Hi One term you keep tossing up is “nominal phase coherence”. Typical GPS will do “phase coherence” at the 10 ns level to a fairly high degree of confidence (90 something percent) with a number of footnotes. You have never mentioned what your requirement is so it’s a bit tough to know what you are up against. If you are trying for “a couple of degrees at L band” from 0.1 second on out, GPS simply isn’t going to do that, no matter what you do.
Bob > On May 30, 2019, at 1:58 PM, life speed via time-nuts > <[email protected]> wrote: > > 2. Re: GPS 1PPS, phase lock vs frequency lock, design (Bob kb8tq) > > Hi > > The TBolt is a very unique design. It directly uses code phase information > against the OCXO. The net result is really no different than the “correction > message” approach, but it is a different implementation. Since you can’t > *buy* the guts of a TBolt to strap into a DIY GPSDO, it’s not generally part > of a “I want to build a GPSDO from scratch” conversation. > > Bob > >> On May 29, 2019, at 9:50 AM, Alberto di Bene <[email protected]> wrote: >> >> On 2019-05-29 14:53, Attila Kinali wrote: >>> The saw-tooth correction is the error of the PPS signal, as generated by >>> the hardware, and where it really should be. The clocks of most GPS >>> receivers >>> are in the order of 20-60MHz and are usually unsteered TCXOs (or even XO for >>> the cheap ones). Hence the granularity at which the PPS can be generated >>> is fixed. The saw-tooth correction gives you a higher accuracy (or removes >>> noise) from what you would get without. >> >> Am I correct if I suppose that the Trimble Thunderbolt, which uses the 10MHz >> OCXO as clock for the processor, does not need any saw-tooth correction ? >> >> TNX >> >> 73 Alberto I2PHD >> /<<< http://www.weaksignals.com >>>/ > Just to be clear, I am an electrical engineer working on a commercial new > product design, which already has a high-performance 10MHz OCXO as part of > the product. Although I realize much of this list is composed of DIY and > hobbyists, it has always been clear to me there are some smart people > participating in these discussions. I am in the investigation phase of a > feature enhancement to the product that is unfamiliar to me, hence my > questions. > Bob, > Would you care to elaborate on "directly uses code phase information against > the OCXO"? > I have noticed that a product my company is currently manufacturing uses a > "GPS receiver" containing a TCXO, which we then use the 1PPS to discipline a > low-end 100MHz OCXO. When I investigated the performance of our current > design it did not meet my requirement of nominal phase coherence of two > separate receivers. > It would seem that a GPS receiver containing an oscillator may not make sense > for a design that already contains a high-end 10MHz OCXO, rather the > implementation should use the oscillator that is already part of the design. > Lifespeed > > | > | > | | > time-nuts Info Page > > > | > > | > > | > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
