The complex antenna factor (CAF) of a dipole antennaa with a balun is evaluated by calibrating the S parameters of the balun and calculating the effective length of the antenna element in the frequency range of 600 MHz to 2 GHz. The result is compared with that of the conventional 3-antenna method. The obtained values of CAF by the two methods agree in their absolute values up to 1.2GHz, Concerning the phases of CAF, two results are close in the whole hand.