Plain-language answer: ERP is transmitter power after feed-system loss, multiplied by antenna gain referenced to a half-wave dipole.
Why the definition matters
It describes radiation in a specified direction and is used in some regulatory limits. It is not simply transmitter output power.
Use the number correctly
Use consistent linear units or decibels, include every feed-line and component loss, use dBd gain, and follow the regulator’s exact averaging and duty-cycle method.
The common mistake
Using dBi in an ERP calculation without converting the reference.
Measurement and safety boundary
Keep reference units, bandwidth, detector, direction, averaging, and test conditions attached to every number. Current regulator requirements and the complete installed system control RF-exposure compliance.
