La Crosse Technology WT966B Atomic Watch

Our La Crosse Technology radio-controlled atomic watch maintains its incredible accuracy by automatically tuning into the WWVB radio signal.

The atomic watch contains a small but highly powerful antenna, specifically tuned for optimal reception of the 60 kHz time signal. The signal received on the antenna is demodulated by a tiny onboard receiver, which sends the information to the atomic watch's ultra-low-power CMOS microprocessor for decoding. Once your atomic watch has automatically set its time for the first time, it ensures continuing accuracy by automatically tuning into the WWVB radio signal once per day after midnight. As long as your atomic wristwatch is kept within transmitter range, your atomic watch will continue to display the absolutely precise time, even performing automatically the adjustment for summer time/winter time changeovers. Should you move your atomic watch out of transmitter range for an extended period of time, your atomic watch will still continue to operate as a highly accurate quartz controlled watch. Upon re-entering the transmitter range, your atomic watch will correct itself again to the precise WWVB time signal.

The NIST (National Institute of Standards and Technology-Time and Frequency Divisions) maintains a radio station, WWVB, in Ft. Collins, Colorado. The WWVB radio station derives its signal from the NIST Atomic clock in Boulder, Colorado. A team of atomic physicists is continually measuring every second, of every day, to an accuracy of ten billionths of a second per 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.

WWVB (the station’s identification just like any other radio station) continuously broadcasts time and frequency signals at 60 kHz. The carrier frequency provides a stable frequency reference traceable to the national standard. There are no voice announcements on the station, but a time code is synchronized with the 60 kHz carrier and is broadcast continuously at a rate of 1 bit per second using pulse width modulation. The time code contains the year, day of year, hour, minute, second, and flags that indicate the status of Daylight Saving Time, leap years, and leap seconds.