[time-nuts] Making the most of SRS Rb source

Mike Nolan nolan at naic.edu
Wed Jan 18 12:44:26 EST 2006

On Wed, Jan 18, 2006 at 09:17:31AM -0700, David Forbes wrote:
> Our need for accurate time/frequency is:
> 1) Local oscillator frequency +/-1kHz at several hundred GigaHertz;
> 2) Time correct to +/-10 milliseconds to keep the telescope pointed correctly.
> I suppose it would make a lot more sense to run the GPS 1PPS into the 
> Rb source so that it will discipline itself, and the phase error be 
> monitored to make sure it stays at zero.
> Am I barking up the right tree here?

For some purposes, where short-term stability is needed, it's better
to let it free run and just record the difference and tweak / reset
it ocasionally at a time when you know people aren't using it.  For our
radar and VLBI observations that's the case, and to some extent for pulsar
timing as well.  Depending on the timescale and resolution requirements
of your observations, either way could be better. But 1-us phase jumps
sound pretty bad. Is that within spec for the Rb? That would wipe out
my observations, and we used Rb until we got the H-maser for VLBI.


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