Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Radio Station WWVH

WWVH entrance




NIST radio station WWVH broadcasts time and frequency information 24 hours per day, 7 days per week to listeners worldwide. The station is located on the Island of Kauai, Hawaii on a 12 hectare (30 acre) site near Kekaha at Kokole Point. The information broadcast by WWVH includes time announcements, standard time intervals, standard frequencies, UT1 time corrections, a BCD time code and geophysical alerts. 
Notice:  Beginning April 19, 2019, Radio Stations WWV and WWVH will be announcing upcoming and current Military Auxiliary Radio System (MARS) and U.S. Department of Defense (DoD) exercises. Founded in 1925, MARS is an organization established by DoD that trains volunteer Amateur Radio operators to provide contingency high-frequency (HF) radio communications assistance in times of natural disasters and other urgent situations. MARS volunteers also assist DoD by providing humanitarian assistance and disaster relief, and morale and welfare communications. The MARS exercises will take place several times per year, on a regional and nationwide basis. The WWV and WWVH announcements will provide information to Amateur Radio participants regarding the purpose, dates, times and locations of the exercises and other information. WWV will air MARS announcements on the 10th minute of each hour, and WWVH will use the 50th minute. The announcements will air for about two weeks, prior to and during each exercise. For more information about MARS, see: and MARS exercise participants are directed to

Broadcast Frequencies

WWVH operates in the high frequency (HF) portion of the radio spectrum and radiates 10 000 W on 10 MHz and 15 MHz, and 5000 W on 2.5 MHz. Notice: the 5 MHz broadcast which normally radiates 10 000 W is currently operating at 5000 W due to equipment failure. 

Each frequency is broadcast from a separate transmitter. Although each frequency carries the same information, multiple frequencies are used because the quality of HF reception depends on many factors such as location, time of year, time of day, the frequency being used, and atmospheric and ionospheric propagation conditions. The variety of frequencies makes it likely that at least one frequency will be usable at all times.


From 2000 to 2007, NIST has installed new antennas encased in fiberglass rather than traditional steel supports, to resist corrosion from the salty ocean air. The fiberglass design will reduce maintenance and repair costs. The new design also enables the flexible, lightweight antennas to be easily lowered to the ground for maintenance, reducing safety hazards to staff. The improved antennas should reduce signal downtime for WWVH users. The 5 MHz antenna system consists of half-wave phased array vertical antennas. The 2.5 MHz, 10 MHz and 15 MHz antennas are base-fed vertical monopoles that radiate omnidirectional patterns. Each frequency also has a vertical monopole standby antenna connected to the standby transmitters, in the event that the primary system fails.

WWVH Antenna Coordinates

Frequency (MHz)

Latitude Longitude
2.5 21° 59' 20.9" N 159° 45' 52.4" W

21° 59' 10.8" N

159° 45' 44.8" W

21° 59' 18.2" N

159° 45' 51.3" W

21° 59' 15.3" N

159° 45' 50.0" W


The signals broadcast by WWVH use double sideband amplitude modulation. The modulation level is 50 percent for the steady tones, 50 percent for the BCD time code, 100 percent for the second pulses and the minute and hour markers, and 75 percent for the voice announcements.

Other Information about WWV and WWVH

Questions? Send mail to: wwvh [at]


Created April 28, 2015, Updated November 15, 2019