CONSIDERATIONS ON RAILROAD MAINLINE COMMUNICATION CABLES,

The MKBAB cables which are presently in lot production and which are used for railroad main trunks have filament-spiraled paper insulation of conductors. This cable provides hf multiplexing by a 12- or 24- channel system up to the 150-kHz range only for several quads 3 quads in a 7 quad cable and 5 quads in a 14 quad cable. The rapidly growing need for more channels necessitates the use of a more powerful system of 60 or even 120 channels which require a frequency range up to 252 and 552 kHz respectively. Therefore, in 1966, Soviet industry began mastered production of MKPAB 7x4x1.2 6x0.9 filament-spiraled polyethylene tube insulation of conductors. This cable has 0.3 neperskm attenuation at a frequency of 250 kHz and permits voltage of a remote power supply to be increased up to 900 v. Further improvement of the cable will be achieved by reducing the diameter of the conductor from 1.2 to 1.05 mm. This reduction in diameter will conserve copper and consequently reduce cable dimension and price without affecting the operation frequency range. In addition to the above-mentioned cable, a 16-quad cable with an inner shield 1-mm thick aluminum tube is proposed for a single-cable main trunk over which six 60-channel carrier systems can operate.