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In radio telecommunications, effective radiated power or equivalent radiated power (ERP) is a standardized theoretical measurement of radio frequency
Radio frequency

Radio frequency is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves....
 (RF) energy using the non-SI
International System of Units

The International System of Units is the modern form of the metric system and is generally a system devised around the convenience of the number ten....
 unit dBd
Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
, and is determined by subtracting system losses and adding system gains. ERP takes into consideration transmitter power output
Transmitter power output

In radio transmission, transmitter power output is the actual amount of power of radio frequency energy that a transmitter produces at its output....
 (TPO), transmission line losses, connector losses, antenna directivity
Directional antenna

A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....
, and height above average terrain
Height above average terrain

Height above average terrain is used extensively in Frequency Modulation radio and television, as it is actually much more important than effective radiated power in determining the range of broadcasts ....
 (HAAT). ERP is typically applied to antenna systems. For a simplified example, if an antenna system has 9 dB gain and 6 dB loss, its ERP is 3 dB over the TPO.

example, an FM
Frequency modulation

In telecommunications, frequency modulation conveys information over a carrier wave by varying its frequency . In analog signal applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal....
 radio station
Radio station

This article is about radio broadcasting, for other uses see Radio .Radio broadcasting is an audio broadcasting service, traditionally broadcast through the air as radio waves from a transmitter to an antenna and a thus to a receiving device....
 which advertises that it has 100,000 watt
WATT

WATT is a radio station broadcasting a News radio-Talk radio-Sports radio format. Licensed to Cadillac, Michigan, it first began broadcasting in 1945....
s of power actually has 100,000 watts ERP, and probably not an actual 100,000-watt transmitter.






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In radio telecommunications, effective radiated power or equivalent radiated power (ERP) is a standardized theoretical measurement of radio frequency
Radio frequency

Radio frequency is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves....
 (RF) energy using the non-SI
International System of Units

The International System of Units is the modern form of the metric system and is generally a system devised around the convenience of the number ten....
 unit dBd
Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
, and is determined by subtracting system losses and adding system gains. ERP takes into consideration transmitter power output
Transmitter power output

In radio transmission, transmitter power output is the actual amount of power of radio frequency energy that a transmitter produces at its output....
 (TPO), transmission line losses, connector losses, antenna directivity
Directional antenna

A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....
, and height above average terrain
Height above average terrain

Height above average terrain is used extensively in Frequency Modulation radio and television, as it is actually much more important than effective radiated power in determining the range of broadcasts ....
 (HAAT). ERP is typically applied to antenna systems. For a simplified example, if an antenna system has 9 dB gain and 6 dB loss, its ERP is 3 dB over the TPO.

FM example

For example, an FM
Frequency modulation

In telecommunications, frequency modulation conveys information over a carrier wave by varying its frequency . In analog signal applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal....
 radio station
Radio station

This article is about radio broadcasting, for other uses see Radio .Radio broadcasting is an audio broadcasting service, traditionally broadcast through the air as radio waves from a transmitter to an antenna and a thus to a receiving device....
 which advertises that it has 100,000 watt
WATT

WATT is a radio station broadcasting a News radio-Talk radio-Sports radio format. Licensed to Cadillac, Michigan, it first began broadcasting in 1945....
s of power actually has 100,000 watts ERP, and probably not an actual 100,000-watt transmitter. The TPO of such a station typically may be 10,000 to 20,000 watts, with a gain factor of 5 to 10 (5× to 10×). In most antenna designs, gain is realized primarily by concentrating power toward the horizon and suppressing it at upward and downward angles. The distribution of power versus elevation angle is known as the vertical pattern. When an antenna is also directional horizontally, gain and ERP will vary with azimuth
Azimuth

An Azimuth is the angle from a reference vector space in a reference plane to a second vector in the same plane, pointing toward, , something of interest....
. The maximum ERP is usually quoted.

United States regulatory usage

ERP for FM radio in the United States is always relative to a theoretical reference half-wave dipole
Dipole antenna

A dipole antenna, developed by Heinrich Rudolph Hertz around 1886, is an Antenna that can be made by a simple wire, with a center-Input driven element for transmitting or receiving radio frequency energy....
 antenna. To deal with antenna polarization
Polarization

Polarization is a property of waves that describes the orientation of their oscillations. For transverse waves such as many electromagnetic waves, it describes the orientation of the oscillations in the plane perpendicular to the wave's direction of travel....
, the Federal Communications Commission
Federal Communications Commission

The Federal Communications Commission is an Independent agencies of the United States government, created, directed, and empowered by United States Congress statute , and with the majority of its commissioners appointed by the current President of the United States....
 (FCC) lists ERP in both the horizontal and vertical planes.

The maximum ERP for US 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
Grandfather clause

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....
 in or, very infrequently, been given special dispensation, and can exceed normal restrictions.

Microwave band issues

For most microwave
Microwave

Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz....
 systems, a completely non-directional isotropic antenna (one which radiates equally and perfectly well in every direction — a physical impossibility) is used as a reference antenna. This includes satellite
Satellite

In the context of spaceflight, a satellite is an Physical body which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
 transponder
Transponder

In telecommunication, the term transponder has the following meanings:* An automatic information appliance that receiver , amplifier, and Transmission a Signalling on a different frequency ....
s, radar, and other systems which use microwave dishes and reflectors rather than dipole-style antennas.

Lower frequency issues

In the case of mediumwave
Mediumwave

Medium Wave is a part of the Medium frequency radio band used mainly for AM broadcasting. Some experiments and trials are planned or under way for a digital modulation such as Digital Radio Mondiale ....
 (AM) stations in the United States
United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
, 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
Nominal power

Nominal power is a measurement of a mediumwave radio station's output used in the United States. AM Broadcastingers are licensed by the Federal Communications Commission to operate at a specific Real versus nominal value power , which may be different from the transmitter power output....
 and an efficiency equal either to the RMS
Root mean square

In mathematics, the root mean square , also known as the quadratic mean, is a statistics measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids....
 efficiency of the directional antenna under consideration, or to the minimum efficiency permitted for the class of station.

Related terms

  • Effective monopole radiated power (EMRP) may be used in Europe, especially in relation to mediumwave
    Mediumwave

    Medium Wave is a part of the Medium frequency radio band used mainly for AM broadcasting. Some experiments and trials are planned or under way for a digital modulation such as Digital Radio Mondiale ....
     broadcasting antennas. This is the same as ERP, except that a short vertical antenna (i.e. a short monopole
    Monopole

    Monopole may refer to:*Magnetic monopole, or Dirac monopole, a hypothetical particle that may be loosely described as a magnet with only one pole...
    ) is used as the reference antenna instead of a half-wave dipole
    Dipole

    In physics, there are two kinds of dipoles :*An electric dipole is a separation of positive and negative charge. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some, usually small, distance....
    .


  • Equivalent isotropically radiated power
    Equivalent isotropically radiated power

    In radio communication systems, Equivalent isotropically radiated power or, alternatively, Effective isotropically radiated power is the amount of power that a theoretical isotropic antenna would emit to produce the peak power density observed in the direction of maximum antenna gain....
     (EIRP)


HAAT

The height above average terrain for VHF and higher frequencies is extremely important when specifying ERP, as the signal coverage (range) produced by a given ERP dramatically increases with antenna height.

See also

  • Beam tilt
    Beam tilt

    Beam tilt is used in radio to aim the main lobe of the vertical plane radiation pattern of an antenna below the horizontal plane.The simplest way is mechanical beam tilt, where the antenna is physically mounted in such a manner as to lower the angle of the signal on one side....
  • Nominal power
    Nominal power

    Nominal power is a measurement of a mediumwave radio station's output used in the United States. AM Broadcastingers are licensed by the Federal Communications Commission to operate at a specific Real versus nominal value power , which may be different from the transmitter power output....
  • List of broadcast station classes
    List of broadcast station classes

    This is a list of broadcast station classes applicable in much of North America under international agreements between the United States, Canada and Mexico....