[ntp:questions] GPS_NEMA, but high offset and jitter?
kgc at sonic.net
Wed Feb 24 19:41:25 UTC 2010
David J Taylor wrote:
> The reach = 0 suggests that the signals from the GPS are not being seen.
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 initial spike was the last restart.
# Garmin GPS 18 LVC
server 127.127.20.1 mode 0 prefer
fudge 127.127.20.1 flag1 1
Does the GPS_NEMA driver actually make use of the PPS signal (currently
wired to DCD on serial port) at all or does it just use the GPS sentences?
I'm wired up following http://www.satsignal.eu/ntp/GPS-interface-2.png
except that I used a NPN transistor to drive the PPS led so it wouldn't
load the PPS signal.
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