[time-nuts] leontp offset?

Bob Camp kb8tq at n1k.org
Sat Oct 15 10:36:28 EDT 2016


Hi

The 10 ms offset *is* suspiciously close to what you would get with a 10 ms pulse stretcher 
*and* a setup that is triggering on the wrong edge. 

Bob



> On Oct 15, 2016, at 9:40 AM, Vlad <time at patoka.org> wrote:
> 
> 
> 
> I am wandering if it will be the same results without 'FatPPS'.  In my Lab I was able to use T-Bolt 1PPS through TADD-3 (not from RS2323). Works stable.
> 
> I am using 'chrony' though
> 
> 210 Number of sources = 5
>                             .- Number of sample points in measurement set.
>                            /    .- Number of residual runs with same sign.
>                           |    /    .- Length of measurement set (time).
>                           |   |    /      .- Est. clock freq error (ppm).
>                           |   |   |      /           .- Est. error in freq.
>                           |   |   |     |           /         .- Est. offset.
>                           |   |   |     |          |          |   On the -.
>                           |   |   |     |          |          |   samples. \
>                           |   |   |     |          |          |             |
> Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
> ==============================================================================
> PPS0                       19  10   291     -0.000      0.003     -1ns   293ns
> ntp2.torix.ca              10   7  154m     +0.848      0.256  +4251us   459us
> time.sidereal.ca            9   5  137m     +0.311      0.539  -3996us   837us
> S0106c04a00f34a5d.vc.shaw  40  18   11h     -0.036      0.050  -5995us  1009us
> omega.goholdings.ca        58  29   16h     -0.040      0.036  +5987us  1345us
> 
> 
> 
> On 2016-10-15 01:17, Bob wrote:
>> 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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> 
> -- 
> WBW,
> 
> V.P.
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