The effect of the ground constants, and of an earth system, on the performance of a vertical medium-wave aerial

The compensation theorem is used to determine the effect of finite ground conductivity, and of an earth system, on the performance of a vertical aerial, such as is used for medium-frequency broadcasting.The characteristics affected are the input impedance, the ground-wave field strength for a given aerial current and the vertical radiation pattern. The first two of these together determine the efficiency, which is the most important consideration in the design of earth systems. When the effective height of the aerial exceeds 0.1¿, little can be gained by the use of an earth system exceeding 0.2¿ in radius when the ground is highly conducting and 0.3 or 0.4¿ when it is poorly conducting. The effect of the earth system on the vertical radiation pattern is shown to be unimportant practically, but results are given for one case in order to compare with experimental radiation patterns. The agreement is quite good.