[time-nuts] Making the most of SRS Rb source
dforbes at dakotacom.net
Wed Jan 18 16:11:18 EST 2006
Thanks for the informative reply. I guess the short answer is that we
should use a very clean long-term GPS trend record to correct the
PRS10 rather than the 1PPS from the GPS unit, which has horrible
I believe that Tom VB mentioned once that a daily update to the PRS10
EFC should be sufficient. I can see his point. It would be bad to add
all that short-term noise to the rubidium's PLL.
I will discuss with the other engineers here the possibility of using
the phase info from the counter to bump the EFC control on the Rb
source. It seems like a fairly easy thing to do. I imagine a simple
proportional frequency control loop (human or computerized) would be
sufficient for our needs since the integral error would be much
smaller than our milliseond-level time accuracy requirement.
I'll also look into setting up the SR620 counter to average the phase
over perhaps 1000 samples to do the first-level noise reduction. Then
we'll get 86 useful numbers per day instead of 86000.
Finally, we will be getting a maser again in a couple months and we
will probably want to stabilize it this way (with a 30 day adjustment
period, perhaps) after the VLBI run, unless the VLBI folks have a
better idea. I'll have to ask them.
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