Some principles underlying the design of spaced-aerial direction-finders

Abstract

The paper constitutes a theoretical and experimental investigation of the principal forms of the spaced-aerial or Adcock direction-finder. The analysis is concerned mainly with the determination of two important properties of the systems, namely their performance under the influence of downcoming waves and their efficiency as receivers of wireless energy. These characteristics are reduced to quantitative form by introducing the two factors named respectively and pick-up factor, and the various aerial-system modifications are studied with the object of showing how these factors may be predicted for aay given system and how they vary with the dimensions, wavelength, and other characteristics, and also with the constants of the ground on which the aerials are erected. The four principal aerial systems dealt with are the U type, the elevated type, the coupled type, and the balanced type. The of the type of directionfinders which is based on the principle of the closed loop or coil is first derived theoretically; it is found to be approximately 35° for a large range of wavelengths, and to be independent of ground conductivity and dimensions of the loop within wide limits. Experimental confirmation of this is obtained on short waves (20 to 50 m). The theory of the U type is then considered and the method of calculating the standard-wave error for any given case is worked out. The agreement between values obtained in this way and the experimental results is satisfactory. The effect of screening the horizontal members of the system is discussed, but no quantitative formula for calculating the effect of the screen is found to be obtainable. A description is next given of a series of experiments with the U type on short waves, the system being tested by means of locallygenerated downcoming waves of variable polarization. This method was employed to measure the effect of screening and burying the hor