[time-nuts] Disciplining Rubidium

[iovane at inwind.it]

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