Shortwave listening, or SWLing, is the hobby of listening to shortwave radio broadcasts located on frequencies between 1700 kHz and 30 MHz.
Listeners range from casual users seeking international news and entertainment programming, to hobbyists immersed in the technical aspects of radio reception and collecting official confirmations (QSL cards) that document their reception of distant broadcasts (DXing). In some developing countries, shortwave listening enables remote communities to obtain regional programming traditionally provided by local medium wave AM broadcasters. In 2002, the number of households that were capable of shortwave listening was estimated to be in the hundreds of millions.
The practice of long-distance radio listening began in the 1920s when shortwave broadcasters were first established in the US and Europe. Audiences discovered that international programming was available on the shortwave bands of many consumer radio receivers, and a number of magazines and listener clubs catering to the practice arose as a result. Shortwave listening was especially popular during times of international conflict such as World War II, the Korean War and the Persian Gulf War.
Listeners use inexpensive portable world band receivers to access the shortwave bands, and some advanced hobbyists employ specialized shortwave communications receivers featuring digital technology designed for optimum reception of shortwave signals, along with outdoor antennas to enhance performance.
With the advent of the internet, many international broadcasters have scaled back or terminated their shortwave transmissions in favor of web-based program distribution, while others are moving from traditional analog to digital broadcasting modes in order to allow more efficient delivery of shortwave programming. The number of organized shortwave listening clubs has diminished along with printed magazines devoted to the hobby; however, many enthusiasts continue to exchange information and news on the web.
The Short Wave Broadcasting Bands
There are fourteen discrete bands which are allocated for broadcasting over the short wave frequency range:
Band Frequency Range
120 metres – 2300-2495 kHz Only used in tropical areas.
90 metres – 3200-3400 kHz Only used in tropical areas.
75 metres – 3900-4000 kHz Not used in the Americas. Restricted to 3950-4000 kHz in Europe, Africa and the Middle East.
60 metres – 4750-4995 kHz (Only used in tropical areas).
49 metres – 5900-6200 kHz
41 metres – 7200-7450 kHz (Restricted to 7300-7450 kHz in the Americas).
31 metres – 9400-9900 kHz
25 metres – 11600-12100 kHz
22 metres – 13570-13870 kHz
19 metres – 15100-15800 kHz
16 metres – 17480-17900 kHz (Highest frequency band in common daily use).
15 metres – 18900-19020 kHz (Virtually unused)
13 metres – 21450-21850 kHz
11 metres – 25670-26100 kHz (Little activity other than tests of local digital services).
Other Short Wave Frequencies
There are lots of other short-wave frequencies which are used for all manner of purposes including ship-to-shore communications (maritime), air traffic control (aeronautical), military and defence, weather information and even spy stations and radio pirates. Broadcasters normally use AM (though some are now digital), whereas most of the other users are either digital or use SSB as with the radio hams. It therefore requires specialist receivers to listen to these other services and indeed under some jurisdictions it is illegal to do so, however there is a world of fun to be had on short wave if you have the time and patience.
The only other short-wave frequencies which it is usually legal to receive and which require no specialist equipment are ‘time and frequency standard stations’. These are stations which use very accurate transmitters controlled by atomic clocks, and thus serve as highly accurate references. They are very useful for checking the accuracy of your receiver. They also transmit time information, usually as a series of ‘ticks’ each second plus messages each minute. The following stations are believed to be on-air:
Station Location Frequencies
CHU Ottawa, Canada 3330, 7850 and 14670 kHz
RWM Moscow, Russia 4996, 9996 and 14996 kHz (note that RWM transmits pulses rather than ticks)
WWV Colorado, USA 2500, 5000, 10000, 15000 and 20000 kHz
WWVH Hawaii, USA 2500, 5000, 10000 and 15000 kHz
YVTO Caracas, Venezuela 5000 kHz
DSHO São Paulo, Brazil 10000 kHz
BPM Pucheng, China 2500, 5000, 10000 and 15000 kHz
HLA Daejeon, South Korea 5000 kHz
HD2IOA Guayaquil, Ecuador 3810 kHz (not 24/7)
EBC Cadiz, Spain 4998 and 15006 kHz (not 24/7)
BSF Taipei, Taiwan 5000 and 15000 kHz
AM broadcasting is a radio broadcasting technology, which employs amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as “AM band”) transmissions, but also on the longwave and shortwave radio bands.
The Amplitude Modulated (AM radio) carrier frequencies are in the frequency range 535-1605 kHz. Carrier frequencies of 540 to 1600 kHz are assigned at 9 kHz intervals in Europe and 10 kHz in America. The FM radio band is from 88 to 108 MHz
The earliest experimental AM transmissions were begun in the early 1900s. However, widespread AM broadcasting was not established until the 1920s, following the development of vacuum tube receivers and transmitters. AM radio remained the dominant method of broadcasting for the next 30 years, a period called the “Golden Age of Radio”, until television broadcasting became widespread in the 1950s and received most of the programming previously carried by radio. Subsequently, AM radio’s audiences have also greatly shrunk due to competition from FM (frequency modulation) radio, Digital Audio Broadcasting (DAB), satellite radio, HD (digital) radio and Internet streaming.
AM transmissions are much more susceptible to interference than FM and digital signals, and often have limited audio fidelity. Thus, AM broadcasters tend to specialise in spoken-word formats, such as talk radio, all news and sports, leaving the broadcasting of music mainly to FM and digital stations.