[time-nuts] using Fury GPSDO with Rb
SAIDJACK at aol.com
SAIDJACK at aol.com
Wed Apr 9 01:57:48 EDT 2008
this means the gain is set too high so that there is not enough phase margin.
You can try to set the serv:dacgain lower, and serv:efcs / serv:phaseco
Contrary to OCXO's, Rb's are quite stable so they don't need strong control,
they just need a gentle nudge, so you can try starting with low numbers.
Let me know if that works,
In a message dated 4/8/2008 21:31:50 Pacific Daylight Time, smace at intt.net
I've found that once the units gets into an overshoot/oscillation cycle
it never recovers and I have to manually adjust the dac to break the cycle.
Is the notion that you use conservative enough settings so that this
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
> difference between 2) and 3)
> 5) Set Integral part of loop to zero: serv:phaseco 0.0, this helps for
> 6) Set Proportional part of loop to a number that makes the unit lock as
> quickly as desired without oscillation and overshoot (for example:
> to serv:efcs 6.0
> 7) Set the integral part of the loop so that the phase is driven to 0ns
> 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?
> **************Planning your summer road trip? Check out AOL Travel Guides.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> and follow the instructions there.
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
**************Planning your summer road trip? Check out AOL Travel Guides.
More information about the time-nuts