History of WWVB

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The station known today as WWVB began life as radio station KK2XEI in July 1956. The transmitter was located at Boulder, Colorado and the radiated power was less than 2 watts. Even so, the signal was monitored at Harvard University in Massachusetts. The purpose of this experimental transmission was to show that the frequency error due to Doppler shift induced by the ionosphere was small. In April 1960, NIST (then called the National Bureau of Standards or NBS) moved the experimental transmitter to Sunset, Colorado, just northwest of Boulder. A signal of less than 15 watts was broadcast, but was received as far away as New Zealand.

In 1962, NBS began constructing a new transmitter site north of Fort Collins, Colorado. This 158 hectare (390 acre) site would become the home of WWV, WWVB and WWVL (a 20-kHz transmitter). The site was chosen because of its exceptionally high ground conductivity, which was due to the high alkalinity of the soil. On July 5, 1963 WWVB became operational, broadcasting a 7 kW signal on 60 kHz. WWVL began transmitting a 500 W signal on 20 kHz the following month. The WWVL broadcast was discontinued in July 1972.

A time code was added to WWVB on July 1, 1965. This made it possible for radio clocks to be designed that could decode the signal and automatically synchronize. The time code format has changed only slightly since 1965; it uses a scheme known as binary coded decimal (BCD) which uses four binary digits (bits) to send one decimal number.

The radiated power of WWVB was increased to its current level of 50 kW in 1999. This power increase made the coverage area much larger, and resulted in the design of many new low-cost radio clocks that “set themselves” using the WWVB signal.

 Questions? Send mail to: nist.radio@boulder.nist.gov