There are timepieces all around us. Whether it’s a watch on your wrist, the clock on the wall at work, or in the lower right-hand corner of your computer screen, there’s probably some device near you displaying the time. But how do you know it’s the correct time? Also, what if you needed the exact time – down to the nearest second or fraction of a second?
While the average person may not require such precision, many others, such as scientists and astronomers, certainly do. To this end, many countries have established radio stations that broadcast announcements of the exact time of day. These stations, known as standard time and frequency stations, transmit (usually via shortwave radio) not only accurate time based on cesium atomic clock standards, but in some cases meteorological information, standard audio tones, and global positioning data.
Some of the stations (WWV, for example) provide software enabling computers to synchronize their local time, via the Internet, with the station’s standard. Also, there are clocks available, some of them quite inexpensive, that can receive the broadcasts and adjust their internal clock accordingly, providing the user with a timepiece that never needs resetting.
Though with the coming of the Internet many standard time stations have been decommissioned (notably VNG, Australia, and HD210A, Ecuador), there are still some to be found. Some of the better-known stations are:
MSF (Great Britain). MSF is operated by the National Physical Laboratory and is located near Rugby, England. The station's frequency is 60 kilohertz (kHz) and is in operation 24 hours. Time and date broadcasts are provided via on/off variance of the 60 kHz carrier wave in accordance with the minute ticks, with the announcement given in morse code format.
WWV, WWVH, WWVB (United States of America). These stations are operated by the National Institute of Standards and Technology and are located in Fort Collins, Colorado (WWV and WWVB), and Kokole Point, Hawaii (WWVH). WWV broadcasts on 2.5, 5, 10, 15, and 20 Megahertz (MHz); WWVB broadcasts on all but 20 MHz; and WWVB is found on longwave, at 60 kilohertz.
These stations broadcast standard time in the form of pips each second, with voice announcements on the hour and half-hour (WWVB broadcasts in morse code only). In addition to the services mentioned above, WWV and WWVH also provide highly accurate audio tones of 440 and 600 hertz. Time is given in Coordinated Universal Time (UTC).
CHU (Canada). Located near Ottawa at the Institute for National Measurement Standards, CHU transmits 24 hours on 3.330, 7.335, and 14.670 Mhz. The station provides standard time, in UTC via pips each second, with voice announcements on the minute. The announcements are given in English and French.
YVTO (Venezuela). Transmits time pips each second, with voice announcements in Spanish on the minute, from its location near Caracas. Operates 24 hours, only on 5 MHz.
RWM (Russia). This 24-hour station transmits off the usual frequencies, on 4.996, 9.996, and 14.996 MHz, presumably to avoid interference with other stations. RWM broadcasts consist of 1000 hertz pips lasting 100 milliseconds, except for the minute pip, which is instead 500 milliseconds. No voice announcements.
BSF (Taiwan). Transmits time markers only, on 5 MHz. Operates 24 hours and announcements are given in morse code.
SOURCES
American Radio Relay League. The Radio Amateur's Handbook. Newington, Connecticut: Published by the American Radio Relay League, various editions.
"Standard Time and Frequency Stations in Russia." <http://www.irkutsk.com/radio/tis.htm> (October 2003)
Hepburn, William. "SW Time Signal Stations." <http://www.iprimus.ca/~hepburnw/dx/time.htm> (October 2003)
Website of radio station WWV. <http://www.boulder.nist.gov/timefreq/stations/wwv.html> (October 2003)
Website of radio station CHU. <http://inms-ienm.nrc-cnrc.gc.ca/time_services/shortwave_broadcasts_e.html> (October 2003)
Thanks to vorbis for pointing out a glaring error!