Unfortunately I did not have the log activated. Although I did not see a phase shift I think that that may be just luck as looking back at the screen print of tboltmon 1 sec after the roll, I see that the DAC voltage changed by +0,00533mV from the value 10mins prior to the roll. My antenna is not positioned optimally so I am used to seeing occasional 40-200ns phase offsets due to multi path. My phase shift before rollover (-9min) was -118ns and drifting toward 0. The Tbolt and only been powered on 4Hrs prior to rollover but was in position hold and had a good almanac. At rollover +1s it was 50,52ns and at 41secs after rollover the offset was 127,66ns so I didn’t think it unusual. Looking at it again, I see that the 10MHz frequency offset was 0,10ppb prior to the rollover , but 2.01ppb at +1s , so it looks like I did get a glitch, but one of lesser magnitude than you reported.
> Le 30 juil. 2017 à 16:18, Tom Van Baak <[email protected]> a écrit : > > Hi Mike, > >> I was running Tboltmon as the rollover occurred and did not see any phase >> shift. > > I'm pleased you saw no phase shift at all. Did you happen to have a TBoltmon > log running? > >> Maybe your phase offset was due to your Tbolt being in survey mode and its >> apparent position shifted . > > The particular TBolt I used for the screen capture was powered up too soon > before GPS midnight for the survey to complete. So I just entered the > coordinates manually before the photo-op. > > But if you look at the two images again, the phase shift may be due to a > change in DAC value. My theory at this point is that the DAC voltage > calculation includes at least one component based on slope; and slope implies > elapsed time interval. A calculation like that would be upset if the > underlying time frame changes by -1023 weeks instead of +1 week, or -7168 > days instead of +1 day, etc. Or maybe the TBolt reset on rollover and went > back to a previously saved DAC value. I don't know. But for those of you > making your own GPSDO, keep subtle details like this in mind. > > The duration of the recovery depends on the time constant. Notice that Mark > uses a 500 s time constant and I used the default (100 s), so my TBolt > recovered much quicker than his. I'll have more info as I sift through > several TBolt's. > > /tvb > > > ----- Original Message ----- > From: "Mike Cook" <[email protected]> > To: "Tom Van Baak" <[email protected]>; "Discussion of precise time and > frequency measurement" <[email protected]> > Sent: Saturday, July 29, 2017 11:47 PM > Subject: Re: [time-nuts] Trimble Thunderbolt no longer determines the correct > date > > > Hi, > I was running Tboltmon as the rollover occurred and did not see any phase > shift. Old type Tbolt firmware 3.0 > Maybe your phase offset was due to your Tbolt being in survey mode and its > apparent position shifted . > > Mike > > >> Le 30 juil. 2017 à 02:16, Tom Van Baak <[email protected]> a écrit : >> >> Caught it. Some Trimble Thunderbolt TBoltmon.exe screen shots attached: >> >> GPS WN 1959 TOW 604799 (July 29, 2017 23:59:41) advanced to >> GPS WN 936 TOW 0 (December 13, 1997) instead of >> GPS WN 1960 TOW 0 (July 29, 2017 23:59:42). >> >> 1960 - 936 is 1024 weeks, as advertised for this version of the TBolt GPSDO. >> Note this happened at 23:59:42 UTC as expected (that's GPS midnight - 18 UTC >> leap seconds). I did not expect the reported 2.75 us 1PPS phase change and >> will look into that. >> >> /tvb >> <tbolt-20170729T165941.gif><tbolt-20170729T165942.gif><TBoltrollover.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. "The power of accurate observation is commonly called cynicism by those who have not got it. » George Bernard Shaw _______________________________________________ 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.
