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7 Air Com. Bull. 1 (1935-1936)

handle is hein.journals/aicmrcb7 and id is 1 raw text is: U. S. DEPAR.TMENT OF COMMERCE Air Commerce Bulletin Issued Monthly by the Bureau of Air Commerce Vol. 7 WASHINGTON, JULY 15, 1935 No. 1 Simultaneous Transmission of Radio Beacon Signals and Voice in Trial Service at Pittsburgh A Bureau of Air Commerce radio sta- tion now undergoing practical service trials at Pittsburgh, Pa. represents four important advances in' radio transmis- sions for airmen. This broadcast and radio range beacon station: (1) Transmits voice and directional signals simultaneously, so that there is never any interruption of the radio beacon for radio telephone broadcast- ing. (2) Transmits its directional signals so that they can be received aurally in the pilot's headphones, or in an instru- ment which gives visual readings with a needle on a dial. (3) Is better for use with an air- plane's radio direction finder than pres- ent standard radio range beacons. (4) As a result of 1 and 3, gives more efficient assistance than present standard types for an approach to an airport under conditions of poor visi- bility. (However, it is not an alterna- tive to the Department's instrument approach system.) In a demonstration for representa- tives of scheduled air lines and manu- facturers of radio equipment recently, the Pittsburgh station gave evidence that its new features are efficient and practicable. In flights of an hour to an hour and a half each, Bureau pilots simulated conditions under which an airman might be lost and searching for the radio range course, or for the air- port, and in each case the equi-signal zone was found promptly and followed to the landing area. Methods used in visual interpretation of aural radio beacon signals, and in 903-35-1 simultaneous transmission of voice and directional signals were described in the Air Commerce Bulletin, Vol. 5, No. 11. For visual interpretation the aural radio range beacon, as usual, trans- mits two different code signals in dif- ferent quadrants. In the airplane, one signal is received on one side of the course, the second on the other side of the course. The pilot can receive the signals as usual in his headphones, in which case he will fly in such a way as to receive both signals with equal intensity, and thus will know that he is on course. VISUAL INTERPRErATION If the signals-are to be visually interpreted, special receiving equip- ment in the airplane will distinguish be- tween the two code transmissions. In response to one signal it will tend to move a needle pointer on the instru- ment panel to the left-in response to the other it will tend to move the pointer to the right. When the air- plane is on course, and the two signals are equal in intensity, the needle will be centered. Signals ordinarily used in radio range beacon transmission are A (. -) and N (_ .) interlocking to form a continuous monotone for on course. For visual interpretation an asymmetrical pair of code signals is required to operate the receiving ap- paratus. Originally, experiments were conducted with a single dot to repre- sent one side of the course and a dash for the other, the two signals merging Reproduction by Permission of Buffalo & Erie County Public Library Buffalo, NY

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