Abstract :
The paper sets out to show how the more fundamental problems encountered in the development of the commutated-aerial direction-finding system have been solved during a long-term development plan. Reasons are given for the choice of a circular array of aerials, which are commutated sequentially to the receiving equipment. It is shown how such an arrangement permits great economy in the number of aerials required for a given system performance, maximum adjacent aerial spacing being much larger than might at first appear permissible, and the method for computation of the signal bearing is described in some detail. Significant features of the development are described, particularly where problems are peculiar to the system, such as realization of adequate selectivity despite aerial commutation and the avoidance of the effect of aerial interaction. Final practical circuits are described for signal processing and demodulation, and for the display of bearing, and it is shown that the solutions adopted should permit realization of the performance predicted by theoretical study some 10 years ago. Although practical experience in the field is not yet large, adequate practical measurements have been made to substantiate most of the theoretical predictions with regard to performance.
