[time-nuts] This may be my new favorite old oscillator

Ruslan Nabioullin rnabioullin at gmail.com
Tue Nov 8 08:12:38 EST 2016

On 11/08/2016 12:16 AM, Skip Withrow wrote:
> Hello Time-Nuts,
> I recently acquired an HP 5065A rubidium oscillator (with 10811 10MHz
> OCXO). I think I pretty much have it running now and have been letting it
> cook for the last couple of weeks.  I offset the C-field + and - and
> measured the frequency to calculate the C-field sensitivity. My unit came
> out to 1.96x10E-12 per dial unit, which agrees with the manual stated
> 2x10E-12. So, calculated the on frequency C-field value and dialed it in.
> Attached is a Lady Heather plot of the frequency over the last 3 days.  The
> purple line is the 1pps plot with the vertical scale being 20ns per
> division.  So, the unit is off about 125ns over the last 72 hours (running
> about 4.92x10E-13 slow).  So my C-field setting is off about 1/4 of a
> division, but I think I'm going to leave well enough alone.
> The yellow line is the NTBW50AA temperature sensor, and you can clearly see
> when the furnace cycles.  I was away for the weekend, and you can also
> clearly see when I came home this evening and turned up the heat.  At the
> very end of the plot is the spike when I turned on the lights in the shop.
> I love using a Thunderbolt/NTBW50AA for making frequency measurements this
> way.  I remove the OCXO, and insert the 10MHz from the DUT.  Then disable
> disciplining so the DAC voltage doesn't try to chase the open loop
> oscillator.  Of course the short-term performance looks worse than it
> actually is because of measuring against GPS, but the long-term
> measurements are very good.
> I want to log this unit at regular intervals to see what the aging looks
> like.  Also need to do some measurements against the cesium to see what the
> short-term performance might be.  But, I think this oscillator will be a
> good reference in many cases in lieu of using the cesium.
> Regards,
> Skip Withrow
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I hope you will forgive me for reducing the SNR of this forum a bit, but 
is that a pro-Trump message embedded in that Lady Heather plot? 
Furthermore, it might also be promoting electoral fraud, though 
``...vote often!'' is ambiguous (maybe that's plausible deniability?)


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