Fading and Dead Spots

Radio Record, Volume III, Issue 21, 6 December 1929, Page 12

Fading and Dead Spots

KDKA and Byrd J! MEDIATELY following the musical numbers and messages constituting the regular broadcast programme to the Byrd Expedition at Little America which was transmitted recently by the Westinghouse Station KDKA, Pittsburgh, listeners heard a long-drawn-out "buzz," which was maintained for five minutes. This buzz constituted the first of a highly-import-ant series of tests in which the radio experts of KDKA are co-operating with those of the Byrd Expedition. The object of these tests is to secure a better understanding of one of radio’s most mysterious phenomena-"blind spots," or "dead areas." As most radio listeners are aware, there are many small areas where cer‘tain broadcasting stations can be heard only with difficulty, if at all, although the same stations come in clearly all around these areas. While some of these "dead spots" are caused by ‘peculiarities of land configuration, others cannot be explained away so easily, and many scientists now believe that the trouble is chiefly due to the socalled "Heaviside layer." The "Heaviside Layer. ? HE "Heaviside layer," according to theory, is a stratum, possibly magnetic in character, which surrounds the earth. Radio waves cannot pass through it, but are reflected back to earth by it, just as light rays are reflected by a mirror. In some places waves thus reflected are the ones chiefly received, and this applies especially to long- -distance broadcasting: at other places, the waves sent out directly by the transmitter are the ones that convey the messages; but in certain places, both sets of waves are received together, and it is due to the interference of these two sets that dead spots, and possibly fading, are thought to be caused. Tests indicate that the Heaviside layer encircles the earth at an average distance of 350 miles, but there is some reason to think that at @ither the North Pole or the South Pole, or both, this layer approaches close to the earth, of perhaps actually

touches it. Definite confirmation or refutation of this theory is the object of these tests. These tests are sponsored by the U.S. Navy, not merely in the interest of pure science, but also of national defence, as dead spots occur at sea as well as on land, and naturally interfere with naval operations, so that it is most important to secure as much information on the subject as possible, Osiso to Catch Echoes. HE investigative work at Little America is in charge of Malcolm P, Hanson, radio engineer of the Byrd Expedition, and the most important instrument he will use is an ingenious and versatile instrument, known as the Osiso, which was invented by the late Joseph W. Legg, oscillograph engineer of the Westinghouse JHlectric and Manufacturing Company. The Osiso makes photographic records of radio signals and other electric waves, and is so sensitive that it will measure time-differences of only a few millionths of a second. By means of the Osiso, Engineer Hanson can record the reception of both direct radio signals and their echoes, as reflected by the Heaviside layer, and by measuring the time difference between them he is able to determine the height of the Heaviside layer near the South Pole. | . He has already done considerable experimental work along this line, and as reported by Russell Owen in the "New York Times" for July 25, took a trip for this purpose with two companions ten miles outside of camp in weather so cold that the dogs’ noses froze. Hanson carried the Osiso on his back and packed the necessary dry batteries inside his shirt to keep them from freezing. On his return from this trip he radioed the company as follows :- : "Osiso giving splendid results in temperatures down to 70 below zero with ski and knapsack and dog-sled transportation. Suggest Westinghouse co-operate oscillographic study by sending special signals to us, co-operat-ing with Dr. Taylor of Bellevue." KDKA’s radio experts, having receiv-ed-Dr. Taylor’s suggestions, arranged with Hanson to send him a long, powerful signal on exactly 25.4 metres, which ‘enabled him to make more accurate mensurements than was possible with ordinary radio signals. This signal

was also transmitted on KDKA’s regular broadcasting wave so that it could be heard by listeners. Al Jolson’s Voice at Little America. [THE musical programme sent to Byrd included a programme arranged and produced by the Brunswick-Balke-Collender Company and consisted of electrical transcriptions especially prepared for this broadcasting. © Among the participating artists were Al Jolson, Nick Lucas, Harry Richman, Belle Baker, Dick Robertson, Scrappy Lambert with his pianos, and other wellknown Brunswick stars. Five orchestras were also heard. Hanson recorded paris of this programme on his Osiso as a check on his measurements of the main test signal. 4