I've seen similar with my TICC when observing a PPS - can't remember whether the PPS was from the Thunderbolt or LTE Lite.
There was a distinct glitch on the frequency plot when it happened and it was pretty easy in timelab to expand the trace around the glitch to take a better look. I did not see any such problem when dividing the 10MHz to 1PPS with a PICDIV so I figured it was due to the GPSDO steering the PPS signal as satellites appear/disappear - my antenna location is far from optimal. On Sun, Mar 19, 2017 at 12:57 PM, Tom Van Baak <t...@leapsecond.com> wrote: > > I'm probably missing something obvious but don't understand what's > > happened here so any suggestions would be welcome. > > Hi Nigel, > > Your setup sounds fine. Off-list, send me the TIM files and I'll see what > happened. > > I know we all love ADEV but in general always look at the phase, phase > residual, and frequency plots first before you bother with ADEV. These > strip chart plots better show your raw data and measurement. Even a single > glitch will be visible. Only if these plots are "clean" should you go ahead > and use ADEV. Another trick is using the TimeLab "Trace" feature which > splits the data into N segments and computes ADEV for each one > independently. > > But in this particular case where you are comparing two GPSDO a phase > difference plot will likely be more informative than an ADEV plot anyway. > You may also want to play around with the averaging value (command 'g'). > > /tvb > > ----- Original Message ----- > From: "GandalfG8--- via time-nuts" <time-nuts@febo.com> > To: <time-nuts@febo.com> > Sent: Sunday, March 19, 2017 9:08 AM > Subject: [time-nuts] ADEV query Timelab and TICC > > > > Yesterday I used one of John's excellent TICC modules for the first time > > and initially set up a quick test using the 10MHz output from a > Thunderbolt > > as the frequency reference to measure the 1PPS from an Oscilloquartz > Star4 > > GPSDO, with the TICC output feeding a USB3 port on a Windows 10 PC > running > > the 64 bit version of Timelab 1.29. > > > > I'll attach a copy of the test plots I'm referring to but just in case > > this doesn't get through I've also uploaded it to.... > > > > https://www.mediafire.com/?9bue90yp1e8ueu6 > > > > Using the basic settings as described in the TICC manual the first run > was > > for 1 hour and seemed fine so I decided to extend the run time to 6 > hours. > > The first 6 hour test started to follow the 1 hour plot as expected and I > > watched this on and off and can confirm it did so up to somewhere between > > the 100s and 1000s points on the x-axis, but some time after that the > > complete plot shifted upwards and then continued to completion to > produce the > > magenta trace. > > > > I wasn't watching when it shifted so don't know if it was a jump or a > > gradual shift but did see it continue until completion. When I repeated > the 6 > > hour test, again without changing anything, and hoping to observe the > effect > > as it happened, it produced the green trace which was what I'd been > > expecting to start with. Since then I've made other test runs and again > all seems > > to be as expected. > > > > > > Throughout the tests I have been simultaneously streaming data from the > > Star4 to Lady Heather via a "proper" serial port on the same PC so did > wonder > > if there might be some form of data conflict but it doesn't seem to have > > shown up as any obvious form of corruption and hasn't repeated itself. > > > > Nigel, GM8PZR > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.