Hi Been there / done that as well. The “gain slope” as you approach the magic trip point is a big gotcha. Since the effective gain depends a lot on the time offset, it’s not something you really want in the middle of a (should be linear) control loop ….
Having a really rotten oscillator with a whole lot of jitter would make it a little easier as far as gain slope issues … :) Yes, actually it’s the amount of jitter vs the PPS quantization interval that matters. A (much) higher frequency clock driving the PPS generator would also make the gain slope less of an issue. Bob > On Jan 22, 2019, at 12:11 PM, Poul-Henning Kamp <[email protected]> wrote: > > -------- > In message <[email protected]>, Bob kb8tq writes: > >> Once you do replace the TCXO, you then are very dependent on a sawtooth >> correction >> to run your GPSDO. The PPS becomes one big long hanging bridge and thus is >> not useful. > > Well... > > If you do not have the sawtooth, what you can do instead is try to steer your > external clock to give you *maximum* jitter on the PPS. > > That situation arises when you get the GPS to "waffle" between which > two clock-cycles of the external clock it should put the PPS. > > It is incredibly dependent on the GPS receiver internals, and it is > very hard to keep stable, but you _can_ do it. > > I know, because I did :-) > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [email protected] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ 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.
