Shortwave radio

src: upload.wikimedia.org

Shortwave radio is a radio transmission using shortwave radio frequency. There is no official definition of the band, but the range always includes all high frequency bands (HF), and generally extends from 1.7-30 MHz (176.3-10.0 m); from the upper end of the medium frequency band (MF) just above the medium wave AM wave broadcast, to the end of the HF band.

Radio waves in short waves can be reflected or refracted from an atomic layer electrically charged in an atmosphere called the ionosphere. Therefore, short waves directed at an angle to the sky can be reflected back to Earth at great distances, beyond the horizon. This is called skywave propagation or "skip". Thus short-wave radios can be used for long distance communication, in contrast to high-frequency radio waves moving in a straight line (line-of-sight propagation) and limited by the visual horizon, about 40 miles (64 km). Shortwave radios are used to broadcast sound and music to shortwave listeners over a very large area; sometimes the whole continent or so. It is also used for military over-the-horizon radar, diplomatic communications, and two-way international communication by amateur radio enthusiasts for hobby, education and emergency purposes, as well as for long haul flights and sea communications.

Video Shortwave radio

Frequency classification

The most widespread popular definition of shortwave frequency interval is the definition of ITU Region 1 (EU of Russia Africa...), and ranges from 1.6 to 30 MHz, just above the intermediate wave, which ends about 1.6 MHz.

There is also another definition of shortwave frequency intervals:

• 1.71 to 30 MHz in ITU Region 2 (North and South America...)
• 1.8Ã, (amateur radio band 160 meters start) up to 30Ã, MHz
• 2.3Ã, (start band 120 meters) up to 30Ã, MHz
• 2.3 (start band 120 meters) up to 26.1 MHz (end band 11 meters)
• In Germany and possibly Austria, the ITU Region shortwave radio frequency interval can be divided into:
  • de: Grenzwelle ("border wave"): 1,605-3,8 MHz
• In Germany, this shortwave radio frequency interval has also been seen used:
  • other definitions above

Maps Shortwave radio

History

Development

The name "shortwave" originated in the early days of radio in the early 20th century, when the radio spectrum was thought to be divided into long waves (LW), medium wave (MW) and shortwave based on radio wavelength waves. Shortwave radio receives its name because the wavelength in this band is relatively shorter than 200 m (1,500 kHz) which marks the original upper limit of the first frequency band used for radio communications. The medium-wave broadcast band now extends above the 200 m/1,500 kHz limit, and the 1.8 MHz - 2.0 MHz amateur radio (known as the "top band") is the lowest frequency band considered the 'short wave'.

Long distance long distance telegraphy used long wavelengths, below 300 kilohertz (kHz). The disadvantages of this system include the very limited spectrum available for remote communication, and the very expensive giant transmitters, receivers and antennas are required. It is also difficult to broadcast radio waves directly with long waves, which causes the loss of a lot of power over long distances. Prior to the 1920s, shortwave frequencies above 1.5 MHz were considered useless for long distance communications and were set in many countries for amateur use.

Guglielmo Marconi, radio pioneer, commissioned his assistant Charles Samuel Franklin to conduct large-scale research into the characteristics of shortwave wavelength transmissions and to determine their suitability for long-distance transmission. Franklin installed a large antenna at Poldhu Wireless Station, Cornwall, with 25 kW power. In June and July 1923, wireless transmissions were completed during the night at 97 meters from Poldhu to the Marconi Elettra cruise ship in the Cape Verde Islands.

In September 1924, Marconi sent day and night at 32 meters from Poldhu to a cruise ship in Beirut. Franklin went on to improve directional transmission, creating a curtain antenna system. In July 1924, Marconi signed a contract with the British General Post Office (GPO) to install a high speed short-wave telegraph circuit from London to Australia, India, South Africa and Canada as a key element of the Imperial Wireless Chain. British-to-Canada Shortwave "Beam Wireless Service" began commercial operation on October 25, 1926. Beam Wireless Services from the UK to Australia, South Africa and India began operations in 1927.

Shortwave communications began to grow rapidly in the 1920s, similar to the internet at the end of the 20th century. By 1928, more than half of long-distance communications had moved from trans-oceanic cables and long-wave wireless services to shortwave and the overall volume of short-wave trans-oceanic communications had greatly improved. Shortwave stations have the advantage of cost and efficiency over a large longwave wireless installation, but several commercial long wave communications stations remained in use until the 1960s. Long distance radio circuits also reduce the load on existing transoceanic telegraph cables and therefore require new cables, although cables maintain their superiority from high security and quality signals much more reliably and better than shortwave.

Cable companies began losing huge sums of money in 1927, and a serious financial crisis threatened the survival of cable companies vital to British strategic interests. The British Government held the Imperial Cable and Wireless Conference in 1928 "to examine the situation arising as a result of Beam Wireless's competition with Cable Services". It recommended and received Government approval for all overseas cable and wireless Empire resources to be incorporated into a system controlled by a newly formed company in 1929, Imperial and International Communications Ltd. Company name changed to Cable and Wireless Ltd. in 1934.

The long-distance cable had a resurgence beginning in 1956 with the TAT-1 laying across the Atlantic Ocean, the first voice-frequency cable on this route. It provides 36 high quality telephone lines and is soon followed by higher capacity cables worldwide. This sounds the short-wave radio death knell for commercial communications.

Amateur use of shortwave propagation

Amateur radio operators also found that long distance communication is possible on short waves. The initial remote service uses surface wave propagation at very low frequencies, which are attenuated along the road at wavelengths shorter than 1,000 meters. Further distances and higher frequencies using this method mean more signal loss. This, and the difficulty in generating and detecting higher frequencies, makes the invention of short wave propagation difficult for commercial services.

Radio amateurs may have performed their first successful transatlantic test in December 1921, operating in a 200-meter medium-wave band (close to 1,500 kHz in modern AM broadcast broadcasting) - the shortest wavelength available to amateurs. In 1922, hundreds of North American amateurs were heard in Europe at a height of 200 meters and at least 20 North American amateurs heard amateur signals from Europe. The first two-way communication between Amateur North America and Hawaii began in 1922 at a height of 200 meters. Although surgery at wavelengths shorter than 200 meters is technically illegal (but tolerated because authorities mistakenly believe initially that the frequencies are useless for commercial or military use), amateurs began experimenting with these wavelengths using the new vacuum tubes available shortly after World War I..

The extreme interference on the longer edges of the 150-200 meter band - the official wavelength allocated to amateurs by the Second National Radio Conference in 1923 - forced the amateurs to move to shorter and shorter wavelengths; However, amateurs are limited by regulation for wavelengths greater than 150 meters (2 MHz). Some lucky amateurs who obtained special permission for experimental communication at wavelengths shorter than 150 meters completed hundreds of long-range two-way contacts at 100 meters (3 MHz) in 1923 including the first transatlantic two-way contact.

In 1924 many additional licensed amateurs routinely made contacts across the ocean at a distance of 6,000 miles (9,600 km) and more. On September 21, 1924, several amateurs in California completed two-way contact with an amateur in New Zealand. On October 19, amateurs in New Zealand and Britain completed a two-minute, two-way contact almost in the world. On October 10, the Third National Radio Conference made three shortwave bands available for US amateurs at 80 meters (3.75 MHz), 40 meters (7 MHz) and 20 meters (14 MHz). It was allocated worldwide, while the 10-meter band (28 MHz) was created by the Washington Radiotelegraph International Conference on November 25, 1927. The 15-meter (21 MHz) band opened to amateurs in the United States on 1 May 1952.

src: i.ytimg.com

Propagation Characteristics

Short-wave radio frequency energy is able to reach every location on Earth as it is affected by the ionosphere's reflection back to Earth by the ionosphere, (a phenomenon known as "skywave propagation"). The typical phenomenon of shortwave propagation is the occurrence of a springboard in which reception fails. With a fixed working frequency, major changes in ionospheric conditions can make the zone skip at night.

As a result of the multi-layer structure of the ionosphere, propagation often occurs simultaneously on different paths, scattered by E or F regions and with different hop counts, a phenomenon that may be impaired for certain techniques. Especially for lower frequencies of shortwave, the absorption of radio frequency energy in the lowest ionosphere layer, D layer, can impose a serious limit. This is because the collision of electrons with neutral molecules absorbs some of the radio frequency energy and converts it to heat. The prediction of skywave propagation depends on:

• The distance from the transmitter to the target recipient.
• Time of day. During the day, frequencies higher than about 12 MHz can travel longer distances than the lower ones. In the evening, this property is canceled.
• With a lower frequency, the dependence on the time of day is mainly due to the lowest ionosphere layer, Layer D, formed only during the day when photons from the sun break the atoms into ions and free electrons.
• Season. During the winter months of the Northern or Southern hemispheres, AM/MW broadcast bands tend to be more profitable due to longer dark hours.
• The solar flare produces a major increase in the ionization of the D region so high, sometimes for a period of several minutes, all the skywave propagation does not exist.

src: i.ytimg.com

Modulation type

Several types of modulation are used to enter information in shortwave signals.

Audio mode

AM

Amplitude modulation is the simplest and most commonly used type for short wave broadcasting. The carrier's instant amplitude is controlled by signal amplitude (speech, or music, for example). At the receiver, a simple detector recovers the desired modulation signal from the operator.

SSB

Single sideband transmission is a form of amplitude modulation but its effect filters out the modulation results. The amplitude modulated signal has frequency components above and below the carrier frequency. If a set of these components is eliminated as well as the remaining carrier, only the remaining sets are transmitted. This reduces the power in the transmission, since roughly ² / ₃ of the energy sent by the AM signal is in the "operator", which is not required to recover the information contained in the signal. It also reduces the signal bandwidth, allowing less than one half of the AM signal bandwidth to be used.

The drawback is the receiver is more complicated, because it must recreate the carrier to recover the signal. A small error in the detection process greatly affects the tone of the received signal. As a result, a single sideband is not used for music or public broadcasting. Single sideband is used for voice communications remotely by ship and aircraft, Citizen's Band, and amateur radio operators. Lower sideband (LSB) is customarilly used under 9 MHz and USB (upper sideband) above 9 MHz.

VSB

Vestebal sideband transmits the carrier and one complete sideband, but filters out the other sideband. This is a compromise between AM and SSB, which allows simple receivers to be used, but requires transmitter power almost equal to AM. One advantage is only half the bandwidth of the AM signal used. This can be heard in the transmission of certain radio time signal stations. Vestigial sideband is used for television broadcasts through both analog and digital television.

NFM

Narrow-band frequency modulation (NBFM or NFM) is used usually above 20 MHz. Due to the greater bandwidth requirements, NBFM is usually used for VHF communications. Regulations limit the bandwidth of the transmitted signals in HF bands, and gain from the greatest frequency modulation if the FM signal has a wide bandwidth. NBFM is limited to short-range transmissions due to the multiphasic distortion made by the ionosphere.

DRM

Digital Radio Mondiale (DRM) is a digital modulation for use on bands under 30 MHz. This is a digital signal, such as data mode, below, but for transmitting audio, such as analog mode above.

Data mode

CW

Continuous wave (CW) is an ongoing and used bearer lock, used for Morse code communication and Hellschreiber fax-based teleprinter transmission. This is data mode, though often listed separately.

RTTY, FAX, SSTV

Radioteletype, fax, digital, slow-scan television, and other systems use the form-part locking frequency or subcarrier audio on short wave carriers. These generally require special tools for decoding, such as software on computers equipped with sound cards.

Note that in modern computer-driven systems, digital mode is usually sent by combining computer sound output to the SSB radio input.

src: 1.bp.blogspot.com

Users

Some well-established users of shortwave radio bands may include:

• International broadcasting is mainly by government-sponsored propaganda, international news (eg, BBC World Service) or cultural stations for foreign audiences: the most common use of all.
• Domestic broadcasting: for a widespread population with several long wave stations, medium and FM waves serving them; or for special political, religious and alternative media networks; or individual commercial and non-commercial paid broadcasts.
• Ocean air traffic control uses HF/shortwave bands for long-distance communication to aircraft over the oceans and poles, which are far beyond the reach of traditional VHF frequencies. Modern systems also include satellite communications, such as ADS-C/CPDLC
• "Utility" stations that transmit messages that are not intended for the general public, such as merchant shipments, sea weather, and boat to shore stations; for aviation and air-to-ground communications; for military communications; for long distance government needs, and for other non-broadcast communications.
• Amateur radio operators in bands 80/75, 60, 40, 30, 20, 17, 15, 12, and 10 meters. Licenses are granted by authorized government agencies.
• Time signals and clock radio stations: In North America, WWV radio and WWVH radios transmit at these frequencies: 2.5 MHz, 5 MHz, 10 MHz, and 15 MHz; and WWV also transmits at 20 MHz. The CHU radio station in Canada transmits at the following frequencies: 3.33 MHz, 7.85 MHz, and 14.67 MHz. Other similar radio clock stations transmit on shortwave and longwave frequencies around the world. The shortwave transmission is primarily intended for human reception, while long wave stations are generally used for synchronizing watches and clocks automatically.

Sporadic or non-traditional shortwave band users may include:

• a secret station. This is a station broadcast on behalf of various political movements such as rebel or rebel forces. They can advocate for civil war, insurrection, rebellion against the government in charge of the country in which they are directed. Clandestine broadcasts may come from transmitters residing in territories controlled by rebels or from abroad entirely, using other country's transmission facilities.
• Station Numbers. These stations regularly appear and disappear across shortwave radio waves but are unlicensed and untraceable. It is believed that Numbers Station is operated by government agencies and used to communicate with secret operands working in foreign countries. However, there is no definite evidence of such use has emerged. Since most of these broadcasts contain nothing but numerical block readings, in multiple languages, with occasional musical bursts, they are known as "Number Stations". Perhaps the most famous Number Station is the "Lincolnshire Poacher", named after an 18th-century British folk song, which is transmitted just before the sequence of numbers.
• Unauthorized two-way radio activity by individuals such as taxi drivers, bus drivers and fishermen in different countries can be heard on a variety of shortwave frequencies. Unlicensed transmissions by "two-way" pirate "or" pirate "radio operators can often cause signal interference on licensed stations.
• Pirate radio announcers featuring programming like music, chat and other entertainment can be heard sporadically and in different modes of the shortwave band.
• Over-the-horizon radar: From 1976 to 1989, Russia's Soviet Russian radar engine over the horizon wiped out many shortwave broadcasts daily.
• The ionospheric heaters are used for scientific experiments such as the High Frequency Active Auroral Research Program in Alaska, and the Sura ionospheric heating facility in Russia.

src: swling.com

Shortwave broadcasting

View international broadcasts for details on the history and practice of broadcasting to foreign audiences.

View Shortwave relay stations for the kind of integrated technology actually used to carry high power signals to the listener.

Allocation of frequency

The World Communications Radio Conference (WRC), organized under the umbrella of the International Telecommunication Union, allocates bands to various services at conferences every few years. The last WRC occurred in 2007.

At WRC-97 in 1997, the following bands were allocated for international broadcasting. AM short wave broadcasting channel is allocated with 5 kHz separation for traditional analog audio broadcasting.

Although countries generally follow the table above, there may be minor differences between countries or regions. For example, in the official band of the Dutch band, the band 49 m starts at 5.95 MHz, band 41 m ends at 7.45 MHz, 11 m band starts at 25.67 MHz, and 120, 90 and 60 m bands do not present the same once. In addition, international broadcasters sometimes operate outside the tape allocated to normal WRC or use off-channel frequency. This is done for practical reasons, or to attract attention in crowded bands (60m, 49m, 40m, 41m, 31m, 25m).

The new digital audio broadcasting format for shortwave DRM operates a 10-kHz or 20-kHz channel. There is some ongoing discussion with respect to the allocation of special bands for DRM, as it is primarily transmitted in 10 kHz format.

Power used by shortwave transmitters ranges from less than one watts for some experimental and amateur radio transmissions up to 500 kilowatts and higher for intercontinental and over-the-horizon broadcasters. Shortwave transmission centers often use a special antenna design (such as ALLISS antenna technology) to centralize radio energy in the target area.

Benefits

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

• Difficulty censoring programs by authorities in restricting countries: unlike their relative ease in monitoring the Internet, government authorities face technical difficulties in monitoring which stations are being listened (accessed). For example, during an attempted coup against Soviet President Mikhail Gorbachev, when access to limited communications (eg, telephone disconnects, etc.), Gorbachev may remain informed through the BBC World Service on short waves.
• Short-wave low-cost radio is widely available in all the most repressive countries in the world. Simple shortwave regenerative receivers can be easily built with multiple sections.
• In many countries (especially in most developing countries and in the Eastern Bloc during the Cold War era) the ownership of shortwave receivers has been and continues to expand (in many of these countries some domestic stations also use shortwave).
• Many newer, more portable shortwave receivers are portable and battery-operated, making them useful in difficult situations. Newer technologies include hand-turning radios that provide power without batteries.
• Shortwave radios may be used in situations where temporary or long-term Internet or satellite communications services are unavailable (or unreachable).
• Shortwave radio moves farther than FM broadcast (88-108Ã, MHz). Shortwave broadcasts can be easily transmitted over distances of several thousand kilometers, including from one continent to another.
• Particularly in the tropics, SW is somewhat less susceptible to disturbances from hurricanes than intermediate wave radios, and is capable of covering large geographic areas with relatively low power (and hence costs). Therefore, in many countries it is widely used for domestic broadcasting.
• Very little infrastructure is needed for long distance two-way communication using shortwave radios. All it takes is a pair of transceivers, each with an antenna, and an energy source (like a battery, a portable generator, or a power grid). This makes the shortwave radio one of the most powerful means of communication, which can be disrupted only by poor interference or ionospheric conditions. Modern digital transmission modes such as MFSK and Olivia are even more powerful, allowing successful reception of signals well below the conventional receiver sound floor.

Losses

The benefits of shortwave radio are sometimes regarded as an advantage by its flaws, including:

• In most Western countries, the ownership of shortwave radios is usually limited to true fans, as most new standard radios do not accept shortwave bands. Therefore, Western audiences are limited.
• In developed countries, shortwave reception is particularly difficult in urban areas due to excessive noise from active mode power adapters, fluorescent lighting or LED light sources, modems and Internet routers, computers and many other sources of radio interference.

src: d3h6k4kfl8m9p0.cloudfront.net

Listen to shortwave

The Asia-Pacific Telecommunity estimates that there are approximately 600 million shortwave radio receivers used in 2002. WWCR claims that 1.5 billion shortwave receivers worldwide.

Many fans listen to shortcast radio waves. In some cases, the goal is to hear as many stations out of as many countries as possible (DXing) ; others listen to special shortwave utilities, or "ute", transmissions such as maritime, navy, aviation, or military signals. Others focus on intelligence signals from number stations, stations that send strange broadcasts usually for intelligence operations, or two-way communication by amateur radio operators. Some shortwave listeners behave analogously to "strangers" on the Internet, because they just listen and never attempt to transmit their own signals. Other listeners participate in the club, or actively send and receive QSL cards, or become involved with amateur radio and start their own transmissions.

Many listeners set shortwave bands for station programs broadcasted to the public (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 the evolution of the Internet, hobbyists can listen to shortwave signals via remote controls or web-controlled shortwave receivers around the world, even without having shortwave radios. Many international broadcasters offer live streaming audio on their website and a number have closed their shortwave service completely, or severely limiting it, supporting internet transmission.

Shortwave listeners, or SWLs, can get QSL cards from broadcasters, utility stations or amateur radio operators as trophies of hobbies. Some stations even provide special certificates, banners, stickers and other tokens and promotional materials to short-wave listeners.

src: swling.com

Shortwave and shortwave music

Some musicians are attracted to the unique aural characteristics of shortwave radios which - due to the amplitude modulation properties, the various propagation conditions, and the presence of interference - generally have lower allegiance than local broadcasts (especially via FM stations). Shortwave transmissions often have bursts of distortion, and the "hollow" sound loses clarity at a certain aural frequency, altering natural sound harmonics and creating at times strange "weird" qualities due to echoes and phase distortions. Evocations of shortwave reception distortions have been incorporated into rock and classical compositions, by means of delays or feedback, equalizer, or even playing shortwave radio as a live instrument. The broadcast pieces have been mixed into electronic voice collages and live musical instruments, using analog tape loops or digital samples. Sometimes the sounds of existing instruments and music recordings are changed by remixing or equalization, with various distortions added, to mimic the chaotic effects of short wave radio reception.

The first attempt by a serious composer to incorporate radio effects into music was probably from Russian physicist and musician LÃÆ' Â © on Theremin, which refined the shape of a radio oscillator as a musical instrument in 1928 (the radio regenerative circuit at that time was prone to breaking into oscillations, adding various harmonic tonics to music and speech); and in the same year, the development of a French instrument called Ondes Martenot by its discoverer, Maurice Martenot, a French cellist and former wireless telegrapher. Karlheinz Stockhausen uses shortwave radio and effects in works including Hymnen (1966-67), Kurzwellen (1968) - adapted for Beethoven Bicentennial at Opus 1970 Spiral (1968), Pole , Expo (both 1969-70), and Michaelion (1997).

Cypriot composer Yannis Kyriakides entered the transmission of short wave number stations in 1999 ConSPIracy cantata

Holger Czukay, a Stockhausen student, was one of the first to use short waves in the context of rock music. In 1975, the German electronic music band Kraftwerk recorded a full-length draft album around simulated radio waves and shortwave sounds, titled Radio-Activity. The Cineola radio broadcast The Radio draws short wave radio.

src: c8.alamy.com

The future of shortwave

The development of live broadcasts from satellites has reduced the demand for shortwave receiver hardware, but there are still a large number of shortwave broadcasters. New digital radio technology, Digital Radio Mondiale (DRM), is expected to improve the shortwave audio quality from very poor to standard comparable to FM broadcast bands. The future of shortwave radios is threatened by the emergence of power line communications (PLC), also known as Broadband Over Power Lines (BPL), which uses data streams transmitted through unplugged power lines. Because the frequency of BPL used overlaps with shortwave, severe distortion can make listening to analog shortwave radio signals near the power grid difficult or impossible.

Experts disagree on the future of the short wave. According to Andy Sennitt, a former editor of the World Radio TV Handbook, "shortwave is an inherited technology, expensive and environmentally unfriendly.Some countries depend on it, but most have faced the fact that the short wave days have gone. will use it because they do not really care about listening numbers ".

But Thomas Witherspoon, editor of the shortwave news site SWLingPost.com wrote that "shortwave remains the most accessible international communications medium that still provides listeners with complete anonymity protection". According to Nigel Fry, head of Distribution for the BBC World Service Group, "I still see a place for shortwave in the 21st century, especially to reach areas in the world that are vulnerable to natural disasters that destroy local broadcasting and Internet infrastructure".

src: images.homedepot-static.com

See also

• ALLISS - a very large rotatable antenna system used in international broadcasting
• List of American shortcast broadcasters
• List of shortwave radio stations

src: i.pinimg.com

References

• Ulrich L. Rohde, Jerry Whitaker "Recipient of Communication, Third Edition" McGraw Hill, New York, NY, 2001, ISBN: 0-07-136121-9.

src: i.ytimg.com

External links

• SWLing.com - A beginner's guide to listening to shortwave radio.
• World of Radio Glenn Hauser's site
• The Weather Room and Radio Propagation Center View live and historical data and weather images of space and radio propagation.
• Shortwave radio, Snap and crackle erupts, Life in the old wireless article The Economist describes the pros and cons of shortwave radio since the Cold War.
• "Successful Shortwave Radio Telephone in Testing" Popular Mechanics , July 1931, center page experiment conducted for the French and British governments
• Que Escuchar en la Onda Corta en Espaà ± a website

Source of the article : Wikipedia