[time-nuts] Disciplining Rubidium

iovane at inwind.it iovane at inwind.it
Wed Apr 23 19:50:53 EDT 2008

More precisely, if I had two black boxes, one containing a GPS-Rb-XTAL setup and another containing GPS-XTAL, what measurement would you make from outside the boxes to distinguish from one another?

Antonio I8IOV

> Tom Duckworth wrote:
> > Antonio,
> > 
> > Absolutely! With a good XTAL you have parts in the 9th, short term. With a
> > XTAL controlled by a Rubidium, in the phase-lock feedback loop, you have
> > parts in the 12th, short term. With the Rubidium disciplined by the GPS,
> > with its on-board Rubidium/Cesium oscillators updated from the ground every
> > orbit, you have parts in the 14th, short term. In other words, your
> > XTAL/Rubidium/GPS has an effective short-term Allen variance equivalent to a
> > good Cesium; and better than a single Cesium, long term, for a lot less
> > money! 
> You didn't mention the case of GPS disciplined XTAL. As far as I understand (unless I'm missing something), the Allan variance in the two cases (GPS-Rb-XTAL and GPS-XTAL) would be similar. Isn't it?
> The holdover (as answered by David) is another issue, and I was not referring to it with my question.
> Thanks,
> Antonio I8IOV
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