GB461192A - Improvements in or relating to high frequency electric transmission lines - Google Patents

Abstract

461,192. Distributing music &c. MANIFOLD, M. BOWMAN-. Aug. 8, 1935, No. 22453. [Class 40 (iv)] [Also in Group XL] In a carrier distribution system, reflection is avoided by including the load 7 at each tapping point in the shunt arm of a resistance T-network having an impedance equal to the characteristic impedance of the line. The load may be one or several receivers. Where the line is used for two carriers having widely different frequencies, e.g. À5 to 1À5 megacycles for sound signals and 40 megacycles for television, the networks are provided with tuned circuits to give the impedance of the shunt arm different values at the two frequencies, the impedance being still substantially purely resistive at both frequencies. This is necessary to ensure that all receivers at both frequencies receive signals at the same level. As shown, the circuit 14, 15 is tuned to the high-frequency and acts as a short-circuit to resistance 12 at the lowfrequency ; alternatively, a series tuned circuit tuned to the low-frequency may be employed. In further modifications, the shunt arm is constituted by a resistance in parallel with a circuit including in series a second resistance and a series resonant circuit tuned to the lowfrequency, or a parallel resonant circuit tuned to the high-frequency. Design formulae are given in the Specification.