Hi Brooke, Yes, the M12 timing receiver is very nice.
Attached is a preliminary plot comparing 1 PPS jitter among four common GPS time recievers including a M12+ with sawtooth correction. In the plot the VP is dark blue and the M12+ is pink. In the table below, times are RMS over 10k seconds. 31.5 ns -- Oncore VP 9.3 ns -- CNS-1 (M12+) 3.0 ns -- CNS-2/O1 (M12+ h/w sawtooth correction) 1.3 ns -- standard HP 58503B (8ch VP, 10811 GPSDO) The M12+ with sawtooth correction is yellow and the GPSDO is green. You can see that although the M12+ with sawtooth correction has slightly more jitter than the GPSDO, as a time standard on average it looks like it might be more accurate more of the time. As you know from playing with a 58503A or Z3801A a GPSDO does a fair amount of wandering and you can see this in the plot. If you require a real-time 10 MHz or 1 PPS then use a GPSDO but if you're collecting data only for later processing then it looks like an M12+ with sawtooth correction is just as good or better. /tvb ----- Original Message ----- From: "Brooke Clarke" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <[email protected]> Sent: Friday, April 15, 2005 16:23 Subject: [time-nuts] M12+T First Light > Hi: > > To use an astronomical term "First Light" meaning my first use of the M12+T GPS Timing receiver. WOW!!!! > > The manual description of the @@Hn command shows -128 to +127 ns as the range for the sawtooth error. On the 8 channel unit I think the actual sawtooth error was around + and - 50 ns. > > I looked at the @@Hn data stream in TAC32 and saw numbers in the mid teens, much lower than the 8 chan sawtooth error. I'm not sure if this is typical, or maybe I was just lucky. I have the El mask set to 50 degrees and Time RAIM turned off. > > I've made a small number of measurements against the Cesium source whose C field I haven't touched for a month or two and the standard deviation for 5,000 1 PPS measurements ranges from 14 to 27 ns, whereas the 8 channel unit was typically in the mid 30 ns range with excursions much higher. > > So the way timing is being handled in the M12+T is far better than the old 8 channel units, i.e. it's not just more channels. > > Having Fun, > > Brooke Clarke, N6GCE
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