[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 
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.
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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