About Wwvb - La Crosse Technology WS-7390U Instruction Manual

ABOUT WWVB

The NIST (National Institute of Standards and Technology—Time
and Frequency Division) radio station, WWVB, is located in Ft.
Collins, Colorado and transmits the exact time signal continuously
throughout the United States at 60 kHz. The signal can be
received up to 2,000 miles away through the internal antenna in the
indoor weather station. However, due to the nature of the Earth's
Ionosphere, reception is very limited during daylight hours. The
indoor weather station will search for a signal every night when
reception is best. The WWVB radio station derives its signal from
the NIST Atomic clock in Boulder, Colorado. A team of atomic
physicists continually measure every second of every day to an
accuracy of ten billionths of a second a day. These physicists have
created an international standard, measuring a second as
9,192,631,770 vibrations of a Cesium 133 atom in a vacuum. For
more information about WWVB please see the NIST website at
http://www.boulder.nist.gov/timefreq/stations/wwvb.htm
4