Hi With any GPSDO (not just the TBolt) you can do some basic checks: (They are in no particular order)
1) Are there > 6 sats in view at all times, if not, move the antenna 2) Is the unit locked to at least 4 sats at all times, if not, move the antenna. 3) Has the unit completed its survey process? If not, wait for it to complete. 4) Is the EFC > 10% and < 90% of it’s range after an hour on? If not, repair the unit. 5) Has the unit been on for at least 3 days? If not wait. 6) Does the output look ok on a ’scope? ( it’s volts not milivolts …) if not repair the unit 7) Does the unit show “locked” or something similar? 8) Is the EFC consistent ( = stable) and not wandering around? If not repair the unit. 9) Do the sat’s show SNR’s above 40 db? If not, replace the antenna / coax. 10) Does it read same / same /same compared to your counter’s internal timebase? If not, check the counter / repair the GPSDO. 11) Does the reported ( survey ) location make sense on Google Maps? If not restart the survey / repair the unit. If the unit passes all those checks, it’s a really good bet that you can trust the output. It likely is good to < 1 ppb, almost regardless of who made the device. Not every check will be possible on every GPSDO. The checks assume you have a ’scope and a counter. They also assume you can talk to the status port on the device. Some readings ( EFC range, SNR, may take a bit of research to put into rational units ….). ====== If all of that sounds like a lot of work (or not complete enough), buy a second ( or third or fourth ….) GPSDO. Next get a couple Rb’s …. maybe a Cs or three …. have you looked into Masers? :) Bob > On May 5, 2020, at 8:16 PM, Giuseppe Marullo <[email protected]> wrote: > > Hi, > > I have a ProgRock oscillator that generates 10MHz and 125MHz signals. > Checking with my Trimble the ProgRock 10MHz signal is consistently below > 2.5Hz compared to the Trimble and also the 125MHz is below about 24Hz. > > My setup: > > - Simmetricon time antenna (26dB gain) in clear view > - about 10m of RG8X cable > - Trimble GPS (chinese reboxed) > - Racal Dana 1998 frequency counter with Trimble as time base > > DUT > - Progrock (https://www.qrp-labs.com/progrock.html) with > - ovenized oscillator (https://www.qrp-labs.com/ocxokit.html) > - GPSQ board (https://www.qrp-labs.com/qlg1.html) outside on the balcony, > first floor facing south (almost clear view except North of course). > connection is made using rs232 cable (about 6m) > > I tested for harmonics on my FT857D and Argo, every odd harmonic the error > increase. The radio has high stability but it is not exact for sure. I could > test harmonics with my SA but Trimble would be my only reference. > > The question is: how could I be 100% sure that the Trimble frequency is > absolutely trustworthy? I have LH and it says oscillator is within > 300-1000ppt. > Is it enough to conclude the frequency is okay and the ProgRock is wrong? > > TIA > > Giuseppe Marullo > IW2JWW - JN45RQ > > > _______________________________________________ > 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.
