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For biologic transmitters, see transmitter substance. The Crystal Palace transmitting station is a Broadcasting and Telecommunications site in the Crystal Palace area of the London Borough of Bromley The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as Hormones The endocrine system is instrumental
A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical A machine is any device that uses Energy to perform some activity An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Telecommunication, signalling (UK spelling or signaling (US spelling has the following meanings The use of signals for controlling communications Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic In other applications signals can also be transmitted using an analog 0/4-20 mA current loop signal. A current loop describes two different electrical signalling schemes
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Transmitter types
In radio electronics and broadcasting, a transmitter usually has a power supply, an oscillator, a modulator, and amplifiers for audio frequency (AF) and radio frequency (RF). WDET-FM is the NPR member radio station of Wayne State University in Detroit Michigan. Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. For the band see Broadcast (band Broadcasting is the distribution of audio and/or Video signals which transmit Power supply is a reference to a source of Electrical power. A device or system that supplies Electrical or other types of Energy to an output load An electronic oscillator is an Electronic circuit that produces a repetitive electronic signal often a Sine wave or a Square wave. In Telecommunications, modulation is the process of varying a periodic Waveform, i Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz The modulator is the device which piggybacks (or modulates) the signal information onto the carrier frequency, which is then broadcast. In Telecommunications, a carrier wave, or carrier is a Waveform (usually Sinusoidal) that is modulated (modified with an input signal Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz Sometimes a device (for example, a cell phone) contains both a transmitter and a radio receiver, with the combined unit referred to as a transceiver. This article is about a radio receiver for other uses see Radio (disambiguation. A transceiver is a device that has both a Transmitter and a receiver which are combined and share common circuitry or a single housing A common consumer electronics device is a Personal FM transmitter, a very low power transmitter generally designed to take a simple audio source like an iPod, CD player, etc. Consumer electronics include electronic equipment intended for everyday use This article is concerned with low powered transmitters used in some countries for interfacing personal audio devices "FM transmitter" can also refer to high powered broadcast iPod is a popular brand of Portable media players designed and marketed by Apple Inc A Compact Disc player (often written as compact disc player) or CD player, is an electronic device which plays audio Compact Discs CD players are often and transmit it a few feet to a standard FM radio receiver. This article is about a radio receiver for other uses see Radio (disambiguation. In the USA, most personal FM transmitters fall under Part 15 of the FCC regulations to avoid any user licensing requirements. The United States of America —commonly referred to as the
In amateur radio, a transmitter can be a separate piece of electronic gear or a subset of a transceiver, and often referred to using an abbreviated form; "XMTR". Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications [1]
In industrial process control, a "transmitter" is any device which converts measurements from a sensor into a signal to be received, usually sent via wires, by some display or control device located a distance away. Process control is a Statistics and Engineering discipline that deals with Architectures mechanisms and Algorithms for controlling Typically in process control applications the "transmitter" will output an analog 4-20 mA current loop or digital protocol to represent a measured variable within a range. The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second A current loop describes two different electrical signalling schemes For example, a pressure transmitter might use 4 mA as a representation for 50 psig of pressure and 20 mA as 1000 psig of pressure and any value in between proportionately ranged between 50 and 1000 psig. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of (A 0-4 mA signal indicates a system error. ) Older technology transmitters used pneumatic pressure typically ranged between 3 to 15 psig (20 to 100 kPa) to represent a process variable.
Generally and in communication and information processing, a transmitter is any object (source) which sends information to an observer (receiver). Communication is the process of conveying information from a sender to a receiver with the use of a medium in which the communicated information is understood the same way Information processing is the change (processing of Information in any manner detectable by an observer. In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity A sender was a circuit in a 20th century electromechanical Telephone exchange which sent Telephone numbers and other information to another exchange Information as a concept has a diversity of meanings from everyday usage to technical settings When used in this more general sense, vocal cords may also be considered an example of a transmitter.
Radio transmitters
- Further information: Radio transmitter design
History In the early days of radio engineering, radio frequency energy was generated using arcs known as Alexanderson alternator or mechanical alternators (of which a rare example survives at the SAQ transmitter in Grimeton, Sweden). Methods At the beginning of the 20th century there were four chief methods of arranging the transmitting circuits The transmitting system consists of two tuned The Grimeton VLF transmitter is a VLF transmission facility near Grimeton close to Varberg in Sweden. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. In the 1920s electronic transmitters, based on vacuum tubes, began to be used. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall.
Power output
In broadcasting, and telecommunication, the part which contains the oscillator, modulator, and sometimes audio processor, is called the exciter. For the band see Broadcast (band Broadcasting is the distribution of audio and/or Video signals which transmit Audio signal processing, sometimes referred to as audio processing, is the processing of a representation of auditory signals, or Sound. Confusingly, the high-power amplifier which the exciter then feeds into is often called the "transmitter" by broadcast engineers. Broadcast engineering is the field of Electrical engineering, and now to some extent Computer engineering, which deals with Radio and Television The final output is given as transmitter power output (TPO), although this is not what most stations are rated by. In Radio transmission, transmitter power output ( TPO) is the actual amount of power (in Watts of Radio frequency (RF energy
Effective radiated power (ERP) is used when calculating station coverage, even for most non-broadcast stations. In radio Telecommunications, effective radiated power or equivalent radiated power (ERP is a standardized theoretical measurement of radio frequency (RF A calculation is a deliberate process for transforming one or more inputs into one or more results with variable change It is the TPO, minus any attenuation or radiated loss in the line to the antenna, multiplied by the gain (magnification) which the antenna provides toward the horizon. An attenuator is an Electronic device that reduces the Amplitude or power of a signal without appreciably distorting its Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Electronics, gain is a measure of the ability of a circuit (often an Amplifier) to increase the power or Amplitude of a Magnification is the process of enlarging something only in appearance not in physical size The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates This is important, because the electric utility bill for the transmitter would be enormous otherwise, as would the cost of a transmitter. In Economics, utility is a measure of the relative satisfaction from or desirability of Consumption of various Goods and services. For most large stations in the VHF- and UHF-range, the transmitter power is no more than 20% of the ERP.
For VLF, LF, MF and HF the ERP is typically not determined separately. In most cases the transmission power found in lists of transmitters is the value for the output of the transmitter. This is only correct for omnidirectional aerials with a length of a quarter wavelength or shorter. For other aerial types there are gain factors, which can reach values until 50 for shortwave directional beams in the direction of maximum beam intensity.
Since some authors take account of gain factors of aerials of transmitters for frequencies below 30 MHz and others not, there are often discrepancies of the values of transmitted powers.
Power supply
Transmitters are sometimes fed from a higher voltage level of the power supply grid than necessary in order to improve security of supply. For example, the Allouis, Konstantynow and Roumoules transmitters are fed from the high-voltage network (110 kV in Alouis and Konstantynow, 150 kV in Roumoules) even though a power supply from the medium-voltage level of the power grid (about 20 kV) would be able to deliver enough power. The Allouis longwave transmitter first entered service as France 's central Longwave Transmitter, in 1939 The Warsaw radio mast was the world's tallest structure until its collapse on 8 August, 1991. The Roumoules transmitter is the main Broadcasting facility for long- and medium wave broadcasting of Radio Monte Carlo near Roumoules France. [2][3]
Cooling of final stages
Low-power transmitters do not require special cooling equipment. Modern transmitters can be incredibly efficient, with efficiencies exceeding 98 percent. However, a broadcast transmitter with a megawatt power stage transferring 98% of that into the antenna can also be viewed as a 20 kilowatt electric heater.
For medium-power transmitters, up to a few hundred watts, air cooling with fans is used. At power levels over a few kilowatts, the output stage is cooled by a forced liquid cooling system analogous to an automobile cooling system. Since the coolant directly touches the high-voltage anodes of the tubes, only distilled, deionised water or a special dielectric coolant can be used in the cooling circuit. An anode is an Electrode through which Electric current flows into a polarized electrical device This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. This high-purity coolant is in turn cooled by a heat exchanger, where the second cooling circuit can use water of ordinary quality because it is not in contact with energized parts. Very-high-power tubes of small physical size may use evaporative cooling by water in contact with the anode. The production of steam allows a high heat flow in a small space.
Protection equipment
The high voltages used in high power transmitters (up to 40 kV) require extensive protection equipment. Also, transmitters are exposed to damage from lightning. Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or Transmitters may be damaged if operated without an antenna, so protection circuits must detect the loss of the antenna and switch off the transmitter immediately. Tube-based transmitters must have power applied in the proper sequence, with the filament voltage applied before the anode voltage, otherwise the tubes can be damaged. The output stage must be monitored for standing waves, which indicate that generated power is not being radiated but instead is being reflected back into the transmitter. In Telecommunications standing wave ratio ( SWR) is the Ratio of the Amplitude of a partial Standing wave at an antinode (maximum
Lightning protection is required between the transmitter and antenna. This consists of spark gaps and gas-filled surge arresters to limit the voltage that appears on the transmitter terminals. A spark gap consists of an arrangement of two conducting Electrodes separated by a gap usually filled with a Gas such as Air. The control instrument that measures the voltage standing-wave ratio switches the transmitter off briefly if a higher voltage standing-wave ratio is detected after a lightning strike, as the reflections are probably due to lightning damage. If this does not succeed after several attempts, the antenna may be damaged and the transmitter should remain switched off. In some transmitting plants UV detectors are fitted in critical places, to switch off the transmitter if an arc is detected. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive The operating voltages, modulation factor, frequency and other transmitter parameters are monitored for protection and diagnostic purposes, and may be displayed locally and/or at a remote control room.
Building
A commercial transmitter site will usually have a control building to shelter the transmitter components and control devices. This is usually a purely functional building, which may contain apparatus for both radio and television transmitters. To reduce transmission line loss the transmitter building is usually immediately adjacent to the antenna for VHF and UHF sites, but for lower frequencies it may be desirable to have a distance of a few score or several hundred metres between the building and the antenna. Very high frequency (VHF is the Radio frequency range from 30 MHz to 300 MHz. Some transmitting towers have enclosures built into the tower to house radio relay link transmitters or other, relatively low-power transmitters.
Legal and regulatory aspects
Since radio waves go over borders, international agreements control radio transmissions. In European countries like Germany often the national Post Office is the regulating authority. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. In the United States broadcast and industrial transmitters are regulated by the Federal Communications Commission (FCC). The United States of America —commonly referred to as the In Canada technical aspects of broadcast and radio transmitters are controlled by Industry Canada, but broadcast content is regulated separately by the Canadian Radio-television and Telecommunications Commission (CRTC). Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page CRTC may also stand for Cathode Ray Tube Controller. Canadian Radio-television and Telecommunications Commission ( CRTC, in French Conseil In Australia transmitters, spectrum, and content are controlled by the Australian Communications and Media Authority (ACMA). Australian Communications and Media Authority is an Australian government agency whose main roles are to regulate Broadcasting, radiocommunications and Telecommunications The International Telecommunication Union (ITU) helps managing the radio-frequency spectrum internationally.
Planning
As in any costly project, the planning of a high power transmitter site requires great care. This begins with the location. A minimum distance, which depends on the transmitter frequency, transmitter power, and the design of the transmitting antennas, is required to protect people from the radio frequency energy. Antenna towers are often very tall and therefore flight paths must be evaluated. Sufficient electric power must be available for high power transmitters. Transmitters for long and medium wave require good grounding and soil of high electrical conductivity. Locations at the sea or in river valleys are ideal, but the flood danger must be considered. Transmitters for UHF are best on high mountains to improve the range (see radio propagation). Radio propagation is a term used to explain how Radio waves behave when they are Transmitted, or are propagated from one point on the Earth The antenna pattern must be considered because it is costly to change the pattern of a long-wave or medium-wave antenna.
Transmitting antennas for long and medium wave are usually implemented as a mast radiator. A mast radiator (aka 'radiating tower' is a radio mast or tower in which the whole structure works Similar antennas with smaller dimensions are used also for short wave transmitters, if these send in the round spray enterprise. For arranging radiation at free standing steel towers fastened planar arrays are used. Radio towers for UHF and TV transmitter can be implemented in principle as grounded constructions. Towers may be steel lattice masts or reinforced concrete towers with antennas mounted at the top. Some transmitting towers for UHF have high-altitude operating rooms and/or facilities such as restaurants and observation platforms, which are accessible by elevator. Such towers are usually called TV tower. For microwaves one uses frequently parabolic antennas. These can be set up for applications of radio relay links on transmitting towers for FM to special platforms. For the program passing on of television satellites and the funkkontakt to space vehicles large parabolic antennas with diameters of 3 to 100 meters are necessary. These plants, which can be used if necessary also as radio telescope, are established on free standing constructions, whereby there are also numerous special designs, like the radio telescope in Arecibo.
Just as important as the planning of the construction and location of the transmitter is how its output fits in with existing transmissions. Two transmitters cannot broadcast on the same frequency in the same area as this would cause co-channel interference. For a good example of how the channel planners have dovetailed different transmitters' outputs see Crystal Palace UHF TV channel allocations. This reference also provides a good example of a grouped transmitter, in this case an A group. That is, all of its output is within the bottom third of the UK UHF television broadcast band. The other two groups (B and C/D) utilise the middle and top third of the band, see graph. By replicating this grouping across the country (using different groups for adjacent transmitters), co-channel interference can be minimised, and in addition, those in marginal reception areas can use more efficient grouped receiving antennas. Unfortunately, in the UK, this carefully planned system has had to be compromised with the advent of digital broadcasting which (during the changeover period at least) requires yet more channel space, and consequently the additional digital broadcast channels cannot always be fitted within the transmitter's existing group. Thus many UK transmitters have become "wideband" with the consequent need for replacement of receiving antennas (see external links). Once the Digital Switch Over (DSO) occurs the plan is that most transmitters will revert to their original groups, source Ofcom July 2007 .
Further complication arises when adjacent transmitters have to transmit on the same frequency and under these circumstances the broadcast radiation patterns are attenuated in the relevant direction(s). A good example of this is Waltham which broadcasts digital MUXES 5 & 6 on the same frequencies as Sandy Heath, another transmitter 50 miles SSE of it. The Waltham transmitting station is a Broadcasting and Telecommunications facilityat Waltham-on-the-Wolds, 5 miles (8 km north-east of Melton Thus Waltham's transmitter array does not broadcast these two channels in the direction of Sandy Heath and vice versa. All of the above provides a perfect case study in transmission frequency planning.
Where a particular service needs to have wide coverage, this is usually achieved by using multiple transmitters at different locations. Usually, these transmitters will operate at different frequencies to avoid interference where coverage overlaps. Examples include national broadcasting networks and cellular networks. A cellular network is a Radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter known as a Cell In the latter, frequency switching is automatically done by the receiver as necessary, in the former, manual retuning is more common (though the Radio Data System is an example of automatic frequency switching in broadcast networks). Another system for extending coverage using multiple transmitters is quasi-synchronous transmission, but this is rarely used nowadays. In radio broadcasting quasi-synchronous transmission is a method of achieving wider area coverage using multiple transmitters but without needing multiple frequencies
Main and relay (repeater) transmitters
Transmitting stations are usually either classified as main stations or relay stations (also known as repeaters or translators). A radio repeater is a combination of a radio receiver and a radio transmitter that receives a weak or low-level signal and retransmits it at a higher level or higher power so that
Main stations are defined as those that generate their own modulated output signal from a baseband (unmodulated) input. In Telecommunications, modulation is the process of varying a periodic Waveform, i In Signal processing, baseband is an adjective that describes signals and systems whose range of Frequencies is measured from zero to a maximum bandwidth Usually main stations operate at high power and cover large areas.
Relay stations take an already modulated input signal (usually by direct reception of a parent station (off-air)) and simply shift (translate) its frequency before rebroadcasting. Usually relay stations operate at medium or low power, and are used to fill in pockets of poor reception within, or at the fringe of, the service area of a parent main station.
Note that a main station may also take its input signal directly off-air from another station, however this signal would be fully demodulated to baseband first, processed, and then remodulated for transmission. In Signal processing, baseband is an adjective that describes signals and systems whose range of Frequencies is measured from zero to a maximum bandwidth
Transmitters in culture
Some cities in Europe, like Mühlacker, Ismaning, Langenberg, Kalundborg, Hoerby and Allouis became famous as sites of powerful transmitters. Mühlacker is a town in the eastern part of the Enz district Baden-Württemberg, Germany. Ismaning is a municipality in Bavaria, Germany. It is located near Munich at, and has 14638 inhabitants Langenberg is a quarter in Velbert, a German city Located in this district is the famous Sender Langenberg transmission site which transmits MW Kalundborg is a city in Kalundborg municipality in Denmark and the site of its municipal council Allouis is a commune of the Cher département in central France. For example, Goliath transmitter was a VLF transmitter of the German Navy during World War II located near Kalbe an der Milde in Saxony-Anhalt, Germany. Goliath transmitter was a VLF Transmitter of the German Navy near Kalbe an der Milde in Saxony-Anhalt, Germany, which was Very low frequency or VLF refers to radio frequencies (RF in the range of 3 KHz to 30 KHz. The German Navy ( Deutsche Marine ( is the Navy of Germany and part of the Bundeswehr (German Armed Forces World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Kalbe is a town in the Altmarkkreis Salzwedel (district in Saxony-Anhalt, Germany. Saxony-Anhalt ( Sachsen-Anhalt) is one of the sixteen ''Bundesländer'' (federal states that make up the Federal Republic of Germany. Some transmitting towers like the radio tower Berlin or the TV tower Stuttgart have become landmarks of cities. Radio masts and towers are typically tall structures designed Berlin is the capital city and one of sixteen states of Germany. Stuttgart (ˈʃtʊtgaɐ̯t is the capital of the state of Baden-Württemberg in southern Germany. Many transmitting plants have very high radio towers that are masterpieces of engineering.
Having the tallest building in the world, the nation, the state/province/prefecture, city, etc. , has often been considered something to brag about. Often, builders of high-rise buildings have used transmitter antennas to lay claim to having the tallest building. A historic example was the "tallest building" feud between the Chrysler Building and the Empire State Building in New York, New York. The Chrysler Building is an Art Deco Skyscraper in New York City, located on the east side of Manhattan at the intersection of 42nd The Empire State Building is a 102-story Art Deco Skyscraper in New York City at the intersection of Fifth Avenue and West 34th Street The City of New York
Some towers have an observation deck accessible to tourists. An example is the Ostankino Tower in Moscow, which was completed in 1967 on the 50th anniversary of the October Revolution to demonstrate the technical abilities of the Soviet Union. Ostankino Tower (Останкинская телебашня is a free-standing Television and Radio tower in Moscow, Russia. The October Revolution (Октябрьская революция Oktyabrskaya revolyutsiya) also known as the Soviet Revolution The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 As very tall radio towers of any construction type are prominent landmarks, requiring careful planning and construction, and high-power transmitters especially in the long- and mediumwave ranges can be received over long distances, such facilities were often mentioned in propaganda. Other examples were the Deutschlandsender Herzberg/Elster and the Warsaw Radio Mast. The Deutschlandsender Herzberg/Elster was a 500 kilowatt long-wave transmitter at Herzberg/Elster, which was in service from 1939 to 1945 The Warsaw radio mast was the world's tallest structure until its collapse on 8 August, 1991.
Records
- Tallest radio mast
- 1974-1991: Konstantynow for 2000 kilowatt longwave transmitter, 646. The Warsaw radio mast was the world's tallest structure until its collapse on 8 August, 1991. 38 metres (2120 ft 8 in)
- 1963-1974 and since 1991: KVLY Tower, 2,063 ft (628. The KVLY-TV mast (formerly the KTHI-TV mast) is a tall Television -transmitting mast in Blanchard, Traill County, North Dakota 8 m)
- Highest power
- Longwave, Taldom transmitter, 2500 kW
- Medium wave, transmitter Bolshakovo, 2500 kW
References
See also
External links
- International Telecommunication Union
- Jim Hawkins' Radio and Broadcast Technology Page
- WCOV-TV's Transmitter Technical Website
- Major UK television transmitters including change of group information, see Transmitter Planning section.
- Details of UK digital television transmitters
- Richard Moore's Anorak Zone Photo Gallery of UK TV and Radio transmission sites
Dictionary
transmitter
-noun
- something that transmits something (in all senses)
- an electronic device that generates and amplifies a carrier wave, modulates it with a meaningful signal derived from speech, music, TV or other sources, and broadcasts the resulting signal from an antenna
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