Abstract :
The attenuation of waves in a coil-loaded telephone line is calculated on the assumption that the line acts as a smooth equivalent and that the rising attenuation loss towards the ¿cut-off¿ is due to a multiple internal reflection effect. The reflection effect is derived analytically as a function of frequency and expressed as a ¿section watts reflection loss-coefficient¿ which gives the actual percentage power dissipated per section as a result of internal reflection. The function is evaluated for 10-lb., 120-mH, 2 000-yard cable and is shown to rise asymptotically to the known ¿cut-off¿ of the cable. A new form of attenuation/frequency equation is then evolved from the ¿section watts reflection loss-coefficient¿ and the theoretical results are cpmpared with very carefully controlled attenuation measurements on an actual cable. Remarkably close agreement is shown between theoretical and practical results. The conclusion is reached that the attenuation loss in a coil-loaded line is the quantitative resultant of the smooth equivalent line loss and the loss specified by the section watts reflection loss-coefficient. The conclusion demonstrates the mechanism of transmission over coil-loaded lines.
