Transoceanic Telephone Service - Short-Wave Transmission

R U N K circuits between London and New York which furnish telephone service between these two cities and also permit successful conversation by means of toll wire extensions between the United States and Europe more generally are being carried over both long waves and short waves. It is the purpose of this paper to consider the transmission side of the new short-wave circuits which the American Telephone and Telegraph Company and the British General Post Office have made available for this service. In doing this we shall proceed from the more general considerations, relating to wave-lengths and communication channels, through a discussion of the principles governing the general design of the system, into a brief summary of practical performance results. The frequency range so far developed for commercial radio use is roughly 20 to 30 million cycles wide, extending from about 10 kilocycles to perhaps 25,000 kilocycles per second. There are two parts of this whole spectrum suitable for transoceanic radiotelephony--the longwave range which is relatively narrow, extending roughly from 40 kilocycles to 100 kilocycles, and the short-wave range which in its entirety is much broader, extending from about 6000 kilocycles to 25,000 kilocycles. It is evident that the long-wave region, including perhaps only 50 kilocycles, offers opportunity for development of relatively few telephone channels, particularly in view of the fact that it is in use by a number of telegraph stations. Also it must be borne in mind that for telephony these waves are suitable for only moderate distances of the order of 3000 miles and for routes in the temperate zones where static 1 Presented at the Winter Convention of the A.