Hi Attila, I agree, keep the gps away from such fast and large temperature excursions. The internal tcxo is not as stable as one would expect.. Building a larger box and burying it could help slow the temp gradient..
Bye, Said Sent From iPhone On Apr 25, 2012, at 8:52, Magnus Danielson <mag...@rubidium.dyndns.org> wrote: > Hi Attila, > > On 04/25/2012 04:56 PM, Attila Kinali wrote: >> Moin, >> >> We've a customer who does sub mm measurements using GPS in alpine >> enviroment. This is done using LEA-6T modules, logging of raw phase >> data and offline post processing using long averaging windows. >> >> Now, the customer had some problems reaching the precision requirements >> and i'm wondering whether one of the causes might be the use of a >> Trimble Bullet antenna [1] (3V type) and not a geodetic antenna. Can it be >> that the phase center of the Trimble Bullet antenna isn't as well defined >> as it should be for this application? Would the addional gain of the 5V >> version help (35dB instead of 30dB)? Or should we evaluate a different >> antenna all together. >> >> A major restriction in this application is that there is a very harsh >> enviroment, temperature wise. We have measured -40°C to +30°C jumps in >> just 2h. Most of the time the devices are below freezing temperature, >> but can go up to 50°C when in direct sunlight. >> >> The next big restriction is, that this is a research project. So >> there isn't as much money available as there should be to "do it right". >> >> So, if someone could give a few tips how to improve things, this would >> be much appreciated. >> >> Attila Kinali >> >> >> [1] http://www.trimble.com/timing/bullet-gps-antenna.aspx?dtID=overview&; >> > > You can get both L1 choke rings and pin-wheels on Ebay for fairly reasonable > money. That should help on multipath. > > Another aspect is the temperature shielding of the receiver itself. If it can > be kept at a fairly stable temperature would also help. Using a better > reference oscillator could also be worthwhile. Consider what a FEI 5680 could > do for you. > > Also, the way the antenna is mounted can be relevant. Up, up and away... such > that any funny reflections is below the antenna. > > A simple temperature stabilisation might be to simply dig the GPS receiver > down. > > Cheers, > Magnus > > _______________________________________________ > 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.
