Re: [chrony-users] Setting up Chrony with PPS

[Deven Hickingbotham <devenh@xxxxxxxxxxx>]

I believe the stats that appear below with show that the system problem 
was just poor antenna placement.

On 2/19/2016 7:46 AM, Miroslav Lichvar wrote:
> When chronyd has some NTP sources, you may want to tweak the offset
> value of the SHM refclock so the measured offset as reported in
> "chronyc sourcestats" is close to zero and the PPS signal can be
> locked to it properly.

Given the figures below, how should offset and delay be calculated?

Finally, any other suggestions for how to setup chrony.conf to quickly 
converge to PPS time after startup or acquisition of GPS signal?

chrony.conf:

server 0.us.pool.ntp.org
server 1.us.pool.ntp.org
server 2.us.pool.ntp.org
server 3.us.pool.ntp.org

refclock PPS /dev/pps0 lock NMEA refid PPS
refclock SHM 0 offset 0.5 delay 0.2 refid NMEA noselect


210 Number of sources = 6
MS Name/IP address    Stratum Poll Reach LastRx Last sample
========================================================================
#* PPS                      0   4   377    19    -24ns[ -194ns] +/-217ns
#? NMEA                     0   4   377    17   -148ms[ -148ms] +/-102ms
^- services.quadranet.com   3  10   377    41  -2088us[-2088us] +/- 62ms
^- time-c.nist.gov          1  10   237   224    -37ms[  -37ms] +/- 80ms
^- clock.xmission.com       1  10   377    81  -8631us[-8631us] +/- 25ms
^- leeloo.scurvynet.com     2  10   377   662  -3173us[-3141us] +/- 89ms

210 Number of sources = 6
Name/IP Address        NP  NR  Span Frequency Freq Skew  Offset  Std Dev
========================================================================
PPS                     7   5    96    -0.002     0.011    -24ns   128ns
NMEA                    8   7   113  +226.686   403.511   -148ms  5486us
services.quadranet.com  6   3   85m    +0.913     1.222  -1893us   635us
time-c.nist.gov        10   8  241m    +0.946     0.273    -36ms   955us
clock.xmission.com     17   9  275m    +0.881     0.219  -8139us  1216us
leeloo.scurvynet.com   40  21  530m    +1.072     0.228   -120us  4307us

Reference ID    : 80.80.83.0 (PPS)
Stratum         : 1
Ref time (UTC)  : Sun Feb 21 15:10:09 2016
System time     : 0.000000000 seconds fast of NTP time
Last offset     : -0.000000242 seconds
RMS offset      : 0.000015393 seconds
Frequency       : 3.375 ppm fast
Residual freq   : -0.002 ppm
Skew            : 0.016 ppm
Root delay      : 0.000000 seconds
Root dispersion : 0.000020 seconds
Update interval : 16.0 seconds
Leap status     : Normal

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