Said, Did the OEM units (from way back) ship with an open pad for the
thermistor? I thought that wouldn't work unless it was drawing oven
current from the Fury. It would be neat to add some tempco into the mix
instead of just trying to shield it from HVAC cycling. The particular
LPRO-101 that I'm using now, doesn't seem to be as sensitive as others
to temp. I was using a different LPRO originally and when I plotted the
Fury board temp sensor with GPSCON you could see the impact of the
cycling, now with this one you would be hard pressed to pick it out.
The X72 was very sensitive to temp changes, EFC tracked the temp quite well.
Scott
On 07/27/2010 02:57 PM, saidj...@aol.com wrote:
Hi guys,
it may help to increase DAC gain to get faster recovery times from "bumps"
etc.
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.
bye,
Said
In a message dated 7/27/2010 09:58:41 Pacific Daylight Time,
true-...@swbell.net writes:
My experience is very similar to Scott's. I ran many hours with both an
LPRO-101
and FE-5680A. The disciplining behavior and Fury settings were the same
for
either Rb. My biggest disappointment was the recovery time due to various
common
or intentional bumps or especially, after power loss. I also had to let
the
"system" settle in for a week before acceptable tracking smoothed out. Any
long
term slope to the EFC trace (gpscon) caused excessive hunting and this
didn't
settle down until the Rb was VERY stable. My gpscon TI and stddev was
virtually
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.
DACG= 1000
EFCS = 2 to 3
EFCD = 50 (25 allows little better settling time)
PHASECO = 15 (I favor 10 Mhz over PPS)
Regards...
Don
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