[ntp:questions] Home Time Server

David L. Mills mills at udel.edu
Tue Oct 9 19:42:13 UTC 2007


Evandro,

I don't know what non-GPS referece clock you are using, but my two 
PSTI/Traconex WWV clocks are within about 1 ms and the WWV audio driver 
in the NTP distribution is usually better than 0.2 ms. Only my ancient 
Heath G1000 WWV clock can be blamed for greater than 500 ms and that 
because of a runt antenna. Sadly because of UPS power line noise, WWVB 
does not work here any more.

In regards to how the clocks work, all the above WWV clocks use the 
munutes and seconds pulses as well as he 100-Hz subcarrier modulation. 
The PSTI/Traconex clock uses a comb filter for the seconds pulse and 
brute force for the subcarrier demondulation. The NTP WWV driver is a 
mathematically optimum linear receiver with a ton of DSP algorithms.

I have no experience with European and Japanese broacasts but assume the 
DCF-77, MSF, HBG and JJY services are equivalent to WWVB. It looks like 
GOES is out of business, so the only thing left might be the cheap WWV 
wristwatch/weather gizmos and the weather gizmo I have is useless.

Dave

Evandro Menezes wrote:

> On Oct 9, 12:38 am, "David J Taylor" <david-tay... at blueyonder.not-this-
> bit.nor-this-bit.co.uk> wrote:
> 
> 
>>A nice idea, but I would not - as the radio clocks I have seen can be out
>>by 500ms and are not that reliable.  My GPS is far better.  If I didn't
>>have GPS, or I wanted a backup though, I might bet one.
> 
> 
> That's because the clocks use only the minute "chime" in the WWV
> signal.  They might as well use the PPS "chime" in WWV.
> 
> 
>>By the way, I don't see why Internet-connected PCs should be that far out,
>>as Microsoft now runs its own NTP server, and most recent versions of
>>Windows include at least an SNTP client.  Should really be pre-configured.
> 
> 
> Microsoft's time server is a joke, both in terms of accuracy and
> reachability.  It definitely cannot keep up with its clients, even
> though they are configured to sync up only weekly, which in and of
> itself is another joke.
> 
> Cheers.
> 




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