WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radiotime 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. 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. To minimize interference with the WWV broadcasts on the same frequencies, WWVH's broadcasts on 5, 10 and 15 MHz are directional, pointed primarily west. Despite this strategy, in certain places, particularly on the west coast of North America; and 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 information modulated on the carrier is modified to reduce confusion if both are received simultaneously. In particular, voice announcements on one correspond to silent periods on the other. WWVH uses a female voice to distinguish itself from WWV, which uses a male voice. WWVH time signals can also be accessed by telephone.
Station
Year in service
Year out of service
Radio frequencies
Audio frequencies
Musical pitch
Time intervals
Time signals
UT2 correction
Propagation forecasts
Geophysical alerts
WWV
1923
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WWVH
1948
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WWVB
1963
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WWVL
1963
1972
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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 in quadrature phasewith respect to the signal from the other. This results in a cardioidradiation pattern with a maximum gain directed west.
Broadcast format
The WWVH signal is extremely similar to the WWV signal, but some changes have been made to reduce confusion if both are heard at once:
The 5 ms second ticks are 6 cycles of rather than 5 cycles of 1,000 Hz. The 800 ms minute beep is also 1,200 Hz.
The voice announcements use a female voice and last 7.5 seconds starting 15 seconds before the minute.
The audio tones sent during the first 45 seconds of most minutes are swapped: is played during even minutes, and is played during odd minutes.
The A440 tone marking the hour is sent during minute 1. Like WWV, it is omitted during the first hour of each UTC day.
The audio tones are suppressed while WWV is transmitting voice announcements: minutes 00, 08–10, 14–19, and 30.
The voice announcements are rescheduled relative to WWV:
* National Weather Service storm warnings for all sections of the Pacific Ocean are broadcast during minutes 48–51, overflowing to minute 52 when necessary.
* Minutes 03 and 47 are used for NIST special announcements when necessary. Like WWV, prior to the OMEGA Navigation System shutdown in 1997, the OMEGA status report was broadcast at :47 past the hour.
WWVH identifies itself twice each hour, at 29 and 59 minutes past the hour. The text of the identification is as follows: Reception reports sent to that address will on request be answered with a QSL card.
Telephone service
WWVH's time signal can also be accessed by calling +1 335-4363.
