GB509842A - Improvements in or relating to indicator correcting arrangements for use in radio direction finding and other apparatus - Google Patents

Abstract

509,842. Indicating-apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., WRIGHT, G. M., and COCKERELL, C. S. Jan. 22. 1938, No. 2187. [Class 106 (iv] [Also in Group XL] Relates to an indicator correcting arrangement for use in radio direction finding and other apparatus in which a correction curve is superimposed upon the normal scale member. According to the invention, the reading edge or line of the indicator member is arranged to span a plurality of adjacent scale readings and to co-operate with the correction curve so that the intersection of the reading edge or line and the correction curve gives the corrected reading. In Fig. 1, the correction curve 3 is superimposed on the fixed annular scale 1 which is graduated with radial lines 2. The pointer comprises a transparent cursor 4 carried by the arm 5 which is rotated by the aerial shaft and the corrected reading is given by the intersection of the curve 3 and the oblique cursor line 7. The mark 8 gives uncorrected readings and facilitates the taking of "swing" readings when the received signals are too weak to allow accurate observation by the zero method. The transparent cursor may be replaced by an opaque pointer having an oblique or curved reading edge, Figs. 2, 3 and 6 (not shown). If the scale markings are oblique to the radius, the obliquity of the reading edge of the indicator may be varied and by suitably inclining the scale markings the reading edge may be radial, Figs. 4 and 5 (not shown). In any of the embodiments, the scale 1 may be transparent and illuminated from behind and the curve 3 may be drawn on a detachable transparent shield. According to the Provisional Specification, the correction curve may be positioned adjacent to the scale, in which case the reading edge of the indicator extends over the scale and the correction curve, the intersection of the curve and the indicator being projected on to the scale by radial lines drawn on the indicator. Specification 473,746, [Group XL], is referred to.