[time-nuts] Re: Looking for HP 10811D manual (if such exists)

[Bob Camp]

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

> On Aug 29, 2023, at 9:23 PM, Richard (Rick) Karlquist via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 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:
>> Hello Rick and the group,
>> My belief is the 10811D/E used selected crystals/units, third page of the
>> attached PDF may give a clue.  But I'm like you, I have never seen a parts
>> list for the D/E units.  So, don't know if they used any components
>> different from stock A/B/C units other than the crystal.
>> I have attached a PDF of everything I had in my 10811D/E file.  There is an
>> Operating Note (two pages)  inserted between the first two pages of the
>> marketing/specification document.  There is a spec for another variant at
>> the end.
>> Hope this can enlighten the group in some way.
>> Regards,
>> Skip Withrow
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