[time-nuts] Datum TS2100 10MHz frequency drift

Philip Zahariev philip_zahariev at yahoo.com
Wed Oct 28 17:07:46 EDT 2015

Hello Time-nuts group,
few weeks ago I acquire TS2100GPS with TCXO. Few days ago receive MTI OCXO and install in device. After replacement change gain and filter constant as described byJason Rabel's post from 9/26/2010
Unfortunately I'm not happy with results because 10 MHz output signal after GPS lock (both leds on front "Locked" and "tracking" are "ON") has frequency drift (phase shift) with period around one second plus minus ~18 deg (+-5 ns) compared to other 10 MHz. I measure this by 2 channel scope on 10 nS sweep, first channel connected to TS2100 10 MHz output and second channel connected to 10 MHz from other GPSDO and sync by second channel. I'm sure that issue is in TS2100 because if disconnect GPS antenna frequency jumping disappear and frequency is more or less on spot (very very slow movement of one sinusoid against other) Also monitoring EFC voltage to OCXO with voltmeter has the same behavior confirmed by command "root timing util tfp 0" - again jumping up and down between 0xb4b5 and 0xb4c9.Firmware of TS2100 was 3.1 and "upgrade" to 4.1 does not solve problem. I suspect algorithm for adjustment of OCXO, but can't believe that this is normal. Can someone confirm that frequency change is not normal behavior. And of coarse I'm open for any suggestion how to solve problem.

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