Application to Radio of Wire Transmission Engineering1

This article points out that radio and wire communication systems are subject, fundamentally, to the same general requirements, and its purpose is to develop for radio, points of view which are familiar to wire transmission engineers. The transmission characteristics over a wide range of distances are compared. For short distances the comparison is favorable to wires. Although over great distances, the attenuation of electric waves, guided by wires, may be greater than the unguided waves of radio, it is pointed out that at the present time intermediate amplifiers can be more economically applied in wire transmission than in radio to boost the message energy. Economy of transmission requires the handling of messages at as low an energy level as possible and, as the author points out, wire transmission satisfies this requirement much better than radio. Referring to the transcontinental line with radio extensions, which was used recently to talk from Catalina Island in the Pacific Ocean to a ship in the Atlantic Ocean, it is stated that had all of the necessary energy been introduced at one end of the circuit, there being no intermediate amplification, the total power required would have been 1.8 × 1029kilowatts, an amount unavailable in the world. In the actual system, distributing the amplification along the transmission line, the power required sums up to something less than 1 kilowatt. Interference between messages and extraneous disturbances is discussed, and the requirements involved in keeping message energy well above the energy level of the disturbances in both systems are pointed out. The limitations on two-way operation resulting from “singing” of the entire system are considered for both cases and for combination wire and radio circuits as well. The method of improving the efficiency of transmission by suppressing the carrier and one side band is discussed. Finally the factors involved in obtaining high grade quality of transmission are enumerated. — Editor.