Hi Bruce, since the LPRO has significantly worse STS (according to this thread) than the Tapr Tbolt itself, then using the LPRO would only make sense if GPS is not available, and the unit is in holdover. This is similar to what you mentioned with the long time-constant. One would not want the LPRO to make the Tbolt worse than it is when perfectly locked to GPS. Our Fury and FireFly-II units allow an external 1PPS input to be connected, and the switchover will automatically happen if the internal GPS goes into holdover.
Using the LPRO on the external 1PPS, and selecting auto-switchover would give the best of both worlds: the excellent ADEV over all measurement intervals when GPS is available, and the Rubidium stability when GPS is out for longer time periods. Another advantage of this is that when the Fury/FireFly-II is using the LPRO 1PPS it will act as a cleanup-filter for the LPRO, and one would not lose the better STS of the Fury/FireFly OCXO. I am not sure if the Tbolt has an external 1PPS fail-safe backup input, I could not see one on the PCB. bye, Said In a message dated 1/25/2009 11:23:53 Pacific Standard Time, [email protected] writes: Given the large PPS output jitter wrt to the OCXO output frequency, this is probably a bad idea. There's nothing wrong with the idea of using a rubidium standard, you just need to cleanup its output first by phase locking a low noise OCXO with a suitable loop time constant to the rubidium output first. Use the cleaned up output as the 10MHz signal for the Thunderbolt and lock the rubidium standard to GPS using the thunderbolt with a suitably long loop time constant. This should result in low phase noise and drift during holdover. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
