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Aviation History
1945
1945 - 0540.PDF
306 FLIGHT The A SemUautomatuyWireless Direction-findirik Device for/Use in Aircraft By CHARLES B. BOVILL, A.M.l.E.E./A.M.Brit.l.R.l ALTHOUGH recen^public statements indicate thatKadai will eventuaSjy be the means of providingthjL greater part of navigational aid fjsff be realised that when hostilities" cease ffieaefacilities will not be available throughout the world, and that it can be expected that some years will elapse before the necessary ground installations can be working on an organised basis. It is, however, likely that broadcasting stations will be working in all civilised countries within a few months of the end of the war, owing to the fact that very many of them are intact still, if not working. As is already wgli known, any wireless transmission on long or medium waves can be used for navigational aid by an aircraft equipped with wireless direction-finding appara- tus. Just how useful an aid radio signals are considered to be can best be judged by the precautions taken by the enemy when an Allied air raid approaches the Reich. Under such conditions "technical hitches" occur at broadcast stations, which are almost invariably followed by them going oft the air ; these tactics are, of course, solely intended to prevent our aircraft from using the signals for direction- finding purposes. In pre-war days the uses of wireless direction-finding were^rolly recognised, and many aircraft were fitted with B r- loojj^e<fuipment which j|Fas extensively used. It must be Emitted, howeter, thpt the use of such equipment pre- sented cornplications^tnd called for the closest co-operation between the radio Operator and the pilot of the aircraft. A certain amoug^of calculation was also required, all of which took time and led to errors in the final result. The outcome of this was that while loop navigation was con- sidered useful, it was not generally regarded as being a primary navigational aid. Wartime Development During the war much development has taken place in the whole technique of direction-finding, and many of the hitherto less well understood problems have been fully investigated. This work has made possible considerable improvements to apparatus^ and to aircraft installations. Among these are rec£i*€fs which are more simple to.- operate, and visual indication of bearings in place of the old method of aural indication, in which the operator had to swing the loop to the position at which no signal was audible in order to obtain a bearing. Research has also been carried out into the causes of inherent errors of loop installations in aircraft, such as quadrantal errors, which cause bearings to crowd or spread in various parts of the scale. The overall result has been a general improvement in the accuracy with which bearings can be taken from loop readings in an aircraft. By a combination of the latest radio technique with the repeater master compass, a device has recently become available with which loop bearings of a very high order of accji»rfc'y may be obtained from any receivable signals on medium or long waves, all without calculations and consequent delays and risk of errors. This device is known as the Mar- conator and is a development due to Marconi's Wireless Telegraph Co., Ltd., Chelmsford ; it is designed for use with the standard Air Ministry Genera! view of the Marconator : (A) Cover of keyway for initial alignment of compass repeater scale ; (B) Drift scale ; (C) Head of aircraft with respect to true north ; (D) Cursor ; (E) Fixed scale, showing bearing relative to aircraft's head ; (F) Visual indicator needle (shown aligned with Cursor) ; (G) Illumination dimming control ; (H) Signal amplitude monitor, shown in correct central posi- tion ; (I) Distance-reading-compass repeater scale (true) ; (J) Fixed silhouette of aircraft, providing mental picture of orientation. I. Chance position of Cursor at start. Turn Cursor towards Needle.
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