I contacted George A. Sanford about the oil used in the variable cap in the
HP4815a and he replied that the oil was used for a shock absorber effect for
frequency stability in the instrument and not for any other reason. I had a
need for a vac variable and have a large air variable that I had planed to
submerge in oil, but have not yet found a suitable oil.
73 es DX Pat H. Armstrong KF5YZ
Carl k...@jeremy.mv.com wrote:
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_equipm...@yahoogroups.com
Carl
KM1H
- Original Message -
From: Hardy Landskov n...@cox.net
To: Tom W8JI w...@w8ji.com; Bill Wichers bi...@waveform.net
Cc: n...@contesting.com; topband@contesting.com; HAROLD SMITH JR
w0ri...@sbcglobal.net; Shoppa, Tim tsho...@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 w...@w8ji.com
To: Bill Wichers bi...@waveform.net
Cc: n...@contesting.com; topband@contesting.com; HAROLD SMITH JR
w0ri...@sbcglobal.net; Shoppa, Tim tsho...@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 bi...@waveform.net
To: Tom W8JI w...@w8ji.com
Cc: HAROLD SMITH JR w0ri...@sbcglobal.net; Shoppa, Tim
tsho...@wmata.com; n...@contesting.com; topband@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 w...@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
-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4259 / Virus Database: 3684/7051 - Release Date: 02/01/14
_
Topband Reflector Archives - http://www.contesting.com/_topband
_
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: 3684/7053 - Release Date: 02/02/14
_
Topband Reflector Archives - http://www.contesting.com/_topband
_
Topband Reflector Archives - http://www.contesting.com/_topband
