The phase and magnitude of earth currents near radio transmitting antennas

Abstract

This paper deals with various electrical magnitudes involved in the process of radiation from an ordinary antenna. The calculations presented are based on the simplified assumptions of a highly conducting earth and a sinusoidal distribution of antenna current. Also, they neglect any components of the near-by field that may be associated with the flat top. The paper is divided into four main parts and an appendix. In the first party the relative magnitudes and phases of earth currents associated with radiation from antennas of four representative proportions are calculated. The results are shown in Figs. 3 and 4. In the second party both the displacement current density and the electric intensity are studied quantitatively. The results are shown in Fig. 5. The third part consists of an experimental verification of the calculated magnetic flux near an antenna. The agreement is evident from Fig. 6. In the last section, the theory is applied to a simple half-wave antenna with a view to localizing the earth losses. These are found to be greatest at a distance from the base of the antenna of 0.35λ. This is indicated by Fig. 7. An appendix points out the magnitude of error in neglecting components of the near-by field associated with the fiat top.