[ntp:questions] NMEA ref.clock better than my ISP's timeserver?

David J Taylor david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Wed May 27 19:21:28 UTC 2009


pisteoff at start.no wrote:
> After first trying the Haicom HI-204III claiming to have PPS in the
> manual without really having it, I bought a Garmin 18x LVC and
> connected it to the onboard COM-port (COM1) on my Asus M3N78 PRO
> mainboard. The Haicom is residing on a USB serial adapter (COM6) to
> check how stable the offset is.
>
> Running ntp4.2.5p175-win-x86-bin configured with a couple of
> timesources it seems like my ISP's NTP-server gets "disqualified".
> Before setting up my own ref.clock I used to have ntp.online.no as my
> "favorite NTP-server" thinking it would be the best / most local
> server, but now I might offer them to use me as a clock-source? ;)
>
> Anyone wishing to see on their own, might check with ntpq
> solbakken.dyndns.org   What kind of accuracy is expectable with a NMEA
> GPS with PPS connected to the DCD-line of the serial port? It's not
> that I have any special need for extreme accuracy, but I suppose it's
> allright having the most accurate clock in the neighborhood. :)
>
>
>
> Cheers,
> Geir F

Geir,

I typically see an offset within 0.2 milliseconds using a direct 
connection:

  http://www.satsignal.eu/mrtg/feenix_ntp_2.html

With USB I would see within about 0.5 milliseconds.

Both are much better than an Internet-based time source.

Your Haicom has an offset of nearly 0.5s, suggesting that you might be 
using the wrong edge of the PPS signal.

Cheers,
David 




More information about the questions mailing list