CHU-SW, Canada’s Time Station, Ottawa

CHU-SW1938Various3,000National Research Council


The call letters CHU were first used for Canadian time transmission, using frequencies of 3330 kHz, 7335 kHz and 14670 kHz. Before now, the call letters for essentially the same transmissions were VE9OB. The carrier frequency had been the specified standard since1934; before that the quartz oscillators had been tuned to standard wavelengths. The station was operated by the Dominion Observatory in Ottawa. 

Continuous transmissions at a wavelength of 20.4 metres had started in 1933, joining the 40.8 and 90 metre transmissions, which had begun in 1929 – daytime only. Daily transmission on a wavelength of 52.5 metres had begun in 1928 under the call letters 9CC (later VE9CC), but ceased with the start-up of 40.8 metre operation. 9CC had started experimental time transmission in 1923 on 275 metres, and license 3AF had operated in 1922. Determining the actual start date of CHU was a little difficult because of these earlier stations but the NRC tended to lean to 1929 as the official start.


The change to cesium atomic clocks took place.


The responsibility of operating CHU was transferred from the astronomers at the Dominion Observatory, to the physicists at the National Research Council. The council was charged with maintaining official time for Canada.


Before April 1, CHU’s time announcements were given as Eastern Standard Time. As of that date, the time was now given as Coordinated Universal Time (UTC). UTC was the international official time reference. 

The use of digital voice announcements began. The English voice was that of Harry Mannis (former CBC announcer) and the French voice was that of Simon Durivage (Radio-Canada).


CHU changed its 41 metre band frequency from 7335 to 7850 kHz. This was to avoid new interference permitted since 2007, when the International Telecommunications Union reallocated the 7300-7350 kHz band. It had been changed from fixed service to general broadcast use. As a result of the allocation change, the 7335 kHz transmissions began to be obscured by broadcasters from around the world who started to use the 7335 kHz frequency.

For the record, CHU was located 15 km southwest of Ottawa, near near Barrhaven. Main transmitter powers are 3 kW at 3,330 and 14,670 kHz, and 5 kW at 7,850 kHz. Individual vertical antennas were used for each frequency. Also, a similar time signal from the NRC was used by CBC radio services daily at noon (Eastern Time) on SRC’s Première Chaîne network, and 1:00 p.m. (Eastern) on CBC Radio One.

The story continues elsewhere…
Effective September 1st 2019, we will only be adding new material to these station histories in exceptional circumstances. Our intent to chronicle the early days of these radio and television stations has been achieved, and many new sources and technologies, from the CRTC website to Wikipedia, and others, are now regularly providing new information in these areas.

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