[time-nuts] Raspberry PI 3 NTP server with GPS time data.

[jan hugo prins]

Hi,

To get a more stable NTP source into our production network I have
started exprerimenting with a Raspberry PI 3 with a GPS head. GPS data
is coming in fine, but the time is jumping around like a wild horse. The
result is that the only thing I get out of this experiment so far is a
more stable PPS signal in my NTP config but after some time both the GPS
time and the PPS are marked a false ticker and the only thing left is
the external reference clocks from outside our own network.

Parts used:
Raspberry PI 3
Adafruit GPS head: ADA-2324
External GPS antenna with 5 meter cable.

My NTP config looks like this:

logfile /var/log/ntpd.log
logconfig = all
driftfile /var/lib/ntp/ntp.drift
statsdir /var/log/ntpstats/
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
server 127.127.22.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.22.0 refid PPS flag3 1
server 127.127.28.0 minpoll 4 maxpoll 4 iburst
fudge 127.127.28.0 refid GPS time1 +0.550 flag1 1 stratum 4
server ntp0.nl.uu.net
server chime6.surfnet.nl
server chime5.surfnet.nl
server ntp1.virtu.nl

Now I got the idea that I might be able to use a DCF77 receiver to get a
stable timesource, but on the other hand, if the cause of my problem is
internal to the Raspberry PI setup then I might have exactly the same
problem with the DCF77 receiver.

The average on the NTP clocksource is close to 0.
root at raspberrypi:/var/log/ntpstats# cat peerstats |grep 127.127.28.0
|awk '{print $5}'| tail -n 1500 | awk 'NR == 1 { max=$1; min=$1; sum=0 }
{ if ($1>max) max=$1; if ($1<min) min=$1; sum+=$1;} END {printf "Min:
%d\tMax: %d\tAverage: %f\n", min, max, sum/NR}'
Min: 0    Max: 0    Average: 0.001101

Could anyone give me some advice on how to get this working? Or is my
idea to use a GPS clock to create a stable NTP setup the wrong way to go?

Thanks for any advice.
Jan Hugo Prins