[ntp:questions] fudge time1 for gps-18x-LVC?

David Lord snews at lordynet.org
Fri Feb 5 12:48:20 UTC 2010


Now I have gps-18x-LVC nmea along with
parallel port PPS using pps0 at ppbus0.

This seemed to work ok until pps timestamps suddenly jumped to
-350ms then PPS became false then deselected.

To correct for this I've set fudge " time1 0.65"
also "tos mindist 0.4"

Somehow I think I might be in sync with wrong edge of PPS.

Eventually I've got an ethernet cable running upstairs
(3 x long cables + 2 couplers).

I've added 3 x local servers sync to MSF + public servers
and marked noselect.

About 30 min later "ntpq -p" has:
source reach offset(ms)

+ GPS   377  23.247
o PPS   377  -0.298
   serv1 377  -1.295
   serv2 INIT  0.000
   serv3 377  -0.091

I suspect reason for INIT is both serv1 and serv3 have serv2
selected. The GPS offset has been varying +/- a lot but pps
still seems to be converging.

That looks ok to me except only Google hit for gps18x-lvc +
"fudge time1" gives setting of 0.0001

What does anyone else use for this fudge time1?

I'm using default nmea strings as garmin loses its settings
otherwise whilst not powered up.


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