[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
magnus at rubidium.dyndns.org
Sun May 28 08:20:33 EDT 2017
On 05/28/2017 11:52 AM, "Björn Gabrielsson" wrote:
>> So while I'm eager to see Donald's results, I question their merit. The
> 5061 standards already have a very convenient Cs-Off switch right on the
> front panel. It is there so you get the pure 10811 performance when you
> need it. Use it. In fact there's lots of people run their precious 5061
>> Cs-Off mode 23.9 hours a day and just turn on the Cs once a day, or once
>> week, to re-cal the oscillator. It's not there just to conserve cesium;
> you also get full 10811 short-term performance. Note also some 5061 have
>> short/long time-constant switch which also helps you tailor the ADEV you
> want out of the instrument.
> Very nice design by HP.
> For the same era design, the OSA (telecom) module made other choices. When
> turning off CS, they turn off power to the output module and the efc
> tuning circuit.
> So even if there is a nice and warm BVA inside - without burning CS - the
> standard output is not working and also its off any manual tuning.
In addition, and I consider this somewhat of a design flaw, the external
voltage reference to the oscillator (pre-BVA or BVA) is also powered of,
so it drift south rather than stay put. Otherwise it would have been
easy to trim the oscillator for zero lock enforcement and then
free-wheel on the OCXO when Cs is powered down.
The OSA 3000 and 3100 cesiums are nice analog cesiums, but lacking the
refinement of digitally controlled that came later.
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