[time-nuts] ADEV test setup [was GPSDO TC & Damping]

Tom Van Baak tvb at LeapSecond.com
Sat Jan 10 01:35:29 UTC 2009


> Tom
> 
> Doesnt that introduce some correlations for larger tau as both the
> Thunderbolt and the 58503B are both locked to GPS?
> 
> Bruce

Correct, the choice of reference often has some impact on the plots.

Since I used a GPSDO (a nice one), if the plot extended well
past 10^4 or 10^5 the GPS correlation effects would show up in
the long-term, I think. In that case the plots would start to appear
slightly optimistic.

On the other hand, because I used a GPSDO instead of a maser
reference, the plot I posted appears slightly pessimistic in the
short- and mid-term.

So the main thing about the plot was just how well the difference
between tc=10, 100, 1000 showed up, regardless if the reference
was a maser or a GPSDO. A nice Rb might work too.

That the TC setting was so visible using (only) a GPSDO as a
reference is promising. It means normal time-nuts (oxymoron?)
who don't have cesium or masers lying around have a good
chance to investigate the optimal TC for their GPSDO. Looks
like a 5370 or SR620 would also work for the TI counter.

/tvb




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