Radio Broadcast (May-Oct 1922)

Radio Broadcast This absorption of radio waves gives rise to radio "shadows" such as are noticed if a high mountain intervenes between two stations. In such cases better communication is obtained if the distance between the two stations is increased, because the shadow becomes less definite, just as Hght shadows do in similar circumstances. An interesting case of this sort is noticed near the island of Cuba; there is a radio station on the south coast which cannot transmit reliably to ships on, the north coast, there being a mountain range intervening; if, however, the vessel steams north for a hundred miles, thus getting out of the shadow, the communication is much better although the distance from the transmitting station has been more than doubled. In a recent interview. Dr. Charles P. Steinmetz, the chief consulting engineer of the General Electric Co., is reported to have said that "under certain conditions it will be easier for wireless waves to pass through the ground than through the air. Submarines already have sent radio messages successfully while submerged, a primary substantiation of the theory, which looks to the conquering of another element in addition to the ether." If the noted engineer of Schenectady had ever listened to the signals received by a submarine as she submerges, as has the writer, and had listened to them fall off rapidly in intensity until at only a few fathoms depth they are entirely gone, only to reappear as the depth of the submarine is decreased, he would be convinced that it is much more difficult for the radio waves to travel through earth or water than through air. In fact, going through a few feet of water the signal decreases in intensity as much as it would in a hundred miles through air; this difference in behavior of air and water increases as the wavelength is made smaller. A BETTER BROADCASTING STATION BY THE time this is in press a new broadcasting station will be in operation, a station on the design of which probably more thought and talent has been expended than on any other in existence. It is on the top of one of New York's skyscrapers and is operated by the American Telephone and Telegraph Co.; its call will be WBAY. The actual transmitting set was designed and constructed by the engineers of the Western Electric Co., engineers who know not only engineering, theory, and practice, but who are especially trained in the design and construction of communication apparatus. The vacuum tubes used have oxide coated filaments, such as were employed in the detecting tubes used so extensively by the Signal Corps during the war. The larger tubes, of which there are four, are of 250 watt rating, using 1600 volts in the plate circuit. An interesting detail in the construction of these tubes is the blackening of the plates to increase the radiation of heat; a black plate will radiate much more heat, at a given temperature, than a shiny one. A special type of microphone is to be used, the diaphragm of which is a tightly stretched, thin, steel membrane having a natural frequency far above voice frequencies. It is designed to give better reproduction of the consonant sounds than does the ordinary microphone transmitter. It is anticipated that only about 40 per cent, modulation will be employed, this comparatively weak modulation being used with the idea of keeping out the distortion of the voice sounds which occur if complete modulation is attempted.' The studio where the artists are to perform has been especially treated to reduce echoes to a minimum. The ceiling has been deadened by two inches of sound absorbing material; the floor is deadened with thick carpeting, and experiments are being made in padding the side walls with thick felt. It is the engineer's idea that practically no echo should strike the microphone; if it is actuated only by the original voice sounds, it seems that much clearer speech and music will be sent out than if echoes, from walls and ceiling, as well as the original voice, are allowed to fall on the microphone. The absence of echoes in the room give one a strange feeling when talking; it seems as though one were talking into open space. It serves well to show how all of our senses combine to give us a certain total impression; the experience in this room convinces one at once that one's estimate of the size of the ordinary room is fixed not only by what the eye reports but also by the sound of one's voice, which, of course, will depend largely upon the echoes from walls and ceiling. AN EXPERIMENT IN BROADCASTING THIS A. T. and T. station is being constructed, and is to be operated, purely as an experiment. It had its inception in repeated demands upon the company for supply