WWVH
WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radio time signal station located at the Pacific Missile Range Facility Barking Sands, 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 the official U.S. Government time and frequency standard.
Due to ionospheric conditions, at certain times and locations some listeners may receive 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 at +1 335-4363.
| 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 | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | |
| WWVH | 1948 | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ||
| WWVB | 1963 | ✔ | ✔ | ✔ | ✔ | |||||
| WWVL | 1963 | 1972 | ✔ |
Transmission system
WWVH broadcasts its signal on four transmitters, one for each frequency. The 2.5 MHz transmitter puts out 5 kW, while the other transmitters provide 10 kW. The 2.5 MHz antenna is one quarter-wavelength tall, and radiates in an omnidirectional pattern. The 10 and 15 MHz antennas are omnidirectional half-wave antennas. The 5 MHz antenna consists of two elements one half-wavelength tall and horizontally separated by one quarter-wavelength. This phased-array directional antenna produces a broad cardioid radiation pattern with a maximum gain directed west.
Emergency stand-by transmitters and antennas are provided for each frequency.
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 1,200 Hz 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: 600 Hz is played during even minutes, and 500 Hz 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:
- * Station identification is made during minutes 29 and 59
- * GPS satellite health reports are transmitted during minutes 43 and 44
- * NOAA space weather geoalerts are transmitted during minute 45
- * 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.
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:Reception reports sent to that address will on request be answered with a QSL card.