isw wrote:
If you're building a clock, the noise and jitter aren't very important;
long-term drift is.

It's also part of the modern perception that precision is much greater than
it is. A clock that reads hours and minutes is accurate to around 30 seconds.
A clock that reads hours minutes and seconds is accurate to 1/2 second.

Neither are accurate to a millisecond.

I it started with airlines who would write 12:30 for "sometime before 1
o'clock" for departure and 2:00 for "around 1:30" for arrival. People
expect exact numbers where they are approximate, and it is easy to
arrive on time if you allow enough "slop" to commenpensate for anything.

Mousillini (pardon the spelling) "made the trains run on time" by adjusting
the schedules to reality.

I've also seen it in ham radio where the frequency really is around 14.200,
but someone logs it as 14.203154 because that's what their (inacurate)
receiver reads it as and in computers where someone thinks floating
point numbers are integers. :-(

For most people a clock that reads in minutes is ok, and for almost everyone
who needs more accuracy seconds is ok. Just about every clock made stays
within a second for a few minutes, and auto correcting via GPS, NTP or WWV
would do well enough.

I would expect that an HF receiver clock where you set the minutes and it
autocorrects to the minute pips on WWV or CHU would do fairly well, and
in most of the US and Canada do it without the interference problems
the VLF radios have.

Note that I don't have access to any of those sources, or the EU equivalents.
The best that I can do is to run real NTP clients on all my computers,
which sync to a main NTP server on my network.

The main NTP server syncs to a variety of sources, which confuses it because
they are all within a millisecond of each other except for two Apple EU ones
which are 5 seconds off. I put them in a long time ago and probably should
remove them.

The irony of all of this is the only thing that needs accurate timing is
catching a bus, which never comes at any exact time anyway and recording
programs off of the DBS system I susbscibe to.

Since we have their PVR, it gets its time and programing information
from the feed, but is set to start recording early and end late.
They don't even trust themselves. :-)

Geoff

--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379
In 1969 the US could put a man on the moon, now teenagers just howl at it. :-(