§ The system is an adaptation of the old Lorenz type of landing aid for aircraft and consists of a 3 cm. radar type transmitter mounted at a harbour entrance and radiating from two aerials which have overlapping beams. The transmitter is so sited that the line of intersection of the two beams is along a safe course line for entering harbour.
§ The output of the transmitter is switched in turn to each of the aerials in such a sequence that the morse letter B(- …) is transmitted from one aerial and the morse letter V(- -) from the other aerial. The characters of one letter are transmitted during the period of the space intervals between the characters of the other letter with the result that along the line of intersection of the two beams, where the amplitude of the signals from each aerial is equal, a continuous signal is received.
§ The ship's receiver is a pre-tuned crystal receiver coupled to a small horn aerial. The receiver and its power supplies are built around the horn, measure 4in. x 5in. x 5in. and weigh 4½ lb. The power supplies are provided by a 4½ volt flashlamp battery. An improved model of the receiver is supported on a rotatable searchlight mounting. This is intended for fitting through the wheelhouse roof of a small boat. The output of this receiver is brought out to a 'phone jack on the rotating arm into which a loudspeaker attachment may be plugged.
§ The trials and demonstrations of the apparatus have been carried out at Fraserburgh and Arbroath and the equipment operated very satisfactorily out to a range of approximaely seven miles from the harbour.
§ The device has thus been demonstrated to the fishing interests and radio manufacturers. Its future development and use is their responsibility. If they wish to pursue this project any further advice or technical assistance which my Department can give is at their disposal.