Topband: Submerging variable caps in oil assubstituteforvacuumvariables

[Carl]

There are several on the HP forum that are famililar with that product 
Hardy.
I also have one but claim no expertise since it still works well.
hp_agilent_equipment at yahoogroups.com

Carl
KM1H

----- Original Message ----- 
From: "Hardy Landskov" <n7rt at cox.net>
To: "Tom W8JI" <w8ji at w8ji.com>; "Bill Wichers" <billw at waveform.net>
Cc: <n4zr at contesting.com>; <topband at contesting.com>; "HAROLD SMITH JR" 
<w0rihps at sbcglobal.net>; "Shoppa, Tim" <tshoppa at wmata.com>
Sent: Sunday, February 02, 2014 8:58 AM
Subject: Re: Topband: Submerging variable caps in oil 
assubstituteforvacuumvariables


> FYI All,
> The HP4815A Vector Impedance Meter submersed the main tuning capacitor in 
> an oil bath of some kind to get the capacitance up. Apparently dissipation 
> factor was not of concern when the unit was designed. If there are any 
> retired HP folks out there they may be able to identify what they used. I 
> have read some years ago that hydraulic jack oil was very close.
> I need to open mine up and replace one of the capacitors because the 
> oscillator will not start on the higher frequency ranges. I am gun shy at 
> this point until I know exactly what I am dealing with.
> 73 Hardy N7RT
>
>
> ----- Original Message ----- 
> From: "Tom W8JI" <w8ji at w8ji.com>
> To: "Bill Wichers" <billw at waveform.net>
> Cc: <n4zr at contesting.com>; <topband at contesting.com>; "HAROLD SMITH JR" 
> <w0rihps at sbcglobal.net>; "Shoppa, Tim" <tshoppa at wmata.com>
> Sent: Sunday, February 02, 2014 6:16 AM
> Subject: Re: Topband: Submerging variable caps in oil as 
> substituteforvacuumvariables
>
>
>> 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" <billw at waveform.net>
>> To: "Tom W8JI" <w8ji at w8ji.com>
>> Cc: "HAROLD SMITH JR" <w0rihps at sbcglobal.net>; "Shoppa, Tim" 
>> <tshoppa at wmata.com>; <n4zr at contesting.com>; <topband at 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" <w8ji at 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
>>
>>
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>
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