GB542847A - Improvements in or relating to arrangements adapted to minimise the effects of the impedance of the earth wire or earth bus-bar in high-frequency electric circuits - Google Patents

Abstract

542,847. Transmission circuits. SIEMENS BROS. & CO., Ltd., and MOLE, J. H. Sept. 27, 1940, Nos. 14650/40 and 6/41. [Class 40 (iv)] [Also in Group XL] When apparatus involving an earthed busbar, such as a valve amplifier or an iterative impedance-network, is employed with a circuit which is earthed at another point, currents may circulate through the bus-bar and the earth-connections with undesirable results. To prevent this, the input or output circuit is provided in each wire with a choke coil, the two coils being tightly coupled so that they offer no substantial impedance to the loop currents. The choke coils may be in the form of a coil of co-axial cable and either or both may be tuned as by a condenser 11 connected to the outer conductor. In the arrangement shown in Fig. 1, the apparatus concerned is a submerged repeater including a filter 7. The impedance of the bus-bar should be as small as possible and the elements of the circuit should have as small a mutual inductance as possible with the bus-bar and any other path for the unwanted currents. In an impedance network, each element may be screened and the connecting wires may be led through pipes branched from a main pipe which constitutes the busbar. The branch pipes may be omitted if the terminals of the elements are arranged near to the main pipe or if co-axial cable is used for making the connections.