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 Post subject: Variable Capacitor Sealed In Oil
PostPosted: Dec Tue 19, 2017 2:41 am 
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Joined: Dec Tue 19, 2017 2:33 am
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I came across this variable cap at a junk sale, and was wondering if anyone had any info about it. I put a meter on it and got a reading of (30pf -> 800pf) @ 1kHz) I cannot find anything about it on Internet searches (except for a eBay listing with no information,) just looking for any type of datasheet or information about its original uses. Thank you


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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Dec Tue 19, 2017 1:19 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Somers, CT
It probably was done for two reasons: the oil dielectric would increase the operating voltage and also increase the maximum capacity for the variable capacitor.

Where and why it was used is a mystery; although the owner of the one on eBay is planning an early retirement (a rather optimistic one in my opinion...)

Pete

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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Dec Tue 19, 2017 1:27 pm 
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Just about anything has a higher dielectric strength than air.....
https://en.m.wikipedia.org/wiki/Dielectric_strength

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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Dec Tue 19, 2017 3:25 pm 
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Location: Santa Rosa, CA
Very nice! Thanks for posting the pic. Never seen anything like this.
Steve

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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Dec Tue 19, 2017 3:59 pm 
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Joined: Jan Sat 12, 2008 12:25 am
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Location: Kingwood, Texas
Used one of these in the 1960’s in a 75 meter linear amplifier (3-572B’s). I removed it from a piece of WWII surplus equipment but unfortunately, I can’t remember what it was.


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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Dec Tue 19, 2017 5:23 pm 
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Thanks for the info. I am a new HAM, and was thinking of using it to build a magnetic loop antenna,


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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Dec Wed 20, 2017 8:44 am 
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Joined: Nov Mon 02, 2009 7:01 am
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Location: Lincoln City, OR
Greetings to yavin101 and the Forum:

Reminds me of when I worked for Raytheon Electromagnetic Systems division. I wandered into the main testing floor and they had an ALQ-99 jamming pod running under test on a cart. Due to the high voltages inside the thing, the entire pod was filled with oil. It was pretty strange to see a couple of high voltage scope probes half submerged in oil due to being hooked up to something a ways under the surface.

One had to trouble-shoot it that way, however. If you tried to run it without the oil, it would flash over in a dozen places.

Regards,

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 Post subject: Re: Variable Capacitor Sealed In Oil
PostPosted: Mar Fri 09, 2018 8:42 pm 
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I used it to tune a homebrew long wire antenna. the wire is 256' with a coil. it works well on 80 and 40 meters. SWR of 1.1 at 7.189 MHz and 1.3 on 3.968 MHz. I still plan on building a magnetic loop antenna for 40 and 20 meters.


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