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

COMMUNICATIONS WITH WINGS Aoiathn Radio. After 25 Years of Research, Becomes Indispensable In Modern Warfare —Many Improvements Are Secret By H. M. Hucke Manayer, AviatiuH Radio Sales RCA Victor Division AS the United Nations intensify _/\ their offensives apainst enemy forces, with swarms of bombers and supporting fighters daily growing ill number, aviation radio becomes increasingly important in military strategy and tactics. Without ade- quate radio equipment to guide the planes and direct their activities, the extent of the powerful blows would be severely limited. With these aids, difficult missions are carried out with complete success. And yet, startling as the devel- opment of aviation radio has been during wartime, behind today's ac- complishments are 25 years of un- ceasing research. While records show that both radio and aviation had their begin- nings in the earliest days of this century, nearly two decades passed before these great mediums of com- munications were united for prac- tical use. The Wright Brothers made aviation history at Kitty Hawk in 1903 and Marconi trans- mitted the first trans-Atlantic wire- less mes.sage in 1901, but little progress was made in practically adapting radio to planes until 1919. the year the Radio Corporation of America was founded. Radio transmission and reception in planes had been tried earlier but only in telegraph code. At the end of World War I, the use of two-way voice communication was in its first stage of development. Engineers faced severe handicaps. Radio equiiiment was bulky and heavy; planes had little available space and less weight-carrying ability, and the range of the most powerful transmitting sets was extremely limited. But, as plane designers im- proved their craft, radio kept pace until today the communication needs of the aviation industry can be met to the highest degree by radio apparatus tailor-made to the requirements, whatever they may be. How the two vital communica- tion mediums continued to march ahead in step during the past quar- ter century is best told in a brief history of air transportation. In the early 1920's, the U. S. Post Office Department began to carry mail between a limited number of Eastern cities. At first the pilots operated their routes without the aid of radio but shortly, radio equipment salvaged from the war, was installed. Results were only fair. Pioneer Tests in 1919 Radio first demonstrated its place as an adjunct to plane travel in May 1919 when the Navy flying boat NC-4 flew the Atlantic via Newfoundland and the Azores. Through its transmitting and re- ceiving equipment, the big plane maintained communication with ground stations on both sides of the Atlantic and with Navy destroyers and other vessels stationed along the water route. One of the radio operators assigned to that history making hop was Harry Sadenwater, now engineering products sales manager of RCA's New York Re- gional Office. Results of the flight pointed up the necessity for a network of ground stations to make up for the low power of the plane's transmit- ters and the use of low freciuencies which travelled only short distances. Eventually, the development of short waves, which reflect from the Heaviside layer, made it possible to cover great distances with a minimum of power. This was dem- onstrated in 1925 when the Navy AIRCR.AFT RADIO EQUIPME.NT IS SUB- JECTED TO ARCTIC WEATHER IN A CHAM- BER COOLED TO —40°C. dirigible Shenandoah, equipped with short wave apparatus, com- municated with amateurs in all parts of this country as it soared from coast to coast. Two years later, Maitland and Hegenberger flew from San Fran- cisco to the Hawaiian Islands with the aid of long wave radio beacons. These "radio lighthouses" were the forerunners of the system installed by the Department of Commerce on all domestic airways in 1930. After the Post Otfice Department contracted with commercial airlines to carry the mail, additional com- pensation was provided the carriers to cover the cost of installing two- way radio equipment. This resulted in the installation of complete two- way voice systems on most of the routes. A few continued to use code, a practice that is retained today on trans-oceanic lines. Voice Transmission Favored On domestic routes voice trans- mission v.-as preferable. It gave the pilot man-to-man contact with the dispatcher and weather man on the ground. It also increased the payload by eliminating 160 pounds of radio operator. Up to the time the commercial airlines entered the picture, the de- velopment of aviation radio had been carried on by the U. S. Signal Corps, the Navy and to some extent by amateurs and an occasional ad- venturous small manufacturer. These Government departments were kept short-handed by the small appropriations of a peace- minded Congress and like the bulk of the aviation pioneers, were [16 RADIO AGE]