Patent GB-505036-A (GB)
Title: Improvements in or relating to tuning arrangements for radio transmitters
IPC: H03J1/02
Filed: 1937-11-03
Abstract: 505,036. Adjusting wireless apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and PARKIN, T. D. Nov. 3, 1937, No. 30146. [Class 37] [Also in Group XL] A shipboard or like radio-transmitter includes e, tuning indicator comprising a member adapted to be moved relative to a datum-indicating member for indicating any one of a series of timing positions, and means, e.g. a supplementary manual control knob, for simultaneously effecting tuning adjustment of the tramsmitter and adjustment of the datum-indicating member. A manually operated control shaft S<SP>2</SP>, Figs. 3, 4, drives through gearing G<SP>2</SP>, G<SP>1</SP>, the main annular disc M fixed to the shaft S<SP>1</SP> drivimg the tuning shaft. Shaft S<SP>2</SP> also drives through gearing G<SP>2</SP>, G<SP>4</SP>, a subsidiary dial D nested within dial M and rotated at e.g. ten times the speed thereof. The two dials are marked with equal scale divisions, a portion of the two scales being visible through a window W provided on the rear thereof with a hair line index E. Rotation of the shaft S<SP>1</SP> is thus indicated directly by the main scale member M subdivisions of which are read off more accurately by means of the subsidiary scale D. Spring loaded double gears may be used to prevent backlash, and a vernier scale or a second subsidiary dial rotated at a greater speed may be provided to co-oparate with the subsidiary scale D. The main dial could, alternatively, be located within the subsidiary dial. The front frame-plate P<SP>1</SP> is rotatably mounted in a panel P<SP>3</SP> and the device as a whole, i.e. the frame-plates P<SP>1</SP>, P<SP>2</SP>, the gearing carried thereby and the shaft S<SP>1</SP>, is rotatable about the axis of shaft S<SP>1</SP> by means of a knob on a shaft S<SP>8</SP> mounted in the panel and carrying a pinion G<SP>5</SP> gearing with the toothed edge of the rear plate P<SP>2</SP>. The frame-plate P<SP>1</SP> may be locked in adjusted position by a device LCX. This angular movement of the frame P serves simultaneously for effecting tuning adjustment and for adjusting the index H of the scales M, D, when the transmitter is monitored by a crystal controlled oscillator as set forth below. In a modification, Figs. 5, 6 (not shown), the main dial and driving gear therefor are combined, and the frame-plate P<SP>1</SP> rotatably mounted in the panel, is adapted to be looked in position by a nut on the shaft S<SP>3</SP>. The main and subsidiary dials may alternatively be graduated with the scales along their edges parallel to the shaft S<SP>1</SP> and worm or sun and planet gearing may be used. Monitoring. For comparison purposes, oscillations from the transmitter 11, Fig. 1, to be monitored, are applied through an aerial 9 to a known crystal oscillator circuit, variation of the transmitter frequency from that of the crystal oscillator or a multiple thereof producing audible beats in a telephone 6. The transmitter frequency is then adjusted as described above until no beats are heard in the telephone. In a modification, the crystal oscillator is coupled through a frequency multiplier valve circuit to a detector valve to which the aerial 9 influenced by transmitter 11 is also coupled, the correct transmitter frequency being, as before, indicated by absence of signals in the telephone 6.