I worked in the HP Precision Frequency Sources R&D section and also knew
the designers of the 10811 and learned as much as I could about it from
them.  And I never came across an "alternate" schematic for it.  They
all look like the one in the manual.

Except, when designing the 5071A, I made a very logical case for
changing the varactor diode to a hyperabrupt diode to get much
more tuning range to contend with crystal aging.  AFAIK, no 5071 user
has ever had to readjust the piston trimmer on their 10811,
which surely would have happened with the stock design.
I think this was able to be accomplished solely by a BOM change.  I
don't remember having to make a different PC board.  This was all worked
out 35 years ago so my memory might not be perfect.

Rick N6RK

On 8/29/2023 11:30 AM, Skip Withrow via time-nuts wrote:

Hi

Selecting crystals before they go in oscillators is a very difficult process. Effectively,
you build the crystal into an OCXO and test that part for some weeks or months. You
then tear the OCXO apart and build a new one with the crystal.

This is a fine thing if you are making high end space flight gear. It doesn’t work for the
more “normal” space qualified parts. Below that, there is no real reason to build one
part and tear it down. Just build the OCXO and test it.

The 10811 got various dash numbers after the part number. They, rather than letters
indicated “grades” of oscillator (or different specs on the part). Those parts came from
a “select and test” on very normal finished OCXO’s. If 10 parts of a dash number got
ordered this month, a dozen or two parts got tested. The ones that past the spec got
the dash number.

So not a really exciting process.

Bob

Good Morning.
I have 3 5071A  10811,s. I did have a 4th with exceptional AV. I asked Corby to modify it to modify it  I repeatedly did on 10811, ground R 2 and reverse CR 1. Tuning changed to + 0 to 10V  with better AV. Something went wrong. The circuit is not exactly                                                                                            Bert Kehren    like the 10811In a message dated 8/29/2023 9:52:54 PM Eastern Standard Time, time-nuts@lists.febo.com writes: 
I worked in the HP Precision Frequency Sources R&D section and also knew
the designers of the 10811 and learned as much as I could about it from
them.  And I never came across an "alternate" schematic for it.  They
all look like the one in the manual.

Except, when designing the 5071A, I made a very logical case for
changing the varactor diode to a hyperabrupt diode to get much
more tuning range to contend with crystal aging.  AFAIK, no 5071 user
has ever had to readjust the piston trimmer on their 10811,
which surely would have happened with the stock design.
I think this was able to be accomplished solely by a BOM change.  I
don't remember having to make a different PC board.  This was all worked
out 35 years ago so my memory might not be perfect.

Rick N6RK

On 8/29/2023 11:30 AM, Skip Withrow via time-nuts wrote:

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Hi

That likely is not an HP 10811 OCXO. It might be an OCXO somebody made for HP.

It’s a good bet it is a  good OCXO that one can buy in the internal Chinese market for
not a whole lot of money.

Bob

Hi Bob,
It's designed to look like a baby brother of the big HP DOCXO, so I just assumed the obvious.  I may open it up to see what's in it.  It seemed to work OK in the Z3805A, but I didn't do any exhaustive testing, or save any TimeLab plots.

Bob

----- Forwarded Message ----- From: Bob Camp kb8tq@n1k.orgTo: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@lists.febo.comSent: Wednesday, August 30, 2023 at 06:32:04 PM CDTSubject: Re: [time-nuts] Looking for HP 10811D manual (if such exists)
Hi

That likely is not an HP 10811 OCXO. It might be an OCXO somebody made for HP.

It’s a good bet it is a  good OCXO that one can buy in the internal Chinese market for
not a whole lot of money.

Bob

Hi

All sorts of random folks design OCXO’s that get sold to HP / Agilent / Keysight. You
never know just how nutty they might be ….. :) :)

Probably more significant than this or that crazy designer is the spec that HP asked
them to build to. Some parts are pretty fancy and others are very much “nothing special
here”.

Bob