Radio broadcast .. (1922-30)

134 RADIO BROADCAST importance of the problem. What was uppermost in my mind was the problem itself. In fact, it was not until the patents had been obtained, that I considered their significance. One night, shortly after patents were filed, as I lay awake, the possibilities of the system flashed through my mind. The technical and scientific improvement, I must admit, was quickly overshadowed by the whole vision of what the radio telephone could accomplish; its possible effect upon our national life and welfare and the social and economic value of the transmission of speech so that it could be heard all over the country at the same time. It has taken time to see the realization of some of these dreams and even to-day we are only making a beginning." Briefly, the Heising modulation system is as follows: words or music actuate a microphone through which the current from a battery is flowing. The sound variations cause the resistance of the microphone to change as the sound waves impinge upon it. The current in the microphone circuit thus varies with the speech. Hence it is called speech current. The speech current, in turn, is impressed on the grid of a vacuum tube, causing similar but greatly augmented variations in the output of the tube. If high powers are to be controlled, this speech current is magnified by additional modulator tubes, until the voltage variation is sufficiently large to modulate the power output of the oscillator or radio frequency generating tubes. The output of the last modulator tube is impressed upon the source of plate potential of the power tubes so that their source of plate potential rises and falls in accordance with the sound waves of the speech or music to be transmitted. The space current in a" vacuum tube rises and falls with each change of plate potential. As a consequence, when the plate Dotential rises and falls in accordance with the sound waves impressed upon the transmitting microphone, the radiated energy varies in the same way. Amateurs, who are interested in the principles of modulation or who wish to construct radio telephone transmitters, will find Mr. Heising's paper, "The Audion Oscillator," appearing in the April and May, 1920, issues of the Journal of the American Institute of Electrical Engineers, and the paper on "Modulation in Radio Telephony", in the August, 1921, issue of the Proceedings of the Institute of Radio Engineers of great assistance in designing their apparatus. In these papers, Mr. Heising describes fully all circuits used and the advantages and disadvantages of each. Recently Mr. Heising conducted a series of experiments in operating a printing telegraph by radio. Their success proves radio to be as flexible as wire communication. As many as 29,000 characters have been transmitted through two channels working simultaneously in one hour, with but fourteen mistakes attributable to radio shortcomings. The speed with which the printer could be operated was in no way limited by radio. The career of Reginald Heising is remarkable for the extraordinary directness with which he has solved the most perplexing problems — the result of his remarkable and almost intuitional perception of the essential facts in radio. The important invention which led to Mr. Heising's recognition as one of the foremost radio engineers and discoverers of our time — the solution of the problem of modulation— was made within six weeks after he was graduated from college and started to work. Since that time he has greatly improved his system until it has become an essential factor in radio telephony. The many patents which have been granted over Mr. Heising's name and his important contributions to scientific literature are evidences of continued progress. Being still a young man, it is natural that more great things are expected from him. In the meantime, broadcast enthusiasts have much to be grateful for to Mr. Heising.