Transmission System
CHU transmits 3 kW signals on 3330 and 14670 kHz, and a 10 kW signal on 7850 kHz. These are nonstandard time signal channels; however, due to the prospect of interference with WWV and WWVH, the nonstandard frequencies are necessary. The signal is amplitude modulated, with the lower sideband suppressed (emission type H3E). 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 southwest of Ottawa's central business district.
The systems feeding the transmitters are duplicated for reliability, and have both battery and generator protection. The generator can also supply the transmitters. The announcements are made using digitally recorded voices. Individual vertical dipole antennas are used for each frequency.
CHU has long been licensed as "fixed service" within the band allocations of the International Telecommunications Union.
CHU's 10 kW signal has been transmitted on 7850 kHz since January 1, 2009. Before then, the signal was transmitted on 7335 kHz, harmonically related to their 14670 kHz frequency. The frequency change was necessary due to an ITU HF global reallocation conference where the frequency region around 7300 kHz was turned over to different users.
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