Hi Bob, Any user of a Brooks Shera controller will tell you that phase errors can be recovered using a jittery 1PPS reference. While the 1PPS may jitter (+/- 42ns in a UT+ GPS) the jitter averages out to zero error over time. The Shera controller uses the phase difference between the 1PPS and divided by 16 source to drive the EFC to maintain a constant phase difference. The Shera design updates every 30 seconds and in mode 1 the phase error from setpoint is sent directly to a DAC to correct the frequency. Shera adds a selectable filter before the DAC to reduce the EFC noise and increase the correction stability. More samples averaged over a longer period increases the stability, but smaller corrections are applied over a longer period to make the phase (frequency) correction.
Richard > Hi Richard, > > As time goes by, I'll reread your post until I understand it. I'm a newbie, > but > It's hard to believe that there is enough information in a jittery 1PPS > reference > pulse to be able to recover phase errors. > > Bob > > > > ----- Original Message ----- >> From: Richard H McCorkle <[email protected]> >> To: Bob Stewart <[email protected]>; Discussion of precise time and frequency >> measurement <[email protected]> >> Cc: >> Sent: Thursday, June 13, 2013 5:51 PM >> Subject: Re: [time-nuts] Fw: New to list and GPSDO questions >> >> Hi Bob, >> >> The VE2ZAZ controller is a frequency locked loop that keeps the source >> on frequency but over time the phase drifts, as past corrections are >> not compensated for. > _______________________________________________ > 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.
