LC Oscillator Stability

[pwdrive]

From the Tesla Technical Reports December 1949:

http://www.mikrocontroller.net/attachmen...epaper.pdf

I was looking for info on a stable LC valve oscillator in order to try and reduce the effects of oscillator shift due the to varying the regen within a pentode regen det circuit.
I was trying to find out what I could about the Lampkin oscillator, there is almost no free documentaion available on the Lampkin oscillator (G.F. Lampkin) on the web.
A bit of digging produced the above link in which the Lampkin oscillator is mentioned and disscused in part, however, I found the whole article quite interesting as regards LC oscillator stability using valves is concerned.
It also caught my eye because of the writer (Vackar)

Lawrence.

[Skywave]

Yes, Lawrence, an interesting read, even if it is a bit heavy. I've never heard of Lampkin, let alone an oscillator named after him.

As regards frequency stability of variable frequency LC oscillators, in Amateur Radio circles the traditional approach was - and I think still is - to take appropriate measures to prevent changes only to the inductance of the coil, this one single component contributing the greatest effect on frequency stability compared to all the other components comprising the whole LC oscillator. Usual approaches were akin to a traditional crystal oven, but instead of a crystal within that temperature-controlled chamber, the coil was thus situated.
Having said that, one novel attempt to compensate for frequency change with temperature became available to Radio Amateurs back in the '70's. I do recall Oxley Developments manufactured a device called a 'tempratrimmer', which, if memory serves me correctly, was an adjustable capacitor whose rate of change of capacitance with temperature could be manually adjusted. I suspect that Oxley have long since finished trading and that device has gone with them. Should anyone know otherwise, I'm sure that they'll let me know - and if so, is that device still available?

Al. / Aug. 21, 2013 //

[pwdrive]

Al, I think the Lampkin is basically a modified Hartley so far as I can make out, I had heard of it a while back but could not find a lot about it only a date reference to an article written by Lampkin himself in 1939.
The other thing is that the article written in the Tesla mag was written by Vackar (of oscillator fame) I wonder if he wrote that before or after he was credited with the Vackar oscillator circuit.
Heating copper wire before winding it on to a ceramic coil former was also interesting as an aid to inductor stability, that was a new one on me.
I remember the Oxley Tempatrimmer, I think Oxley are are still around in some form or other.
Pos and Neg temp coefficient trimmer capacitors are still available I think but I have not gone into who makes them as yet.

Lawrence.

[Kalee20]

Oxley are still very alive and kicking!

[pwdrive]

I thought they might be, still doing feed throughs too.

Lawrence.

[boiss]

And I always thought that Arthur LAMPKIN rode a trials Bike back in the 70s.........

[Skywave]

Oxley are still very alive and kicking!
http://catalog.oxleygroup.com

Thank you. (Above quote re-arranged by me to clearly display web page of Oxley)

Al. / Aug. 22, 2013 //

[pwdrive]

And I always thought that Arthur LAMPKIN rode a trials Bike back in the 70s.........

Yeah and I always thought Clapp was something else....Lampkins initials were G. F. not sure what his first names were, not a lot about him on the web, might check the US Census records for a clue, if I find owt I shall report back.

Lawrence.

[pwdrive]

Ok, think I have found him, name, Guy F Lampkin, born circa 1906, Indiana, I'll see what else I can dig up.

Lawrence.

[pwdrive]

Chief heir hunter here, I think it's him, G.F. Lampkin aka Guy Forest Lampkin born c 1906 Indiana, his farther was a pastor/clergyman.
Guy was listed as married in the 1940 US Federal Census living at Manatee, Florida, (radio engineer) but no kids on that date.
Also tracked him down on the 1920 and 1930 census (electrician)

1920 living at Van Buren, Arkansas (no occupation)

Mentioned and a picture in the Cincinnati University Year Book as G.F. Lampkin E.E. of Van Buren High School, Van Buren High School, Ark.

The picture below shows him, bottom right I would presume.

Googling his now known full name returns a couple of patent files pertaining to radio communication.

Lawrence.