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Wireless & Mobility · Foundational

Effective Isotropic Radiated Power (EIRP)

The highest signal strength radiated from an antenna: transmitter power minus cable loss plus antenna gain.

Definition

EIRP represents the power an isotropic radiator would need to produce the same peak signal as the actual antenna in its strongest direction. It is calculated as transmitter output (dBm) minus cable and connector losses (dB) plus antenna gain (dBi). Regulators such as the FCC set EIRP limits per band.

Example

20 dBm radio - 3 dB cable + 6 dBi antenna = 23 dBm EIRP.

Exam tip

EIRP includes antenna gain; the intentional radiator power does not.

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