GB486889A - Improvements in or relating to tuning and other indicator and scale arrangements suitable for use for example in radio receivers or wave meters - Google Patents

Abstract

486,889. Adjusting wireless &c. apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., RUST, N. and LEVIN, N. Dec. 11, 1936, No. 34137. [Class 37] [Also in Group XIX] .In a. dial and pointer indicator for use in a radio receiver or wavemeter, for example, both the dial and the pointer are moved by the tuning or other device whose positions are to be indicated in coordinate directions so that the locus of the indications on the dial consists of a plurality of lines spaced apart along the dial and each extending across the scale at an angle to the direction of movement of the scale. As shown, applied to a radio receiver, the tuning shaft CGS is rotated by a slow motion knob SM through gearing F, E, C, D, B, A, and the tuning scale 7 rotates therewith. The solid wheel D is slotted at 8 and a fixed lamp and optical system 9 projects an image of the slots in succession on to the moving scale 7 by means of mirrors 10, 11 such that the image 8<1> traverses substantially radial lines 71 on the scale 7 in succession as the tuning shaft is operated. The lines 7<1> are calibrated with station names or other markings in the 17, 19, 25, 31 and 49 metre wave-bands, the medium and long wave band stations being indicated in known manner on fixed scales 3, 2, on a disc 6 co-operating with a pointer 1 on the tuning shaft. Further fixed scales 4, 5 for short wave ranges may also be provided. For approximate tuning, a fast motion knob FM is pressed in against the action of a biassing spring to uncouple the gears C, D when the tuning shaft is adjusted by knob FM through gearing B, A, the image 8<1> on the scale 7 being de-focused during approximate tuning by the axial displacement of wheel D. Modifications. The slotted wheel 8 may be replaced by a mirror wheel rotated by the tuning control, or the slots 8 may be replaced by lenses, and an arrow-head or other pattern image 8<1> produced as the actual indicator. Alternatively, the indicator may be a shadow on an illuminated scale. The scale 7 could be, for example, an endless tape moved longitudinally by the tuning control, there being one tape, if desired, for each wave range and an indicator for each. Calibration. The scale 7 is conveniently made in strip form of material to take pencil markings which may be erased, the receiver being lined up for known stations in each band before attaching the corresponding strips: Alternatively, cam actuated switches operated by the tuning shaft may set trimming condensers to adjust the local oscillator frequency as required for each wave-band, or a separate trimming condenser with its own scale and adapted for use either in actual reception or for factory setting, could be provided.