GB490529A - Improvements in or relating to oscillation generators - Google Patents

Abstract

490,529. Valve generating circuits. TELEFUNKEN GES. FUR DRAHTLOSE TELEGRAPHIE. Feb. 15, 1937, Nos. 4542, 4543, 4544, 4545, and 4546. Convention dates, Feb. 13, 1936, Feb. 28, 1936, Feb. 28, 1936, March 27, 1936, and Sept. 7, 1936. [Class 40 (v)] Symmetrical saw-tooth oscillations are generated by arranging equal charging-resistances on each side of a condenser connected in parallel with a grid-controlled discharge valve ; alternatively each resistance may be in parallel with a separate condenser, and the valve connected between them. In Fig. 1, the condenser 10 is slowly charged through equal resistances 11, 12 connected to opposite poles of the supply source, and is abruptly discharged through a tube 13, preferably a hard vacuum tube, to the grid of which a synchronizing pulse is applied. The grid may be biassed by a source 14, or by a condenserresistance combination, Fig. 4 (not shown). The voltages of opposite phase at the terminals of the condenser 10 are applied through condensers 18, 19 to the deflecting-plates 16 of the cathode-ray tube 17, which plates are connected to earth by resistances 20, 21. The tube 13 may be connected as a back-coupled blocking oscillator 81 as shown in Fig. 10, and its grid circuit may include a resistance 85 connected to a rectifier 87 and a coil 86. A received carrier wave may be applied to the coil 86, and on receipt of a synchronizing signal represented by a low carrier amplitude, the negative grid bias applied by the resistance 85 is so reduced that the condenser 70 an discharge through the valve. A bias source for the valve 81 may be included in the grid circuit, Fig. 11 (not shown), or in the cathode lead, Fig. 12 (not shown) ; or resistancecapacity elements may be so connected, Figs. 13 and 14 (not shown). In a modified form of the invention, two separate condensers 39, 40, Fig. 6, are connected across the symmetrical resistances 31, 32. The condensers are abruptly charged when the tube 30 is conductive, and slowly discharge through the respective resistances 31, 32 when the tube 30 is blocked. The inner plates of the condensers 39, 40 are connected as before to the deflecting- plates 38. The tube 30 is shown as a hard vacuum tube in a blocking-oscillator circuit, but it may be replaced by a gas-filled tube, Fig. 5 (not shown), trigged by positive pulses on its grid. A hard vacuum tube without back-coupling may alternatively be used, the grid circuit including a condenser and leak resistance, Fig. 7 (not shown). The grid condenser is charged by grid current during the synchronizing-pulse, so that the valve is blocked until the charge has leaked away and another pulse is received. The voltage applied to the grid circuit of the tube 13, Fig. 1, may be of sine-wave form derived from an ordinary back-coupled oscillator with a tuned anode circuit, Figs. 8 and 9 (not shown). The grid circuit of the tube 13 then includes a condenser and leak resistance, arranged to block the tube whilst the condenser 10 is being charged. The condenser 10 may be of variable capacity and may be regulated jointly with the condenser of the oscillator anode circuit. The Specification includes a disclaiming reference to Specifications 426,537 and 459,998. Reference has been directed by the Comptroller to Specifications 473,650 and 482,725.