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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!

Standard Time Stations as Radio Propagation Meters


Standard time stations, besides providing time synchronization and meterological information, aid radio hobbyists with a primitive gauge of radio propagation. Although ham radio and shortwave listening magazines and books (such as QST and WRTH) provide general propagation information, many times these sketches are out of date before hitting the stands. With a good ear and a steady hand, radio hobbyists can take the pulse of "openings" to different parts of the world and local frequencies. It's truly nifty to turn on my set at dusk or dawn and hear the various time stations roll in, announcing which programs I'll greet in the coming hours before I start my day.

I rely on time stations CHU and WWV/WWVB/WWVH for the bulk of my propagation information given my North American location. Given that CHU broadcasts from Ottawa, CHU's relative signal strength, as compared to its proximity, indicates little more than "first hop" short range propagation. CHU's location on isolated frequencies not shared with other time stations hinders its ability to contrast signal strength with other uniform signals.

More often, time stations are purposefully aligned on the same frequencies to create the cascading propagation effect designed to aid the listener in locating stations. The WWV, WWVH, and YVTO (Caracas) trifecta, when aligned well, exhibit fairly accurate propagational information to both the west and south of my location. Frequently WWVH pops up under WWV, during which WWVH's female voice announces the coming time a few seconds before WWV's male voice. WWVH's relative strength against WWV indicates the propagation activity towards the west and southwest. When combined with YVTO on 5000 kHz, the three stations' signal strenghts indicate western and southern directions.

I offer this example as the time signal propagation patterns most commonly experienced at my end of the wire, yet the technique can be applied to other time station configurations. Be mindful that the majority of time stations operate only during peak local times, or with power significantly less than WWV. Reduced operating hours are useful insofar as comparison of these less frequent signals suggests the best times to receive domestic shortwave broadcasts. I agree with Wiccanpiper that the decline of time stations (or reduction to longwave service only) detracts from time stations' myriad usages. Given that shortwave communications have declined to mostly hobbyist use over the past decade, I expect futher reductions in radio's jack-of-all-trades.

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