Definition of Effective Radiated Power(ERP)

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ERP(Effective Radiated Power) is a calculated measurement that describes the peak transmitted power output of the system. It is measured in Watts, and includes peak transmitter power, transmission line losses, and peak antenna gain(as compared to a half-wave dipole).

The formula for calculating ERP is:

ERP = Transmitter Power * Feedline Loss * Antenna Gain

For example, if you hooked your 2 Watt MURS handheld to a 3dB gain rooftop antenna, thru a 50ft. coax cable having a total loss of -3dB, the gains and losses would cancel, and you would have an ERP of 2 Watts.

FCC Definition of ERP

TITLE 47 -- TELECOMMUNICATION
CHAPTER I -- FEDERAL COMMUNICATIONS COMMISSION
PART 2 -- FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS
Subpart A -- Terminology
Sec. 2.1 Terms and definitions.

Effective Radiated Power (e.r.p) (in a given direction). The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction."

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