L5 System: Repeatered Line

The basic function of the L5 repeatered line is to provide a lossless transmission facility between any two L5 terminal stations, which may be located as far as 4000 miles (6400 kilometers) apart, with minimum noise penalty. The objective is to establish and maintain the insertion loss of the 4000-mile line over the message band to be within ±4 dB and the noise to be less than 39.4 dBrncO in any of the 10,800 channels transmitted. The transmission medium for the L5 line is the standard Bell System 0.375-inch disc-insulated coaxial cable.1 This cable has a loss* that can be conveniently expressed as follows: Cable loss (dB/mile) = 1 + - * A 2.1-percent factor has been included in this loss to account for miscellaneous factors such as stranding. 1935 Fig. 1--Equalization strategy.