Editing Effective radiated power (section)

{{short description|Definition of directional radio frequency power}}
[[File:Effective isotropic radiated power illustration.svg|thumb|upright=1.6|Illustration of definition of effective isotropically radiated power (EIRP). The axes have units of signal strength in decibels. <math>R_\mathsf{a}</math> is the [[radiation pattern]] of a given transmitter driving a [[directional antenna]], emitting a beam of radio waves along the z axis.  It radiates a [[far field]] signal strength of <math>S</math> in its direction of maximum radiation ([[main lobe]]) along the z-axis. The <span style="color:green;">green</span> sphere <math>R_\mathsf{iso}</math> is the radiation pattern of an ideal [[isotropic radiator|isotropic antenna]] that radiates the same maximum signal strength as the directive antenna does. The transmitter power that would have to be applied to the isotropic antenna to radiate this much power is the EIRP.]]

{{anchor|Equivalent radiated power (Redirected)}}
'''Effective radiated power''' ('''ERP'''), synonymous with '''equivalent radiated power''',  is an [[Institute of Electrical and Electronics Engineers|IEEE]] standardized definition of directional [[radio frequency]] (RF) power, such as that emitted by a [[radio transmitter]].  It is the total [[Power (physics)|power]] in [[watt (unit)|watt]]s that would have to be radiated by a [[dipole antenna|half-wave dipole antenna]] to give the same radiation intensity (signal strength or [[irradiance|power flux density]] in watts per square meter) as the actual source antenna at a distant receiver located in the direction of the antenna's strongest beam ([[main lobe]]).  ERP measures the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. It is equal to the input power to the antenna multiplied by the [[antenna gain|gain]] of the antenna.  It is used in electronics and [[telecommunications]], particularly in [[broadcasting]] to quantify the apparent power of a [[broadcasting station]] experienced by listeners in its reception area.

{{anchor|Effective isotropic radiated power (Redirected)|EIRP (Redirected)}}
An alternate parameter that measures the same thing is '''effective isotropic radiated power''' ('''EIRP'''). Effective isotropic radiated power is the hypothetical power that would have to be radiated by an [[isotropic antenna]] to give the same ("equivalent") signal strength as the actual source antenna in the direction of the antenna's strongest beam. The difference between EIRP and ERP is that ERP compares the actual antenna to a half-wave dipole antenna, while EIRP compares it to a theoretical isotropic antenna. Since a half-wave dipole antenna has a gain of 1.64 (or 2.15 [[decibel|dB]]) compared to an isotropic radiator, if ERP and EIRP are expressed in watts their relation is
<math display="block">\ \mathsf{EIRP}_\mathsf{(W)} = 1.64 \times \mathsf{ERP}_\mathsf{(W)}\ </math>
If they are expressed in decibels
<math display="block">\ \mathsf{EIRP}_\mathrm{(dBm)} = \mathsf{ERP}_\mathrm{(dBm)} + 2.15\ \mathsf{dB}\ </math>