[time-nuts] Disciplining Rubidium
SAIDJACK at aol.com
SAIDJACK at aol.com
Fri Apr 25 03:26:24 EDT 2008
Hi Bruce,
the 1ns performance per second was mentioned by someone else in the previous
threads.
When you lock a BVA OCXO to carrier phase, I would still expect the PLL loop
time constant to be >>20s, thus the 8E-014 / 2s you mentioned is very likely
the performance of the BVA Crystal, not likely the carrier phase real-time
system output.
For example, our Fury with double oven has an ADEV of a couple of parts per
E-012 1s to 20s, but that performance is entirely generated by the OCXO, not
the M12+.
I would expect the carrier phase to improve things at the point where the
BVA starts having a rising ADEV. Maybe around a couple 100s? If for example the
phase comparator has 1ps resolution (that's really quite a high resolution)
to compare the OCXO and carrier phases (1E-012) then it would take >12s
averaging intervals in the PLL just to prevent the measurement errors from
affecting the system performance above 8E-014.
It's late, and I may just be wrong about all this.
bye,
Said
In a message dated 4/24/2008 17:51:25 Pacific Daylight Time,
bruce.griffiths at xtra.co.nz writes:
They can be almost 2 orders of magnitude better than you assume for
short time intervals.
8E-14 performance from 2 to 20 s with 1E-14 at 1 day has been claimed
when carrier phase disciplining a BVA OCXO.
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