The development of a high-frequency cathode-ray direction-finder for naval use

The operation of the direction-finder described in this paper is based on the familiar principle by which two balanced amplifiers, connected to Bellini-Tosi crossed loops, operate the appropriate deflecting plates of a cathode-ray tube. The bearing is displayed as a trace on the c.r.t. fluorescent screen, providing a direct instantaneous reading. The sense of the bearing is obtained by combining the signals from an omni-directional sense aerial with the signal from either of the loops. The sense signal modulates the intensity of the electron beam, which is being swept, either vertically or horizontally, by the signal provided by the respective loop. The relative phase of the two signals is such that one or other end of the fluorescent trace is blacked out, depending upon which of the two lobes of the figureof- ight loop characteristic is effective for a given wave-direction. The first experimental equipment, designed for surface vessels, was already in operational use at the end of 1941, but the development proceeded until 1944, when the equipment reached its final form. With small modifications the same equipment was adopted for use at naval shore-stations, operating with an Adcock aerial system. The paper describes the latest design of the shipborne equipment and also discusses, more generally, some of the problems of the twinchannel receiving technique encountered during the development.