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In radio telecommunications, effective radiated power (ERP) is determined by subtracting system losses and adding system gains to the actual electrical power output of a transmitter. ERP is not equivalent to the power that is radiated, but is a quantity that takes into consideration transmitter power and antenna directivity. ERP is typically applied to antenna systems. For example, if an antenna system has 9 dB gain and 6 dB loss, its ERP is 3 dB over the transmitter power output (TPO). Image File history File links Question_book-3. ... Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... A yagi antenna Most simply, an antenna is an electronic component designed to send or receive radio waves. ... Transmitter power output (TPO) is the actual amount of power (in watts) of RF energy that a transmitter produces at its output. ...

FM example

For example, an FM radio station which advertises that it has 100,000 watts of power actually has 100,000 watts ERP, and probably not an actual 100,000-watt transmitter. The TPO (transmitter power output) of such a station is perhaps around 10,000 to 20,000 watts, with a gain factor of, in this case, 5 to 10 (5× to 10×). Since to have any gain an antenna must be to some extent directional, the ERP will also vary by direction and, like the antenna gain, the maximum is usually quoted. In telecommunications, frequency modulation (FM) conveys information over a carrier wave by varying its frequency. ... A radio station is an audio (sound) broadcasting service, traditionally broadcast through the air as radio waves (a form of electromagnetic radiation) from a transmitter to an antenna and a thus to a receiving device. ... Generally speaking, advertising is the paid promotion of goods, services, companies and ideas by an identified sponsor. ... For other uses, see Watt (disambiguation). ... Antenna tower of Crystal Palace transmitter, London 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. ...

US regulatory usage

ERP for FM radio in the United States is always relative to a theoretical reference half-wave dipole antenna. (Double the TPO if the station broadcasts with circular polarization (CP), that is, with equal horizontal and vertical signal components; it takes twice as much transmitter power for CP.) This paragraph applies to analog TV also; it only generally applies to digital TV and digital FM. In electrodynamics, circular polarization of electromagnetic radiation is a polarization such that the tip of the electric field vector, at a fixed point in space, describes a circle as time progresses. ...

In the United States, the maximum ERP for FM broadcasting is usually 100,000 watts (FM Zone II) or 50,000 watts (the more densely populated FM Zones I/I-A), though exact restrictions vary depending on the class of license. Some stations have been grandfathered in or, very infrequently, been given special dispensation, and can exceed normal restrictions. A grandfather clause is an exception that allows an old rule to continue to apply to some existing situations, when a new rule will apply to all future situations. ...

Microwave band issues

For most microwave systems, a completely non-directional isotropic antenna (one which radiates equally and perfectly well in every direction — a physical impossibility) is usually used as a reference antenna. This includes satellite transponders, radar, and other systems which use microwave dishes and reflectors rather than dipole-style antennas. (When referencing the theoretical isotropic antenna, the abbreviation EIRP is used.) Although it is physically impossible to make an isotropic antenna, the assumption makes calculations simpler. This article is about the type of Electromagnetic radiation. ... An isotropic antenna is an ideal antenna that radiates power with unit gain uniformly in all directions and is often used to reference antenna gains in wireless systems. ... Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ... For other uses, see Satellite (disambiguation). ... An Ontario Highway 407 toll transponder In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR or TPDR) has the following meanings: An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator). ...

Lower frequency issues

In the case of mediumwave (AM) stations in the United States, actual radiated power is used for an omnidirectional station; for a directional station, power is computed relative to an omnidirectional radiator with the same nominal power and an efficiency equal either to the RMS efficiency of the directional antenna under consideration, or to the minimum efficiency permitted for the class of station. Mediumwave radio transmissions serves as the most common band for broadcasting. ... Nominal power is a measurement of a mediumwave radio stations output used in the United States. ... In mathematics, the root mean square or rms is a statistical measure of the magnitude of a varying quantity. ...

Related terms

In Europe, sometimes the term effective monopole radiated power or EMRP is used, especially in relation to mediumwave broadcasting antennas. This is the same as ERP, except that a quarter-wavelength monopole is used as the reference antenna instead of a half-wave dipole. Mediumwave radio transmissions serves as the most common band for broadcasting. ... In physics, magnetic monopole is a term describing a hypothetical particle that could be quickly clarified to a person familiar with magnets but not electromagnetic theory as a magnet with only one pole. In more accurate terms, it would have net magnetic charge. Interest in the concept stems from particle... The Earths magnetic field, which is approximately a dipole. ...

HAAT vs ERP

Height above average terrain (HAAT) is also a factor in determining the broadcast range of a station. Licenses granted by the Federal Communications Commission are based on ERP, antenna height and radiation pattern, with range ultimately being the limiting factor. For example, some stations exceed normal height restrictions and therefore must downgrade ERP in order to fit within the appropriate range and thereby protect other stations using the same or neighbouring frequencies. HAAT is used extensively in radio, as it is actually much more important than power. ... FCC redirects here. ...

Wavelength issues

It should be noted here that, unlike with the so-called "AM" broadcast band (mediumwave), which uses far lower frequencies, power or ERP on an FM broadcast station cannot by itself indicate the station's range; the height of its antenna is crucial. A station may put out a megawatt but if it is situated in a low valley surrounded by mountains, the signal will be contained therein. This action is called Line-of-sight propagation in VHF (FM) Radio Communications. Mediumwave radio transmissions serves as the most common band for broadcasting. ... This article or section does not adequately cite its references or sources. ...

On the other hand, given a sufficiently high perspective, a transmitter needs little power to cover a significant area. In the extreme case, a communications satellite orbiting with unobstructed view of its terrestrial target may need only 5 to 10 watts, even though it is thousands of miles away. This is why broadcast FM (and TV) transmitters are placed on high towers or mountains for best coverage. U.S. military MILSTAR communications satellite A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications. ...

See also

Related topics

• Beam tilt
• Nominal power
• List of broadcast station classes

From FS-1037C: Beam tilt is used in radio to aim the main lobe of the vertical plane radiation pattern of an antenna below (or above) the horizontal plane. ... Nominal power is a measurement of a mediumwave radio stations output used in the United States. ... This is the list of broadcast station classes. ... Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ...

Effective radiated power:

1. The power supplied to an antenna multiplied by the antenna gain in a given direction.

• Note 1: If the direction is not specified, the direction of maximum gain is assumed.
• Note 2: The type of reference antenna must be specified.

2. The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction (used by the NTIA and FCC). The National Telecommunications and Information Administration (NTIA) is an agency of the United States Department of Commerce that serves as the Presidents principal adviser on telecommunications policies pertaining to the United States economic and technological advancement and to regulation of the telecommunications industry. ... FCC redirects here. ...

• Note: If the direction is not specified, the direction of maximum gain is assumed.

Effective isotropically-radiated power (EIRP): In radio communication systems, Effective isotropically-radiated power (EIRP) is the amount of power that would have to be emitted by an isotropic antenna (that evenly distributes power in all directions) to produce the peak power density observed in the direction of maximum antenna gain. ...

The arithmetic product of (a) the power supplied to an antenna and (b) its gain relative to an isotropic source. In mathematics, multiplication is an elementary arithmetic operation. ...