[time-nuts] Trimble NetRS PPS output

[Mark Sims]

I recently got in a Trimble NetRS L1/L2/L2C survey grade receiver (Evil Uncle Bob made me do it ;-)  ).   It consistently gives position error ellipses in the 6mm range after post-processing 24 hours of data.

I had high hopes it would have a decent 1PPS output...  nope.  The PPS output usually has a 40 nsec span (looks like a 25 MHz clock is in the device), with some occasional 80 nsec or so spans.  The internal oscillator looks to be an OCXO... the PPS does not show your typical wobbly PPS sawtooth error plots.  It is more like a pulse train with a slowly drifting duty cycle.

But the killer is the occasional (2-3 times per hour) "zingers" in the PPS output.  These show up as a large negative error spike followed immediately by an equal positive errors.   These "zingers" are typically in the 1-100 millisecond range.   I can't imagine how/why the circuitry would do this...

Lady Heather can now monitor the NetRS (and probably other receivers that can output RT17 and Trimcomm data.   The NetRS does not respond to requests for status and configuration commands over the RT17 ports, so a lot of useful/informative stuff is not available.  It can write RINEX files.
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