OK, I believe you. I can see I have a lot to learn. Bob
----- Original Message ----- > From: Richard H McCorkle <mccor...@ptialaska.net> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency > measurement <time-nuts@febo.com> > Cc: > Sent: Thursday, June 13, 2013 7:04 PM > Subject: Re: [time-nuts] Fw: New to list and GPSDO questions > > 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 <mccor...@ptialaska.net> >>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and > frequency >>> measurement <time-nuts@febo.com> >>> 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 -- time-nuts@febo.com >> To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.