<Dd> G dBi = 10 log ⁡ I I iso (\ displaystyle G_ (\ text (dBi)) = 10 \ log (I \ over I_ (\ text (iso))) \,) </Dd> <P> A second unit used to measure gain is the ratio of the power radiated by the antenna to the power radiated by a half - wave dipole antenna I dipole (\ displaystyle \ scriptstyle I_ (\ text (dipole))); these units are called "decibels - dipole" (dBd) </P> <Dl> <Dd> G dBd = 10 log ⁡ I I dipole (\ displaystyle G_ (\ text (dBd)) = 10 \ log (I \ over I_ (\ text (dipole))) \,) </Dd> </Dl> <Dd> G dBd = 10 log ⁡ I I dipole (\ displaystyle G_ (\ text (dBd)) = 10 \ log (I \ over I_ (\ text (dipole))) \,) </Dd>

The impedance represented by an antenna at its terminals