Telephone Engineer, April, 1920, pages 13-14:
Long-Distance Radio Talk With Small Power
One-Third Kilowatt Set Talks from New York to Topeka, Fifteen Hundred Miles
By MERLIN MOORE TAYLOR
GUGLIELMO MARCONI, the wireless expert, said in a moment of enthusiasm the other day that "within the year wireless telephones will supplant the present clumsy system with great economic advantage." This is taken to indicate that Mr. Marconi thinks that the wire plant, as part of a system of telephone communication, is soon to become a thing of the past. But is it?
"Central" need not worry over the possible loss of her job in the near future. She will be needed for a long time to come, even if the radio telephone does become the commercial possibility that recent experiments would indicate. Right now it would be possible to put the wireless telephone into practical use for long distance work in such cities as Chicago and New York, were it not for the expense of generating power. Even that is being overcome by nightly tests which have proved that it is possible to send the human voice through space as far as 1,500 miles with a generator that boasts only one-third of a kilowatt of power.
The De Forest Radio Company of New York has enlisted the aid of the half-million members of the American Radio Relay League in its experiments. Almost nightly tests are arranged whereby at specified hours in all parts of the United States operators sit with the receivers clamped to their ears, straining to hear the music of a phonograph being played in New York or the voice of a New York operator trying to reach them. Only one or two stations are equipped with the vacuum tubes which make it possible to send the human voice, so the results of the tests are reported by wireless telegraph, and later confirmed by mail.
The tests began in February with Robert F. Gowen, engineer of the De Forest Company, on the New York end, and R. H. G. Mathews of Chicago, former United States navy instructor and vice-president of the American Radio Relay League, at the receivers in his laboratory on the banks of Lake Michigan in Chicago. Night after night, from ten o'clock until midnight, they worked in an effort to get in communication. Mathews meanwhile had notified his fellow members of what was being done and asked them to be on the alert. Various arrangements of amplifiers and coils were tried until finally, one night, Mathews caught Gowen's voice, low and hazy, but plain enough to distinguish the words.
"I hear you, I hear you," he tapped out on his radio key and Gowen sent back instructions for a change in the modulation. Mathews made them and listened again. Suddenly he got the right combination and others, standing around his instrument board, could plainly hear Gowen without the aid of receivers. Then the New York man put on a jazz record in a talking machine, and, had the Chicago station been large enough a dance could have been held, so plain was the music.
The greatest surprise was yet to come. Gowen, elated over having made his voice heard in Chicago, 750 miles away, with a low-power generator, got letters proving that operators in Topeka, Kans., 1,500 miles away; Valley City, N. D.; Battle Creek, Mich., and Gaffney, S. C., also had heard him. They repeated the remarks he had made and named the tune he had played. Not only had he accomplished what he was trying to do, make himself heard 750 miles away, but he had sent his voice twice that far!
Wireless telephones as a success are not new. The navy used them during the war, the Department of the Interior has equipped its rangers in the forests of the west with small sets with a small range, in China the radio telephone is being used for communication between the cities and rural districts, and London and Rome have been holding successful communication. But to make the voice audible for hundreds of miles with only a small power generator is absolutely new and it is upon that the success of the wireless telephone hinges.
When a year ago United States navy operators, with President Wilson, Secretary Daniels and other notables as guests, sent the human voice around the world, a generator of 300-kilowatt power was used, a long wave length (something like 3,000 meters) was used, and it cost several thousand dollars to talk for only a few brief moments. With the low power generator in use, one of a third to a half-kilowatt power, and a wave length of around 360 meters the radio telephone becomes something within the reach of almost anyone interested in wireless.
Now as to what it means to the telephone companies. Use of the telephone for long-distance communication is more and more replacing the mails and the telegraph in business transactions. The number of trunk lines between cities necessarily is limited, and it is no unusual thing for a patron to be asked to wait two or more hours before his connection can be made, because there are so many calls ahead of him. With the radiophone there is no limit to the number of trunk lines, for the air is boundless.
When the telephone companies accept the wireless telephone with low power generators as a substitute for the wire system, it will be only the work of a few minutes to set up a long-distance connection. This does not mean that it is possible, or probable, that residences or business houses will at any time in the near future discard the present telephone for radio but it does mean that the telephone "central" can plug a patron in on an air trunk and tell him to go ahead and talk without waiting for one of the wires to become idle.
And the patron? He won't know, unless he is in touch with scientific developments, that his voice is being carried through the air instead of over a copper wire. He may notice that the voice of the man he is talking to is more clear and distinct than in the usual telephone conversation, and he may be aware of the fact that the clash and clatter in his ears are missing, but that is all.
An interesting experiment to prove that this is possible was staged at a convention of automotive engineers, who spent a day in Michigan, across the lake from Chicago. A motorboat, equipped with the wireless telephone, was sent out on the lake several miles. Then the operator got into communication with a radio switchboard set up for the benefit of the engineers in Michigan, was connected with a regular telephone, and the rest of the conversation was finished over the wires to a telephone in Chicago.
Interesting as all this is, the operator need not worry. The radiophone will not supplant the wire telephone during her lifetime. It will supplement it, just as the wireless telegraph is supplementary to the cable lines.
Just now a pocket-size wireless telephone is being made which will be able to establish communication with its companion apparatus at any time. Thus a business man can talk to his home or his office from any point he may happen to be, within the radius of his pocket instrument, if the notion seizes him.
England is far ahead of the United States in the development of the wireless telephone, because the government bought up the patent rights on such instruments and made them available to all experimenters. In the United States the patents are held by their inventors, and cannot be used without the payment of a stiff royalty.
The wireless station at Chelmsford, England, now is making efforts to establish communication by radio telephone with the United States without the use of great power. So far the attempt has been a failure, because the hour that best suits the British is not the most favorable for the American operators by reason of the great number of operators who are experimenting in the early hours of the evening.