INSTRUMENTATION AND DEVICES FOR IMPROVING THE ISOLATION BETWEEN HF TRANSMISSION SYSTEMS.

The quality of a long-distance communication channel depends on the magnitude of the interference due to thermal and nonlinear noise of the amplifiers, and on the magnitude of the crosstalk. The crosstalk is caused by electromagnetic coupling between the cable circuits and is the main form of interference in balanced cable trunk-lines. The protection of the useful signal against interference is achieved during construction of these systems by reducing the crosstalk power. The required protection against interference must also be maintained throughout the operation of the HF transmission systems. A method for improving the isolation between the line circuits of HF transmission systems between two attended repeater stations is discussed. Structural and technical characteristics of instruments and devices are given which can be used to increase the isolation between HF transmission systems.