CHU (radio station)

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CHU
City of licenseOttawa, Ontario, Canada
Broadcast areaNorth America
Frequency3330 kHz, 7850 kHz, 14670 kHz
First air date1923
FormatTime
Power3 kW (3330, 14670 kHz), 10 kW (7850 kHz)
Transmitter coordinates45°17′47″N 75°45′22″W / 45.29639°N 75.75611°W / 45.29639; -75.75611
Former callsigns9CC (1923-1928),
VE9CC (after 1928)
VE9OB (until 1938)
OwnerNational Research Council of Canada
Websitehttp://www.nrc-cnrc.gc.ca/eng/services/time/short_wave.html
 
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CHU
City of licenseOttawa, Ontario, Canada
Broadcast areaNorth America
Frequency3330 kHz, 7850 kHz, 14670 kHz
First air date1923
FormatTime
Power3 kW (3330, 14670 kHz), 10 kW (7850 kHz)
Transmitter coordinates45°17′47″N 75°45′22″W / 45.29639°N 75.75611°W / 45.29639; -75.75611
Former callsigns9CC (1923-1928),
VE9CC (after 1928)
VE9OB (until 1938)
OwnerNational Research Council of Canada
Websitehttp://www.nrc-cnrc.gc.ca/eng/services/time/short_wave.html

CHU is the call sign of a shortwave time signal radio station operated by the Institute for National Measurement Standards of the National Research Council of Canada.

Contents

History

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 when continuous daytime transmission began under the callsign of VE9OB. In 1938 the call was changed to CHU. The station continued to be operated by the Observatory until 1970, when its operation was transferred to the Institute for National Measurement Standards at the National Research Council.

Broadcast format

CHU's signal is used for continuous dissemination of official Canadian government time signals. The CHU time signal and radio frequencies are derived from atomic clocks. CHU's announcers are Harry Mannis in English and Simon Durivage in French.

CHU will acknowledge listeners' reception reports.

A similar time signal from the National Research Council is used by CBC radio services daily at noon ET on Radio-Canada's Première Chaîne, and 1pm ET on CBC Radio One.

Transmission system

CHU transmits 3 kW signals on 3330 and 14670 kHz, and a 10 kW signal on 7850 kHz.[1] 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.

Time signal format

The primary time signal is a series of 300 ms-long 1000 Hz tones, transmitted once per second, on the second. 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. This follows the Bell 103 standard, a 2225 Hz tone to represent a mark (1 bit) and 2025 Hz tone for a space (0 bit). Immediately after the 10 ms tick, a mark tone is sent until 133.3̅ ms, then 110 data bits, ending at precisely 500 ms. The final stop bit is extended by 10 ms of mark tone to ensure it is detected reliably, and the final 490 ms of the second are silent.[2] The time of day (day of year through second) is transmitted twice during each second from 32 to 39. During second 31, additional information (year, DUT1, daylight saving time, and leap second warning bits) is transmitted.

Western Canada signal coverage

Coverage of proposed CHU transmitter for Western Canada

CHU quite often cannot be received in Western Canada on any of its broadcast frequencies, as it universally uses lower transmitter powers than WWV.[citation needed]

Propagation conditions, lower transmitter power coupled with the typical two ionospheric hops distances from Ottawa result in relatively weak time signals for Western Canada. Electrical interference can further aggravate reception difficulty in suburban areas in the West. CHU can be practically unusable in most of Western Canada, as well as Nunavut and the Northwest Territories, for significant stretches of time.

Subject to limitations of their own, WWV and WWVH are the fallback in Western Canada as far as getting reliable time signals via shortwave is concerned. In the High Arctic, however, both the US shortwave time stations and CHU become essentially unreliable or unusable.

Unlike the US, Canada has no longwave time signals dissemination option. Technically WWVB is the only option for reliable time signals during solar storms in the Western Arctic, based on WWVB's published pattern maps. If WWVB is not available, those who need precision time transfer may be able to use GPS time transfer instead.

In popular culture

A CHU time signal can occasionally be heard as a background sound effect in Star Wars Episode V: The Empire Strikes Back, in the underground rebel base.[citation needed]

References

  1. ^ Marten, M. (2011) (in german). Spezial-Frequenzliste 2011-2012, Band 2. Meckenheim, Germany: Siebel Verlag. pp. 83,259,436. ISBN 978-3-88180-692-3.
  2. ^ a b "CHU Broadcast Codes". National Research Council of Canada, Institute for National Measurement Standards. 2009-08-28. http://www.nrc-cnrc.gc.ca/eng/services/inms/time-services/broadcast-codes.html. Retrieved 2010-03-14.

External links