Re: "Atomic" Watches

This is a little deceptive because the antenna inside the watch is a coil
of fine wire wound around ferrite core. If you were to unwind the coil, it
still would not be 1250 meters long or anywhere close to it, but it would be
much longer than the length of the core - not a fraction of an inch but more
like several feet of wire. The physics of ferrite core antennas (the same
kind as are found in AM radios) are such that they don't have to be anywhere
near as big as 1/4 wave in order to receive a good signal. Also, the
receiver has a relatively easy job - it doesn't have to play beautiful music
without static. It just has to listen for 1 bit per second and decide
whether the bit it is hearing over that second is a one (on) or a zero (off)
and distinguish that signal from background noise. Still, the antenna
inside the watch case is awfully small even for a ferrite core and is going
to have limited receiving power, so your basic point is still correct.




"Jeffrey Herman" <jeffreyh@xxxxxxxxxx> wrote in message
news:e72snq$sba$1@xxxxxxxxxxxxxxxxxx
Keep in mind that the transmitting frequency of station WWVB
is 60 kHz, meaning its wavelength is 5,000 meters. An
efficient antenna (at any freq'y) is one-quarter wavelength,
so to effectively receive WWVB, the radio receiver in your
watch would need an antenna of length 1,250 meters. The
antenna actually contained in your watch is probably only
a fraction of an inch.

My Timex watch will not sync with WWVB when I'm in Hawaii, but
on my trips to SoCal, it links up fine.

Jeff (KH6O)

--
Chief Petty Officer, U.S. Coast Guard, Dept. of Homeland Security

Mathematics Lecturer, University of Hawaii System


.

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