Hi, I hope you don't mind me starting a "newcomer" thread based on your sentence: "with a GPSDO, finding one that’s got a clean output is not at all easy".
Are there any up-to-date resources that would provide such information about a larger selection of GPSDOs? Are there any GPSDOs that people really recommend purchasing right now, costing say up to $500? Or is the "just build your own" approach the most cost-effective way? P.S: "Study John Vig's Introduction to Quartz Frequency Standards" link on http://www.leapsecond.com/time-nuts.htm is broken On Tue, Aug 24, 2021 at 3:20 PM Bob kb8tq <[email protected]> wrote: > Hi > > The problem with the approach used in the basic GPS / GNSS modules is > that the TCXO is not tuned on frequency. Even with an integer relation to > the > internal oscillator, you still see the pulse drop / pulse add into the > divider. The > result is that they are noisy. > > There are a couple of modules that *do* tune the frequency. ( as noted in > the > paper). There the very coarse DAC used is what gets you in terms of noise. > Again, it’s regardless of output frequency. The signal *is* cleaner, it’s > just not > as clean as what most folks are looking for. > > Even with a GPSDO, finding one that’s got a clean output is not at all > easy. > Yes, this all depends a lot on just what you mean by clean. It normally > comes > up in the context of folks wanting to run radios at microwaves. Indeed the > normal answer there is that you use multiple oscillators in your multiplier > chain. > > Bob > > > On Aug 24, 2021, at 7:18 AM, Marek Doršic <[email protected]> > wrote: > > > > Hello, > > > > thank you for sharing valuable comprehensive comparisions. > > > > In the high timepulse rate experiment, have you also investigated other > rates than the standard 10 MHz? Most Ublox receivers use 48MHz internal > clock thus the 10MHz timepulse must be missing some of the clock pulses > which generates additional jitter. 8MHz or 12MHz rates which are integer > divisions might have cleaner output. > > > > .marek > > > >> On 24 Aug 2021, at 03:51, John Ackermann N8UR <[email protected]> wrote: > >> > >> In 2020 I did an extensive evaluation of the timing ability of the > u-blox LEA-M8F, NEO-M8N, NEO-M8T, NEO-M9N, ZED-F9P, and ZED-F9T. The work > was made possible by support from the HamSci consortium ( > https://hamsci.org) under NSF grants supporting HamSci activities. > >> > >> I was sure I'd posted about the paper on time-nuts, but I can't find > any record that I did, so this is a belated announcement. It's available > for download from > >> > >> > https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf > >> > >> As BobC says, "Lots of fun!" > >> > >> John > >> > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] -- To unsubscribe > send an email to [email protected] > >> To unsubscribe, go to and follow the instructions there. > > _______________________________________________ > > time-nuts mailing list -- [email protected] -- To unsubscribe > send an email to [email protected] > > To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send > an email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
