Decoupling of Transmission Lines to Radio-Influence Voltages

Abstract

Theoretically, the R-C decoupler network has been shown to provide both better attenuation and impedance-matching characteristics. Reactive elements alone (L-C) may give sufficient attenuation, but their low-loss characteristic is likely to alter the RI performance of the source side, returning part of the energy of some impinging pulses while passing others so that pulse fronts, tails, and amplitudes are transformed. Two sets of field tests were made to determine whether several sections of transmission line could be satisfactorily decoupled or isolated to RI, using the R-C decoupler network with the resistance shunted, for 60-cps purposes, by a relatively high inductance. Although questions regarding correct line termination and line attenuation at higher frequencies have not been answered, use of properly designed RI filters or decouplers has been shown to provide a high degree of RI isolation between sections of line. The tests were intentionally made on a single-phase line with no ground wire. Extensive field investigations would involve 3-phase conductors, plus one or two ground wires. All these conductors must be decoupled to get proper results during simultaneous testing of different line sections. From previous tests at Tidd, it has been found that heating the conductors-so as to produce in them a few degrees of temperature rise above ambient-greatly alters the RI and corona loss obtained during fog, drizzle, and damp weather in general. Current for heating cannot be drawn through the resistors of R-C decouplers.