On 05/14/2012 09:11 PM, Mark Sims wrote:
Attached is a Lady Heather screen dump of a Trimble Resolution-SMT timing receiver behaving badly. The first quarter of the plot the unit was tracking all sats above 0 degrees/0 dBc. The next quarter the masks were set to 30 degrees/30 dBc. Then at the half way point, something strange happened... The green plot is the sawtooth correction value. It should be +/- 15 nS, but was only running +10/-13 ns. At the half way point the sawtooth started spiking down to -38.000000 ns... obviously some internal clipping limit. It ran this way for a day, then I reset the unit and all has been well since. The purple plot is the unit's "local clock bias". It is reported like the Tbolt's PPS value. It is a sawtooth that covers a 1000 usec (almost) range. It repeats over a 28 minute period. The white plot is the "clock bias rate". In comes in like the Tbolt OSC value. Yellow is temperature. Note how well those two plots track each other. Suggests that some active temperature control might be useful. One nice thing about the Resolution receiver is that it returns tracking info for all sats, even those below the elevation/signal masks. This lets you build a signal level map even when you have elevation and signal level masks set. Also note the high signal levels. On a Tbolt, I never see signals past green... the receiver is 6 db more sensitive.
Thanks for your notes on this device. I just got mine in the mail today, along with a 40dB antenna. Unfortunately I don't yet have the cable to connect the two, so right now it's running from a short length of bare wire, indoors, and as such can't really get a decent fix :-) It has managed to lock onto 4 satellites though, so it seems to work well enough to give me something to look at until I get materials to make a cable.
I am planning on making a simple NTP server using the Resolution SMT as the PPS input and a Rb oscillator (or any other 10MHz clock) to clock the CPU on the computer. If people are interested in a friendly interface board to the device let me know. My initial interface board design puts the PPS on the Carrier Detect line at RS-232 levels as is typical for this sort of thing, but USB is also very easy to do.
Regarding the default protocol being TEP, I easily managed to reconfigure it for TSIP using GPS Studio. The current version (1.08.0) supports TEP, and using Tools -> Configurator you can reprogram the Resolution SMT to use TSIP or NMEA by default. There are several other parameters that can be reprogrammed per the manual, including the width of the PPS.
Cheers, -- m. tharp _______________________________________________ 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.
