Clock keeps correct time by listening to the radio (WWV/WWVH)

[Bob Devine]

davids at well.UUCP (David Schachter) writes:
> My company [Precision Standard Time, Inc] makes a product that may
> solve the hassles of shifting Daylight Savings Time start/stop dates.
> The Precision Clock/Time Receiver, Model OEM-10(tm) receives shortwave
> radio broadcasts from the U.S. National Bureau of Standards containing
> the time and date.  These broadcasts, on radio stations WWV and WWVH,
> are converted by the clock into a format suitable for use by computer
> systems and output through an RS-232 port.  The N.B.S. transmissions
> include a bit which is twitched twice a year, to indicate the start and stop
> of Daylight Savings time and the clock has a switch to let you control whether
> the bit is accepted or ignored.

  Note that the NBS broadcast of time services only gives the national
rule for changes from/to DST.  That means those parts of the country that
have different rules must always ignore the bit.  However, most states
could follow it.

  A second point:  Because the WWV and WWVB transmitters are in Fort Collins
Colorado, the signal strength is low on the east coast.  I don't know if
this will necessarily cause intermittent reception or not.  The field
intensity map supplied by NBS shows strength < 100 microvolts/meter east
of central New York state.

  For those not familiar with the signal of WWV/WWVB call (303)499-7111
for the audio portion of WWV.  WWVH (Hawaiian site) is (808)335-4363.
NBS says that what you hear over the phone line is within 30 milliseconds
of the actual time (lower 48 states only).

Bob Devine