Abstract :
Direction-finding practice in Britain is reviewed over the frequency band 10kc/s¿400Mc/s; the survey is restricted to land-based systems. Current applications are outlined, the factors affecting accuracy are discussed with particular reference to those concerned with propagation, and equipment is described. The applications are numerous, ranging from location of thunderstorms at the lowest frequencies to widespread aeronautical uses at the highest frequencies. Over the lower parts of the frequency range the effects of the ionosphere on accuracy have to be borne in mind in many of the applications. In the v.h.f. and u.h.f. bands these limitations are absent for short-range working and the accuracy is determined largely by site and instrumental properties. The majority of direction-finders in current use have fixed aerial systems, the most common being the Adcock type. At the lower frequencies, however, loops are used, and wide-aperture systems having circular arrays of aerial elements are rinding application at the higher frequencies. Regarding the display of bearing information, although some use is still made of the aural-null method, automatic presentation of the bearing either on a meter or on a cathode-ray tube is generally employed. For aeronautical purposes in the v.h.f. and u.h.f. bands, where development has been particularly marked, remote control of the equipment and remote display of the bearings (on a number of frequencies simultaneously, if required) are of increasing importance. The paper also includes a description of automatic position-fixing systems for which these remotely operated instruments are especially adapted.
