[time-nuts] Re: Upgrade HP 5065A oscillator from 105 to 10811

[Bob kb8tq]

Hi

The various “sub species” of 10811’s were a test and select item done
on the HP line. When they found enough to fill the need for this or that
part number they stopped testing. Some of the normal parts could indeed
be better than the selected versions. 

We are now a *long* way past when this selection process was done. 
These OCXO’s have been through a lot since they came off the production
line. There is no reason to believe this or that “sub part” actually is any
better than a different dash number. 

The only answer these days is to do some shopping. Find a seller with
a big pile of them and a low price. Buy a dozen and test them. If some 
look good, buy another dozen and test them. Eventually you will have a
pile of pretty good ones. You also will have a pile of junk units. 

Why buy a few and test before diving in for a group? You want to be sure
you aren’t buying from somebody who already has done a sort. Even if
they aren’t aware of it, the group could have been sorted before they 
came into the picture. 

Is this a bit of a pain? Sure it is. It also is how people have always come
up with those “poster child” versions of the 10811 you see here and there. 
Is this or that one a one in twenty or a one in a hundred? My guess is that
even back in the day, one month it went one way and the next month it 
swung the other way.

There is nothing particularly special about the board HP used to adapt
the 10811 to do what it needed to do in the 5065A. There is a very similar
part that goes into one of the Cs standards. It also can be adapted to use.
If anything, the mounting bracket is the part you really need :) There are 
a number of old threads that pretty much all come to the conclusion 
“you could do better” after looking at the HP board. Building one from 
scratch is very do-able. 

Bob



> On Feb 11, 2022, at 11:20 AM, Matt Huszagh <huszaghmatt at gmail.com> wrote:
> 
> Hello,
> 
> Has anyone attempted or successfully upgraded an older HP 5065A to use a
> new 10811 oscillator?
> 
> HP created an upgrade kit for this purpose and provided a manual with full
> schematics. While I would expect that upgrade kit is difficult
> (impossible?) to find I imagine it might be possible to use a 10811-60109
> oscillator and recreate the other PCBs.
> 
> Another question I had is whether the 60109 is mandatory or another 10811
> could be used in its place. The 60109 sometimes shows up in the secondary
> marketplace but is harder to find than other variants. If another variant
> can be used what characteristics are important to consider and which
> variants might be suitable? The specifications for the 60109 are documented
> so ideally a replacement would perform as well or better in ADEV and phase
> noise. The 10811D/E seems to have similar specs though worse ADEV at 1s. On
> the other hand, the phase noise is a bit better for the D/E.
> 
> Matt
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