[ntp:questions] Garmin GPS 18LVC Setup but questions on best way

George R.Kasica georgek at netwrx1.com
Tue Dec 30 18:12:47 UTC 2008


On Tue, 30 Dec 2008 17:24:36 GMT, "David J Taylor"
<david-taylor at blueyonder.neither-this-part.nor-this-bit.co.uk> wrote:

>George R. Kasica wrote:
>[]
>> Next step....I added back GPS NEMA data without the gpsd daemon (I
>> don't pass the data out to anywhere so there's no real need for it)
>>
>> and I see
>>
>> # ntpq -p
>>     remote           refid      st t when poll reach   delay   offset
>> jitter
>> ==============================================================================
>> xGPS_NMEA(0)     .GPS.            0 l   13   16  377    0.000  -616.37
>> 10.466
>> *SHM(0)          .PPS.            0 l   14   16  377    0.000   -0.557
>> 0.712
>> eagle-local     192.168.1.7      2 u   36   64  377    0.153  -44.398
>> 0.607
>> apollo-local    192.168.1.7      3 u   24   64  377    0.250  -16.713
>> 1.912
>> -mirror          209.132.176.4    2 u   29   64  377   10.272    6.391
>> 135.974
>> +tesla.fireduck. 198.82.1.202     3 u   28   64  377   36.123    2.841
>> 115.565
>> +rikku.vrillusio 209.51.161.238   2 u   21   64  377   38.531   -3.260
>> 156.267
>>
>>
>> I have good PPS and am getting GPS NEMA in as well but the offset for
>> the NEMA data seems quite large....what would I do to fix that??
>>
>> George
>
>George,
>
>On my FreeBSD system, the ntpq -p output looks like this (some servers 
>omitted):
>
>     remote           refid      st t when poll reach   delay   offset 
>jitter
>==============================================================================
>-utserv.mcc.ac.u 193.62.22.98     2 u   58   64  377   25.548    3.732 
>2.715
>*GPS_NMEA(1)     .PPS.            0 l   52   64  377    0.000    0.002 
>0.008
>
>With just the reference clock type 20, I get the accuracy needed.  The PPS 
>line from the GBS-18 LVC is wired to the DCD line of the serial port.  In 
>my ignorance, I don't see why you even need the SHM driver, but as I said 
>before, I'm no expert!  I don't see why my system picks up the PPS from 
>just the type 20 driver, and yours does not.
>
Do you have the PPS kernel hack compiled in? That may be doing it for
you. I can't easily add that here with the Fedora Core 9 RPM kernel I
have. What are you using in your ntp.conf settings for the clock setup
lines and fudge?

George




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