[time-nuts] using Fury GPSDO with Rb

Scott Mace smace at intt.net
Mon Apr 7 14:08:14 UTC 2008


Here's what I've been using over the weekend:

Efratom FRS-A

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.

	Scott


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,
> bye,
> Said
>  
>> -----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?
>>
>>  Scott
>>  
> 
> 
> 
> 
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