[lightswitch05]

I’m not familiar with Chrony. With NTPsec, the PPS driver docs say [0]:

> While this driver can discipline the time and frequency relative to the PPS source, it cannot number the seconds. For this purpose an auxiliary source is required;

And so (with NTPsec), you need to define two sources even though it’s coming from the same device. One for the PPS signal for clock discipline, the other for the clock value.

> refclock pps ppspath /dev/gpspps0 prefer

> refclock nmea baud 57600 prefer

0: https://docs.ntpsec.org/latest/driver_pps.html

[willis936]

Sure, but that aux data should not be used for any sub-second accuracy information. The PPS is the end-all be-all definition of the start-of-second. Improving performance of another band should never affect the performance of the sub-second jitter.

They should hook up a scope to that PPS output and compare it to a solid reference. I suspect if they're experiencing intermittent dropouts on a poor GPS module that the PPS signal likely is not a high quality reference. Those ublox counterfeits might be okay, but I've been really impressed with Navspark's pin-compatible ublox "knockoffs". Super cheap, super performant.