Power-frequency induction on coaxial cables with application to transistorized systems

When d.c. is used for transmitting power to dependent repeaters in coaxial systems, long metallic circuits are formed of inner conductors which may be exposed to inductive interference from electric traction or power lines. A method is presented for evaluating the currents induced in the inner conductors, and the voltage induced between inner and outer conductors. Complete insulation throughout power-feeding section, earthing at one end of such sections and earthing of all outer conductors in the section are considered and it is found that complete insulation of the coaxial conductors and all associated equipment produces the best results. The current-in the above case-reaches a maximum when the induction takes place in the middle of the power section; the voltage is at a maximum at the ends of the exposed sector. For a given length and position of the exposed sector, currents and voltages are proportional to the induced longitudinal electromotive force; they increase with the length of the power-feeding section when the total longitudinal e.m.f. remains constant.