Shortwave radio refers to the upper MF

Medium frequency

Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...

 (medium frequency) and all of the HF

High frequency

High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...

 (high frequency) portion of the radio spectrum

Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....

, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelength

Wavelength

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

s in this band are shorter than 200 m (1500 kHz) which marked the original upper limit of the medium frequency

Medium frequency

Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...

 band first used

History of radio

The early history of radio is the history of technology that produced radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy"...

 for radio communications. The broadcast medium wave band now extends above the 200 m/1500 kHz limit, and the amateur radio

Amateur radio

Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

 1.8 MHz – 2.0 MHz band (known as the "top band") is the lowest-frequency band considered to be 'shortwave'.

Initially thought to be useless, shortwave radio now has many applications where the behaviour of radio waves

Radio propagation

Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...

 in the Earth's atmosphere make long-range communication possible. Shortwave radio is used for broadcasting

Broadcasting

Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...

 of voice and music, and long-distance communication to ships and aircraft, or to remote areas out of reach of wired communication or other radio services. Amateur radio

Amateur radio

Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

  on these frequencies can provide hobby, educational and emergency communication.

The discovery of long-distance shortwave propagation

Amateur radio operators

Amateur radio

Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

 are credited with the discovery of long-distance communication on the shortwave bands. Early long-distance services used surface wave

Surface wave

In physics, a surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient...

 propagation at very low frequencies

Very low frequency

225px|thumb|right|A VLF receiving antenna at [[Palmer Station]], Antarctica, operated by Stanford UniversityVery low frequency or VLF refers to radio frequencies in the range of 3 kHz to 30 kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals...

, which are attenuated along the path. Longer distances and higher frequencies using this method meant more signal attenuation. This, and the difficulties of generating and detecting higher frequencies, made discovery of shortwave propagation difficult for commercial services.

Radio amateurs conducted the first successful transatlantic tests in December 1921, operating in the 200 meter mediumwave

Mediumwave

Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...

 band (1500 kHz)—the shortest wavelength then available to amateurs. In 1922 hundreds of North American amateurs were heard in Europe at 200 meters and at least 20 North American amateurs heard amateur signals from Europe. The first two-way communications between North American and Hawaiian amateurs began in 1922 at 200 meters. Although operation on wavelengths shorter than 200 meters was technically illegal (but tolerated as the authorities mistakenly believed at first that such frequencies were useless for commercial or military use), amateurs began to experiment with those wavelengths using newly available vacuum tube

Vacuum tube

In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

s shortly after World War I.

Extreme interference at the upper edge of the 150-200 meter band—the official wavelengths allocated to amateurs by the Second National Radio Conference in 1923—forced amateurs to shift to shorter and shorter wavelengths; however, amateurs were limited by regulation to wavelengths longer than 150 meters (2 MHz). A few fortunate amateurs who obtained special permission for experimental communications below 150 meters completed hundreds of long distance two way contacts on 100 meters (3 MHz) in 1923 including the first transatlantic two way contacts. in November 1923, on 110 meters (2.72 MHz)

By 1924 many additional specially licensed amateurs were routinely making transoceanic contacts at distances of 6000 miles (~9600 km) and more. On 21 September several amateurs in California completed two way contacts with an amateur in New Zealand. On 19 October amateurs in New Zealand and England completed a 90-minute two-way contact nearly halfway around the world. On October 10, the Third National Radio Conference made three shortwave bands available to U.S. amateurs at 80 meters (3.75 MHz), 40 meters (7 MHz) and 20 meters (14 MHz). These were allocated worldwide, while the 10-meter band (28 MHz) was created by the Washington International Radiotelegraph Conference on 25 November 1927. The 15-meter band (21 MHz) was opened to amateurs in the United States on 1 May 1952.

Marconi

In June and July 1923, Guglielmo Marconi

Guglielmo Marconi

Guglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...

's transmissions were completed during nights on 97 meters from Poldhu Wireless Station

Poldhu

Poldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula; it comprises Poldhu Point and Poldhu Cove. It lies on the coast west of Goonhilly Downs, with Mullion to the south and Porthleven to the north...

, Cornwall

Cornwall

Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...

, to his yacht Elettra in the Cape Verde Islands

Cape Verde

The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...

. In September 1924, Marconi transmitted during daytime and nighttime on 32 meters from Poldhu to his yacht in Beirut. Marconi, in July 1924, entered into contracts with the British General Post Office (GPO) to install high speed shortwave telegraphy circuits from London to Australia, India, South Africa and Canada as the main element of the Imperial Wireless Chain

Imperial Wireless Chain

The Imperial Wireless Chain, also known as the Empire Wireless Chain, was a strategic international wireless telegraphy communications network, created to link the countries of the British Empire. Although the idea was conceived prior to World War I, Britain was the last of the world's Great Powers...

. The UK-to-Canada shortwave "Beam Wireless Service" went into commercial operation on 25 October 1926. Beam Wireless Services from the UK to Australia, South Africa and India went into service in 1927.

Far more spectrum is available for long distance communication in the shortwave bands than in the longwave bands; and shortwave transmitters, receivers and antennas were orders of magnitude less expensive than the multi-hundred kilowatt transmitters and monstrous antennas needed for longwave.

Shortwave communications began to grow rapidly in the 1920s, similar to the internet in the late 20th century. By 1928, more than half of long distance communications had moved from transoceanic cables and longwave wireless services to shortwave and the overall volume of transoceanic shortwave communications had vastly increased. Shortwave also ended the need for multi-million dollar investments in new transoceanic telegraph cables and massive longwave wireless stations, although some existing transoceanic telegraph cables and commercial longwave communications stations remained in use until the 1960s.

The cable companies began to lose large sums of money in 1927, and a serious financial crisis threatened the viability of cable companies that were vital to strategic British interests. The British government convened the Imperial Wireless and Cable Conference in 1928 "to examine the situation that had arisen as a result of the competition of Beam Wireless with the Cable Services". It recommended and received Government approval for all overseas cable and wireless resources of the Empire to be merged into one system controlled by a newly-formed company in 1929, Imperial and International Communications Ltd. The name of the company was changed to Cable and Wireless Ltd.

Cable & Wireless

Cable & Wireless Worldwide PLC is a global telecommunications company headquartered in Bracknell, United Kingdom. Cable & Wireless specialises in providing communication networks and services to large corporates, governments, carrier customers and resellers...

 in 1934.

Propagation characteristics

Shortwave radio frequency energy is capable of reaching any location on the Earth as it can be refracted

Refraction

Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

 back to the earth by the ionosphere

Ionosphere

The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

, (a phenomenon known as Skywave

Skywave

Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...

 propagation). A typical phenomenon of shortwave propagation is the occurrence of a skip zone

Skip zone

A skip zone, also called a silent zone or zone of silence, is a region where a radio transmission can not be received located between regions both nearer and further from the transmitter where reception is possible....

 (see first figure on that page) where reception fails. With a fixed working frequency, large changes in ionospheric conditions may create skip zones at night.

As a result of the multi-layer structure of the ionosphere, propagation often simultaneously occurs on different paths, refracted by the E or F region and with different numbers of hops, a phenomenon that may be disturbing for certain techniques. Particularly for lower frequencies of the shortwave band, absorption of radio frequency energy in the lowest ionospheric layer, the D layer, may be a serious limit. This is due to collisions of electrons with neutral molecules, absorbing radio wave energy and converting it to heat.
Predictions of sky wave propagation depend on:

• The distance from the transmitter to the target receiver.
• Time of day. During the day, frequencies higher than approximately 12 MHz can travel longer distances than lower ones. At night, this property is reversed.
• With lower frequencies the dependence on the time of the day is mainly due to the lowest ionospheric layer, the D Layer, forming only during the day when photons from the sun break up atoms into ions and free electrons.
• Season. During the winter months the AM broadcast band tends to be more favorable because of longer hours of darkness.
• Solar flare
  Solar flare
  A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
  
  s produce a large increase in D region ionization so high, sometimes for periods of several minutes, all sky wave propogation is nonexistant.

Types of modulation

Several different types of modulation are used to impress information on a short-wave transmission.

Amplitude modulation

Amplitude modulation

Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...

 is the simplest type and the most commonly used for shortwave broadcasting. The instantaneous amplitude of the carrier is controlled by the amplitude of the signal (speech, or music, for example). At the receiver, a simple detector

Detector (radio)

A detector is a device that recovers information of interest contained in a modulated wave. The term dates from the early days of radio when all transmissions were in Morse code, and it was only necessary to detect the presence of a radio wave using a device such as a coherer without necessarily...

 recovers the desired modulation signal from the carrier.

Single sideband transmission is a form of amplitude modulation but in effect filters the result of modulation. An amplitude-modulated signal has frequency components both above and below the carrier frequency. If one set of these components is eliminated as well as the residual carrier, only the remaining set is transmitted. This saves power in the tranmission, as roughly 2/3 of the energy sent by an AM signal is unnecessary to recover the information contained on it. It also saves "bandwidth", allowing about one-half the carrier frequency spacing to be used. The drawback is that the receiver is more complicated, since it must re-recreate the carrier to recover the signal. Small errors in the detector process can greatly affect the pitch of the received signal, so single side band is not usual for music or general broadcast. Single side band is used for long-range voice communications by ships and aircraft, Citizen's Band,and amateur radio operators. LSB (lower sideband) is generally used below 9 MHz and USB (upper sideband) above 9 MHz.

Vestigal sideband transmits the carrier and one complete side-band, but filters out the redundant side-band. It is a compromise between AM and SSB, allowing simple receivers to be used but requiring almost as much transmitter power as AM. One advantage is that only half the bandwidth of an AM signal is used. It can be heard in the transmission of certain radio time signal

Time signal

A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...

 stations.

Continuous wave

Continuous wave

A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...

 (CW) is on-and-off keying of a carrier, used only for Morse code

Morse code

Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...

 communications.

Narrow-band frequency modulation

Frequency modulation

In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...

 (NBFM) is mainly used in the higher HF frequencies (typically above 20 MHz). Because of the larger bandwidth required, NBFM is much more commonly used for VHF communication. Regulations limit the bandwidth

Bandwidth

Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies. It is typically measured in hertz, and may sometimes refer to passband bandwidth, sometimes to baseband bandwidth, depending on context...

 of a signal transmitted in the HF bands, and the advantages of frequency modulation are greatest if the FM signal is allowed to have a wider bandwidth. NBFM is limited to short-range SW transmissions due to the multiphasic distortions created by the ionosphere.

Digital Radio Mondiale

Digital Radio Mondiale

Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...

 (DRM) is a digital modulation for use on bands below 30 MHz.

Radioteletype

Radioteletype

Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...

, fax, digital, slow-scan television

Slow-scan television

Slow-scan television is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color.A technical term for SSTV is narrowband television...

 and other systems use forms of frequency-shift keying or audio subcarriers on a shortwave carrier. These generally require special equipment to decode, such as software on a computer equipped with a sound card.

Uses

Some major uses of the shortwave radio band are:

• International broadcasting
  International broadcasting
  International broadcasting is broadcasting that is deliberately aimed at a foreign, rather than a domestic, audience. It usually is broadcast by means of longwave, mediumwave, or shortwave radio, but in recent years has also used direct satellite broadcasting and the Internet as means of reaching...
  
   primarily by government-sponsored propaganda
  Propaganda
  Propaganda is a form of communication that is aimed at influencing the attitude of a community toward some cause or position so as to benefit oneself or one's group....
  
   stations to foreign audiences: the most common use of all.
• Domestic broadcasting
  Broadcasting
  Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
  
  : to widely dispersed populations with few longwave
  Longwave
  In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
  
  , mediumwave
  Mediumwave
  Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
  
   and FM stations serving them; or for specialty political, religious and alternative media
  Alternative media
  Alternative media are media which provide alternative information to the mainstream media in a given context, whether the mainstream media are commercial, publicly supported, or government-owned...
  
   networks; or of individual commercial and non-commercial paid broadcasts.
• Utility stations
  Utility station
  The term utility station is used to describe fixed radio broadcasters disseminating signals that are not intended for reception by the general public...
  
   transmitting messages not intended for the general public, such as aircraft flying between continents, encrypted diplomatic messages, weather
  Weather
  Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
  
   reporting, or ships at sea.
• Clandestine stations. These are stations that broadcast on behalf of various political movements, including rebel or insurrectionist forces, and are normally unauthorised by the government-in-charge of the country in question. Clandestine broadcasts may emanate from transmitters located in rebel-controlled territory or from outside the country entirely, using another country's transmission facilities. Clandestine stations were used during World War II to transmit news from the Allied point of view into Axis-controlled areas. Although the Nazis confiscated many radios and executed their owners, many people continued to listen.
• Numbers Station
  Numbers station
  A numbers station is a shortwave radio station of uncertain origin. In the 1950s, Time magazine reported that the numbers stations first appeared shortly after World War II and were using a format that had been used to send weather data during that war.Numbers stations generally broadcast...
  
  s These stations regularly appear and disappear all over the shortwave radio band but are unlicenced and untraceable. It is believed that Numbers Stations are operated by government agencies, and are used to communicate with clandestine operatives working within foreign countries. However, no definitive proof of such use has emerged. Because the vast majority of these broadcasts contain nothing but the recitation of blocks of numbers, in various languages, with occasional bursts of music, they have become known colloquially as "Number Stations". Perhaps the most noted Number Station is the "Lincolnshire Poacher"
  Lincolnshire Poacher (numbers station)
  "The Lincolnshire Poacher" was the nickname of a mysterious, powerful shortwave numbers station that used two bars from the English folk song "The Lincolnshire Poacher" as an interval signal. The radio station was believed to be operated by the British Secret Intelligence Service and emanated from...
  
  , named after the 18th century English folk song, which is transmitted just before the sequences of numbers.
• Amateur radio
  Amateur radio
  Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
  
   operators.
• Time signal
  Time signal
  A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...
  
   and radio clock
  Radio clock
  A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock...
  
   stations: In North America, WWV radio and WWVH radio
  WWVH
  WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii....
  
   transmit at these frequencies: 2500 kHz, 5000 kHz, 10000 kHz, and 15000 kHz; and WWV also transmits on 20000 kHz. The CHU radio station
  CHU (radio station)
  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.- History :...
  
   in Canada transmits on the following frequencies: 3330 kHz, 7850 kHz, and 14670 kHz. Other similar radio clock
  Radio clock
  A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock...
  
   stations transmit on various shortwave and longwave frequencies around the world. The shortwave transmissions tend to be intended primarily for human reception, while the longwave stations are generally used for automatic synchronization of watches and clocks.
• Over-the-horizon radar
  Over-the-horizon radar
  Over-the-horizon radar, or OTH , is a design concept for radar systems to allow them to detect targets at very long ranges, typically up to thousands of kilometers...
  
  : From 1976 to 1989, the Soviet Union
  Soviet Union
  The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
  
  's Russian Woodpecker
  Russian Woodpecker
  The Russian Woodpecker was a notorious Soviet signal that could be heard on the shortwave radio bands worldwide between July 1976 and December 1989. It sounded like a sharp, repetitive tapping noise, at 10 Hz, giving rise to the "Woodpecker" name...
  
   over-the-horizon radar system blotted out numerous shortwave broadcasts daily.

The term DXing

DXing

DXing is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens' band radio or other two way radio communications. Many DXers also attempt to receive written verifications of reception from the...

, in the context of listening to radio signals of any user of the shortwave band, is the activity of monitoring distant stations. In the context of amateur radio operators, the term "DXing" refers to the two-way communications with a distant station, using shortwave radio frequencies.

The Asia-Pacific Telecommunity estimates that there are approximately 600,000,000 shortwave broadcast-radio receivers in use in 2002. WWCR

WWCR

WWCR is a shortwave radio station located in Nashville, Tennessee in the United States. WWCR uses four 100 kW transmitters which broadcast on 14 different frequencies....

 claims that there are 1.5 billion shortwave receivers worldwide.

Shortwave broadcasting

See International broadcasting

International broadcasting

International broadcasting is broadcasting that is deliberately aimed at a foreign, rather than a domestic, audience. It usually is broadcast by means of longwave, mediumwave, or shortwave radio, but in recent years has also used direct satellite broadcasting and the Internet as means of reaching...

 for details on the history and practice of broadcasting to foreign audiences.
See shortwave relay station

Shortwave relay station

Shortwave relay stations are transmitter sites used by international broadcasters to extend their coverage to areas that cannot be reached easily from their home state, for example the BBC operates an extensive net of relay stations....

 for the actual kinds of integrated technologies used to bring high power signals to listeners.

Frequency allocations

The World Radiocommunication Conference

World Radiocommunication Conference

World Radiocommunication Conference is organized by ITU to review, and, as necessary, revise the Radio Regulations, the international treaty governing the use of the radio-frequency spectrum and the geostationary-satellite and non-geostationary-satellite orbits. It is held every three to four years...

 (WRC), organized under the auspices of the International Telecommunication Union

International Telecommunication Union

The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...

, allocates bands for various services in conferences every few years. The last WRC took place in 2007.

At WRC-97 in 1997, the following bands were allocated for international broadcasting

International broadcasting

International broadcasting is broadcasting that is deliberately aimed at a foreign, rather than a domestic, audience. It usually is broadcast by means of longwave, mediumwave, or shortwave radio, but in recent years has also used direct satellite broadcasting and the Internet as means of reaching...

. (listed in the table):

Metre Band	Frequency Range	Remarks
120 m	2300 – 2495 kHz	tropic band
90 m	3200 – 3400 kHz	tropic band
75 m	3900 – 4000 kHz	shared with the North American amateur radio Amateur radio Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...  80m band
60 m	4750 – 5060 kHz	tropic band
49 m	5900 – 6200 kHz
41 m	7200 – 7450 kHz	shared with the amateur radio Amateur radio Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...  40m band
31 m	9400 – 9900 kHz	Currently most heavily used band
25 m	11,600 - 12,100 kHz
22 m	13,570 - 13,870 kHz	substantially used only in Eurasia
19 m	15,100 - 15,800 kHz
16 m	17,480 - 17,900 kHz
15 m	18,900 - 19,020 kHz	almost unused, could become a DRM band
13 m	21,450 - 21,850 kHz
11 m	25,600 - 26,100 kHz	may be used for local DRM broadcasting

AM shortwave broadcasting channels are allocated with a 5 kHz separation for traditional analog audio broadcasting.

International broadcasters for practical reasons sometimes operate outside the normal WRC-allocated bands or use off-channel frequencies to attract attention in crowded bands (60m, 49m, 40m, 41m, 31m, 25m).

The new digital audio broadcasting

Digital audio broadcasting

Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....

 format for shortwave DRM

Digital Radio Mondiale

Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...

 operates 10 kHz or 20 kHz channels. There are some ongoing discussions with respect to specific band allocation for DRM, as it mainly transmitted in 10 kHz format.

The power used by shortwave transmitters ranges from less than one watt for some experimental and amateur radio transmissions to 500 kilowatts and higher for intercontinental broadcasters and over-the-horizon radar

Over-the-horizon radar

Over-the-horizon radar, or OTH , is a design concept for radar systems to allow them to detect targets at very long ranges, typically up to thousands of kilometers...

. Shortwave transmitting centers often use specialized antenna

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

 designs (like the ALLISS

ALLISS

ALLISS is a fully rotatable antenna system for high power shortwave radio broadcasting in the 6 MHz to 26 MHz range. An ALLISS module is a self contained shortwave relay station that is used for international broadcasting.- FAQ :...

 antenna technology) to concentrate radio energy at the target area.

Advantages

Shortwave does possess a number of advantages over newer technologies, including the following:

• The difficulty in censoring programming by authorities in target countries: unlike the Internet, government authorities have technical difficulties to monitor which stations (sites) are being listened to (accessed). For example, during the coup against President Mikhail Gorbachev, when his access to communications was limited, Gorbachev was able to stay informed by means of the BBC World Service on shortwave. However, it was reported that during the Cultural Revolution
  Cultural Revolution
  The Great Proletarian Cultural Revolution, commonly known as the Cultural Revolution , was a socio-political movement that took place in the People's Republic of China from 1966 through 1976...
  
  , the Chinese Government was able to trace listeners of western shortwave stations by monitoring the EM emission from the tuning circuit of receiver and power usage.
• Low-cost shortwave radios are widely available in all but the most repressive countries in the world.
• In many countries (particularly in most third world nations and in the Eastern bloc during the Cold War era) ownership of shortwave receivers is widespread (in many of these countries some domestic stations also used shortwave).
• Many newer shortwave receivers are portable and can be battery operated, making them useful in difficult circumstances. Newer technology includes hand-cranked radios which provide power without batteries.
• Shortwave radios can be used in situations where Internet
  Internet
  The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
  
   or satellite communications service is unavailable (or unaffordable).
• Shortwave radio travels much farther than broadcast FM (88-108 MHz). Shortwave broadcasts can be easily transmitted over a distance of several thousands of kilometers, e.g., from one continent to another.
• Particularly in tropical regions SW is somewhat less prone to interference from thunderstorms than medium wave radio and is able to cover a large geographic area with relatively-low power (and hence cost). Therefore in many of these countries it is widely used for domestic broadcasting.

Disadvantages

The benefits are widely regarded as being outweighed by the drawbacks such as these:

• Shortwave broadcasts often suffer from serious interference problems because of overcrowding on the wavebands, atmospheric disturbances and electrical interference problems (particularly in cities) from TV sets, computers, poorly designed domestic appliances, and substandard electrical installations.
• Even under ideal reception conditions, the audio quality of a shortwave broadcast is usually inferior to that of domestic stations, particularly FM stations, and it is always in mono.
• As more people around the world have access to television and the Internet, old technologies such as shortwave radio find it difficult to compete for listeners' attention.
• In most Western countries, ownership of shortwave radios is usually limited to interested enthusiasts since many new standard radios do not have the shortwave band facility. Therefore, Western audiences are limited.
• The dependence of shortwave radio on atmospheric conditions (the best frequency for hearing certain parts of the world varies by time of day and season) means that it can be difficult to use by non-technically-minded listeners.

Amateur radio

The practice of operating a shortwave radio transmitter for non-commercial two-way communications is known as amateur radio

Amateur radio

Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

. Licenses are granted by authorized government agencies.

Amateur radio operators have made many technical advancements in the field of radio and make themselves available to transmit emergency communications when normal communications channels fail. Some amateurs practice operating off the power grid so as to be prepared for power loss. Many amateur radio operators started out as Shortwave Listeners (SWLs) and actively encourage SWLs to become amateur radio operators.

Shortwave listening

Many hobbyists listen to shortwave broadcasters without operating transmitters. In some cases, the goal is to hear as many stations from as many countries as possible (DXing

DXing

DXing is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens' band radio or other two way radio communications. Many DXers also attempt to receive written verifications of reception from the...

); others listen to specialized shortwave utility, or "ute", transmissions such as maritime, naval, aviation, or military signals. Others focus on intelligence signals from numbers stations, or the two way communications by amateur radio operators.

Many listeners tune the shortwave bands for the programmes of stations broadcasting to a general audience (such as Radio Taiwan International

Radio Taiwan International

Radio Taiwan International is the English name and call sign of the international radio service, the Central Broadcasting System of the Republic of China, commonly known as Taiwan...

, Voice of Russia

Voice of Russia

Voice of Russia is the Russian government's international radio broadcasting service owned by the All-Russia State Television and Radio Company. Its predecessor Radio Moscow was the official international broadcasting station of the Union of Soviet Socialist Republics.-Early years:Radio Moscow...

, China Radio International

China Radio International

China Radio International , the former Radio Beijing and originally Radio Peking, founded on December 3 of 1941, is one of the three state-owned media in China along with China National Radio and China Central Television in the People's Republic of China .As the PRC's external radio station, CRI...

, Radio Canada International

Radio Canada International

Radio Canada International is the international broadcasting service of the Canadian Broadcasting Corporation . Until 1970, it was known as the CBC International Service and was sometimes referred to as the "Voice of Canada" in its early years.- The early years :The idea for creating an...

, Voice of America

Voice of America

Voice of America is the official external broadcast institution of the United States federal government. It is one of five civilian U.S. international broadcasters working under the umbrella of the Broadcasting Board of Governors . VOA provides a wide range of programming for broadcast on radio...

, Radio France Internationale

Radio France Internationale

Radio France Internationale was created in 1975 as part of Radio France by the Government of France, and replaced the Poste Colonial , Paris Mondial , Radio Paris , RTF Radio Paris and ORTF Radio Paris...

, BBC World Service

BBC World Service

The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...

, Radio Australia

Radio Australia

Radio Australia is the international broadcasting and online service operated by the Australian Broadcasting Corporation , Australia's public broadcaster.- History :...

, Radio Netherlands

Radio Netherlands

Radio Netherlands Worldwide is a public radio and television network based in Hilversum, producing and transmitting programmes for international audiences outside the Netherlands...

, Voice of Korea

Voice of Korea

Voice of Korea is the international broadcasting service of the Democratic People's Republic of Korea. It broadcasts primarily information in Korean, Chinese, Spanish, German, English, French, Russian, Japanese, and Arabic...

, Sarawak Report

Sarawak Report

The Sarawak Report is a Sarawak investigative journalism news online resource in UK founded by Clare Rewcastle Brown, sister-in-law of former UK prime minister Gordon Brown...

 etc.). Today, through the evolution of the Internet, the hobbyist can listen to shortwave signals via remotely controlled shortwave receivers around the world, even without owning a shortwave radio. Many international broadcasters (such as Radio Canada International http://www.rcinet.ca/rci/includes/rcilive.asx, the BBC and Radio Australia) offer live streaming audio on their websites.
Shortwave listeners, or SWLs, can obtain QSL cards from broadcasters, utility stations or amateur radio operators as trophies of the hobby. Some stations even give out special certificates, pennants, stickers and other tokens and promotional materials to shortwave listeners.

Utility stations

Utility stations are stations that do not broadcast to the general public. There are shortwave bands allocated to the use of merchant shipping, marine weather, and ship-to-shore stations; for aviation weather and air-to-ground communications; for military communications; for long-distance governmental purposes, and for other non-broadcast communications. Many radio hobbyists specialize in listening to "ute" broadcasts, which often come from places without shortwave broadcasters.

Unusual signals

The short wave bands are also used by unlicensed individuals who want mostly short range "party line" like communications. Two examples are the use of HF for communication between fishing boats in many areas of the world, and the unlicensed use of the 11-meter band. Called "pirates"

Pirate radio

Pirate radio is illegal or unregulated radio transmission. The term is most commonly used to describe illegal broadcasting for entertainment or political purposes, but is also sometimes used for illegal two-way radio operation...

, these unlicensed operators can cause interference to licensed stations. Many third-world countries have shops selling HF transmitter radios to any customer without regard to license or operator knowledge. In 2011, there is virtually no national nor international efforts to control such pirate operations.

The short wave bands are also used for various experiments, some going on for years. In 2011, signals tracable to China regularly send powerful HF transmissions that scan over wide HF ranges, perhaps to determine the maximum usable frequency

Maximum usable frequency

Maximum usable frequency describes, in radio transmission, using reflection from the regular ionized layers of the ionosphere, the upper frequency limit that can be used for transmission between two points at a specified time, independent of transmitter power...

 (MUF) or other issues.

Shortwave's future

The development of direct broadcasts from satellites has reduced the demand for shortwave receivers, but there are still a great number of shortwave broadcasters. A new digital radio

Digital radio

Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...

 technology, Digital Radio Mondiale

Digital Radio Mondiale

Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...

 (DRM), is expected to improve the quality of shortwave audio from very poor to standards comparable to the FM broadcast band. The future of shortwave radio is threatened by the rise of power line communication

Power line communication

Power line communication or power line carrier , also known as power line digital subscriber line , mains communication, power line telecom , power line networking , or broadband over power lines are systems for carrying data on a conductor also used for electric power transmission.A wide range...

 (PLC), also known as Broadband over Power Lines (BPL), where a data stream is transmitted over unshielded power lines. As the frequencies used overlap with shortwave bands, severe distortions make listening to shortwave radio near power lines difficult or impossible. However, because it is a cheap and effective way to receive communications in countries with poor infrastructure, shortwave will be around for years to come.

Short wave use by licensed hobbyists, amateur ham radio operators, continues, but it is diminishing due to competing interests in computers and other communication devices. Some hobbyists have combined amateur radio HF with experimental and established data modes that can communicate very close to under the noise floor of receivers.

Shortwave broadcasts and music

Some musicians have been attracted to the unique aural characteristics of shortwave radio which—due to the nature of amplitude modulation, varying propagation conditions, and the presence of interference—generally has lower fidelity than local broadcasts (particularly via FM stations). Shortwave transmissions often have bursts of distortion, and "hollow" sounding loss of clarity at certain aural frequencies, altering the harmonics of natural sound and creating at times a strange "spacey" quality due to echoes and phase distortion. Evocations of shortwave reception distortions have been incorporated into rock and classical compositions, by means of delays or feedback loops, equalizers, or even playing shortwave radios as live instruments. Snippets of broadcasts have been mixed into electronic sound collages and live musical instruments, by means of analogue tape loop

Tape loop

In music, tape loops are loops of prerecorded magnetic tape used to create repetitive, rhythmic musical patterns or dense layers of sound. Contemporary composers such as Steve Reich and Karlheinz Stockhausen used tape loops to create phase patterns and rhythms...

s or digital samples. Sometimes the sounds of instruments and existing musical recordings are altered by remixing or equalizing, with various distortions added, to replicate the garbled effects of shortwave radio reception.

The first attempts by serious composers to incorporate radio effects into music may be those of the Russian physicist and musician Léon Theremin

Léon Theremin

Léon Theremin was a Russian and Soviet inventor. He is most famous for his invention of the theremin, one of the first electronic musical instruments. He is also the inventor of interlace, a technique of improving the picture quality of a video signal, widely used in video and television technology...

, who perfected a form of radio oscillator as a musical instrument in 1928 (radios of the time were prone to break into whistles, adding various tonal harmonics to music and speech); and in the same year, the development of a French instrument called the Ondes Martenot

Ondes Martenot

The ondes Martenot , also known as the ondium Martenot, Martenot and ondes musicales, is an early electronic musical instrument invented in 1928 by Maurice Martenot. The original design was similar in sound to the theremin...

 by its inventor Maurice Martenot

Maurice Martenot

Maurice Martenot was a French cellist, a radio telegrapher during the first World War, and an inventor.Born in Paris, he is best known for his invention of the ondes Martenot, an instrument he first realized in 1928 and spent decades improving. He unveiled a microtonal model in 1938...

, a French cellist and former wireless telegrapher. A notable chamber piece by Mexican composer Silvestre Revueltas

Silvestre Revueltas

Silvestre Revueltas Sánchez was a Mexican composer of classical music, a violinist and a conductor.-Life:...

—Ocho x radio, 1933—features a complex texture of pseudo-mariachi musics, overlapping and cross-fading as if heard from distant stations: quite similar to shortwave radio signal propagation disturbance. John Cage

John Cage

John Milton Cage Jr. was an American composer, music theorist, writer, philosopher and artist. A pioneer of indeterminacy in music, electroacoustic music, and non-standard use of musical instruments, Cage was one of the leading figures of the post-war avant-garde...

 used actual radios (of unspecified wavelength) live on several occasions, starting in 1942 with Credo in Us, while Karlheinz Stockhausen

Karlheinz Stockhausen

Karlheinz Stockhausen was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th and early 21st centuries. Another critic calls him "one of the great visionaries of 20th-century music"...

 used shortwave radio and effects in works including Hymnen

Hymnen

Hymnen is an electronic and concrete work, with optional live performers, by Karlheinz Stockhausen, composed in 1966–67, and elaborated in 1969. In the composer's catalog of works, it is "Nr. 22".-Musical form and content:...

(1966–67), Kurzwellen

Kurzwellen

Kurzwellen , for six players with shortwave receivers and live electronics, is a composition by Karlheinz Stockhausen, written in 1968. It is Number 25 in the catalog of the composer’s works.-Conception:...

(1968)—adapted for the Beethoven Bicentennial in Opus 1970 with filtered and distorted snippets of Beethoven pieces—Spiral

Spiral (Stockhausen)

Spiral , for a soloist with a shortwave receiver, is a composition by Karlheinz Stockhausen, written in 1968. It is Number 27 in the catalogue of the composer’s works.-Conception:...

(1968), Pole, Expo (both 1969–70), and Michaelion (1997). Holger Czukay

Holger Czukay

Holger Czukay is a German musician, probably best known as a co-founder of the krautrock group Can. Described by critic Jason Ankeny as "successfully bridg[ing] the gap between pop and the avant-garde," Czukay is also notable for creating early important examples of ambient music, for exploring...

, a student of Stockhausen, was one of the first to use shortwave in a rock music

Rock music

Rock music is a genre of popular music that developed during and after the 1960s, particularly in the United Kingdom and the United States. It has its roots in 1940s and 1950s rock and roll, itself heavily influenced by rhythm and blues and country music...

 context. In 1975, German electronic music

Electronic music

Electronic music is music that employs electronic musical instruments and electronic music technology in its production. In general a distinction can be made between sound produced using electromechanical means and that produced using electronic technology. Examples of electromechanical sound...

 band Kraftwerk

Kraftwerk

Kraftwerk is an influential electronic music band from Düsseldorf, Germany. The group was formed by Ralf Hütter and Florian Schneider in 1970, and was fronted by them until Schneider's departure in 2008...

 recorded a full length concept album

Concept album

In music, a concept album is an album that is "unified by a theme, which can be instrumental, compositional, narrative, or lyrical." Commonly, concept albums tend to incorporate preconceived musical or lyrical ideas rather than being improvised or composed in the studio, with all songs contributing...

 around simulated radiowave and shortwave sounds, entitled Radio-Activity.

Among others, The The

The The

The The are an English musical and multimedia group that have been active in various forms since 1979, with singer/songwriter Matt Johnson being the only constant band member.-Early years :...

 whose Radio Cineola monthly broadcasts draw heavily on shortwave radio sound, The B-52s, Shearwater

Shearwater

Shearwaters are medium-sized long-winged seabirds. There are more than 30 species of shearwaters, a few larger ones in the genus Calonectris and many smaller species in the genus Puffinus...

, Tom Robinson

Tom Robinson

Tom Robinson is an English singer-songwriter, bassist and radio presenter, better known for the hits "Glad to Be Gay", "2-4-6-8 Motorway", and "Don't Take No for an Answer", with his Tom Robinson Band...

, Peter Gabriel

Peter Gabriel

Peter Brian Gabriel is an English singer, musician, and songwriter who rose to fame as the lead vocalist and flautist of the progressive rock group Genesis. After leaving Genesis, Gabriel went on to a successful solo career...

, Pukka Orchestra

Pukka Orchestra

The Pukka Orchestra was a Canadian New Wave band in the 1980s. The core of the band consisted of vocalist Graeme Williamson and guitarists Neil Chapman and Tony Duggan-Smith, although the band made frequent use of guest musicians....

, AMM

AMM (group)

AMM are an important British free improvisation group, founded in London, England in 1965.AMM have never been well known to the general public, but have been incredibly influential on the field of improvised music...

, John Duncan

John Duncan (artist)

This page is about John Duncan the contemporary artist. For the Symbolist artist see John Duncan .John Duncan is an artist who has lived and worked in Los Angeles, Tokyo and Amsterdam, currently lives and works in Bologna...

, Orchestral Manoeuvres in the Dark

Orchestral Manoeuvres in the Dark

Orchestral Manoeuvres in the Dark are a synthpop group whose founding members are originally from the Wirral Peninsula, England...

 (on their Dazzle Ships

Dazzle Ships (album)

The "Manor Version" of "Telegraph" was recorded at the same time as Architecture & Morality. "Swiss Radio International" was dropped from the album at the last minute...

album), Pat Metheny

Pat Metheny

Patrick Bruce "Pat" Metheny is an American jazz guitarist and composer.One of the most successful and critically acclaimed jazz musicians to come to prominence in the 1970s and '80s, he is the leader of the Pat Metheny Group and is also involved in duets, solo works and other side projects...

, Aphex Twin

Aphex Twin

Richard David James , best known under the pseudonym Aphex Twin, is an Irish-born electronic musician and composer described as "the most inventive and influential figure in contemporary electronic music"...

, Boards of Canada

Boards of Canada

Boards of Canada are a Scottish electronic music duo consisting of brothers Mike Sandison and Marcus Eoin...

, Rush

Rush (band)

Rush is a Canadian rock band formed in August 1968, in the Willowdale neighbourhood of Toronto, Ontario. The band is composed of bassist, keyboardist, and lead vocalist Geddy Lee, guitarist Alex Lifeson, and drummer and lyricist Neil Peart...

, Able Tasmans

Able Tasmans

The Able Tasmans were an indie band from Auckland, New Zealand.At various times, the band consisted of Leslie Jonkers, Peter Keen, Graeme Humphreys, Craig Mason, Jane Dodd , and Ronald Young. They formed in 1984, and named themselves after the Dutch explorer Abel Tasman. They released four albums...

, Team Sleep

Team Sleep

Team Sleep is an American experimental alternative rock group led by singer/guitarist Chino Moreno, better known for fronting the Sacramento-based band Deftones....

, Meat Beat Manifesto

Meat Beat Manifesto

Meat Beat Manifesto, often shortened to Meat Beat or MBM, is an electronic music group originally consisting of Jack Dangers and Jonny Stephens formed in 1987 in Swindon, UK...

, Tim Hecker

Tim Hecker

Tim Hecker is an electronic musician and sound artist based in Montreal, Canada. Hecker previously recorded under the moniker Jetone, but has become better known internationally for his ambient recordings released through Kranky, Mille Plateaux, Alien8, Force Inc, Staalplaat, and Fat Cat under his...

, Jonny Greenwood

Jonny Greenwood

Jonathan Richard Guy "Jonny" Greenwood is an English musician and composer, best known as a member of the English rock band Radiohead. Greenwood is a multi-instrumentalist, but serves mainly as lead guitarist and keyboard player. In addition to guitar and keyboard, he plays viola, harmonica,...

 of Radiohead

Radiohead

Radiohead are an English rock band from Abingdon, Oxfordshire, formed in 1985. The band consists of Thom Yorke , Jonny Greenwood , Ed O'Brien , Colin Greenwood and Phil Selway .Radiohead released their debut single "Creep" in 1992...

, Roger Waters

Roger Waters

George Roger Waters is an English musician, singer-songwriter and composer. He was a founding member of the progressive rock band Pink Floyd, serving as bassist and co-lead vocalist. Following the departure of bandmate Syd Barrett in 1968, Waters became the band's lyricist, principal songwriter...

 (on Radio KAOS

Radio Kaos

Radio Kaos is Mexican Rock band formed in Los Angeles in 1992. The band currently features Claudio Pérez , David Pérez . The release of their first album Botas Negras under EMI Capitol was a success in Mexico...

album), Wilco

Wilco

Wilco is an American alternative rock band based in Chicago, Illinois. The band was formed in 1994 by the remaining members of alternative country group Uncle Tupelo following singer Jay Farrar's departure. Wilco's lineup has changed frequently, with only singer Jeff Tweedy and bassist John...

, code 000 and Samuel Trim have also used or been inspired by shortwave broadcasts.

See also

• Medium wave
• Long wave
• ALLISS
  ALLISS
  ALLISS is a fully rotatable antenna system for high power shortwave radio broadcasting in the 6 MHz to 26 MHz range. An ALLISS module is a self contained shortwave relay station that is used for international broadcasting.- FAQ :...
  
   – a very large rotatable antenna system used in International Broadcasting
• Amateur radio
  Amateur radio
  Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
  
   also uses the shortwave bands, but with power levels under 2 kW
• International broadcasting
  International broadcasting
  International broadcasting is broadcasting that is deliberately aimed at a foreign, rather than a domestic, audience. It usually is broadcast by means of longwave, mediumwave, or shortwave radio, but in recent years has also used direct satellite broadcasting and the Internet as means of reaching...
  
  
• Shortwave bands
  Shortwave bands
  Shortwave bands are frequency allocations for use within the shortwave radio spectrum . They are the primary medium for applications such as maritime communications, international broadcasting and worldwide amateur radio activity because they take advantage of ionospheric skip propagation to send...
  
   shortwave's spectrum allocation
• shortwave relay station
  Shortwave relay station
  Shortwave relay stations are transmitter sites used by international broadcasters to extend their coverage to areas that cannot be reached easily from their home state, for example the BBC operates an extensive net of relay stations....
  
   the fundamental way in which programmes are broadcast on shortwave
• SSB
• List of American shortwave broadcasters

External links

• SWLing.com - A beginner's guide to shortwave radio listening.
• Glenn Hauser
  Glenn Hauser
  Glenn Hauser is an internationally-known DXer and radio host from Enid, Oklahoma, United States. He produces and narrates the weekly 30-minute radio show "World Of Radio", heard on various non-commercial AM and FM radio stations throughout the U.S., plus worldwide on shortwave radio.Glenn Hauser...
  
  's World of Radio website
• Space Weather and Radio Propagation Center View live and historical data and images of space weather
  Space weather
  Space weather is the concept of changing environmental conditions in near-Earth space or thespace from the Sun's atmosphere to the Earth's atmosphere. It is distinct from the concept ofweather within the Earth's planetary atmosphere...
  
   and radio propagation
  Radio propagation
  Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
  
  .
• Short-Wave Radio Hangs On For Life The Economist
  The Economist
  The Economist is an English-language weekly news and international affairs publication owned by The Economist Newspaper Ltd. and edited in offices in the City of Westminster, London, England. Continuous publication began under founder James Wilson in September 1843...
  
   article describing pros and cons of short wave radio since the Cold War
  Cold War
  The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
  
  .
• "Short-Wave Radio Telephone is Success in Tests" Popular Mechanics, July 1931, mid page experiments carried out for the French and British governments