On Sun, 20 Jan 2008 15:19:06 +0000 (UTC), (Geoffrey
S. Mendelson) wrote:

John Kasupski wrote:
Note that we're probably talking errors in the amount of nanoseconds
(per second) here, certainly not errors that are going to cause
somebody to be ten minutes late for work, but for commercial or
scientific applications requiring a time reference that is related
directly to a national or international reference, GPS may not
necessarily cut the mustard.

Yes, but don't loose sight of the fact that this discussion is really
about consumer items. One person metioned in a previous post that his
clock syncs three times a week, other than that, it "runs free".

Well, my comments about GPS stemmed from David's comments that "Any
commercial entity who really needs accurate time switched over to GPS
a decade ago." But you're right, this has drifted off the topic of the
original post to the thread, which was related to consumer devices -
and David's comment downthread is also correct in pointing out that
there are GPS receivers (such as those made by ESE) that are properly
designed and can, in fact, provide a GPS time and frequency standard
that is traceable to a national or international time standard.

So IMHO if you build a consumer device that syncs every 5 minutes to
a GPS or GPS based standard, it will be a lot more accurate than
the average one that syncs every 2-3 days to a radio signal.

Yes, assuming it can get a signal...which problem exists with the
WWVB-based devices as well (and which was the whole point of the
article cited by the OP).

If it were to sync every minute to a time signal inserted in a cellular
control channel, it be even more accurate. Last I checked, the AT&T
Wireless 850mHz GSM (whatever name it is called now) network covers 98%
of the surface area of the U.S.

Since it is a receiver it can be broadbanded and if it were to cover
the GSM 850/900 mHz and 1800/1900 mHz bands it would work everywhere
there is GSM coverage. Except for Estonina and Brazil, an 850/900 mHz
receiver would be enough.

This does leave out parts of the Pacific Rim (Japan and Korea) and
some parts of Oz, but on the whole it cover almost the entire
populated earth.

FWIW, this Wikipedia article states that around 80% of the world's
population enjoys mobile phone coverage as of 2006 and that this is
expected to increase to 90% by the year 2010:

http://en.wikipedia.org/wiki/Mobile_phone

Despite that claim, even here in the United States there is still a
significant amount of territory away from major cities and interstate
highways where no wireless phone will work at all - but radios will
work, and consumers have other sources for getting the correct time
provided that they aren't too lazy to do it themselves rather than
expecting every device they own to do it for them.

IOW, self-setting clocks as consumer items are a convenience, not a
necessity. I'd be more concerned about wireless phones not working due
to the fact that this renders them useless for placing emergency
calls, rather than because it prevents these devices from updating
their time displays.

73 DE John, KC2HMZ