Short Antenna Characteristics-Theoretical

The experimental data obtained by Smith and Johnson on short antennas top-loaded by an umbrella were analyzed mathematically. The theory developed therein is within practical agreement with the measurements. It shows that, for single-tower operation, the horizontally polarized radiation is negligible. In addition, it is shown that with the optimum length of umbrella, the vertical radiation characteristic is the same as it would be from the radiator without top loading. The paper provides a tool for further investigation of other top-loading arrangements.