running without pool or other servers

[shouldbe q931]

I am attempting to run ntpsec in a "standalone" instance where it is
only provided time and PPS from a GPS receiver (via gpsd).

The relevant lines in ntp.conf I have arrived at are

# GPS PPS reference (NTP1)
refclock shm unit 1 refid PPS minpoll 0 maxpoll 0

# GPS Serial data reference (NTP0)
refclock shm unit 0 prefer minpoll 4 maxpoll 4 time1 +0.118 stratum 1
refid GPS flag1 1

The time1 time has been calculated for the instance.

ntpsec was configured with "./waf configure --refclock=all"

While running "watch -n1 ntpq -p" I see the PPS line alternate between
x and o and sometimes +, and the GPS line alternate between x and *

The reach remains at 377 for both the PPS and GPS lines when the line
prefix changes between x and * or o or +

While running cgps -s at the same time I do not see any drops in the GPS signal.

I presume I have missed something basic, but have reached a "can't see
the wood for the trees" point and would appreciate any guidance as to
what I have missed.

Cheers