The design of transmitting aerials for broadcasting stations

The paper is divided into two sections and a conclusion. The first section gives the theory of the aerial as a radiator, with special reference to its ability to radiate rays parallel to the surface of the earth at its base. An account is given of experiments with different types of aerial designed to achieve this result. The reduction of the indirect ray, that is the ray producing a component of radiation at angles less than 90° to the vertical, should produce less fading of signals, and theoretical predictions are made as to the extent of such reduction. An account is given of practical tests on the fading of signals from different forms of aerial. There is some discussion as to how the desired results can be achieved in practice, having special reference both to the use of T aerials and very high masts. The second section deals with the theory of attenuation of waves having frequencies between 500 and 1 500 kilocycles per second, and gives a complete set of curves actually taken from a transmitting aerial near London. The conclusion sums up the results and gives data to enable the broadcasting engineer to specify, in general terms, the extent of service area and the effectiveness of the service to be expected, using a given power, frequency of emission of carrier wave, height of aerial and earth conductivity.