[time-nuts] GPS message jitter (preliminary results)
holrum at hotmail.com
Wed Jul 20 19:51:35 EDT 2016
I added the ability of Lady Heather to calculate the time offset of the timing message from "wall clock" time. It calculates the difference between the system clock time to the time that the (end of) the timing message arrived. The result is only as good as your system clock, so the system clock really needs to be synced to something like NTP (otherwise it does a decent job of showing how much your system clock is drifting). Heather can plot the results and calculate xDEVs on both the message jitter and the message offset time in real time.
On another note, I did some jitter measurements on Jupiter-T and Jupiter-T Pico receivers. I can't imagine how they do it, but those things are insanely good. Running at 9600 baud, their message jitter into a hardware serial port is less than a millisecond peak-peak! Somebody paid a LOT of attention to getting the message timing consistent...
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