[time-nuts] Furuno GT-87
Mark Sims
holrum at hotmail.com
Sat Mar 17 20:43:03 EDT 2018
The TICC reference is a HP-5071A cesium beam oscillator with high performance tube. The GT-87 is connected to the TICC channel B input. The TICC is running in timestamp mode.
The orange plot is the Time Interval Error of the 1PPS signal... the difference between 1 second and the measured 1PPS.
The grey plot is the accumulated phase error for channel B.
I just finished the measurement of the GT87 running on GLONASS sats only. The PPS span was still in the +/-4 ns range with a couple of points +/- 6 ns. However the ADEV measurements on the 1PPS were 3 (at tau-100 secs) to 5 times higher. (at tau=10000 seconds). I am typically tracking 5-8 GLONASS sats.
The GT87 sends an "accuracy" value. In GLONASS only mode the GT87 reports an accuracy of 12 ns. With GPS enabled it tends to say 5-6 ns, but I have seen it as low as 2 ns.
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