Radio age research, manufacturing, communications, broadcasting, television (1941)

Solving a Radio Traffic Problem By E. A. Laport Director, Communications Engineering, RCA c /ONTINU1NG expansion of high-frequency radio service making use of rhe limited frequency spectrum provided by nature has created a world-wide communica- tions traffic problem of major proportions. The result has been increasingly serious interference among sta- tions close to one another in the frequency band, re- ducing the efficiency of radio communications in fixed and mobile services operated by private, public and government agencies here and abroad. A long stride toward solution of the problem has now been made by RCA with the development of a new two-way radio system which cuts bandwidth re- quirements by half, yet is comparable in cost and sim- plicity to widely used conventional systems employing twice as much of the frequency spectrum. This new equipment is usable for telephony, manual telegraphy, and teleprinter operation over short and medium dis- tances in both fixed and mobile applications. Also, it is adapted to use by non-technical personnel for many of the simpler telecommunications requirements around the world, with utmost bandwidth conservation. We have designated the new system as the SSB-1 — the initials standing for the single-sideband technique which cuts the bandwidth requirements of the system. While single-sideband technology has been in use for three decades, it has been almost exclusively confined to wire-line carrier systems and long-haul radiotelephone circuits. In the form in use up to now, its cost and complexity have been beyond the means of most high- frequency users. Advantages of the New Equipment In the new RCA equipment, single-sideband tech- niques are provided at a cost that is of the same order as that of the conventional amplitude-modulated (AM) equipment of comparable power employed by most of these services today. At the same time, it can be in- stalled and used by people of little or no technical skill, and it is applicable to both one-way and simultaneous two-way forms of communication. With this develop- ment, it becomes possible to use single-sideband trans- mission for short-haul systems wherever conventional AM is now used. The SSB-1 was developed for the RCA International Division by an engineering team under the direction of K. L. Neumann, Supervisory Engineer, Radiomarine RCA's new single-sideband radio is demonstrated by K. L. Neumann, of Radiomarine Corporation of America, who directed its development. Corporation of America. During the summer, it was tested extensively in communication between fixed shore stations of Radiomarine and vessels on the Mississippi and Ohio Rivers. In these tests, the new equipment showed consistently satisfactory performance at all dis- tances up to the available maximum of 920 miles, and it proved its ability to communicate with conventional AM equipment aboard the vessels. More recently, units have been acquired by the United States Coast Guard for study and testing in both fixed and mobile applications. Using these units, the Coast Guard has conducted demonstrations for other interested government agencies, including the Federal Communications Commission and the Civil Aeronautics Authority. The interest of the FCC in single-sideband techniques already has been made known, and the Commission has urged study of these techniques by users and manufacturers to provide a sound technical back- ground for future consideration of proposals to increase use of single-sideband operation by a variety of services that now use radiotelephone on frequencies below 25,- 000 kilocycles. RCA is now making the SSB-1 available com- mercially through the RCA International Division in foreign markets, and through rhe Radiomarine Corpora- tion of America in the United States. We expect that it will contribute substantially to reducing frequency congestion and interference among stations. RADIO AGE 27