[time-nuts] leontp offset?

[Bob]

Here is a BSD computer running ntpd, configured with hardware serial port attached GPS, PPS through FatPPS into the serial port seen as GPS_NMEA below, along with the two LeoNTP servers at 192.168.20.5 and 192.168.20.6, offset and jitter appear reasonable, as expected on a LAN, and I've seen no anomalies over the past month.

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
oGPS_NMEA(0)     .GPS.            0 l   20   16  377    0.000    0.002   0.001  <- BSD+PPS
+192.168.20.5    .GPS.            1 u   24   64  377    0.162   -0.011   0.006  <- LeoNTP #1
+192.168.20.6    .GPS.            1 u   44   64  377    0.159   -0.009   0.004  <- LeoNTP #2

The three devices above have separate GPS antennas installed within a couple meters of each other, all three see between 10 and 12 satellites.

A couple weeks ago I also used an HP 5334B to compare each LeoNTP PPS to a TVB screened T-Bolt PPS, the T-Bolt was configured with LH extended location calibration and in over-determined time mode, T-bolt sees 7 or 8 satellites. Each LeoNTP 1PPS BNC output agreed with the T-Bolt 1PPS to within some tens of nanoseconds over a 30 hour run.  The LeoNTP and T-Bolt shared a Microsemi gps splitter and the same antenna.

After reading your email, as a final sanity check we just set up a Linux ntpd configured with both LeoNTP servers along with four random us ntp pool servers.  After an hour here is ntpq -p.

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+192.168.20.5    .GPS.            1 u   46   64  377    0.604   -0.059   0.123
*192.168.20.6    .GPS.            1 u   40   64  377    0.602   -0.050   0.116
-x.ns.gin.ntt.ne 249.224.99.213   2 u  528 1024  377   12.232    2.023  10.209
xclockb.ntpjs.or 132.163.4.101    2 u  421 1024  373   61.785    2.924   0.244
+four10.gac.edu  216.218.254.202  2 u 1017 1024  377   63.364   -0.137   0.381
-c-73-37-183-90. 142.66.101.13    2 u  418 1024  377   64.903    1.928   2.507

In the above, 192.168.20.5 and 192.168.20.6 are each LeoNTP, they agree with the four pool servers as nicely as can be expected with a cable modem connection.

Summary:  I do not see any issues with the LeoNTP servers, both devices worked as expected.  LeoNTP is also by far the friendliest commercial NTP server I've ever configured, the human interface is well thought out.

As Hal suggested, perhaps there is some systematic configuration issue with your other pair of clocks?  I keep a $40 Adafruit Ultimate GPS with PPS output and little puck antenna, for the sort of situation you see, it powers up indoors in 60 seconds and its PPS into ntpd would let you have a 3rd clock if using internet servers doesn't get you an answer.

I have no relationship with the vendor other than as a satisfied customer.

Bob


> On Oct 14, 2016, at 5:31 PM, gmx tallahassee <gmx.tallahassee at gmail.com> wrote:
> 
> Hi all,
> 
> I'm checking out the leontp ntp time server (leontp.com).  After a week of
> use I am getting the following ntp -q output:
> 
> $ ntpq -pn
>     remote           refid      st t when poll reach   delay   offset
> jitter
> ==============================================================================
> *172.17.21.11    .GPS.            1 u   13   16  377    0.137    0.077
> 0.054             <- Arbiter 1084C GPS Clock
> +172.17.21.12    .GPS.            1 u   11   16  377    0.101    0.085
> 0.174             <- Arbiter 1084C GPS Clock
> x172.17.21.233   .GPS.            1 u   11   16  377    0.071    9.760
> 0.061            <- LeoNTP
> 
> the offset of the leontp device from the other clocks has consistently been
> in the 9.5 -10.5 range.  since I'm measuring all three sources  from the
> same (EL7) computer, I would expect that the offset of the leontp unit to
> converge to be in the close neighborhood of the offsets of the arbiters.
> It has not converged, instead maintaining the ~10ms offset.
> 
> Thoughts?
> 
> Thanks.
> 
> Details:
> 
> 172.17.21.11 is approx 400M away through two Cisco 3750G switches no
> routing.
> 172.17.21.12 is in the same rack as the leoNTP unit and plugged into the
> same 3750G switch
> 
> Antenna location for the .12 arbiter and the leontp is on the same rung of
> the same tower.  Tower has clear horizon to horizon view.  cable runs are
> the same (obviously).
> 
> I did run with the included puck in my south facing office window (rather
> than the GPS antenna on the tower) for a couple of days when I first got
> the unit.  The offset behaviour was the same.
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