Assuming it's just tracking the CDMA pilots, the 1PPS output is likely not aligned with UTC. The problem is that the pilot channel is just a PN sequence with no modulating data - so when you lock to it you can know that your local clock is 19200Hz * 64 chips/bit (1.228MHz) - but that's all you know. Even the code phase doesn't tell you anything, since there are two unknowns - the first is the distance to the cell and the second is the code phase offset on this specific pilot (each BTS has it's modulating sequence offset by an integer multiple of 64 chips to reduce mutual interference) - the second piece of information you can obtain by reading one of the overhead channels, but the first is basically not available just using a receiver (your phone
On Wed, Nov 30, 2011 at 3:06 AM, Kevin Rosenberg <[email protected]> wrote: > Hi Charles, > > Thanks very much for the information on the pinout of the TOD connector > on the TS2700. > > I verified the PPS signal between pins 6 and 1. It's duration and voltage > matches your report. I compared the timing of the PPS signal with the PPS > of two synchronized thunderbolts. > > Interesting, the PPS signal from the TS2700 is delayed a rather constant > 280ms compared to the two TBolts over about a minute of observation. > > One reason why I'm interested in the PPS output is to provide a varied > NTP source for my Soekris 4501s. I have TBolts, M12M, Netclock/2 WWVB, > and Garmin 18x. I thought it's be nice to have a CDMA clock as well. > > If of the PPS offset remains a constant, then I could use the TS2700 as > an NTP reference clock. (I realize I'd have to write an NTP driver for > the device). But, the fact that the TS2700 is a 1/4 sec off of GPS > PPS makes me suspicious that the device was never interested to provide > a precise PPS -- just a reference frequency source as advertised. > > Anyway, many thanks for all your help in understanding the device. > I'll report more if I learn anything interesting. > > Kevin > > > _______________________________________________ > 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. _______________________________________________ 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.
