Hi Nick,
Let's use the example of a Ublox timing receiver. In the TIM-TP data package,
there is a qErr value, which is the quantization error of the *next* PPS pulse
output by the receiver. At the next PPS, you would subtract that from the
unwrapped phase measurement your GPSDO makes and that would give you the actual
phase difference between your OCXO (or generated PPS) and what Tom has called
"The PPS", which is the pulse occurring exactly at the top of the second ---
give or take coax length, etc.
Bob
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From: Nick Sayer via time-nuts <[email protected]>
To: Chris Arnold via time-nuts <[email protected]>
Sent: Monday, July 18, 2016 5:31 PM
Subject: [time-nuts] How does sawtooth compensation work?
I've read Tom's page about sawtooth PPS jitter and I believe I understand where
it comes from. My current GPSDOs ignore the phenomenon. Certainly at the
moment, I'm satisfied with that. The systems gravitate towards PLL time
constants that average it all away.
What I'd like to understand is how sawtooth compensation works with receivers
that support it. Is it that I expect an NMEA sentence with a nanosecond offset
value that I add to any phase difference observation that I get?
Sent from my iPhone
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