Hi All, I'll respond to all here, since I'm a little slow at times...
John, This unit has been up and running for at least a month. I've restarted the GPSDO a few times, but the GPS has remained on. So, if your unit is up for extended periods of time and you see something similar, please report back.
Azelio, That spec is much worse than what I've been seeing. Not having a CS and other equipment it's hard to know exactly how good/bad the GPS really is. However the TIC in the GPSDO reporting short term (<500s) differences against the OCXO on the order of +/-3nS Peak (6nS Peak-Peak). Long term (24 hours) there are furnace/HVAC swings that appear to push that up to +/- 7nS or 8nS (14 to 16nS Peak-Peak). About a week ago, those short term levels jumped to +/-25nS Peak (50nS Peak-Peak). I let it run, over several days saw no improvement. After the 48hour survey, it dropped back to the 'normal' levels instantly.
Bob, This unit is using sawtooth correction. The saw tooth correction is on the order of +/-10.3 nS max. It absolutely improves the measurement! It appears in the log file that the PPS was still getting corrected. My feeling is it's doubtful the OXCO was doing it, as the survey in changed the results.
Do you have a feel for what a 1.8m/6ft error in antenna coordinates would do PPS results?
Any other insights you might have would be appreciated. Thanks! Dan
Hello Dan, I have a LEA-6T running; have a nice external antenna, etc - it's been running for several days - I will check the 1PPS and report if I find anything like what you've discussed. Regards, John
I have noticed the sudden improvement of the PPS wander after the survey on a LEA-5T but the RMS wander is 30ns (see the timing appnote GPS.G6-X-11007 from uBlox) uncorrected and 15ns if sawtooth corrected. Your 3ns is strange, not the 30ns.
Hi It sounds like you are not doing sawtooth correction. If that is correct, then you may have been watching hanging bridges. Bob
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