The performance of high-frequency direction-finders in various types of H.M. Ships

The reasons for the choice of the fixed crossed-loop aerial system, !for shipborne h.f. d.f. equipment operating on ground waves, are summarized. The problem of siting an h.f. d.f. aerial is discussed, with particular reference to the effects of vertical re-radiators and the hull. The importance of elevating the h.f. d.f. aerial above all the superstructure in a ship is stressed. Fitting and rigging requirements are stated; particularly those concerning the mast supporting the d.f. aerial, the insulation of stays, the condition of communication aerials, and the screening of the d.f. office. The method of carrying out a calibration is described. The method of estimating the overall accuracy of an h.f. d.f. installation is discussed, and the value of the maximum acceptable correction to d.f. bearings is estimated. Calibration results for some typical installations are shown, and a method of presenting these in the form of ¿performance curves¿ is explained. The performance curves for installations in various kinds of ship are given and analysed. The possibilities of improvements in performance are discussed.