| 摘要 |
454,341. Valve circuits. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and BLIGH, N. R., STENNING, L. C., and STEWART, J., c/o General Electric Co., Ltd., Wembley, Middlesex. Feb. 26, 1935, No. 35253. Divided application. [Classes 40 (iii) and 40 (v)] Remote tuning of a wireless receiver is effected by a variable reactor constituted by a network including a thermionic valve which may simulate an inductance or capacity and is variable by changing the mutual conductance of the valve by varying its grid bias from the remote point. In Fig. 2, the anode of the valve V is connected to its cathode through a resistance R and condenser C in series, the common point 5 being connected to the grid. Condenser 15 and inductance L are a blocking condenser and choke respectively. The condenser C0 is the one to be tuned by a variable inductance and to this end the grid bias of V is varied by a potentiometer 9, 16 being a series choke of large inductance. The anode circuit may be transformer-coupled to the grid circuit at point 3 instead of condenser 15, Fig. 3 (not shown). With these arrangements the network behaves as a variable inductance across C0. In Fig. 4, the arrangement acts as a variable capacity by virtue of the addition of a further amplifier 20, which increases the variations in mutual conductance of V due to grid bias changes. The junction of R1 C1 is joined to the grid of 20 across which is connected a further combination R2 C2 with junction connected to the grid of V. The potential at point 26 lags 45‹ in phase behind that at point 3, and the voltage of anode 23 thus leads that of point 3 by 135‹; that of the grid 6 therefore leads 3 by 90‹ and the network behaves as a capacity variable by potentiometer 9. A mathematical exposition of the effect of varying or adding to the constants of the network is given. Specifications 360,891, 369,112, 378,256, and 420,687 are referred to. |
