Standard Time and Frequency Broadcasts

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The National Institute of Standards and Technology (NIST) operates radio stations WWV from Ft. Collins, Colorado and WWVH from Kauai, Hawaii. WWV and WWVH broadcast time and frequency information on a 24/7 basis. Broadcast information includes time announcements, standard time intervals, standard frequencies, UT1 time corrections, a BCD time code, geophysical alerts, and marine storm warnings.

Each frequency carries the same information. Multiple frequencies are used because the quality of HF reception depends on many factors. WWV and WWVH broadcast on the frequencies listed in the table below, using double sideband, amplitude modulation.

The National Research Institute of Canada operates radio station CHU to disseminate the official time on a 24/7 basis. Each minute, CHU broadcasts time data on the frequencies listed below and includes: time of day (UTC), day of year (1-366), Gregorian year (4 digits), and additional time details. CHU broadcasts time codes using full-carrier upper-sideband modulation that can be read by a computer with a Bell 103 compatible modem.

WWV / WWVH Frequencies (MHz) CHU Frequencies (MHz)
20.0000 (WWV only)