[ntp:questions] GPS and the December 5/6 Solar Flare

Eugen COCA ecoca at eed.usv.ro
Fri Apr 6 15:34:47 UTC 2007


I made a test with the following configuration file:

server 127.127.20.1 minpoll 6 maxpoll 6 prefer
fudge 127.127.20.1 flag3 0 time1 0.000 refid GPS

server 127.127.22.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.22.1 flag3 1 time1 0.000 refid PPS

(the lines are in this order in the file)

All other servers are with the "noselect" keyword in their lines.

After 67 hours I obtained the following result:

ntp1.usv.ro

ntpq> pe
     remote           refid      st t when poll reach   delay
offset  jitter
==============================================================================
 GPS_NMEA(1)     .GPS.            0 l  67h   64    0    0.000
0.000   0.004
 ptbtime1.ptb.de .PTB.            1 u  181  256  377   56.661
-0.200   0.639
 ntps1-1.cs.tu-b .PPS.            1 u  211  256   37   56.950
0.857   0.040
 ntp-p1.obspm.fr .1PPS.           1 u  177  256  377   56.803
-0.315   6.425
 gps-2.mit.edu   .GPS.            1 u  229  256  377  133.582
2.334   0.335
oPPS(1)          .PPS.            0 l    5   16  377    0.000
-0.001   0.004
 ntp2.usv.ro     .PPS.            1 u   42   64  377    0.193
0.001   0.007
 ntp3.usv.ro     .PPS.            1 u   50   64  377    0.238
0.004   0.007
 ptbtime2.ptb.de .PTB.            1 u  142  256  377   56.393
1.514   0.465
 gps-1.mit.edu   .GPS.            1 u  195  256  377  132.778
2.054   0.305

The system has a GPS 18LVC receiver and a PRS-10 Rubidium Frequency
Standard conditioning the PPS signal from the GPS receiver. During the
test the GPS power was cut off and the only source of sync was the PPS
signal. ntp2.usv.ro and ntp3.usv.ro are in the same network and where
synchronized with the GPS signal during this test.

Strange to notice the "double" PREFER keyword lines in the ntp.conf
file. This configuration is not explained - but the configuration
WORKS ! And is the only one that worked.

Are there other ideeas to make a GPS synchronized server to pass over
a GPS failure for such an extended period ?





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