[time-nuts] Using HP5071A with dead tube along with GPS

[Bob kb8tq]

Hi

The OCXO in the 5071 is an HP10811 it was selected at the time of manufacture for 
good performance. As far as anybody knows that testing was for short term stability.

How well it retains that performance many years later - who knows? Is the original 
OCXO in the device - who knows…. Other than a bit better ADEV at 1 second, the 
performance of the device may be no better / no worse than what you get on eBay. 

Like all “normal” 10811’s they are an open construction and move a bit from humidity
and barometric pressure. How much either issue impacts a GPSDO is open to debate. 

Bob

> On Dec 18, 2019, at 10:13 PM, Taka Kamiya via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I can't quite remember who gave me this idea...  but I'm pretty sure he was a member of this mailing list.
> I have an HP5071A high performance version with a dead tube.  But rest of the unit, as far as I know, works just fine.  I know it has a PPS INPUT on it.  I also know it has a very good OCXO in that, too.  Would it be possible to steer this OCXO using GPS when Cs tube is completely dead and unlocked?  I do not want to take this apart, just in case nice usable tube lands in my hand in future.
> The reason I ask...  I can just do it and see, but I have no way to verify the performance.  I have an old Cs with no characterization, and rest are Rbs and T-bolts.  Seems like what I propose would result in OCXO pulled by two different servos.  (and even if the results were awful, I wouldn't know it)
> 
> Happy holidays!
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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