[time-nuts] using Fury GPSDO with Rb
smace at intt.net
Mon Apr 7 10:08:14 EDT 2008
Here's what I've been using over the weekend:
DAC GAIN: 5000.00
EFC SCALE: 0.50
EFC DAMPING: 25
OCXO SLOPE: POSITIVE
PHASE CORRECTION: 0.500000
I think the FRS-A is adjustable from +-1.2e-9.
So far it seems to keep it within +-3ns from GPS.
SAIDJACK at aol.com wrote:
> Hi Scott,
> let me reply on this list since other users are also using Rb's.
> Here is a quick pointer:
> 1) determine EFC slope of Rb (pos = frequency goes higher with higher EFC
> voltage). Set the slope with serv:efc:slop [positive/negative]
> 2) Determine maximum frequency deviation at EFC = 0V (serv:coarsedac 0)
> using a frequency counter
> 3) Determine maximum frequency deviation at EFC = 5V (serv:coarsedac 255)
> 4) Set Dacgain according to table in user manual depending on the frequency
> difference between 2) and 3)
> 5) Set Integral part of loop to zero: serv:phaseco 0.0, this helps for now
> 6) Set Proportional part of loop to a number that makes the unit lock as
> quickly as desired without oscillation and overshoot (for example: serv:efcs 1.0
> to serv:efcs 6.0
> 7) Set the integral part of the loop so that the phase is driven to 0ns UTC
> offset as quickly as desired without overshoot/oscillation, for example:
> serv:phaseco 20.
> Repeat 6) and 7) after some hours.
> Hope that helps,
>> -----Original Message-----
>> From: Scott Mace
>> Sent: Saturday, April 05, 2008 17:51
>> To: Said Jackson
>> Subject: Re: Fury GPSDO
>> Said, I finally got my fury up and running, I'm using a efratom
>> FRS-A and also a LPRO-101.
>> Do you have any recommending starting points for tuning the servo
>> for a rubidium unit?
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