Plain-language answer: ERP combines transmitter power, feed-system loss, and antenna gain referenced to a half-wave dipole in the stated direction.
Why it matters at the radio
It describes directional radiated power, not the transmitter’s front-panel number. Regulations may instead use EIRP, referenced to an isotropic radiator, so the reference must be named.
What to watch in the field
Begin with accepted transmitter power, subtract line and component losses in decibels, then add antenna gain in dBd.
The common misunderstanding
Mixing dBi antenna gain into an ERP calculation without converting the reference.
Learning boundary
This lesson explains established radio and antenna practice. Current regulations and the exact equipment or antenna guide control legal limits, ratings, compatibility, and safety.
