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Wow!  NIST/WWV's "radio-controlled clock" web site has changed
significantly since I last visited it and is just chock-full of
information about how the clocks work and WWVB signal strength (at
night, it should cover most of North America).

As Richard noted, the signal includes information that allows clocks to
automatically change to Daylight (summer) time -- plus a warning that
for areas that don't do the change (Arizona, Hawaii, and parts of
Indiana), one will have to look at the clock's instructions to find out
how to tell it not to do the changeover.

One thing the site does make clear, though, is that the clock's owner
must "prime" the clock with his/her time zone.  So that still leaves the
mystery of how the Swatch watch changes time zones.

Lu Abel

Richard Langley wrote:
> On Mon, 18 Apr 2005, Lu Abel wrote:
>
>
>>I don't know about watches, but there are certainly a lot of clocks (and
>>some pretty small ones, too) that synchronize themselves to WWV.  They
>>are available everywhere from Sharper Image to Radio Shack.  When I
>>taught USPS's celestial course and started talking about time sources,
>>the next week three or four of my students showed up with examples of
>>these clocks because I hadn't mentioned them.   Some of them are very
>>inexpensive (30~50 USD), way less than the cost of a decent shortwave
>>receiver capable of receiving WWV or CHU.
>>
>>The synchronization signals are actually provided by WWVB, a very low
>>frequency companion to  WWV.   According to the WWV web site, WWVB
>>provides coverage for the contiguous 48 states (and therefore probably
>>also for southern Canada)
>
>
> The siganl even reaches the Maritimes -- received well in N.B.
>
>
>>To the best of my knowledge, though, there's no way one can determine
>>time zone (or even summer (daylight) vs winter (standard) time) simply
>
>>from the WWVB signal.
>
> The WWVB signal uses a code which includes bits for indicating DST.
> See  for more
> information.
>
> -- Richard Langley
>
>
>>If the Swatch watch was changing time zones, it
>>must have some additional geographic-location-determining device.
>>
>>Lu Abel
>>
>>Manson, John wrote:
>>
>>>Now there is a toy I have to have....off to the www to get details
>>>John
>>>
>>>-----Original Message-----
>>>From: Navigation Mailing List
>>>[mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Dan Allen
>>>Sent: Monday, April 18, 2005 8:55 AM
>>>To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
>>>Subject: Re: Cell phone time, etc
>>>
>>>
>>>On Apr 15, 2005, at 11:50 PM, Frank R wrote:
>>>
>>>
>>>
>>>>That is, do you get time zone changes as you drive along a highway?
>>>
>>>
>>>Yes I do, that is why I found it curious that I did not get DST updates
>>>without turning the phone on and off.
>>>
>>>Now I have a new toy: a Swatch watch which automatically tracks WWV
>>>stations and other unspecified satellite or cell tower sources to handle
>>>DST, time zones, and so forth.  It did not work too well as I crossed
>>>America by air yesterday until right before I landed - then the time
>>>zone changed from Eastern to Mountain.  I need more technical details
>>>about how it obtains position information (no GPS in it).
>>>
>>>Dan
>>
>
>
> ===============================================================================
>  Richard B. Langley                            E-mail: lang@unb.ca
>  Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
>  Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
>  University of New Brunswick                   Fax:      +1 506 453-4943
>  Fredericton, N.B., Canada  E3B 5A3
>      Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
> ===============================================================================
>
>

   

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