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57-580: The AN/MPQ-49 Forward Area Alerting Radar ( FAAR ) is a lightweight early warning radar system consisting of the AN/TPQ-43 radar, AN/TPX-50 Mark XII IFF receiver, a 5 kW generator set, and a Gama Goat providing mobility. FAAR was developed by the US Army in the 1960s to support their field anti-aircraft weapons, the M48 Chaparral and M163 Vulcan Air Defense System , deployed through

114-576: A Gama Goat and set up behind the front lines . The generator is towed behind the Gama Goat's own trailer, and then detached and operated at a distance from the trailer. The entire system is easily air-transportable. Early warning radar EW radars tend to share a number of design features that improve their performance in the role. For instance, EW radar typically operates at lower frequencies, and thus longer wavelengths, than other types. This greatly reduces their interaction with rain and snow in

171-410: A rock music context. In 1975, German electronic music band Kraftwerk recorded a full length concept album around simulated radiowave and shortwave sounds, entitled Radio-Activity . The The 's Radio Cineola monthly broadcasts drew heavily on shortwave radio sound. The development of direct broadcasts from satellites has reduced the demand for shortwave receiver hardware, but there are still

228-403: A great number of shortwave broadcasters. A new digital radio technology, Digital Radio Mondiale (DRM), is expected to improve the quality of shortwave audio from very poor to adequate. The future of shortwave radio is threatened by the rise of power line communication (PLC), also known as Broadband over Power Lines (BPL), which uses a data stream transmitted over unshielded power lines. As

285-421: A large-scale study into the transmission characteristics of short-wavelength waves and to determine their suitability for long-distance transmissions. Franklin rigged up a large antenna at Poldhu Wireless Station , Cornwall , running on 25 kW of power. In June and July 1923, wireless transmissions were completed during nights on 97 meters (about 3 MHz) from Poldhu to Marconi's yacht Elettra in

342-521: A layer of electrically charged atoms in the atmosphere called the Ionosphere . Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon. This is called skywave or "skip" propagation . Thus shortwave radio can be used for communication over very long distances, in contrast to radio waves of higher frequency, which travel in straight lines ( line-of-sight propagation ) and are limited by

399-417: A result of the multi-layer structure of the ionosphere , propagation often simultaneously occurs on different paths, scattered by the ‘E’ or ‘F’ layer and with different numbers of hops, a phenomenon that may be disturbed 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 impose

456-436: A serious limit. This is due to collisions of electrons with neutral molecules, absorbing some of a radio frequency 's energy and converting it to heat. Predictions of skywave propagation depend on: Several different types of modulation are used to incorporate information in a short-wave signal. Amplitude modulation is the simplest type and the most commonly used for shortwave broadcasting . The instantaneous amplitude of

513-534: A shortwave carrier. These generally require special equipment to decode, such as software on a computer equipped with a sound card. Note that on modern computer-driven systems, digital modes are typically sent by coupling a computer's sound output to the SSB input of a radio. Some established users of the shortwave radio bands may include: Sporadic or non-traditional users of the shortwave bands may include: The World Radiocommunication Conference (WRC), organized under

570-405: A single transmitter, making it difficult for government authorities to censor them. Shortwave radio is also often used by aircraft. The name "shortwave" originated during the beginning of radio in the early 20th century, when the radio spectrum was divided into long wave (LW), medium wave (MW), and short wave (SW) bands based on the length of the wave. Shortwave radio received its name because

627-532: A very limited spectrum available for long-distance communication, and the very expensive transmitters , receivers and gigantic antennas. Long waves are also difficult to beam directionally, resulting in a major loss of power over long distances. Prior to the 1920s, the shortwave frequencies above 1.5 MHz were regarded as useless for long-distance communication and were designated in many countries for amateur use. Guglielmo Marconi , pioneer of radio, commissioned his assistant Charles Samuel Franklin to carry out

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684-494: Is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF) , which extends from 3 to 30 MHz (100 (exactly 99.930819333) to 10 (exactly 9.9930819333) meters); above the medium frequency band (MF) , to the bottom of the VHF band . Radio waves in the shortwave band can be reflected or refracted from

741-400: Is customarily used below 10 MHz and USB (upper sideband) above 10 MHz, non-amateur services use USB regardless of frequency. Vestigial sideband transmits the carrier and one complete sideband, but filters out most of the other sideband. It is a compromise between AM and SSB, enabling simple receivers to be used, but requires almost as much transmitter power as AM. Its main advantage

798-458: Is eliminated as well as the residual carrier, only the remaining set is transmitted. This reduces power in the transmission, as roughly 2 ⁄ 3 of the energy sent by an AM signal is in the carrier, which is not needed to recover the information contained in the signal. It also reduces signal bandwidth , enabling less than one-half the AM signal bandwidth to be used. The drawback is the receiver

855-476: Is for transmitting audio, like the analog modes above. Continuous wave (CW) is on-and-off keying of a sine-wave carrier, used for Morse code communications and Hellschreiber facsimile -based teleprinter transmissions. It is a data mode, although often listed separately. It is typically received via lower or upper SSB modes. Radioteletype , fax, digital, slow-scan television , and other systems use forms of frequency-shift keying or audio subcarriers on

912-414: Is greatly extended. This allows the radar to use high-frequency signals, offering high resolution, while still offering long range. A major exception to this rule are radars intended to warn of ballistic missile attacks, like BMEWS , as the high-altitude exo-atmospheric trajectory of these weapons allows them to be seen at great ranges even from ground-based radars. Shortwave radio Shortwave radio

969-417: Is more complicated, since it must re-create the carrier to recover the signal. Small errors in the detection process greatly affect the pitch of the received signal. As a result, single sideband is not used for music or general broadcast. Single sideband is used for long-range voice communications by ships and aircraft, citizen's band , and amateur radio operators. In amateur radio operation lower sideband (LSB)

1026-549: Is that only half the bandwidth of an AM signal is used. It is used by the Canadian standard time signal station CHU . Vestigial sideband was used for analog television and by ATSC , the digital TV system used in North America. Narrow-band frequency modulation (NBFM or NFM) is used typically above 20 MHz. Because of the larger bandwidth required, NBFM is commonly used for VHF communication. Regulations limit

1083-591: The ALLISS antenna technology) to concentrate radio energy at the target area. Shortwave possesses a number of advantages over newer technologies: Shortwave radio's benefits are sometimes regarded as being outweighed by its drawbacks, including: The Asia-Pacific Telecommunity estimates that there are approximately 600 million shortwave broadcast-radio receivers in use in 2002. WWCR claims that there are 1.5 billion shortwave receivers worldwide. Many hobbyists listen to shortwave broadcasters. In some cases,

1140-514: The Cape Verde Islands . In September 1924, Marconi arranged for transmissions to be made day and night on 32 meters (about 9.4 MHz) from Poldhu to his yacht in the harbour at Beirut , to which he had sailed, and was "astonished" to find he could receive signals "throughout the day". Franklin went on to refine the directional transmission by inventing the curtain array aerial system. In July 1924, Marconi entered into contracts with

1197-416: The 1920s. 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 stations had cost and efficiency advantages over massive longwave wireless installations. However, some commercial longwave communications stations remained in use until

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1254-421: The 1960s. Long-distance radio circuits also reduced the need for new cables, although the cables maintained their advantages of high security and a much more reliable and better-quality signal than shortwave. The cable companies began to lose large sums of money in 1927. A serious financial crisis threatened viability of cable companies that were vital to strategic British interests. The British government convened

1311-472: The 1970s and 80's, and retired from active service in 1991. FAAR units have been used for drug trafficking surveillance in Palm Beach , and since September 1991, offered for sale to foreign users. The AN/TPQ-43 radar was mounted on a boom that extended upward from the rear of the Gama Goat's trailer. It is a pulse doppler radar that operates in the D band and has a range of about 20 km. Data from

1368-545: The 50 MW range by the 1960s. Since then, improvements in receiver electronics has greatly reduced the amount of signal needed to produce an accurate image, and in modern examples the transmitted power is much less; the AN/FPS-117 offers 250 nautical miles (460 km; 290 mi) range from 25 kW. EW radars are also highly susceptible to radar jamming and often include advanced frequency hopping systems to reduce this problem. The first early-warning radars were

1425-535: The BPL frequencies used overlap with shortwave bands, severe distortions can make listening to analog shortwave radio signals near power lines difficult or impossible. According to Andy Sennitt, former editor of the World Radio TV Handbook , shortwave is a legacy technology, which is expensive and environmentally unfriendly. A few countries are hanging on to it, but most have faced up to the fact that

1482-537: The Beethoven Bicentennial in Opus ;1970 with filtered and distorted snippets of Beethoven pieces – Spiral (1968), Pole , Expo (both 1969–1970), and Michaelion (1997). Cypriot composer Yannis Kyriakides incorporated shortwave numbers station transmissions in his 1999 ConSPIracy cantata . Holger Czukay , a student of Stockhausen, was one of the first to use shortwave in

1539-755: The British Chain Home , the German Freya , the US CXAM (Navy) and SCR-270 (Army), and the Soviet Union RUS-2  [ ru ] . By modern standards these were quite short range, typically about 100 to 150 miles (160 to 240 km). This "short" distance is a side effect of radio propagation at the long wavelengths being used at the time, which were generally limited to line-of-sight. Although techniques for long-range propagation were known and widely used for shortwave radio ,

1596-665: 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 . 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. Shortwave communications began to grow rapidly in

1653-594: 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

1710-606: The Internet, in that they listen only, and never attempt to send out their own signals. Other listeners participate in clubs, or actively send and receive QSL cards, or become involved with amateur radio and start transmitting on their own. Many listeners tune the shortwave bands for the programmes of stations broadcasting to a general audience (such as Radio Taiwan International , China Radio International , Voice of America , Radio France Internationale , BBC World Service , Voice of Korea , Radio Free Sarawak etc.). Today, through

1767-534: 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 at wavelengths shorter than 150 meters completed hundreds of long-distance two-way contacts on 100 meters (3 MHz) in 1923 including

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1824-620: The ability to process the complex return signal was simply not possible at the time. To counter the threat of Soviet bombers flying over the Arctic, the U.S. and Canada developed the DEW Line . Other examples ( Pinetree Line ) have since been built with even better performance. An alternative early warning design was the Mid-Canada Line , which provided "line breaking" indication across the middle of Canada , with no provision to identify

1881-427: The air, and therefore improves their performance in the long-range role where their coverage area will often include precipitation. This also has the side-effect of lowering their optical resolution , but this is not important in this role. Likewise, EW radars often use much lower pulse repetition frequency to maximize their range, at the cost of signal strength, and offset this with long pulse widths , which increases

1938-458: The assigned bands, there may be small differences between countries or regions. For example, in the official bandplan of the Netherlands , the 49 m band starts at 5.95 MHz, the 41 m band ends at 7.45 MHz, the 11 m band starts at 25.67 MHz, and the 120 m, 90 m, and 60 m bands are absent altogether. International broadcasters sometimes operate outside

1995-501: The auspices of the International Telecommunication Union , allocates bands for various services in conferences every few years. The last WRC took place in 2023. As of WRC-97 in 1997, these bands were allocated for international broadcasting . AM shortwave broadcasting channels are allocated with a 5 kHz separation for traditional analog audio broadcasting: Although countries generally follow

2052-502: The bandwidth of a signal transmitted in the HF bands, and the advantages of frequency modulation are greatest if the FM signal has a wide bandwidth. NBFM is limited to short-range transmissions due to the multiphasic distortions created by the ionosphere. Digital Radio Mondiale (DRM) is a digital modulation for use on bands below 30 MHz. It is a digital signal, like the data modes, below, but

2109-431: The carrier is controlled by the amplitude of the signal (speech, or music, for example). At the receiver, a simple detector 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

2166-593: The company was changed to Cable and Wireless Ltd. in 1934. A resurgence of long-distance cables began in 1956 with the laying of TAT-1 across the Atlantic Ocean, the first voice frequency cable on this route. This provided 36 high-quality telephone channels and was soon followed by even higher-capacity cables all around the world. Competition from these cables soon ended the economic viability of shortwave radio for commercial communication. Amateur radio operators also discovered that long-distance communication

2223-556: The distribution of radio programs, such as satellite radio and cable broadcasting as well as IP-based transmissions , shortwave broadcasting lost importance. Initiatives for the digitization of broadcasting did not bear fruit either, and so as of 2024 , few broadcasters continue to broadcast programs on shortwave. However, shortwave remains important in war zones, such as in the Russo-Ukrainian war , and shortwave broadcasts can be transmitted over thousands of miles from

2280-575: The evolution of the Internet, the hobbyist can listen to shortwave signals via remotely controlled or web controlled shortwave receivers around the world, even without owning a shortwave radio. Many international broadcasters offer live streaming audio on their websites and a number have closed their shortwave service entirely, or severely curtailed it, in favour of internet transmission. Shortwave listeners, or SWLs, can obtain QSL cards from broadcasters, utility stations or amateur radio operators as trophies of

2337-724: The first successful transatlantic tests in December ;1921, operating in the 200 meter mediumwave band (near 1,500 kHz, inside the modern AM broadcast band), which at that time was the shortest wavelength / highest frequency available to amateur radio. In 1922 hundreds of North American amateurs were heard in Europe on 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

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2394-615: The first transatlantic two-way contacts. By 1924 many additional specially licensed amateurs were routinely making transoceanic contacts at distances of 6,000 miles (9,600 km) and more. On 21 September 1924 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

2451-472: The goal is to hear as many stations from as many countries as possible ( DXing ) ; 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 , stations which transmit strange broadcast usually for intelligence operations, or the two way communications by amateur radio operators. Some short wave listeners behave analogously to "lurkers" on

2508-492: 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 loops or digital samples . Sometimes

2565-573: The hobby. Some stations even give out special certificates, pennants, stickers and other tokens and promotional materials to shortwave listeners. 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

2622-816: The normal the WRC-allocated bands or use off-channel frequencies. This is done for practical reasons, or to attract attention in crowded bands (60 m, 49 m, 40 m, 41 m, 31 m, 25 m). The new digital audio broadcasting format for shortwave DRM 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 . Shortwave transmitting centers often use specialized antenna designs (like

2679-516: The radar was generally not used at the radar site itself, but broadcast over FM radio to the "Target Alerting Data Display Set" (TADDS), a small battery-powered receiver and display unit. Field units, including the Chaparral, Vulcan and FIM-43 Redeye units, used the TADDS as an early-warning display, aiming their optically-guided weapons in the general direction it provided. FAAR is transported by

2736-459: The signal at the cost of lowering range resolution. The canonical EW radar is the British Chain Home system, which entered full-time service in 1938. It used a very low pulse repetition of 25 pps and very powerful transmissions (for the era) reaching 1 MW in late-war upgrades. The German Freya and US CXAM (Navy) and SCR-270 (Army) were similar. Post-war models moved to the microwave range in ever-increasingly powerful models that reached

2793-510: 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 , who perfected a form of radio oscillator as a musical instrument in 1928 ( regenerative circuits in radios of

2850-401: The target's exact location or direction of travel. Starting in the 1950s, a number of over-the-horizon radars were developed that greatly extended detection ranges, generally by bouncing the signal off the ionosphere . Today the early warning role has been supplanted to a large degree by airborne early warning platforms. By placing the radar on an aircraft, the line-of-sight to the horizon

2907-480: The time were prone to breaking into oscillation , adding various tonal harmonics to music and speech); and in the same year, the development of a French instrument called the Ondes Martenot by its inventor Maurice Martenot , a French cellist and former wireless telegrapher. Karlheinz Stockhausen used shortwave radio and effects in works including Hymnen (1966–1967), Kurzwellen (1968) – adapted for

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2964-454: The visual horizon, about 64 km (40 miles). Shortwave broadcasts of radio programs played an important role in the early days of radio history. In World War II it was used as a propaganda tool for an international audience. The heyday of international shortwave broadcasting was during the Cold War between 1960 and 1980. With the wide implementation of other technologies for

3021-414: The wavelengths in this band are shorter than 200 m (1,500 kHz) which marked the original upper limit of the medium frequency band first used for radio communications. The broadcast medium wave band now extends above the 200 m / 1,500 kHz limit. Early long-distance radio telegraphy used long waves, below 300  kilohertz (kHz) / above 1000 m. The drawbacks to this system included

3078-635: The world. On 10 October 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)

3135-607: Was opened to amateurs in the United States on 1 May 1952. Shortwave radio frequency energy is capable of reaching any location on the Earth as it is influenced by ionospheric reflection back to Earth by the ionosphere , (a phenomenon known as " skywave propagation"). A typical phenomenon of shortwave propagation is the occurrence of a skip zone where reception fails. With a fixed working frequency, large changes in ionospheric conditions may create skip zones at night. As

3192-472: Was possible on shortwave bands. Early long-distance services used surface wave propagation at very low frequencies , which are attenuated along the path at wavelengths shorter than 1,000 meters. Longer distances and higher frequencies using this method meant more signal loss. This, and the difficulties of generating and detecting higher frequencies, made discovery of shortwave propagation difficult for commercial services. Radio amateurs may have conducted

3249-405: Was technically illegal (but tolerated at the time as the authorities mistakenly believed that such frequencies were useless for commercial or military use), amateurs began to experiment with those wavelengths using newly available vacuum tubes shortly after World War I. Extreme interference at the longer edge of the 150–200 meter band – the official wavelengths allocated to amateurs by

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