The antenna factor (AF) is a conversion factor between the field strength at the antenna and the input voltage at the input impedance of the RF receiver. It is determined by the ratio of the field strength at the antenna to the voltage
generated from it at the antenna output and characterizes the reception properties of the antenna. In a logarithmic representation, the antenna factor (dB/m) results from the electric field strength (dBV/m) divided by the generated voltage (dBV). On the other hand, the antenna voltage at the base of the antenna can be calculated from the field strength and the antenna factor.
The antenna factor is determined individually for individual antenna types and is used for the comparability of antennas and their generated voltages. Since the antenna factor is affected by reflections from buildings or from ground elevations, it is a prerequisite that measurements of the antenna factor are made in free space and that the polarization of the transmitting and receiving antennas are the same.