Orin sent me his data files and I ran them through Lady Heather. Attached is a screen dump showing the Time Interval Error (TIE) plot of the 1PPS signal. This is the deviation of the 1PPS signal from the expected 1 second interval. Three of the bad points are flagged (1, 2, and 3 at the top of the plot area). It is interesting that these discontinuities are not simple spikes in the 1PPS signal (a couple of his bad points are simple spikes) but are followed by a "recovery" period of 30 seconds to a minute. It is also interesting that the LTE GPSDO 1PPS has such a wide range of TIE. A Tbolt / Z38xx GPSDO typically has a TIE in the 1PPS signal of around 1 nsec. The LTE TIE spans over 40 nanoseconds (not including the spikes). It seems like the LTE 1PPS may be from the GPS and not derived from dividing down the disciplined oscillator output.

The LTE-Lite User Manual (version 1.3) says: 2.3.7 1 PPS Module outputs The LTE-Lite SMT Module provides GPS raw 1 PPS CMOS pulse on pin 15 with sawtooth present, and a clean TCXO-generated, sawtooth-removed, UTC(GPS) phase-locked 1PPS output on pin 4. It is the pin 4 output that connects to the 1PPS-OUT jack on the eval board. So it is supposed to be cleanly divided down from the TCXO. (But I don't think Jackson Labs has published any of the circuitry on the LTE-Lite module itself). - Dave On Mon, Mar 20, 2017 at 2:07 AM, Mark Sims <holrum@hotmail.com> wrote: > > It is also interesting that the LTE GPSDO 1PPS has such a wide range of > TIE. A Tbolt / Z38xx GPSDO typically has a TIE in the 1PPS signal of > around 1 nsec. The LTE TIE spans over 40 nanoseconds (not including the > spikes). It seems like the LTE 1PPS may be from the GPS and not derived > from dividing down the disciplined oscillator output. > _______________________________________________ >