Reference Beam antennas and ERP.
Effective Radiated Power (ERP) is a standardized measure of the directional radio frequency (RF) power emitted by a transmitting antenna system. It is defined as the total power that would have to be radiated by a theoretical half-wave dipole antenna to produce the same signal strength (power flux density) at a distant receiver as the actual antenna system in the direction of its strongest beam.
ERP accounts for the entire transmission chain, calculated by taking the transmitter output power, subtracting losses from transmission lines and connectors, and multiplying the result by the antenna’s gain relative to a half-wave dipole.
The calculation is expressed as:
ERP=Pin×Gd
Where:
$P_{\text{in}}$ is the power supplied to the antenna (transmitter output minus line losses).
$G_{d}$ is the antenna gain relative to a half-wave dipole.
In decibel terms, this is often simplified to:
ERP (dBm)=Pt,dBm+Gd,dBd−lossesdB