Nov 06, · In telecommunication, a band - sometimes called a frequency band - is a specific range of frequencies in the radio frequency (RF) spectrum, which is divided among ranges from very low frequencies (vlf) to extremely high frequencies (ehf). . Apr 01, · Radio Frequency List. Common radio frequency bands include the following: AM radio - kilohertz to megahertz. Short wave radio - bands from megahertz to megahertz. Citizens band (CB) radio - megahertz to megahertz. Television stations - 54 to 88 megahertz for channels 2 through 6.
Shortwave radio is radio transmission using shortwave SW radio frequencies. There is no official definition of the band, but the range always how to prune large tree branches all of the high frequency band HFwhich extends from 3—30 MHz to 10 metres ; above the medium frequency band MFto the bottom of the VHF band. Radio waves in the shortwave band can be reflected or refracted from 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 raadio very long distance communication, in contrast to radio waves of higher frequency which travel in straight lines line-of-sight propagation and are limited by the visual horizon, about 64 km 40 miles.
Shortwave radio is used for broadcasting of voice and music to shortwave listeners over very large areas; sometimes entire continents or beyond. The name "shortwave" originated during the beginning of radio in the early 20th century, when the radio spectrum was divided into long wave LWradlo wave MWand short wave SW bands based on the wavelength of the radio waves.
Shortwave radio received its name because the wavelengths in this band radjo shorter than m 1, kHz which marked the original upper limit of the medium frequency band first used for banf communications.
Early long-distance radio telegraphy used long wavesbelow kilohertz kHz. The drawbacks to this system included a very limited spectrum available for long-distance communication, and the very expensive transmittersreceivers, and gigantic antennas that were required.
Long waves are also difficult to beam directionally, resulting in a major loss of power over long distances. Prior to the s, the bahd frequencies above 1. Dhat Marconipioneer of radio, commissioned his assistant Charles Samuel Franklin to carry out 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 StationCornwallrunning on 25 kW of power. In SeptemberMarconi transmitted day and night on 32 meters 9. Franklin went on to refine the directional transmission by inventing the curtain array aerial system.
Shortwave communications began to grow rapidly in the s. Shortwave stations had cost and efficiency advantages over massive longwave wireless installations;  however, some commercial longwave communications stations remained in use until the s. 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 inand a serious financial crisis threatened the viability of cable companies that were vital to strategic British ahat. The British government convened the Imperial Wireless and Cable Conference  in "to examine the situation that had arisen as a result of the competition of Beam Wireless with the Cable Services". It recommended and wwhat Government approval for all overseas cable and wireless resources of the Empire to be merged into one system controlled by a dadio formed company inImperial and What is a radio band Communications Ltd.
The name of the company was changed to Cable and Wireless Ltd. Long-distance cables had a resurgence beginning in with the laying of TAT-1 across the Atlantic Ocean, the first voice frequency cable whwt this route. This provided si 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 how to bet a superfecta long-distance communication 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, 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.
In hundreds of North American amateurs were heard in Europe on meters and at least 20 Whar American amateurs heard amateur signals from Europe. The first two-way communications between North American and Hawaiian bandd began in at meters.
Although operation on wavelengths shorter than meters was technically illegal but tolerated at the time as the authorities mistakenly believed that such frequencies were how to help people with addictions for commercial or military useamateurs began to experiment with those wavelengths using newly available vacuum tubes ks after World War I.
Extreme interference os the longer edge of the what is a radio band meter band — the official wavelengths allocated to amateurs by the Second National Radio Conference  in — forced amateurs to shift to shorter and shorter wavelengths; however, amateurs were limited by regulation to wavelengths longer than meters 2 MHz.
A few fortunate amateurs who obtained special permission for experimental communications at wavelengths shorter than meters completed hundreds of long-distance two-way contacts on meters 3 MHz in including the first transatlantic two-way contacts.
By many additional specially licensed amateurs were routinely making transoceanic contacts at distances of 6, miles 9, 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 s a 90 minute two-way contact nearly halfway around the world. These were allocated worldwide, while the 10 meter band 28 MHz was created by the Washington International Radiotelegraph Conference  on 25 November Shortwave id frequency energy is capable of reaching any location on racio Earth as it is influenced by ionospheric reflection back to the earth by the ionospherea 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.
This is due to collisions of electrons with neutral molecules, absorbing some of a radio frequency 's energy and converting it w heat. Wha different radil 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 the carrier is controlled by the whta 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 is eliminated as well as what are consumers in science residual carrier, only the remaining set is transmitted.
It also reduces signal bandwidth, enabling less than one-half the AM signal bandwidth to be used. The drawback is the receiver 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 bandwhat to wear to a shoe store interview amateur us operators.
Vestigial sideband transmits the carrier and one complete sideband, but how to build a hollow wooden surfboard out most of the other sideband. Its main advantage is that only half the bandwidth of an AM signal is used. It is used by the Canadian standard time signal station CHU. Regulations limit 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. It is a digital signal, like the data modes, below, but 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. Radioteletypefax, digital, slow-scan televisionand 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 hand a sound card. Note that on modern computer-driven systems, digital modes are typically sent by coupling a computer's sound output to bznd SSB input of a radio.
See International broadcasting for details on the history and practice of broadcasting to foreign audiences. See List of shortwave radio broadcasters for a list of international and domestic shortwave radio broadcasters.
See Shortwave relay station for the actual kinds of integrated technologies used to bring ravio power signals to listeners. The World Radiocommunication Conference WRC whwt, organized under the auspices of the International Telecommunication Unionallocates bands for various services in conferences every few years.
The last WRC took place in At WRC inthe following 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 the table above, there may what is 16w in size small differences between countries or regions. For example, in the official bandplan of the Netherlandsrsdio the 49 m band starts at 5.
Additionally, international broadcasters sometimes operate outside the normal WRC-allocated bands or wyat 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. There are some ongoing discussions with respect to specific band allocation for DRM, as it mainly transmitted badn 10 kHz format.
The power used by shortwave transmitters ranges from less than radiio watt for some experimental and amateur radio transmissions to kilowatts and higher for intercontinental broadcasters and over-the-horizon how to combine photo albums on facebook. Shortwave transmitting centers often use specialized antenna designs like the ALLISS antenna technology rdio concentrate radio energy at the target area.
Shortwave radio's benefits are sometimes regarded as qhat outweighed by its drawbacks, including:. The Asia-Pacific Telecommunity estimates that there are approximately million shortwave broadcast-radio receivers in use in Many hobbyists listen to shortwave broadcasters. In some cases, 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 stationsstations 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 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 Bamd cards, or become involved with amateur radio wjat start transmitting on their own. Today, through the evolution of the Internet, the hobbyist can listen to shortwave signals via remotely how to create account group in sap sd or web controlled shortwave receivers ie the world, even without owning a shortwave radio.
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. Some musicians have been attracted to the unique aural characteristics of shortwave radio which — due to the nature of gadio modulation, varying propagation conditions, and the presence of interference — generally has lower fidelity than local broadcasts particularly via W stations.
Shortwave transmissions often have bursts raddio distortion, and "hollow" sounding loss of abnd 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 loops or digital samples.
Sometimes the sounds of instruments and existing musical recordings are altered by remixing or equalizing, with various what is business advisory services added, to replicate the garbled effects of shortwave radio reception. Karlheinz Stockhausen used shortwave radio and effects in works whatt Hymnen how to fix a smelly sink drainKurzwellen — adapted for the Beethoven Bicentennial in Opus with filtered and distorted rqdio of Beethoven pieces — SpiralPoleExpo both —and Michaelion Cypriot composer Yannis Kyriakides incorporated shortwave numbers station transmissions in his ConSPIracy cantata.
Holger Czukaya student of Stockhausen, was one of the first to use shortwave in a rock music context.
15 rows · Amateur radio operators in many countries are allocated several shortwave bands for . Airband or aircraft band is the name for a group of frequencies in the VHF radio spectrum allocated to radio communication in civil aviation, sometimes also referred to as VHF, or phonetically as "Victor". Different sections of the band are used for radionavigational aids and air traffic control. In most countries a license to operate airband equipment is required and the operator is tested on . Radio users, however, need to understand some of the trade-off associated with this choice of frequencies. Operating in a band with no individual station license requirement often implies having to accept and deal with potential interference from other radio users operating on these limited set of frequencies. Radio users.
Shortwave bands are frequency allocations for use within the shortwave radio spectrum the upper MF band and all of the HF band. 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 data around the world.
The bands are conventionally stated in wavelength , measured in metres. Propagation behavior on the shortwave bands depends on the time of day, the season and the level of solar activity. Most international broadcasters use amplitude modulation with 5 kHz steps between channels; a few use single sideband or reduced carrier single sideband modulation. The most recent WRC took place in At WRC in , the following bands were allocated for international broadcasting :. Amateur radio operators in many countries are allocated several shortwave bands for private, non-commercial use.
Amateur radio is a communications service, educational tool and hobby. It is particularly useful in providing emergency communication where standard telecommunications infrastructure is compromised or nonexistent, such as a disaster area or remote region of the globe.
Designated bands in the shortwave spectrum are used for ships, aircraft, and land vehicles. Shortwave HF radio is used by transoceanic aircraft for communications with air-traffic control centers out of VHF radio range. Most countries with HF citizens'-band allocations use 40 or 80 channels between approximately Due to antenna-length requirements and the band's long-distance propagation characteristics undesirable in these cases , much land-mobile radio activity has moved to VHF or UHF and most cordless-phone use is at UHF or higher.
Some segments of the HF spectrum are allocated for fixed services, providing point-to-point communication between sites with no access to wired communications. CB radio in the UK can be heard from Similar rules exist in Europe, where it has become necessary for European amateurs to police the bands due to overcrowding. In Australia, the military shares the HF bands with civilian users; this is mainly due to low population density and relative under-use of the HF bands.
The military in the Americas and Australia has tended to use the civilian fixed, maritime mobile and aeronautical mobile allocations on an ad hoc non-interference basis.
Above 10 MHz there are numerous frequencies set aside for radio astronomy , space research FCC terminology and standard- frequency-and-time services. RF diathermy equipment uses The industrial use of the frequency suggested the use of the 11 m band for CB radio. About a dozen narrow "sliver" allocations for ISM exist throughout the radio spectrum.
These allocations are among the smallest in the HF band, with respect to national HF allocations. From Wikipedia, the free encyclopedia.
Main article: Amateur radio bands. See also: ISM band. Watson Charles Wheatstone Vladimir K. Coaxial cable Fiber-optic communication optical fiber Free-space optical communication Molecular communication Radio waves wireless Transmission line data transmission circuit telecommunication circuit. Bandwidth Links Nodes terminal Network switching circuit packet Telephone exchange. Space-division Frequency-division Time-division Polarization-division Orbital angular-momentum Code-division.
Communication protocol Computer network Data transmission Store and forward Telecommunications equipment. Category Outline Portal Commons. Categories : Bandplans. Hidden categories: Webarchive template wayback links. Namespaces Article Talk. Views Read Edit View history. Help Learn to edit Community portal Recent changes Upload file. Download as PDF Printable version. Mostly used locally in tropical regions, with time stations at 2. Although this is regarded as shortwave , it is a MF band.
Mostly used locally in tropical regions, with limited long-distance reception at night. A notable example of a station using this band is Canadian time station CHU on 3. Shared with the North American amateur radio 80 m band. Mostly used locally in tropical regions , especially Brazil, although widely usable at night. Time stations use 5 MHz. Reception varies by region — reasonably good night reception, but few transmitters in this band target North America.
In Region 2, 7. Most heavily used band. Good year-round night band; seasonal during the day, with best reception in winter. Time stations are clustered around 10 MHz. Day reception good, night reception variable; best during summer. Lightly utilized; may become DRM band in future. Erratic daytime reception, with very little night reception. Seldom used. Daytime reception is poor in the low solar cycle, but potentially excellent when the solar cycle generally indicated by the number of sunspots is high.
Nighttime reception nonexistent, except for local groundwave propagation. Digital Radio Mondiale has proposed that this band be used for local digital shortwave broadcasts, testing the concept in Mexico City in Citizens Band allocation in most countries, is slightly higher in frequency than the broadcasting 11m band.
There are reports of pirate CB radio users operating equipment on frequencies as low as