The feed point impedance of a half wave dipole antenna is best calculated using computer programs such as NEC2/4.1. However, a theoretical expression for the feed point impedance of a half wave dipole, remote from everything else , made of an infinitely thin conductor is 73 + j42.5 Ohms. for reference. This impedance is affected by the wavelength to diameter ratio of the conductors.used for the dipole. It is assumed that the signal source is directly at the antenna feed point. Please contact Signal Processing Group Inc., with further information on the modeling and simulation of antennas using NEC2/4 or FEKO