[ntp:questions] GPS_NEMA, but high offset and jitter?

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Wed Feb 24 21:36:57 UTC 2010

In article <4b8580e5$0$1616$742ec2ed at news.sonic.net>,
 Kelsey Cummings <kgc at sonic.net> writes:

>I'm not sure why it lost sync but I went ahead and upgraded to 4.2.7p5 
>from the ntp-dev port.
>I'm still seeing high offset and variable jitter.
>xGPS_NMEA(1)  .GPS.      0 l   45   64  377    0.000  -311.36  75.859
>-time.sr    207.200.81.. 2 u  348  512  377    0.643    0.977   2.984
>*clock.sjc.he .CDMA.     1 u  362  512  377    6.348   -2.584   0.289

The NMEA driver is a bit strange.  It processes two sources of time.
One is the text on the serial port.  The other is the PPS signal.

I think it has to get close enough on the text mode before the PPS
processing kicks in.

How about turning off the PPS fudge flag so you know you are
using the text mode.  Then watch it for a while and add a
fudge time2 to get it reasonably close.  When that works,
turn the PPS back on.

These are my opinions, not necessarily my employer's.  I hate spam.

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