Re: K3 Time

Posted by Julian, G4ILO on Mar 16, 2009; 6:24pm
URL: http://elecraft.85.s1.nabble.com/K3-Time-tp2481285p2487651.html

David Woolley (E.L) wrote

As this often causes confusion, it is worth pointing out that this is
not something written by Meinberg, but simply the reference
implementation of NTP, which Meinberg have compiled for Windows and to
which they have added an installer.  The reference implementation is the
definitive implementation that needs to be produced before an RFC can be
issued.  The NTP reference implementation is open source.

> NOAA satellite images and when using WSPR when you need better than one
> second accuracy. This program runs as a service and after it has worked out
> the drift in your computer clock it applies constant millisecond corrections

Technically it applies frequency corrections - NTP uses a PLL - it was
designed by an electronics engineer and ham.

> so it is spot on all the time. The time synchronizer built in to Windows XP

Windows is a poor platform for time and, on most other platforms the
reference implementation gives even better time, although there is some
evidence that another open source implementation, chrony, that uses the
same over the wire formats but a different (linear regression based)
mathematical approach, has better behaviour for start up and temperature
change transients, in real world use.  However chrony is only supported
on Linux, and doesn't support local radio reference clocks.

> only syncs the clock once a week which may not be enough on some PCs.

The poll period is configurable, and the Windows 2003 version can be
configured to almost use the proper NTP algorithm.  The reference
implementation is still much better, as it uses various tricks to get
round the fact that Windows only reports time to applications with a
10ms resolution, by default, or 1ms with the fastest multi-media timers.

I would generally ignore the non-open source alternatives as many are
very crude and none are better than the reference implementation, or chrony.

I agree with all of that, David. It might also be worth mentioning for the benefit of those considering other alternatives that the last time I recommended this to someone it was a VK ham who had apparently been blocked from accessing his local NTP server because the non-open source software he used polled it too often. Because the NTP software regulates the clock itself it can get by with infrequent checks to the time server, even if the computer clock is quite inaccurate.