Radio Broadcast (May-Oct 1925)

324 Radio Broadcast waves in regard to the speed of propagation, reflection, refraction, and diffraction. Some twenty-nine years ago in my own first experiments, in Italy, and shortly afterward in England, I used short waves in combination with metallic reflectors and, curiously enough, I was then able to transmit signals with them over a distance of a mile and three quarters, while with the elevated antenna and much longer waves, i. e., using the same system that is used to-day in all the high-power stations of the world, I could only manage to communicate over a distance of half a mile. It is perhaps regrettable that the subsequent rapid development of the longwave system, which in three or four years achieved such spectacular results, drew away the attention of most of us not only from the possibilities of the short waves, but also from the use of suitable reflectors to concentrate them into a beam in a definite direction, which is possible only with short waves. I never " quite abandoned the idea, however, of utilizing the latter and, in addition, I always realized the importance of evolving a practical directive system of radio communication. I believe it is generally admitted now that electric waves are far too valuable to be always allowed to spread out in every direction when it is desired to communicate with only one particular place. If a station in Great Britain wishes to communicate with one in the United States, for example, there seems to be no good reason why, if it can be helped, what it has to say should be heard in Siberia, and Egypt, as well as in Nicaragua and India. Naturally, non-directional stations, which scatter their waves in every direction, are of great utility for many naval and war purposes, What Senator Marconi Is Doin& /^\N HIS last trip to the United States, Senator Marconi presented a paper before the Institute of Radio Engineers de scribing various radio experiments being conducted under his direction. That paper was read June 30, 1922, and dealt to a large extent with experiments with short radio waves. It should not be thought that short wave radio transmission is new, simply because experiment in this field has lately received a good deal of attention from amateur and commercial engineer alike. Senator Marconi's earliest experiments with wireless waves in 1895 and 1896 used waves not more than a few inches long. s And now, after radio stations have been built to use waves as long as 20,000 meters, the cycle of radio investigation swings back to something very similar to that of the first radio experiments. But in these experiments, the aim is to do away with the fading and absorption of signals, interference by natural electric waves, and to make transmission directional. In this article, Senator Marconi himself tells of what he and his engineers have lately done to revolutionize radio. — The Editor and of course for broadcasting, where the very soul of the process lies in the fact that the waves are scattered all around to be picked up by any one with a suitable receiving set. But it has always seemed to me that, if possible, the right thing to do would be to concentrate the whole of the radiated energy into a beam directed toward the locality with which it is desired to communicate, just as the beam of light waves from a searchlight is thrown in one direction by means of reflectors. Such a result is greatly to be desired on many grounds, such as the low cost of installation and economy of upkeep entailed by the much lower amount of energy required, the reduction of interference with other stations, and the com parative secrecy which can be obtained. Economy of energy is a matter which is instantly translatable into pounds, shillings, and pence. If we consider a high power station similar to the one recently built in the Argentine for communication with Europe over a distance of about 6ooo miles, every time the operator depresses the key and sends a signal flashing through the ether, some 8oo kilowatts (about i ioo h. p.) is expended, although in the case of these long waves, only a small fraction of the power is radiated from the antenna, which, in this case, is supported by ten steel towers each 690 feet high. It is evident that if a signal as easily readable can be sent with 30 or 40 kilowatts (about 50 h. p.) and by means of an antenna supported by much lower and fewer masts, there will be not only a greatly decreased cost of installation of the station, but also a great reduction in the cost of maintaining the station. With regard to the question of interference