[time-nuts] Fury - Rubidium

[Don @ True-Cal]

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 




________________________________
From: Scott Mace <smace at intt.net>
To: time-nuts at febo.com
Sent: Tue, July 27, 2010 10:41:16 AM
Subject: Re: [time-nuts] Fury - Rubidium

I have done this with several LPRO-101, X72, and a FRS-C.  The FRS-C that I used 
was out of a Lucent RFG-RB box.  It had a hot TTL output that was causing issues 
with the Fury,  The level was the problem, not the ttl.  The EFC was 
hypersensitive, and it took a long time for the unit to settle down before the 
Fury would handle it.  Same thing with the LPRO, and X72, you have to wait for 
it settle for a week or so before it starts to work well if it's been off for a 
long time.  The X72 was by far the worst, and it would jump from time to time, 
which would make the fury unhappy.  I didn't have a chassis that would fit the 
FRS-C and the fury, so I just went back to the LPRO.  The lpro-101 has been the 
best so far.  I put everything in a 1U chassis and placed it in the bottom of my 
rack away from the AC vent.

This is what I use with the LPRO-101.

dac gain: 1000
efc scale: 1.30
efc damping: 35
ocxo slope: positive
phaseco: 35

I test it by changing the antenna delay.  It should recover within a reasonable 
time.  Bumping the coarsedac is typically too much change and takes longer to 
recover.  I run it with a 20ns offset to my z3801a, and they always stay within 
20ns of other.

I've had the Fury running for about 5400 hours since the last reboot, running 
v1.21 firmware.  It stays within +-10ns,  usually it's between +-5ns.  Over 
24hrs, gpscon reports TI average 0.15 or so and stddev around 2.5ns.

    Scott

On 7/27/2010 9:07 AM, Brian Kirby wrote:
> Has anybody on the list interfaced a Fury GPS controller to a rubidium ?
> 
> If you have, please advise the rubidium are using and your SERV:DACG ,
> SERV:EFCS , and SERV:EFCD settings.
> 
> I am working with a FRS-C at the moment and I have not found the right
> combination to get a stable lock.
> 
> Thanks - Brian KD4FM
> 
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