[time-nuts] Fury - Rubidium
SAIDJACK at aol.com
SAIDJACK at aol.com
Tue Jul 27 15:57:53 EDT 2010
it may help to increase DAC gain to get faster recovery times from "bumps"
On an OCXO, the frequency recovery from an upset should happen within a
couple of minutes, definitely less than 15 minutes to achieve frequency lock.
The phase recovery (to 0ns offset) may take a couple of hours to do.
If it takes a very long time to recover, then I think increasing the DAC
gain, or alternatively the EFCS and PHASECO together may help.
Wikipedia has some good instructions on how to optimize PID type controller
gains to get the fastest response with minimal noise...
Also, please make sure to disable temperature compensation when using the
external source, unless a thermistor is connected to the board, sensing the
Rb temperature. Otherwise the temperature compensation may add noise due to
it scaling the gain to huge values due to the missing thermistor.
In a message dated 7/27/2010 09:58:41 Pacific Daylight Time,
true-cal at swbell.net writes:
My experience is very similar to Scott's. I ran many hours with both an
and FE-5680A. The disciplining behavior and Fury settings were the same
either Rb. My biggest disappointment was the recovery time due to various
or intentional bumps or especially, after power loss. I also had to let
"system" settle in for a week before acceptable tracking smoothed out. Any
term slope to the EFC trace (gpscon) caused excessive hunting and this
settle down until the Rb was VERY stable. My gpscon TI and stddev was
the same as Scott's if I had EFCS set to 1.0 to 1.5 but recovery was
unacceptable (maybe 24-hours) so I usually ran at 2.0 or 3.0 with
slight degrading of stddev to around 3.2. This EFCS setting allowed a much
better settling time around 3-hours.
EFCS = 2 to 3
EFCD = 50 (25 allows little better settling time)
PHASECO = 15 (I favor 10 Mhz over PPS)
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