WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii.

WWVH is the Pacific sister station to WWV, and has a similar broadcast format to WWV. Like WWV, WWVH's main function is the dissemination of official U.S. Government time, through exactly the same methods as found on WWV's signal. WWVH broadcasts on the same frequencies as WWV, except for 20 MHz. The time announcements on WWVH, which, like on WWV, are given in UTC, are made by a female voice (in this case, that of the late Jane Barbe), as opposed to the use of a male voice on WWV. Also, the once-per-second ticks and top-of-the-minute tones are , as opposed to on WWV; additionally, the ticks are far quieter for seconds 51 through 58. These differences make it easy for the listener to tell whether he or she is listening to WWV or to WWVH. However, the top-of-the-hour tone WWVH transmits is the same frequency as that used by WWV, . WWVH, like WWV, transmits the standard audio frequencies of and in alternating minutes, but when WWV is transmitting 500 Hz, WWVH transmits 600 Hz, and vice versa. WWVH also transmits the standard tone each hour except for the first hour of each UTC day, but at 1 minute past instead of 2 minutes past on WWV.

To minimize interference, WWVH broadcasts a directional signal on 5, 10 and 15 MHz, pointed primarily west. But despite this strategy, in certain places at certain times due to ionospheric conditions, the listener can actually hear both WWV and WWVH on the same frequency at the same time. The combination of the simultaneous 500 Hz and 600 Hz tones gives the listener a sound similar to a continuously-ringing chime. The two voices that give the time announcements never speak at exactly the same time, to further minimize interference between the two stations. Also, when one station is transmitting its supplementary voice broadcasts, such as GPS reports (heard on WWVH at 43 and 44 minutes past each hour), geophysical alerts (heard on WWVH at 45 minutes past) and high-seas weather warnings (transmitted on WWVH between 48 and 51 minutes past the hour inclusive), the other station will not transmit any steady audio tones.

WWVH antenna coordinates
2.5 MHz
5 MHz
10 MHz
15 MHz

Transmission system

WWVH broadcasts its signal on four transmitters, one for each frequency. The 2.5 MHz transmitter puts out an ERP of 5 kW, while the other transmitters use 10 kW of ERP. The 2.5 MHz antenna is one half-wavelength tall, and radiates in an omnidirectional pattern. The remaining antennas each consist of two elements one half-wavelength tall and horizontally separated by one quarter-wavelength. The signal radiating from one element is out of phase by 90 degrees with respect to the signal from the other. This results in a cardioid radiation pattern with a maximum gain directed west.

Half-hourly station identification announcement

WWVH identifies itself twice each hour, at 29 and 59 minutes past the hour. The text of the identification is as follows:
"National Institute of Standards and Technology Time. This is radio station WWVH, Kauai, Hawaii, broadcasting on internationally allocated standard carrier frequencies of 2.5, 5, 10 and 15 megahertz, providing time of day, standard time interval, and other related information. Inquiries regarding these transmissions may be directed to the National Institute of Standards and Technology, Radio Station WWVH, Post Office Box 417, Kekaha, Hawaii 96752. Aloha."

Telephone Service

WWVH's time signal can also be accessed by calling +1 (808) 335-4363.

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