Effective radiated power

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. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into 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). In Radio transmission, transmitter power output ( TPO) is the actual amount of power (in Watts of Radio frequency (RF energy

1 FM example
- 1.1 US regulatory usage
2 Microwave band issues
3 Lower frequency issues
4 Related terms
5 HAAT vs ERP
6 Wavelength issues
7 See also

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. This article is about radio broadcasting for other uses see Radio (disambiguation. Advertising is a form of Communication that typically attempts to persuade potential Customers to Purchase or to consume more of a particular Brand The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. For biologic transmitters see Transmitter substance. A transmitter is an electronic device which usually with the aid of an antenna 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.

US regulatory usage

ERP for FM radio in the United States is always relative to a theoretical reference half-wave dipole antenna. A dipole antenna, developed by Heinrich Rudolph Hertz around 1886, is an antenna with a center- fed Driven element for transmitting (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. In Electrodynamics, circular polarization (also circular polarisation) of Electromagnetic radiation is a Polarization such that the tip of the ) This paragraph applies to analog TV also; it only generally applies to digital TV and digital FM.

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. The United States of America —commonly referred to as the Some stations have been grandfathered in or, very infrequently, been given special dispensation, and can exceed normal restrictions. A grandfather clause is a term used in US English for 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. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 An isotropic radiator is a theoretical Point source of waves which exhibits the same magnitude or properties when measured in all directions Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. This includes satellite transponders, radar, and other systems which use microwave dishes and reflectors rather than dipole-style antennas. This article is about artificial satellites For natural satellites also known as moons see Natural satellite. In Telecommunication, the term transponder (short-for Trans mitter-res ponder and sometimes abbreviated to XPDR XPNDR TPDR or TP has the following meanings (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.

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. Medium Wave (MW is a part of the Medium frequency (MF radio band used mainly for AM broadcasting. The United States of America —commonly referred to as the Nominal power is a Measurement of a Mediumwave Radio station 's output used in the United States. In Mathematics, the root mean square (abbreviated RMS or rms) also known as the quadratic mean, is a statistical measure of the

Related terms

In Europe, sometimes the term effective monopole radiated power or EMRP is used, especially in relation to mediumwave broadcasting antennas. Medium Wave (MW is a part of the Medium frequency (MF radio band used mainly for AM broadcasting. This is the same as ERP, except that a quarter-wavelength monopole is used as the reference antenna instead of a half-wave dipole. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a

HAAT vs ERP

Height above average terrain (HAAT) is also a factor in determining the broadcast range of a station. Height above average terrain ( HAAT) (or less popularly EHAAT, Effective Height Above Average Terrain is used extensively in FM Radio and 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.

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. Medium Wave (MW is a part of the Medium frequency (MF radio band used mainly for AM broadcasting. 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. Line-of-sight propagation refers to Electro-magnetic radiation including light emissions traveling in a straight line

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. A communications satellite (sometimes abbreviated to comsat) is an artificial Satellite stationed in space for the purposes of Telecommunications. This is why broadcast FM (and TV) transmitters are placed on high towers or mountains for best coverage.

Contents