FM broadcasting is a method of radio broadcasting using frequency modulation technology. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high-fidelity sound over broadcast radio. FM broadcasting is capable of better sound quality than AM broadcasting, the chief competing radio broadcasting technology, so it is used for most music broadcasts. Theoretically wideband AM can offer good sound quality, provided the reception conditions are ideal. FM radio stations use the VHF frequencies; the term "FM band" describes the frequency band in a given country, dedicated to FM broadcasting. Throughout the world, the FM broadcast band falls within the VHF part of the radio spectrum. 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions: In the former Soviet republics, some former Eastern Bloc countries, the older 65.8–74 MHz band is used. Assigned frequencies are at intervals of 30 kHz; this band, sometimes referred to as the OIRT band, is being phased out in many countries.
In those countries the 87.5–108.0 MHz band is referred to as the CCIR band. In Japan, the band 76–95 MHz is used; the frequency of an FM broadcast station is an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines and the Caribbean, only odd multiples are used. In some parts of Europe and Africa, only multiples are used. In the UK odd or are used. In Italy, multiples of 50 kHz are used. In most countries the maximum permitted frequency error is specified, the unmodulated carrier should be within 2000 Hz of the assigned frequency. There are other unusual and obsolete FM broadcasting standards in some countries, including 1, 10, 30, 74, 500, 300 kHz. However, to minimise inter-channel interference, stations operating from the same or geographically close transmitter sites tend to keep to at least a 500 kHz frequency separation when closer frequency spacing is technically permitted, with closer tunings reserved for more distantly spaced transmitters, as interfering signals are more attenuated and so have less effect on neighboring frequencies.
Frequency modulation or FM is a form of modulation which conveys information by varying the frequency of a carrier wave. With FM, frequency deviation from the assigned carrier frequency at any instant is directly proportional to the amplitude of the input signal, determining the instantaneous frequency of the transmitted signal; because transmitted FM signals use more bandwidth than AM signals, this form of modulation is used with the higher frequencies used by TV, the FM broadcast band, land mobile radio systems. The maximum frequency deviation of the carrier is specified and regulated by the licensing authorities in each country. For a stereo broadcast, the maximum permitted carrier deviation is invariably ±75 kHz, although a little higher is permitted in the United States when SCA systems are used. For a monophonic broadcast, again the most common permitted. However, some countries specify a lower value for monophonic broadcasts, such as ±50 kHz. Random noise has a triangular spectral distribution in an FM system, with the effect that noise occurs predominantly at the highest audio frequencies within the baseband.
This can be offset, to a limited extent, by boosting the high frequencies before transmission and reducing them by a corresponding amount in the receiver. Reducing the high audio frequencies in the receiver reduces the high-frequency noise; these processes of boosting and reducing certain frequencies are known as pre-emphasis and de-emphasis, respectively. The amount of pre-emphasis and de-emphasis used is defined by the time constant of a simple RC filter circuit. In most of the world a 50 µs time constant is used. In the Americas and South Korea, 75 µs is used; this applies to both stereo transmissions. For stereo, pre-emphasis is applied to the left and right channels before multiplexing; the use of pre-emphasis becomes a problem because of the fact that many forms of contemporary music contain more high-frequency energy than the musical styles which prevailed at the birth of FM broadcasting. Pre-emphasizing these high frequency sounds would cause excessive deviation of the FM carrier. Modulation control devices are used to prevent this.
Systems more modern than FM broadcasting tend to use either programme-dependent variable pre-emphasis. Long before FM stereo transmission was considered, FM multiplexing of other types of audio level information was experimented with. Edwin Armstrong who invented FM was the first to experiment with multiplexing, at his experimental 41 MHz station W2XDG located on the 85th floor of the Empire State Building in New York City; these FM multiplex transmissions started in November 1934 and consisted of the main channel audio program and three subcarriers: a fax program, a synchronizing signal for the fax program and a telegraph “order” channel. These original FM multiplex subcarriers were amplitude modulated. Two musical programs, consisting of both the Red and Blue Network program feeds of the NBC Radio Network, were transmitted using the same system of subcarrier modulation as part of a studio-to-transmitter link system. In April 1935, the AM subcarriers were replaced with much improved results.
The first FM subcarrier transmissions emanating from Major Armstrong's experimental station KE2XCC at Alpine, New Jersey occurred in 1948. These transmissions consisted of two-cha
Extremely high frequency
High frequency is the International Telecommunication Union designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz. It lies between the super high frequency band, the far infrared band, the lower part of, referred to as the terahertz gap. Radio waves in this band have wavelengths from ten to one millimetre, so it is called the millimetre band and radiation in this band is called millimetre waves, sometimes abbreviated MMW or mmW. Millimetre-length electromagnetic waves were first investigated in the 1890s by Indian scientist Jagadish Chandra Bose. Compared to lower bands, radio waves in this band have high atmospheric attenuation: they are absorbed by the gases in the atmosphere. Therefore, they have a short range and can only be used for terrestrial communication over about a kilometer. Absorption by humidity in the atmosphere is significant except in desert environments, attenuation by rain is a serious problem over short distances; however the short propagation range allows smaller frequency reuse distances than lower frequencies.
The short wavelength allows modest size antennas to have a small beam width, further increasing frequency reuse potential. Millimeter waves propagate by line-of-sight paths, they are not reflected by the ionosphere nor do they travel along the Earth as ground waves as lower frequency radio waves do. At typical power densities they are blocked by building walls and suffer significant attenuation passing through foliage. Absorption by atmospheric gases is a significant factor throughout the band and increases with frequency. However, it is maximum at a few specific absorption lines those of oxygen at 60 GHz and water vapor at 24 GHz and 184 GHz. At frequencies in the "windows" between these absorption peaks, millimeter waves have much less atmospheric attenuation and greater range, so many applications use these frequencies. Millimeter wavelengths are the same order of size as raindrops, so precipitation causes additional attenuation due to scattering as well as absorption; the high free space loss and atmospheric absorption limits useful propagation to a few kilometers.
Thus, they are useful for densely packed communications networks such as personal area networks that improve spectrum utilization through frequency reuse. Millimeter waves show "optical" propagation characteristics and can be reflected and focused by small metal surfaces and dielectric lenses around 5 to 30 cm diameter; because their wavelengths are much smaller than the equipment that manipulates them, the techniques of geometric optics can be used. Diffraction is less than at lower frequencies. At millimeter wavelengths, surfaces appear rougher so diffuse reflection increases. Multipath propagation reflection from indoor walls and surfaces, causes serious fading. Doppler shift of frequency can be significant at pedestrian speeds. In portable devices, shadowing due to the human body is a problem. Since the waves penetrate clothing and their small wavelength allows them to reflect from small metal objects they are used in millimeter wave scanners for airport security scanning; this band is used in radio astronomy and remote sensing.
Ground-based radio astronomy is limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz can determine temperature in the upper atmosphere by measuring radiation emitted from oxygen molecules, a function of temperature and pressure; the ITU non-exclusive passive frequency allocation at 57–59.3 GHz is used for atmospheric monitoring in meteorological and climate sensing applications and is important for these purposes due to the properties of oxygen absorption and emission in Earth's atmosphere. Operational U. S. satellite sensors such as the Advanced Microwave Sounding Unit on one NASA satellite and four NOAA satellites and the special sensor microwave/imager on Department of Defense satellite F-16 make use of this frequency range. In the United States, the band 36.0 – 40.0 GHz is used for licensed high-speed microwave data links, the 60 GHz band can be used for unlicensed short range data links with data throughputs up to 2.5 Gbit/s.
It is used in flat terrain. The 71–76, 81–86 and 92–95 GHz bands are used for point-to-point high-bandwidth communication links; these higher frequencies do not suffer from oxygen absorption, but require a transmitting license in the US from the Federal Communications Commission. There are plans for 10 Gbit/s links using these frequencies as well. In the case of the 92–95 GHz band, a small 100 MHz range has been reserved for space-borne radios, limiting this reserved range to a transmission rate of under a few gigabits per second; the band is undeveloped and available for use in a broad range of new products and services, including high-speed, point-to-point wireless local area networks and broadband Internet access. WirelessHD is another recent technology. Directional, "pencil-beam" signal characteristics permit different systems to operate close to one another without causing interference. Potential applications include radar systems with high resolution; the Wi-Fi standard IEEE 802.11ad operates in the 60 GHz spectrum to achieve data transfer rates as high as 7 Gbit/s.
Uses of the millimeter wave bands include point-to-point communications, intersatellite links, point-to-multipoint communications. There are tentative plans to use millimeter waves in future 5G mobile phones. In addition, use of millimeter wave
Low frequency or LF is the ITU designation for radio frequencies in the range of 30 kilohertz to 300 kHz. As its wavelengths range from ten kilometres to one kilometre it is known as the kilometre band or kilometre wave. LF radio waves exhibit low signal attenuation, making them suitable for long-distance communications. In Europe and areas of Northern Africa and Asia, part of the LF spectrum is used for AM broadcasting as the "longwave" band. In the western hemisphere, its main use is for aircraft beacon, navigation and weather systems. A number of time signal broadcasts are broadcast in this band; because of their long wavelength, low frequency radio waves can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ground wave, is the main mode in the LF band. Ground waves must be vertically polarized, so vertical monopole antennas are used for transmitting; the attenuation of signal strength with distance by absorption in the ground is lower than at higher frequencies.
Low frequency ground waves can be received up to 2,000 kilometres from the transmitting antenna. Low frequency waves can occasionally travel long distances by reflecting from the ionosphere, although this method, called skywave or "skip" propagation, is not as common as at higher frequencies. Reflection occurs at F layers. Skywave signals can be detected at distances exceeding 300 kilometres from the transmitting antenna. In Europe and Japan, many low-cost consumer devices have since the late 1980s contained radio clocks with an LF receiver for these signals. Since these frequencies propagate by ground wave only, the precision of time signals is not affected by varying propagation paths between the transmitter, the ionosphere, the receiver. In the United States, such devices became feasible for the mass market only after the output power of WWVB was increased in 1997 and 1999. Radio signals below 50 kHz are capable of penetrating ocean depths to 200 metres, the longer the wavelength, the deeper.
The British, Indian, Swedish, United States and other navies communicate with submarines on these frequencies. In addition, Royal Navy nuclear submarines carrying ballistic missiles are under standing orders to monitor the BBC Radio 4 transmission on 198 kHz in waters near the UK, it is rumoured that they are to construe a sudden halt in transmission of the morning news programme Today, as an indicator that the UK is under attack, whereafter their sealed orders take effect. In the US, the Ground Wave Emergency Network or GWEN operated between 150 and 175 kHz, until replaced by satellite communications systems in 1999. GWEN was a land based military radio communications system which could survive and continue to operate in the case of a nuclear attack; the 2007 World Radiocommunication Conference made this band a worldwide amateur radio allocation. An international 2.1 kHz allocation, the 2200 meter band, is available to amateur radio operators in several countries in Europe, New Zealand and French overseas dependencies.
The world record distance for a two-way contact is over 10,000 km from near Vladivostok to New Zealand. As well as conventional Morse code many operators use slow computer-controlled Morse code or specialized digital communications modes; the UK allocated a 2.8 kHz sliver of spectrum from 71.6 kHz to 74.4 kHz beginning in April 1996 to UK amateurs who applied for a Notice of Variation to use the band on a noninterference basis with a maximum output power of 1 Watt ERP. This was withdrawn on 30 June 2003 after a number of extensions in favor of the European-harmonized 136 kHz band. Slow Morse Code from G3AQC in the UK was received 3,275 miles away, across the Atlantic Ocean, by W1TAG in the US on 21-22 November 2001 on 72.401 kHz. In the United States, there is a exemption within FCC Part 15 regulations permitting unlicensed transmissions in the frequency range of 160 to 190 kHz. Longwave radio hobbyists refer to this as the' LowFER' band, experimenters, their transmitters are called'LowFERs'.
This frequency range between 160 kHz and 190 kHz is referred to as the 1750 Meter band. Requirements from 47CFR15.217 and 47CFR15.206 include: The total input power to the final radio frequency stage shall not exceed one watt. The total length of the transmission line and ground lead shall not exceed 15 meters. All emissions below 160 kHz or above 190 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier; as an alternative to these requirements, a field strength of 2400/F microvolts/meter may be used. In all cases, operation may not cause harmful interference to licensed services. Many experimenters in this band are amateur radio operators. A regular service transmitting RTTY marine meteorological information in SYNOP code on LF is the German Meteorological Service; the DWD operates station DDH47 on 147.3 kHz using standard ITA-2 alphabet with a transmission speed of 50 baud and FSK modulation with 85 Hz shift. In parts of the world where there is no longwave broadcasting service, Non-directional beacons used for aeronavigation operate on 190–300 kHz.
In Europe and Africa, the NDB allocation starts on 283.5 kHz. The LORAN-C radio navigation system operated on 100 kHz. In the past, the Decca Navigator System operated betw
Very low frequency
Low frequency or VLF is the ITU designation for radio frequencies in the range of 3 to 30 kilohertz, corresponding to wavelengths from 100 to 10 kilometers, respectively. The band is known as the myriameter band or myriameter wave as the wavelengths range from one to ten myriameters. Due to its limited bandwidth, audio transmission is impractical in this band, therefore only low data rate coded signals are used; the VLF band is used for a few radio navigation services, government time radio stations and for secure military communication. Since VLF waves can penetrate at least 40 meters into saltwater, they are used for military communication with submarines; because of their large wavelengths, VLF radio waves can diffract around large obstacles and so are not blocked by mountain ranges or the horizon, can propagate as ground waves following the curvature of the Earth. The main mode of long distance propagation is an Earth-ionosphere waveguide mechanism; the Earth is surrounded by a conductive layer of electrons and ions in the upper atmosphere at the bottom of the ionosphere called the D layer at 60 to 90 km altitude, which reflects VLF radio waves.
The conductive ionosphere and the conductive Earth form a horizontal "duct" a few VLF wavelengths high, which acts as a waveguide confining the waves so they don't escape into space. The waves travel in a zigzag path around the Earth, reflected alternately by the Earth and the ionosphere, in TM mode. VLF waves have low path attenuation, 2-3 dB per 1000 km, with little of the "fading" experienced at higher frequencies, This is because VLF waves are reflected from the bottom of the ionosphere, while higher frequency shortwave signals are returned to Earth from higher layers in the ionosphere, the F1 and F2 layers, by a refraction process, spend most of their journey in the ionosphere, so they are much more affected by ionization gradients and turbulence. Therefore, VLF transmissions are stable and reliable, are used for long distance communication. Propagation distances of 5000 to 20000 km have been realized. However, atmospheric noise is high in the band, including such phenomena as "whistlers", caused by lightning.
VLF waves can penetrate seawater to a depth of at least 10 to 40 meters, depending on the frequency employed and the salinity of the water, so they are used to communicate with submarines. VLF waves at certain frequencies have been found to cause electron precipitation. VLF waves used to communicate with submarines have created an artificial bubble around the Earth that can protect it from solar flares and coronal mass ejections. A major practical drawback to this band is that because of the length of the waves, full size resonant antennas cannot be built because of their physical height. Vertical antennas must be used because VLF waves propagate in vertical polarization, but a quarter-wave vertical antenna at 30 kHz would be 2.5 kilometres high. So practical transmitting antennas are electrically short, a small fraction of a wavelength long. Due to their low radiation resistance they are inefficient, radiating only 10% to 50% of the transmitter power at most, with the rest of the power dissipated in the antenna/ground system resistances.
High power transmitters are required for long distance communication, so the efficiency of the antenna is an important factor. High power transmitting antennas for VLF frequencies are large wire antennas, up to a mile across, they consist of a series of steel radio masts, linked at the top with a network of cables shaped like an umbrella or clotheslines. Either the towers themselves or vertical wires serve as monopole radiators, the horizontal cables form a capacitive top-load to increase the efficiency of the antenna. High power stations use variations on the umbrella antenna such as the "delta" and "trideco" antennas, or multiwire flattop antennas. For low power transmitters, inverted-L and T antennas are used. A large loading coil is required at the antenna feed point to cancel the capacitive reactance of the antenna to make it resonant. To minimize power dissipated in the ground, these antennas require low resistance ground systems; because of soil resistance and dielectric losses in the ground, the buried cable ground systems used by higher frequency transmitters tend to have unacceptably high losses, counterpoise systems are used, consisting of radial networks of copper cables supported several feet above the ground under the antenna, extending out radially from the mast or vertical element.
The high capacitance and inductance and low resistance of the antenna-loading coil combination makes it act electrically like a high Q tuned circuit. VLF antennas have narrow bandwidth and to change the transmitting frequency requires a variable inductor to tune the antenna; the large VLF antennas used for high power transmitters have bandwidths of only a few tens of hertz, when transmitting frequency shift keying, the usual mode, the resonant frequency of the antenna must sometimes be dynamically shifted with the modulation, between the two FSK frequencies. The high Q of the antenna results in high voltages at the ends of the horizontal topload wires where the nodes of the standing wave pattern occur, good insulation is required; the practical limit to the power of large VLF transmitters is determined by onset of air breakdown and arcing from the antenna. The re
Digital audio broadcasting
Digital audio broadcasting is a digital radio standard for broadcasting digital audio radio services, used in many countries around the world, though not North America. The DAB standard was initiated as a European research project in the 1980s; the Norwegian Broadcasting Corporation launched the first DAB channel in the world on 1 June 1995, the BBC and Swedish Radio launched their first DAB digital radio broadcasts in September 1995. DAB receivers have been available in many countries since the end of the 1990s. DAB is more efficient in its use of spectrum than analogue FM radio, thus can offer more radio services for the same given bandwidth; however the sound quality can be noticeably inferior if the bit-rate allocated to each audio program is not sufficient. DAB is more robust with regard to noise and multipath fading for mobile listening, although DAB reception quality degrades when the signal strength falls below a critical threshold, whereas FM reception quality degrades with the decreasing signal, providing effective coverage over a larger area.
The original version of DAB used the MP2 audio codec. An upgraded version of the system was released in February 2007, called DAB+, which uses the HE-AAC v2 audio codec. DAB is not forward compatible with DAB+, which means that DAB-only receivers are not able to receive DAB+ broadcasts. However, broadcasters can mix DAB and DAB+ programs inside the same transmission and so make a progressive transition to DAB+. DAB+ is twice as efficient as DAB, more robust. In spectrum management, the bands that are allocated for public DAB services, are abbreviated with T-DAB, where the "T" stands for terrestrial; as of 2018, 41 countries are running DAB services. The majority of these services are using DAB+, with only Ireland, UK, New Zealand and Brunei still using a significant number of DAB services. See Countries using DAB/DMB. In many countries, it is expected that existing FM services will switch over to DAB+. Norway is the first country to implement a national FM radio analog switchoff, in 2017, however that only applied to national broadcasters, not local ones.
DAB has been under development since 1981 at the Institut für Rundfunktechnik. The first DAB demonstrations were held in 1985 at the WARC-ORB in Geneva, in 1988 the first DAB transmissions were made in Germany. DAB was developed as a research project for the European Union, which started in 1987 on initiative by a consortium formed in 1986; the MPEG-1 Audio Layer II codec was created as part of the EU147 project. DAB was the first standard based on orthogonal frequency division multiplexing modulation technique, which since has become one of the most popular transmission schemes for modern wideband digital communication systems. A choice of audio codec and error-correction coding schemes and first trial broadcasts were made in 1990. Public demonstrations were made in 1993 in the United Kingdom; the protocol specification was finalized in 1993 and adopted by the ITU-R standardization body in 1994, the European community in 1995 and by ETSI in 1997. Pilot broadcasts were launched in several countries in 1995.
In October 2005, the World DMB Forum instructed its Technical Committee to carry out the work needed to adopt the AAC+ audio codec and stronger error correction coding. This work led to the launch of the DAB+ system. By 2006, 500 million people worldwide were in the coverage area of DAB broadcasts, although by this time sales of receivers had only taken off in the United Kingdom and Denmark. In 2006 there were 1,000 DAB stations in operation worldwide; as of 2018, over 68 million devices have been sold worldwide, over 2,270 DAB services are on air. DAB uses a wide-bandwidth broadcast technology and spectra have been allocated for it in Band III and L band, although the scheme allows for operation between 30 and 300 MHz; the US military has reserved L-Band in the USA only, blocking its use for other purposes in America, the United States has reached an agreement with Canada to restrict L-Band DAB to terrestrial broadcast to avoid interference. DAB had a number of country specific transmission modes.
Mode I for Band III, Earth Mode II for L-Band and satellite Mode III for frequencies below 3 GHz, Earth and satellite Mode IV for L-Band and satelliteIn January 2017, an updated DAB specification removed Modes II, III and IV, leaving only Mode I. From an OSI model protocol stack viewpoint, the technologies used on DAB inhabit the following layers: the audio codec inhabits the presentation layer. Below, the data link layer, in charge of statistical time division multiplexing and frame synchronization; the physical layer contains the error-correction coding, OFDM modulation, dealing with the over-the-air transmission and reception of data. Some aspects of these are described below. DAB uses the MPEG-1 Audio Layer II audio codec, referred to as MP2 because of the ubiquitous MP3; the newer DAB+ standard adopted the HE-AAC version 2 audio codec known as'AAC+' or'aacPlus'. AAC+ is three times more efficient than MP2, which means that broadcasters using DAB+ are able to provide far higher audio quality or far more stations than they could with DAB, or a combination of both higher audio quality and more stations.
One of the most important decisions regarding the design of a digital radio broadcasting system is the choice of which audio codec to use, because the efficiency of the audio codec determines how many radio stations can be carried on a fixed capacity multiplex at a given level of audio quality. Error-correction coding is an import
The X band is the designation for a band of frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is rather indefinitely set at 7.0 to 11.2 GHz. In radar engineering, the frequency range is specified by the IEEE at 8.0 to 12.0 GHz. The X band is used for radar, satellite communication, wireless computer networks. X band is used in radar applications including continuous-wave, single-polarization, dual-polarization, synthetic aperture radar, phased arrays. X band radar frequency sub-bands are used in civil and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defense tracking, vehicle speed detection for law enforcement. X band is used in modern radars; the shorter wavelengths of the X band allow for higher resolution imagery from high-resolution imaging radars for target identification and discrimination. In Ireland, Saudi Arabia and Canada, the X band 10.15 to 10.7 segment is used for terrestrial broadband.
Alvarion, CBNL, CableFree and Ogier make systems for this. The Ogier system is a full duplex Transverter used for DOCSIS over microwave; the home / Business CPE has a single coaxial cable with a power adapter connecting to an ordinary cable modem. The local oscillator is 9750 MHz, the same as for Ku band satellite TV LNB. Two way applications such as broadband use a 350 MHz TX offset. Portions of the X band are assigned by the International Telecommunications Union for deep space telecommunications; the primary user of this allocation is the American NASA Deep Space Network. DSN facilities are in Goldstone, near Canberra and near Madrid, Spain; these three stations, located 120 degrees apart in longitude, provide continual communications from the Earth to any point in the Solar System independent of Earth rotation. DSN stations are capable of using the older and lower S band deep-space radio communications allocations, some higher frequencies on a more-or-less experimental basis, such as in the K band.
Notable deep space probe programs that have employed X band communications include the Viking Mars landers. The new European double Mars Mission ExoMars will use X band communication, on the instrument LaRa, to study the internal structure of Mars, to make precise measurements of the rotation and orientation of Mars by monitoring two-way Doppler frequency shifts between the surface platform and Earth, it will detect variations in angular momentum due to the redistribution of masses, such as the migration of ice from the polar caps to the atmosphere. An important use of the X band communications came with the two Viking program landers; when the planet Mars was passing near or behind the Sun, as seen from the Earth, a Viking lander would transmit two simultaneous continuous-wave carriers, one in the S band and one in the X band in the direction of the Earth, where they were picked up by DSN ground stations. By making simultaneous measurements at the two different frequencies, the resulting data enabled theoretical physicists to verify the mathematical predictions of Albert Einstein's General Theory of Relativity.
These results are some of the best confirmations of the General Theory of Relativity. The International Telecommunications Union, the international body which allocates radio frequencies for civilian use, is not authorised to allocate frequency bands for military radio communication; this is the case pertaining to X band military communications satellites. However, in order to meet military radio spectrum requirements, e.g. for fixed-satellite service and mobile-satellite service, the NATO nations negotiated the so-called NATO Joint Civil/Military Frequency Agreement. The Radio Regulations of the International Telecommunication Union allow amateur radio operations in the frequency range 10.000 to 10.500 GHz, amateur satellite operations are allowed in the range 10.450 to 10.500 GHz. This is known as the 3-centimeter band by amateurs and the X-band by AMSAT. Motion detectors use 10.525 GHz. 10.4 GHz is proposed for traffic light crossing detectors. Comreg in Ireland has allocated 10.450 GHz for Traffic Sensors as SRD.
Many electron paramagnetic resonance spectrometers operate near 9.8 GHz. Particle accelerators may be powered by X-band RF sources; the frequencies are standardized at 11.9942 GHz or 11.424 GHz, the second harmonic of C-band and fourth harmonic of S-band. The European X-band frequency is used for the Compact Linear Collider. Cassegrain reflector Directional antenna XTAR Sea-based X band Radar New Horizons telecommunications Voyager program#Spacecraft design Earth observation satellites transmission frequencies TerraSAR-X: a German Earth observation satellite http://www.ntia.doc.gov/osmhome/allochrt.pdf http://www.g3pho.free-online.co.uk/microwaves/wideband.htm
International Telecommunication Union
The International Telecommunication Union the International Telegraph Union, is a specialized agency of the United Nations, responsible for issues that concern information and communication technologies. It is the oldest among all the 15 specialised agencies of UN; the ITU coordinates the shared global use of the radio spectrum, promotes international cooperation in assigning satellite orbits, works to improve telecommunication infrastructure in the developing world, assists in the development and coordination of worldwide technical standards. The ITU is active in areas including broadband Internet, latest-generation wireless technologies and maritime navigation, radio astronomy, satellite-based meteorology, convergence in fixed-mobile phone, Internet access, voice, TV broadcasting, next-generation networks; the agency organizes worldwide and regional exhibitions and forums, such as ITU Telecom World, bringing together representatives of government and the telecommunications and ICT industry to exchange ideas and technology.
ITU, based in Geneva, Switzerland, is a member of the United Nations Development Group, has 12 regional and area offices in the world. ITU has been an intergovernmental public–private partnership organization since its inception, its membership includes 193 Member States and around 800 public and private sector companies, academic institutions as well as international and regional telecommunication entities, known as Sector Members and Associates, which undertake most of the work of each Sector. ITU was formed in Paris, at the International Telegraph Convention; the International Radiotelegraph Union was unofficially established at first International Radiotelegraph Convention in 1906. Both were merged into the International Telecommunication Union in 1932. ITU became a United Nations specialized agency in 1947; the ITU comprises three sectors, each managing a different aspect of the matters handled by the Union, as well as ITU Telecom. The sectors were created during the restructuring of ITU at its 1992 Plenipotentiary Conference.
Radio communication Established in 1927 as the International Radio Consultative Committee or CCIR, this sector manages the international radio-frequency spectrum and satellite orbit resources. In 1992, the CCIR became the ITU-R. Standardisation Standardisation was the original purpose of ITU since its inception. Established in 1956 as the International Telephone and Telegraph Consultative Committee or CCITT, this sector standardizes global telecommunications. In 1993, the CCITT became the ITU-T. Development Established in 1992, this sector helps spread equitable and affordable access to information and communication technologies. ITU Telecom ITU Telecom organizes major events for the world's ICT community. A permanent General Secretariat, headed by the Secretary General, manages the day-to-day work of the Union and its sectors; the basic texts of the ITU are adopted by the ITU Plenipotentiary Conference. The founding document of the ITU was the 1865 International Telegraph Convention, which has since been amended several times and is now entitled the "Constitution and Convention of the International Telecommunication Union".
In addition to the Constitution and Convention, the consolidated basic texts include the Optional Protocol on the settlement of disputes, the Decisions and Recommendations in force, as well as the General Rules of Conferences and Meetings of the Union. The ITU is headed by a Secretary-General, a Deputy Secretary General and the three directors of the Bureaux, who are elected to a four-year terms by the member states at the ITU Plenipotentiary Conference. On 23 October 2014 Houlin Zhao was elected 19th Secretary-General of the ITU at the Plenipotentiary Conference in Busan, Republic of Korea, his four-year mandate started on 1 January 2015, he was formally inaugurated on 15 January 2015. Houlin Zhao was reelected at the 2018 Plenipotentiary Conference in Dubai. Membership of ITU is open to only Member States of the United Nations, which may join the Union as Member States, as well as to private organizations like carriers, equipment manufacturers, funding bodies and development organizations and international and regional telecommunication organizations, which may join ITU as non-voting Sector Members.
There are 193 Member States of the ITU, including all UN member states except the Republic of Palau, plus the Vatican City. The most recent member state to join the ITU is South Sudan, which became a member on 14 July 2011; the Republic of China was blocked from membership by the People's Republic of China, but received a country code, being listed as "Taiwan, China". Palestine was admitted as an observer in 2010. Six Regional Offices and seven Area Offices guarantee a regional presence of ITU: Regional Office for CSI Africa Regional Office in Addis Ababa, with Area Offices in Dakar and Yaoundé Arab States Regional Office in Cairo Asia-Pacific Regional Office in Bangkok, with Area Office in Jakarta America Regional Office in Brasilia, with Area Offices in Bridgetown and Tegucigalpa; the sixth is a Coordination office for Europe Region Europe at ITU Headquarters. Other Regional organizations, connected to ITU, are: Asia-Pacific Telecommunity Arab Spectrum Management Group African Telecommunications Union European Conference of Posta