[time-nuts] Sawtooth Effects in 1PPS
Tom Clark, K3IO
K3IO at verizon.net
Mon Aug 21 02:46:52 EDT 2006
Faisal Kahn asked
I am currently working on problems with GPS timings, as I said in my previous e
mails. I presented some of my problems and got quite helping feedbacks. I just
wanted to update regarding my progress If u visit the page http://www.leapse
you will found some sawtooth waveforms there. I have been observing the M12, No
vAtel OEM4 rcvrs' timing pulses (1PPS) and getting a similar sawtooth effect. b
ut I am unable to findout what is causing such thing. It would be quite helpful
for me if anyone could guide me in this regard.
I cannot comment on the Novatel receivers, but you can answer the
question for the Motorola receivers by looking at a couple of the
papers on our http://gpstime.com website. In particular, take a
look at the "Low Cost ..." paper from 2000, the "Critical Evaluation
..." paper from 2002 and the latest "Timing for VLBI" paper from 2005.
What you seek is in the "Timing for VLBI" paper, take a look at slide
#21 for a technical explanation, Slide #25 for an example of how it
can be "fixed" in data processing, Slide #26 for a simple circuit that
can fix it in real-time, and slide #29 to see how well the hardware
Rick Hambly (http://www.cnssys.com) sells a clock with the hardware
"fix" installed and provides his TAC32 software that can be used for a
post-processing fix. Rick & I are planning to describe the circuit at
the upcoming December PTTI meeting in Virginia; I've attached a PDF
version of the abstract for that paper.
Hope that helped -- Tom
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