Could someone please define and explain the term 'hanging bridge' in this context?
Thanks, Dana On Tue, Aug 14, 2018 at 7:02 AM, Azelio Boriani <azelio.bori...@gmail.com> wrote: > Hanging bridges out of a GPSDO's PPS? Interesting... time to try to > setup a measurement and see the relation between the GPS's PPS hanging > bridges and the corresponding DO's ones. > On Tue, Aug 14, 2018 at 9:55 AM Mike Cook <michael.c...@sfr.fr> wrote: > > > > > > > Le 14 août 2018 à 09:29, Mike Cook <michael.c...@sfr.fr> a écrit : > > > > > > Sorry about the previous blank mail. Finger jitter. > > > > > > > > > > > >> Le 14 août 2018 à 04:29, Chris Caudle <ch...@chriscaudle.org> a > écrit : > > >> > > >> On Mon, August 13, 2018 9:16 pm, Chris Burford wrote: > > >>> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+ > OCXO > > >>> that I am using to steer a PRS10 RFS. I'm a little confused on where > the > > >>> 1PPS is coming from with respect to the GPSDO. > > > > > > As Chris points out the 1PPS from a GPSDO will « generally » be > derived from the primary frequency and can show better performance than > directly from a GPS receiver. > > > However this is becoming less and less true. > > > If you look at the Oscilloquarz blurb for the Star 4+ ( I found some > here <http://pdf.directindustry.com/pdf/oscilloquartz-sa/ > star3-4/62169-330779.html#search-en-oscilloquartz-star-4> ) , you will > see that the phase stability (jitter) on the 1PPS output is +/- 30ns when > locked to GPS, an it has a timing grade GPS receiver. This is not as good > as other GPS modules now. 15ns is normal, with some less than half that. > > > The PRS10 has outstanding PLL control already. The SRS product doc > gives +/- 10ns accuracy with +/-1ns resolution. > > > I don’t think that you are buying much with disciplining the PRS10 > with a GPSDO 1PPS. Do you have any TIC measurements in this config to > compare with a direct GPS 1PPS feed? > > > > > > > I forgot to mention one other thing which may be of interest to some. > The 1PPS wave form output from the PRS10 is pretty mediocre. I put the > details in another post here sometime back. > > The Star4 spec is +/- 10ns, something I can only get from my PRS10s with > a 74HC7001 shaper. > > > > > > > > > >> > > >> A GPS disciplined oscillator contains a GPS receiver which outputs > 1PPS > > >> based on receiving the GPS signals and calculating the position + > time > > >> equation. That PPS signal is noisy in time, it jitters around > relative to > > >> the ideal 1 second period. The GPSDO implements a long time constant > PLL > > >> to synchronize the output of the OCXO to the long term average > frequency > > >> and phase of the GPS PPS, so what you see externally is 10MHz directly > > >> from the OCXO, 1 Hz (PPS) which is divided down from the 10MHz OCXO, > and > > >> those are controlled by a PLL so that long term the phase of the PPS > > >> divided down from the OCXO follows the PPS calculated by the GPS > receiver, > > >> but with lower jitter. > > >> > > >> -- > > >> Chris Caudle > > >> > > >> > > >> > > >> _______________________________________________ > > >> time-nuts mailing list -- time-nuts@lists.febo.com > > >> To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > > >> and follow the instructions there. > > > > > > Don’t worry about how powerful the machines are. Worry about who the > machines are giving power to. > > > > > > > > > _______________________________________________ > > > time-nuts mailing list -- time-nuts@lists.febo.com > > > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > > > and follow the instructions there. > > > > Don’t worry about how powerful the machines are. Worry about who the > machines are giving power to. > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.