Patent GB-315219-A (GB)
Title: Improvements in amplifying systems employing thermionic valves
IPC: H04B1/036
Filed: 1929-07-01
Abstract: 315,219. British Thomson-Houston Co., Ltd., (Assignees of Weir, I. R., and Richardson, L. W.). July 9, 1928, [Convention date]. Transmitting systems and apparatus; thermionic generators.-A high frequency transmitting system, comprises symmetrically arranged, push-pull connected valves, having an output inductance coil joining their anodes, tuning being effected by movable conducting bodies arranged between the valves and their housing, or by a conducting body located within and rotatable with respect to the inductance. The valves 1, 2, Figs. 1, 4, 5, are arranged in a housing 6, from which is supported between the valves on members 6<1> an input inductance 5. Below the inductance 5 and between the water-cooled abodes, surrounded by water-jackets 3, 4, is located an output inductance 11 consisting of water-cooled copper tubing, joined electrically at its ends to the valve anodes, and also to the water-jackets 3, 4, by means of conducting water-connections 12, 13. Variable neutralizing condensers 20, 21, shielded by plates 18 are mounted, preferably between the valves and the housing 6, the plates 18 being supported from the base of the housing by insulated supports 19. The stationary plates 22 of these condensers are supported from plates 18 by members 23, 24, and the moving plates 27, are carried on shafts 28 driven by worm gears 29 and shafts 30 controlled from the front of the panel 59 comprising one of the side walls of the housing 6. The condensers 20, 21, are connected, as shown in Fig. 5, which also shows the anodes of valves 1 and 2 connected through the coil 11 and the grids through the coil 5, the anode circuits being energized from a source 31, the negative side of which is connected to the valve cathodes and housing 6. Grid bias from a source 32, is connected between the housing 6 and the mid point of coil 5. To vary the oscillation frequency conducting plates 33, 34, are provided supported from and connected to the housing 6 by a shaft 35, and may be rotated into proximity with the plates 18 through worm gears 37 and shaft 36 extending through the panel 59, the plates 18 being connected to the anodes of the valves. Additional tuning means, comprising a member 38 of copper, aluminium, &c., rotatably mounted within the coil 11, may be provided, while a portion of each end of the coil may be short-circuited by switches 75, 76. Controlling high-frequency potentials from a source 67, are supplied to the contacts 61, 62 on the coil 5 through slip-rings 43, 44 mounted on a shaft 42 coaxial with the coil actuated by handle 47. Supports 45, 46 attached to the shaft 42 within the oppositely-wound halves 39, 40 of the coil 5, and connected to the slip-rings 43, 44 by leads 48, 49, carry the coil-contacts 61, 62 which may be advanced towards or away from the centre of the coil, connected to a slip-ring 41, by rotating the shaft 42. In a similar way, the gridcontacts 65, 66, may be moved along the coil, by rotating the whole coil which is mounted on insulators 54, 55 attached to supports 52, 56, controlled by a handle 58, which may be locked to the panel 59 by a device 60. The supports 63, 64 for the contacts 65, 66, are connected to the valve grids through junction contacts 7, 8, and short leads 9, 10. A brush 69 engages the central slip-ring 41. After adjusting the position of contacts 61, 62, the handle 47 may be locked to handle 58 by a device 70, and the contacts 65, 66 adjusted without affecting the position of contacts 61, 62. For tuning purposes additional capacity may be connected across contacts 7, 8, but at the higher frequencies inter-electrode capacities allow the coil 5 to resonate.