WWVHWWVH is the callsign of NIST'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 Jane Barbe), as opposed to the use of a male voice on WWV (using the voice of John Doyle). Also, the once-per-second ticks and top-of-the-minute tones are 1200 Hz, as opposed to 1000 Hz on WWV. These differences make it easy for the listener to tell whether he or she is listening to WWV or to WWVH. WWVH, like WWV, transmits the standard audio frequencies of 500 and 600 Hz in alternating minutes, but when WWV is transmitting 500 Hz, WWVH transmits 600 Hz, and vice versa. WWVH also transmits the standard 440 Hz 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 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.