Speaker 1: Welcome to Brain staff Fronts dot com where smart happens.
Speaker 1: Hi Am Marshall Brain with today's question, how do the
Speaker 1: automatic self setting clocks set themselves to the atomic clock?
Speaker 1: In Colorado? Many gadget catalogs and high tech stores sell
Speaker 1: radio controlled clocks and wrist watches that are able to
Speaker 1: receive these radio signals. These clocks and watches truly are
Speaker 1: synchronizing themselves with the atomic clock in Colorado. This feature
Speaker 1: is made possible by a radio system set up and
Speaker 1: operated by NIST, the National Institute of Standards and Technology,
Speaker 1: located in Boulder, Colorado. NIST operates radio station w w
Speaker 1: v B, which is the station that transmits the time codes.
Speaker 1: W w v B is a very interesting radio station.
Speaker 1: It has high transmitter power about fifty thousand watts, a
Speaker 1: very efficient antenna, and an extremely low frequency of only
Speaker 1: sixty thousand herds. For comparison, a typical AM radio station
Speaker 1: broadcasts and a frequency of a million herds. The combination
Speaker 1: of high power and low frequency gives the radio waves
Speaker 1: from w w v B a lot of bounds, and
Speaker 1: this single station can therefore cover all of the continental
Speaker 1: United States, plus much of Canada and central America as well.
Speaker 1: The time codes are sent from w w v B
Speaker 1: using one of the simplest systems possible, and at a
Speaker 1: very low data rate of one bit per second. For comparison,
Speaker 1: a typical modem transmits over phone lines at tens of
Speaker 1: thousands of bits per second. Imagine receiving a web page
Speaker 1: at one bit per second. The sixty thousand hurts signal
Speaker 1: is always transmitted, but every second it's significantly reduced in
Speaker 1: power for a period of point two point five or
Speaker 1: point eight seconds. Point two seconds of reduced power means
Speaker 1: a binary, zero point five seconds of reduced power is
Speaker 1: a binary, one and point eight seconds of reduced power
Speaker 1: is a separator. The time code is sent in B
Speaker 1: C D or binary coded decimal, and it indicates minutes, hours,
Speaker 1: day of the year and year, along with information about
Speaker 1: daylight savings time and leap years. The time is transmitted
Speaker 1: using fifty three bits and seven separators, and therefore takes
Speaker 1: exactly sixty seconds to transmit. A clock or watch can
Speaker 1: contain an extremely small and relatively simple antenna and receiver
Speaker 1: To decode the information in the signal and set the
Speaker 1: clock's time accurately. All that you have to do is
Speaker 1: set the time zone, and the clock can display a
Speaker 1: very accurate time. The only thing more accurate that you
Speaker 1: can carry around easily is a GPS receiver which dere
Speaker 1: arrives atomic clock accuracy in real time from the atomic
Speaker 1: clocks in the orbiting GPS satellite. For moralness, and thousands
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