Hi all,
I have my USB GPS working pretty good at this point on both Windows and
Linux. I have some more Linux specific questions that I'll post later.
At the moment, I'm working on Windows. As has been suggested by others,
I know I can get hugely better accuracy using a different GPS and PPS,
and I plan to experiment with that when I get time and money. (I've
been ignoring lots of other household things while pursuing this
project.) For the moment, I just want to get optimum performance out of
the equipment that I have. For my immediate needs, +/- 6-10 ms accuracy
is perfectly adequate for what I'm doing.
Here's a recent ntpq -p printout:
C:\Windows\system32>ntpq -p
remote refid st t when poll reach delay offset
jitter
==============================================================================
*GPS_NMEA(5) .GPS1. 0 l 1 8 377 0.000 -1.181
0.977
+nist1-ny.ustimi .ACTS. 1 u 25 64 377 53.990 3.458
6.160
#216.119.63.113 .ACTS. 1 u 42 64 377 59.998 22.534
5.595
+india.colorado. .ACTS. 1 u 36 64 377 63.986 1.739
6.604
+ping-audit-207- .ACTS. 1 u 50 64 377 83.998 0.715
3.206
Note that my GPS is closely synchronized with 3 of the 4 NIST Stratum 1
servers. I have intentionally set the fudge factor on the GPS so this
is the case.
Now, here are the relevant server lines in ntp.conf:
server 127.127.20.5 prefer minpoll 3 maxpoll 3 mode 72
fudge 127.127.20.5 time2 0.2950 refid GPS1
server nist1-ny.ustiming.org prefer minpoll 6 maxpoll 13
server nist1.columbiacountyga.gov minpoll 6 maxpoll 13
server utcnist.colorado.edu minpoll 6 maxpoll 13
server nist1.aol-ca.truetime.com minpoll 6 maxpoll 13
Now, note that the NIST servers are being polled every 64 seconds. This
thing has been running this way since yesterday evening. However, in
the configuration file, those servers are allowed to poll up to every 2
hours. My question is, why are the internet servers being polled so
often continuously even though I have a stable GPS source available
which is the currently selected active clock? If I comment out the GPS
line, the internet servers will eventually go back to polling at longer
intervals. Note that I don't want to get banned from using any of these
public servers for hitting them too often.
Sincerely,
Ron
--
(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such. I don't always see new messages very quickly. If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)
Ron Frazier
timekeepingdude AT c3energy.com
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