[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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