CHU (radio station)

[2] The station was started in 1923 by the Dominion Observatory in Ottawa, Ontario, Canada, with a call sign of 9CC on an experimental basis until 1928.

[1] Initially, the signal consisted of a constant frequency interrupted by patterns of Morse Code pulses to indicate the time.

Fredrick Martin Meach of the Canadian embassy in Paris recorded the time announcements in English, which were stored on strips of photographic film and played back under control of the observatory clocks.

In 1960, the speaking clock was replaced with one manufactured by Audichron corporation and rented by the Dominion Observatory; this unit had more intelligible voice quality and lower maintenance.

Bilingual announcements started in 1964, with French speech provided by Miville Couture of CBC Montreal.

A divider chain was put into service so that all of the CHU signals were derived from Western Electric standard crystal oscillators with pulses for seconds monitored by continuous comparison with the observatory clocks.

[1] The station is unmanned and equipped with modified 1960s-era 10 kW transmitters and is controlled remotely from the National Research Council's headquarters on Montreal Road.

The same information is carried on all three frequencies simultaneously including announcements every minute, alternating between English and French.

The CHU transmitter is located near Barrhaven, Ontario, 15 km (10 miles) southwest of Ottawa's central business district.

CHU has long been licensed as a "fixed service" within the band allocations of the International Telecommunication Union.

The following exceptions to the pattern provide additional information: The digital time code sends 10 characters at 300 bits per second using 8N2 asynchronous serial communication.

Propagation conditions, low transmitter power coupled with the typical two ionospheric hops distances from Ottawa result in relatively weak time signals for Western Canada.

CHU can be practically unusable in most of Western Canada, Nunavut, and the Northwest Territories, for significant stretches of time.