Hi Scott, a good setting is when the unit recovers in minimal time and with only minor overshoot from a manual coarsedac change. Try dacgain 1000 - 2000. TI of 1.2ns / SD 2.2ns is not bad. The M12 errors can be expected to be larger than this over 8 hours. bye, Said In a message dated 4/9/2008 07:06:45 Pacific Daylight Time, [EMAIL PROTECTED] writes:
I've been running with dacgain 4000, efcscale 1.2, efcdamping 25, phaseco 15. It has been locked for about 8 hours (since I started the test). average TI 1.2ns sd 2.2ns. I tried bumping the coarsedac by 2 increments to see what happens. It tries to recover, but will oscillate wildly after about 45min or so. I wonder what will happen after an extended holdover period. It looks like the EFC on this this FRS-A is more than twice as sensitive as the LPRO. Scott [EMAIL PROTECTED] wrote: > Hello Scott, > > forgot to mention: also try setting the serv:efcdamping lower. It's an IIR > low pass filter, and will introduce phase-shift that can cause instability if > it is set too high. > > bye, > Said > > > In a message dated 4/8/2008 22:59:22 Pacific Daylight Time, [EMAIL PROTECTED] > writes: > > Hello Scott, > > 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 > lower. > > 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, > bye, > Said > > > > > In a message dated 4/8/2008 21:31:50 Pacific Daylight Time, [EMAIL PROTECTED] > writes: > > 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 > never happens? > > Scott > > [EMAIL PROTECTED] 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 >>> >> >> >> >> >> **************Planning your summer road trip? Check out AOL Travel > Guides. > >> > (http://travel.aol.com/travel-guide/united-states?ncid=aoltrv00030000000016) >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > 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. > > (http://travel.aol.com/travel-guide/united-states?ncid=aoltrv00030000000016) > _______________________________________________ > time-nuts mailing list -- [email protected] > 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. > (http://travel.aol.com/travel-guide/united-states?ncid=aoltrv00030000000016) > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] 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. (http://travel.aol.com/travel-guide/united-states?ncid=aoltrv00030000000016) _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
