GB207526A - Improvements in radio receiving systems - Google Patents

Abstract

207,526. British Thomson - Houston Co., Ltd., (Assignees of Rice, C. W.). Nov. 21, 1922, [Convention date]. Addition to 183,838. Undesired signals, elimininating; thermionic amplifiers and detectors.-Strong interfering signals are eliminated by coupling the aerial to an artificial line having an effective length equal to several wave lengths of the signals, and by coupling the receiving set to the artificial line at two different points, which are so chosen that the interfering signal waves neutralize each other, whilst the desired waves produce a resultant effect in the receiver. As shown in Fig. 1, the aerial 2 is coupled to an artificial line 1 which is open ended so as to produce stationary waves due to reflection from the open end. A coil 3 is coupled to the line near its open end, and is converted in series with a coil 4 coupled to the line at a'point where the interfering signal wave is in opposite phase, this position being found by trial. The two coils are connected to a detector such as a valve 5. In a modification shown in Fig 2, a resistance 6 is connected across the end of the line 1 so as t.o prevent reflection. The line is directly coupled to the aerial 2 and the coil 4 is variably coupled to a coil at the aerial end of the line 1. The coil 3 is adjusted along the line and the degree of coupling of the coil 4 is varied until undesired signals are balanced out. A reaction coil in the plate circuit of the valve is coupled to the aerial or to the grid circuit to compensate for losses in the line. Additional coupling coils may be used to neutralize other interfering waves.