[ntp:questions] best gps receiver for time synchronization

David J Taylor david-taylor at blueyonder.neither-this-bit.nor-this.co.uk
Mon Mar 9 21:30:39 UTC 2009


jack wrote:
> Hi all,
>
> I am trying to sync my Windows box to an external GPS source. I
> currently have BU353, whose output is not very periodic. I read up on
> ntpd implementation that uses PPS signal but I don't even have an RS
> 232 port on my computer.
>
> My questions:
> 1) what's the best GPS antenna (and protocol) in terms of
> consistencies in its output?
> 2) what kind of accuracy can i expect?
>
> Thanks to all.
>
> Jack

Jack,

I recently wanted to add a serial feed to a PC but, like your PC, there 
was no serial port.  In my case, I could choose a different PC, but I 
could have bought a PCI serial card (which seem to be quite rare, now).

I don't know if anyone has written a driver which will suit your USB-based 
BU353.

As to accuracy, I've been helping Dave Hart test a new NTP port for 
Windows, and on my PC I'm seeing reported offsets typically less than 300 
microseconds from a serial and PPS GPS device (Garmin GPS18 LVC), and 
there is strong evidence that the variations are temperature related, as 
the PC is in a domestic environment, and the reported offset correlates 
well with the ambient temperature.

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

That type of device will give better accuracy than a USB-connected GPS, 
and it needs no external antenna.

Cheers,
David 




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