mailto:topband@contesting.com>
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.
>
>
> _________________
> 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: 3684/7045 - Release Date: 01/30/14
> 

_________________
Topband Reflector Archives - http://www.contesting.com/_topband

<Prev in Thread] Current Thread [Next in Thread>