La Crosse Technology 512-807 - Manual (Page 5)

5
WWVB RADIO CONTROLLED TIME
The NIST 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 atomic weather station. However, due to the
nature of the Earth’s Ionosphere, reception is very limited during daylight hours. The atomic
weather station will search for a signal every night when reception is best. The WWVB radio
station derives its signal from the NIST atomic weather station in Boulder, Colorado. A team of
atomic physicists continually measures 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. This atomic weather station
regulates the WWVB transmitter.
Once the outdoor temperature is displayed on the atomic weather station, the WWVB tower icon
in the weather station display will start flashing in the top center of the LCD. This indicates that the
weather station has detected a radio signal and is trying to receive it. When the time code is
received, the WWVB tower becomes permanently lit and the time will be displayed.
If the tower icon flashes, but does not set the time or the WWVB tower does not appear at all, then
please take note of the following:
Recommended distance to any interfering sources like computer monitors or TV sets is a
minimum of 6 feet (2 meters).
Within ferro-concrete rooms (basements, superstructures), the received signal is naturally
weakened. In extreme cases, please place the unit close to a window and/ or point its front
or back towards the Fort Collins, Colorado, transmitter.
During nighttime, the atmospheric disturbances are usually less severe and reception is
possible in most cases. A single daily reception is adequate to keep the accuracy deviation
below 1 second.
NOTE:
In case the atomic weather station is not able to detect the WWVB-signal (disturbances,
transmitting distance, etc.), the time can be manually set (please refer to notes SET TIME).
WWVB RECEPTION icon with full signal strength will appear on screen if the reception of
atomic time is successful. The atomic weather station will have a daily synchronization at 02:03
and 03:03 everyday. Each reception cycle is minimum 2.5 minutes and maximum 10 minutes.