Fabio, Happens in all the GPS receivers we have tested here. The difference between receivers is how fast they can recognize this error and how fast they can re-aquire once they shut off the 1PPS output due to tcxo instability.
There was a recent thread here about effects of adding a fan to a Z380x and the behavior you have seen is one of the reasons why that is a bad idea. Some receivers like Rockwell, Trimble etc allow for external 10MHz input from an ocxo or atomic clock, and some GPSDOs make use of that feature. Having a very stable and accurate 10MHz reference for the GPS is also supposed to reduce time to second fix. Bye, Said Sent From iPhone On Dec 28, 2012, at 14:27, Fabio Eboli <fabi...@quipo.it> wrote: > Like I mentioned in a precedent message > (answering Magnus) I'm seeing some temp > effects on my GPS module, see this message: > http://www.febo.com/pipermail/time-nuts/2012-December/073310.html > > In this graph there are the FE5680 voltages > and temperatures, and the temperature sensed > on the PCB near the GPS: > http://www.flickr.com/photos/14336723@N08/8318815981/ > > At time 20000s I heated the GPS receiver directly > with hot air gun and the drift started to change > rapidly. > At 25000 I heated the FE5680#2 I was using > as reference, but no visible effects, (apart > the slight variation in it's voltage :) > At 30000 33000 35000 seconds I heated the > GPS with a resistor placed near the PCB, > this generated more gradual temperature > variation on the GPS. > > Here can be seen the results of the heating > on the drift, (logging GPS PPS against Rb): > http://www.flickr.com/photos/14336723@N08/8318816213/ > the hotair generated so much variation, that > the script was unable to unscrable the data. > The resistor heater generated slower temperature > variation on the GPS, it's visible a glitch > everytime there was a temperature variation, > and the drift magnitude seem to follow the > variation of the temperature in time (dT/dt). > > I will try to reduce temperature sensivity > incrementing the thermal capacitance and > isolating the GPS from the ambient. > > Is this normal or it's a defect ("feature") of > my unit? I'm also curious about what internal > structure can generate this wander in PPS. > Like I said before it's like if the PPS pulse > (for intervals of few 100's of nS) depends on > something that is very temperature dependent. > > Thanks, > Fabio. > > _______________________________________________ > 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.
