Experiments with Yagi aerials at 600 Mc/s

An account is given of experiments leading to the design of 600-Mc/s radar aerials of Yagi type, suitable for mounting on naval gun-control directors. The basic array finally adopted had eight director rods, and a semi-circular cylindrical sheet reflector. Two such arrays, one for transmission and one for reception, were mounted with a separation of 1¿ wavelengths on pom-pom directors; numbers of these arrays were fed in parallel as aerials for larger directors. The transmitting and receiving aerials on each director were later combined for common-aerial working, and beam-switching technique was applied by suitably phasing the currents in the dipoles. The performance characteristics of the above aerials are described. The experimental results show that when a number of Yagi arrays are fed in parallel with comparable powers and phases, the interaction between the arrays has only a small effect on the radiation pattern if the arrays are more than a wavelength apart. The overall radiation pattern is then given by the product of the radiation pattern of one of the arrays and a ¿group factor¿ calculated on the assumption of a point source of the necessary amplitude and phase at the centre of each array.