[time-nuts] Fury - Rubidium

[Scott Mace]

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, SAIDJACK at 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-cal at 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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