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

forced to get along with the sal- vaged left-overs from ^\'^)rld War I. Airmail income, however, stimu- lated the airlines. They had suffi- cient funds even in the depression years of 1931-1935 to maintain sub- stantial radio laboratories. For this rea.son, the period from 1929-1940 might be called the "Airline Era." Radio designs and procedures pro- gressed : Congress opened its purse to the PJureau of Air Commerce and its successor, the Civil Aeronautics Authority, and many worthwhile radio refinements resulted. Radio Compass Widely Used One of these new developments, the long-wave radio beacon, has been mentioned. Others were the two-way voice system, the radio compass, the shielded loop and the automatic direction finder. At first the two-way voice sys- tem had only a single channel. This was inconvenient due to the neces- sity of having separate frequencies for day and night. With only one channel, pilots were forced to stop at daybreak and again at dusk to retune transmitter and receiver. Consequently, the two-channel quick frequency shift was a natural ad- vance in design. Later the airline traffic increased so greatly that many frequencies were needed in crossing the continent. Today, ten quick shift channels are used in both aircraft and ground stations. The radio compass provided means for homing on broadcast stations or radio beacons. Private flyers who flew off airway routes adopted it at once because of its value in using broadcast transmit- ters as guides. The Army became still another enthusiastic booster for the compass and for the same reasons. Airlines remained satisfied with the beacon system until RCA first suggested that they try the anti- static qualities of the metallically shielded loop which had been devel- oped by the Radio Marine Corpora- tion of America for use on steam- ships. Tests were successful and the Civil Aeronautics Authority, in 1937, made its use mandatory as a safety feature. This step brought aural-null direction finding into use on all airlines. About that time RCA and Sperry Gyroscope Co. combined their tal- ents to develop the automatic direc- tion finder. This soon found favor with the airlines, since it gave an immediate azimuth indication with- out changing the course of the air- plane as was necessary with the radio compass. It also retained the anti-static properties of the metalli- cally shielded loop without the necessity for turning it by hand. Sky-wave Effect Reduced One of the first refinements in the radio beacon was the Adcock system, w-hich greatly reduced sky- w-ave course distortion. The Adcock also had a sharper cone of silence indication over the station and it became necessary to develop a more positive system for indicating when the pilot had reached his destina- tion. Fortunately, the ultra-high frequencies had been developed by that time and a 75-megacycle ground transmitter which sent a vertical beam upward solved the problem. The airplane receiver was relatively simple except that its out- put was arranged to turn on a light when the airplane passed through the beam. During the early part of the "Air- line Era" the manufacturers, air- lines and Army and Navy made various efforts to develop equip- ment for testing radio apparatus under simulated altitude, tempera- ture, vibration and humidity con- ditions. Such efforts are still in progress, but in 1939 the C.A.A printed Manual 10 which repre- sented the combined thinking of the various interests. This manual set certain standards by which good aviation equipment could be judged and represents a contribution as important to the art as a new trans- mitter or receiver. Landing by instruments on a fog- bound airport has been the subject of much re.search since the begin- ning of the "Era." Many systems have been proposed and all found wanting until comparatively recent- ly. Practically all systems consisted of a localizer beam which gave in- dications to the left and right of the runway and a glide path which gave an up-and-down indication to bring the airplane down a slanted path which ended at about the cen- ter of the runway. The localizer beam was developed early, but the glide path was delayed until ultra- high frequency techniques were ad- vanced sufficientl.v to provide a sat- isfactory beam path. This has been achieved and will be used by the commercial services after the war. Radio Altimeter Developed by RCA Just prior to World War II there appeared two developments which we will hear more about when the war is over. The first of these is the radio above-terrain altimeter. During the war, RCA has advanced this device tremendously and its use commercially after the war is assured. The second is the ultra- high frequency omni - directional radio range. This RCA develop- ment is destined to reappear in new forms after the war and may re- place all existing types of range svstems. INSTRUMENT PANEL OF TRANSPORT PLANE SHOWS RADIO COMPASS CON- TROL APPARATUS IN THE LOWER FOREGROUND. BELOW : RCA VICTOR'S FLY- ING LABORATORY TAKES OFF FOR ANOTHER TEST OF AIRCRAFT EQUIPMENT. [RADIO AGE 17;