Tune to 10 MHz almost anywhere in the Americas and you’ll hear a tick every second and a voice announcing the time once a minute. That is WWV, run by the US National Institute of Standards and Technology (NIST) from Fort Collins, Colorado, and one of the oldest radio stations in continuous operation.

Two stations, one frequency

NIST runs two shortwave time stations: WWV in Colorado and WWVH on Kauai, Hawaii. Both transmit on 2.5, 5, 10 and 15 MHz; WWV also uses 20 MHz. They send the same information, so in many places you hear both at once, slightly offset.

To tell them apart, NIST uses a man’s voice on WWV and a woman’s on WWVH. The WWVH announcement comes first, about 15 seconds before the minute, then WWV’s, about 7.5 seconds before.

What you’re hearing

  • Ticks every second, except the 29th and 59th seconds of each minute.
  • Tones during most minutes, and a longer tone marking the start of each minute and hour.
  • A voice giving the time in Coordinated Universal Time (UTC), once a minute.
  • Bulletins at set minutes of the hour, including space-weather reports that radio operators use to predict propagation.

Why listen?

Before the internet, WWV was how you set a clock precisely. Today it is the best test signal on shortwave: it’s on around the clock, on several frequencies, so it tells you instantly which bands are open. NIST’s rule of thumb is that the frequencies above 10 MHz work best by day and the lower ones by night, the same pattern described in how skywave works. See the 10 MHz WWV page for more.

Canada’s CHU has gone quiet

For decades, Canada’s National Research Council ran its own time station, CHU in Ottawa, on 3330, 7850 and 14670 kHz, with time announcements in English and French. CHU’s shortwave broadcasts ended on 22 June 2026. The NRC still provides the official time by web clock, telephone and Network Time Protocol. Skywave DX no longer lists CHU.

Try it

Skywave DX tunes WWV through a public shortwave receiver that can hear it. Start on 10 MHz; if it’s weak, try 5 MHz at night or 15 MHz by day.