I agree with Hal and if you have a reference you can tell how much the crystal is off. My timing GPS receiver after 1 hour has a total uncorrected wander of 112ns. Never seen 400ns on a timing receiver (maybe I haven't waited long enough).
On Tue, Apr 23, 2013 at 12:49 AM, Azelio Boriani <azelio.bori...@screen.it>wrote: > Have you any reference? A TBolt, Z3801 or similar? > > > On Mon, Apr 22, 2013 at 9:53 PM, Daniel Ginsburg <dginsb...@gmail.com>wrote: > >> Hi all, >> >> I have bought a Resolution SMT GG for me to play with, and build a very >> simple breakout board. >> >> The receiver appears to be working (in a sense). That is, it powers up, >> it emits valid TSIP, it was able to survey it's position - a sane one. >> Trimble GPS Studio is able to recognize it, and extract validly looking >> data from it. In other words, I don't believe I have botched the module >> while hand-soldering it. >> >> Now I have hooked it up to a stm32f4discovery board to sync with PPS. >> That's were the weirdness begins. >> >> First, the frequency offset of the microcontroller. I use a built-in >> counting timer in the uC which runs at 84MHz to measure the duration >> between 2 PPS. What I get is ~84008000 timer ticks between two pulses, >> which corresponds to about 95ppm offset. While the crystal on the board is >> of the cheapest variety, I think 95ppm is just too much. Is that correct, >> and 95ppm offset even for a the most crappy oscillator is not a reasonable >> value? >> >> Second, the GPS sawtooth. The PPS does exhibit sawtooth, which is >> expected. But the sawtooth is HUGE. While the spec claims +-15ns, I see >> more that +-400ns with period about 30 seconds. This is not sane. I must >> have done something totally wrong. >> >> Something has to be terribly wrong with my measurements. I'd really >> appreciate any hints on how to find out the cause of the described >> weirdness. >> _______________________________________________ >> 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.