Mark, I forgot to add -- see pages 12 to 19 of http://www.gpstime.com/files/PTTI/PTTI_2006.pdf where Rick uses a DS1020, especially page 16 where he compares both the traditional TIC-based sawtooth correction method with the [new] delay line method. The agreement is about 1 ns rms.
/tvb ----- Original Message ----- From: "Tom Van Baak" <[email protected]> To: "Discussion of precise time and frequency measurement" <[email protected]> Sent: Monday, July 18, 2016 9:41 PM Subject: Re: [time-nuts] How does sawtooth compensation work? >> Or use the sawtooth compensation value to control an external variable >> delay line circuit > > Hi Mark, > > Right, one example is https://datasheets.maximintegrated.com/en/ds/DS1020.pdf > or google for silicon delay line. Not sure they're in production still but > you can find them at the reseller sites. > > This delay line idea came up in the early Oncore-VP era gps mailing list (pre > time-nuts) by someone who first explored sawtooth correction and "hanging > bridges"; and it's the method that Rick then chose for his CNS Clock product > line. See: http://cnssys.com and http://gpstime.com for details. > > The advantage of the delay line method is that you don't need a nanosecond > TIC in the box; you correct for the sawtooth error live on the 1PPS. Very > simple and effective. The main GPS feed in my lab is a CNS Clock. > > This disadvantage is that if you already have a TIC connected to your > GPS/1PPS, there's not much point in pre-sawtooth correcting with a delay > line. The error is something that you're going to correct with arithmetic > anyway so there's no need to correct it in pulse phase. Rick's TAC32 software > (that many time nuts use) handles integration of serial TIC data (such as hp > 53132) along with GPS binary data to provide sawtooth corrected measurements. > Several of Rick's papers at the above sites explain this in fine detail. > > /tvb > > > ----- Original Message ----- > From: "Mark Sims" <[email protected]> > To: <[email protected]> > Sent: Monday, July 18, 2016 8:28 PM > Subject: [time-nuts] How does sawtooth compensation work? > > >> Or use the sawtooth compensation value to control an external variable >> delay line circuit to move around the PPS signal from the receiver. This >> can get interesting to implement if the receiver can output negative values >> for the sawtooth compensation (hint: add a bias to the sawtooth value to >> make the compensation values always positive and adjust the antenna cable >> delay command to remove the bias value that you add. Oh, and for some >> receivers you have to reverse the meaning of positive and negative sawtooth >> corrections and/or cable delay values). It is even more interesting if the >> receiver outputs the sawtooth correction after the pulse it just >> generated... hint: get a different GPS receiver). >> >> -------------------- >>> A device that uses the sawtooth data shoves it into the control loop along >>> with the measured early / late information on the PPS. >> > _______________________________________________ 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.
