Amateur Radio

Power converter

Watts to dBm, dBW, ERP, and EIRP. Bidirectional with antenna gain input.

Power converter
0 for isotropic, 2.15 for a dipole
Watts --
dBm --
dBW --
ERP --
EIRP --

Watts, dBm, and why

Decibels are ratios, not absolute values. dBm is referenced to 1 milliwatt. dBW is referenced to 1 watt. ERP (effective radiated power) adds the antenna's gain relative to a dipole. EIRP adds the gain relative to an isotropic radiator, which is 2.15 dB higher than ERP for the same setup.

FCC power limits for GMRS are specified in ERP. Amateur limits are specified in PEP (peak envelope power) at the transmitter output, before the antenna. Knowing which number the regulation uses matters.