[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

Bob kb8tq kb8tq at n1k.org
Sat May 27 21:01:40 EDT 2017


Having run a 5071A with a *very* good 10811 in it, the OCXO does dictate what happens at 0.1 seconds. 
Once you get past that, you are headed into a bit of a gray zone. You are partly looking at the Cs and partly
looking at the OCXO. Pushing out the crossover between the two could help you at 1 second. The gotcha is
that the “hump” will still be there, just a bit further out. The net effect at (say) 100 seconds could easily be worse
with the “fix”. 


> On May 27, 2017, at 8:15 PM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:
> On 5/27/2017 2:08 PM, Donald E. Pauly wrote:
>> I am investigating the total redesign of the HP5061B lock system for
>> vastly improved performance.  It looks like the performance of the
>> HP5071A can be beaten by 10 to 1 for averaging times on the order of a
>> few seconds.
>> πθ°μΩω±√·Γλ
>> WB0KV
> That's an interesting claim, but it could be valid.
> The 5071A flywheel is a 10811 selected for performance
> and modified to have additional electronic tuning
> range (I was involved in that) but otherwise it is
> plain vanilla 10811.  At a few seconds averaging time,
> this oscillator is basically open loop.  It might be
> possible to improve a 5071A by simply finding a 10811
> with exceptional short term stability.  The tail of
> the distribution curve went down at least an order of
> magnitude, according to Jack Kusters at HP.
> In any event, you could use an unmodified 5071A or maybe
> a 5061B high performance option and discipline some
> really good XO.  Certainly, the 10811 isn't the world's best
> XO.  You'll need to prevent your XO from getting bothered
> by microphonics, stray magnetic fields, 2G turnover, temperature
> fluctuations, and humidity if not hermetic , etc.  The 5071A is
> impervious to all that as it is.
> Is that what you had in mind?
> I remember before I worked for HP visiting JPL's Goldstone
> tracking station.  They had a 5061A that disciplined a
> hydrogen maser for VLBI.  They said a plain 5061A was useless for their
> work.  OTOH, a hydrogen maser without drift correction was
> also useless for their work.  They had a huge room with 100's
> of racks of equipment, but the 5061A and H maser had their
> own dedicated room.
> Rick Karlquist N6RK
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