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

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


Hi

Now I have gps-18x-LVC nmea 127.127.20.0 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 "127.127.20.0 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.

David




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