I’ve used the PA6H so far for all of my GPSDOs. The two reasons I am considering the Venus838LPx-T to replace it are that it has a sawtooth correction message and it has a survey and static solution mode to allow it to tolerate poorer reception.
I’m driven to want to experiment with a static mode GPS receiver from this page on Atilla Kinali’s blog: https://attila.kinali.ch/blog/2016/02/07/gps-disciplined-oscillator, which references some e-mail here from some time ago. My take-away was that navigation mode receivers could achieve good results as long as they had ideal reception, but with poor reception they would do much worse than a receiver in static mode that’s done a good survey. As for the sawtooth correction, I’m less convinced that it’s required given that I’m using averaging on the phase detector output. I can’t detect hanging bridges with the current setup, but since I haven’t actually looked for them, ignorance is bliss. Tom, if you still have the data, can you speak to whether you saw anything of the sort? In any event, it’s a box I’d like to check if for no other reason than to learn something. > On Jul 30, 2016, at 2:32 PM, Tom Van Baak <[email protected]> wrote: > > Hi Brooke, > > That's a reasonable assumption. I haven't ever tried mine at 10 Hz. But note > that fast update rates is more meant for navigation and positioning than it > is for timing. > > Just in case we have some newcomers to the thread I'd like to point out that > this recent series of measurements of RS232 / NMEA have no bearing at all on > the quality of the timing output. Timing NMEA is more of a curiosity; > something to measure at the hundreds or tens of millisecond level. As anyone > knows, the real timing output of these receiver is the 1PPS pulse itself, > which is good to the tens of nanoseconds level. So a factor of a million > different. > > I actually like the Adafruit GPS receiver, and would recommend it to anyone. > I use it for projects around the house more than any other receiver. It's so > simple to use -- no configuration needed, no sawtooth correction needed, no > survey required, fast acquisition, works fixed or mobile, sensitive antenna > included on board, small and low power, just give it 5 volts and out comes a > UTC 1PPS. > > Its 1PPS output is superb. Attached is the ADEV/MDEV of the raw 1PPS of the > Adafruit GPS board. > > /tvb > > ----- Original Message ----- > From: "Brooke Clarke" <[email protected]> > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Sent: Saturday, July 30, 2016 1:50 PM > Subject: Re: [time-nuts] Adafruit Ultimate GPS timing message arrival times > > >> Hi Mark: >> >> Isn't this the receiver that hears a very large number of GNSS satellites >> and also has a 10 Hz update rate? >> If so, I'd expect that there would a large variation in message lengths. >> How stable is the 10 PPS or 1 PPS output? >> >> -- >> Have Fun, >> >> Brooke Clarke >> http://www.PRC68.com >> http://www.end2partygovernment.com/2012Issues.html >> The lesser of evils is still evil. >> >> -------- Original Message -------- >>> A couple of people have asked about the poor message arrival time >>> performance of the popular Adafruit Ultimate GPS receiver. I modified >>> Lady Heather to analyze the message arrival times using a histogram instead >>> of a simple average. When I looked at the histogram data (.01 msec >>> resolution), I was rather shocked... With an hour of data, most receivers >>> have maybe a couple dozen bins hit, with the peak bin several hundred >>> counts above the next lower peak. The Adafruit had over 1800 bins hit, >>> with the peak bin having six hits. Attached is the histogram... you >>> probably don't want to use this receiver to drive a clock based upon >>> message arrival times... >>> > <gps-mtk3339-adev-mdev.gif>_______________________________________________ > 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. _______________________________________________ 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.
