Radiotelephony

“ If full opportunities for such non-official research work are not restored, the progress of the art of radio telegraphy and radio telephony will be greatly hindered."
Professor W.H. Eccles wrote:
"Improvements and invention must be stimulated to the utmost. It is not impossible to devise laws to impose restrictions upon the emission of wireless waves as will preclude interference with the public radio service of the future (R.F.I. & T.V.I.?!!) and yet allow liberal opportunities for the experimental study of wireless telegraphy." ”

“ To make wireless telephony a success it was necessary to find some way of making perfectly uniform carrier-waves, and then of loading on them waves of speech. Of course, the latter are not sound-waves, because they are not waves of air, but they are electro-magnetic waves corresponding exactly to the sound-waves of air and at the receiving-end they affect the telephone receiver in the191 same way that it is affected by the electric waves which are sent over telephone wires. ”

“ It might reasonably be asked why a telephone receiver could not be directly connected to the aerial and ground so that it would respond directly to the high frequency currents generated by the incoming waves without the medium of a detector. There are two very good reasons why such a method would not be possible, the first being that the little magnet coils contained in the telephone receivers exert a choking action upon alternating currents of high frequency which effectually blocks their passage. ”

“ You can see that very few telephone messages can be sent in the long-wave-length part of the radio range and many more, although not very many after all, in the short wave-length part of the radio range. You can also see why it is desirable to keep amateurs in the short wave-length part of the range where more of them can transmit simultaneously without interfering with each other or with commercial radio stations. ”

“ As the waves shoot out and reach the distant station, the filings in the tube cohere and the current passing through them draws up the armature of the relay magnet. This closes the circuit of the recording instrument. It is broken constantly [156] by the tapper and instantly re-established by receiving waves.
The towers employed in 1920 for the transmission of wireless messages were very high. The manifest advantages of the system were apparent and long before 1930 wireless telegraphy came into general use. The new system proved the death-knell of telegraph poles, as well as ocean cables. ”

“ One of the greatest disadvantages of most systems of wireless telegraphy lies in the fact that no arrangement is provided for simultaneously transmitting and receiving wireless signals. It is usually necessary for one operator listening to another to have to wait until the finish signal is given before he can reply or interrupt in case he cannot understand part of the message, because the receiving apparatus of the transmitting station is necessarily disconnected from the aerial and the ground during the period a message is being sent. ”

“ Wireless telegraphy is part of the established order of things. The wireless telephone is practical for limited distance, but is not a commercial rival of the telegraph. Great distances are claimed, but they are matters for proof and speculation.
There is no immediate possibility that wireless telephony will take the place of local exchanges. If the time ever does come that it in any way tends to supplant the line telephone for some uses, it is more than probable that each subscriber must have his own generating station and call up direct. ”

“ A wireless telegraph transmitter is less costly than a wireless telephone transmitter and it is a very good scheme for you to learn to send and receive telegraphic messages.
At the present time, however, there are fifteen amateur receiving stations in the United States to every sending station, so you can see that the majority of wireless folks care more for listening in to the broadcasting of news and music than to sending out messages on their own account. The easiest way to begin wireless, then, is to put up an aerial and hook up a receiving set to it. ”

“ Many of those who had followed wireless telegraphy from its beginnings and knew somewhat of the theory of how it worked, set up a hue and a cry that the signals he had received were sent by ships at sea, or else they were due to static, as we call it now, that is, little charges of atmospheric electricity which accumulates on the aerial wire and finally discharges through the detector into the ground and this makes a click in the head-phones that sounds like a dot. ”

“ Discovery may need to intervene, to enable invention to restimulate.
In both telegraphy and telephony, the longer the line the weaker the current which is received at the distant end. In both telegraphy and telephony, there is a length of line with a given kind and size of wire and method of construction over which it is just possible to send intelligible speech or intelligible signals. A repeater, in telegraphy, is a device in the form of a relay which is adapted to receive these highly attenuated signal impulses and to re-transmit them with fresh power over a new length of line. ”

“ As a result of exhaustive researches, too extensive to describe here, it has been ascertained that the function of the wireless telephone is not to do away with the use of wires, but rather to be employed in situations where wires are not available or practicable, such as between ship and ship, and ship and shore, and across large bodies of water. The ether is a universal conductor for wireless telephone and telegraph impulses and must be used in common by all who wish to employ those agencies of communication. ”

“ While in the ordinary wireless instruments the discharge surges back and forth between the antenna and the earth, in the flying-machine wireless the discharge surges back and forth between the two antennæ. In the Wright machine, when equipped for wireless telegraphy, the two antennæ are placed one under the upper plane, the other under the lower plane of the flying-machine. [221]
More power is required for the wireless than for the wire telegraph. In the wire telegraph about one-hundredth horse-power is required to send a message one hundred and twenty miles. ”

“ Just the same, only in radio telephony we are confronted by a problem not met with in wireless telegraphy. We have not only to transmit sound, such as isolated dots and dashes, but to send through the air every rise and fall and inflection of the human voice just as it is recorded in the minute lines of a phonographic record. ”

“ It is a matter of common knowledge that a large part of the important inventions in connection with wireless telegraphy have been the work of amateurs and private research and not the outcome of official brains or the handiwork of military or naval organisations. In fact we may say that wireless telegraphy itself in its inception was an amateur product. Numerous important inventions such as the crystal detector, the oscillating valve, the triode valve—have been due to private or amateur work. ”

“ So when after Chapter V had been written Captain Morris found new and interesting information on the use of wireless telegraphy in aircraft in the days before the war, the whole of this difficult chapter had to be reopened for new patching. “In regard to wireless,” he wrote, “I am like a blind man who has never talked to painters employed to write a critique of a picture exhibition. It’s paralysing. The only escape is to keep on broad lines. Every one knows that wireless sends messages. ”

“ That is why any wireless receiving station, within a certain radius, can catch any messages that may be flying through the air--that is unless certain apparatus is tuned, or adjusted, to prevent this."
"Well, once the impulses, or electric currents, are sent out into space, all that is necessary to do is to break, or interrupt them at certain intervals, to make dots, dashes and spaces. These make corresponding clicks in the telephone receiver which the operator at the receiving station wears on his ear. ”

“ In that way, a single pair of wires can be used for transmitting, simultaneously and without any interference, several different telephone conversations. It takes very much less power than would radio transmission and the conversations are secret. The ordinary telephone conversation can go on at the same time without any interference with those which are being carried by the modulations in high-frequency currents. ”

“ Electrical tuning and electrical rectification are fundamental operations in the radio art to-day, but the wireless telegraphy of the early days is a distant and poor relation of our present radio art. The world had to wait quite some time for new discoveries which gave birth to the epoch-making inventions of new men, like Lee De Forest and Major E. H. Armstrong. It had to wait also for the great industrial research laboratories before electrical tuning and rectification could come into their own. ”

“ Maybe thar is some way, except by water, in spite of what he said."
"Maybe there is," said Jack. "It seems a shame to think of all that rich stuff lying there neglected and unobtainable."
"It does indeed," agreed the professor. "In that sample I find traces of metals from which filaments for electric lights could be made and substances invaluable in medicine for X-ray purposes as well as the Z.2.X. which your father is convinced would make the radio telephone as practical as the wireless telegraph." ”

“ Wireless telephony, like wireless telegraphy, but to an even greater extent, is peculiarly suited for the conveyance of marine intelligence. Wireless telephony occupies a unique position in this regard-no operator is required. The additional expense of an operator is an objection to the wireless telegraph in many cases, and forbids its installation. Anybody can operate the wireless telephone. It is also much quicker-words can be spoken more rapidly than they can be put into Morse signals and translated. ”

“ No such trouble can occur with wireless telegraphy, and if it becomes necessary to move a wireless station with great rapidity, as for instance on an unexpected advance of the enemy, it is an advantage to have no wire to bother about. ”

“ FIG. 153.—The aerial system of a transatlantic station.
The wireless telephone enables a passenger on board ship to communicate direct with his home by relaying the message over the line wires. By the same means the captain of a ship can call his home office and communicate with the owner of the vessel.
Telegraphs and telephones are the nerves of the world, carrying swift messages from its brain centers to its hands, annihilating distance in thought. All differences between men as individuals and people as nations can be traced to the lack of close contact. ”

“ If it were possible for sound to carry that far, a “Hello” uttered in New York and traveling through the air without the aid of wires and electricity would not reach San Francisco until four hours later. The telephone not only transmits speech, but transmits it thousands of times faster than its own natural speed.
But while the telephone is breaking speech records, it must also guarantee safe delivery of these millions of little passengers it carries every few minutes in the way of sound waves created at the rate of 2,100 a second. There must be no jostling or crowding. ”

“ We still have our neighbors' call bells, and we could listen to their messages if we were gossips. The telephone service has been extended to great distances—for instance, from Boston to Omaha—not by relays, but by strengthening the blows upon the medium between the transmitting circuit and the receiving one, just as we desire to do in what is called wireless telegraphy, the apparatus of which is almost identical in principle to that employed in telephony. The individual call in telephony is not a success for nearly the same reasons that exist in the case of wireless telegraphy. ”

“ When listening-in to distant stations the energy of the received wireless waves is often so very feeble that in order to hear distinctly an amplifier must be used. To amplify the incoming sounds a vacuum tube made like a detector is used and sometimes as many as half-a-dozen of these tubes are connected in the receiving circuit, or in cascade, as it is called, when the sounds are amplified, that is magnified, many hundreds of times.
The telephone receiver of a receiving set is equally as important as the detector. ”

“ If the electricity with which any conducting body is charged be suddenly disturbed, electrical waves are generated which travel outwards in all directions with the velocity of light. The problem of wireless telegraphy is the problem of producing these waves by means of an instrument called a transmitter, and of recording their impact at a distance by means of an instrument called a receiver. ”

“ Although a war invention, its peacetime service will be to save lives. It is a very simple matter to rig up a wireless-telegraph system that will send messages to a considerable distance, and simpler still to rig up a receiving-set. European governments have always discouraged amateur radiotelegraphy, but in this country restrictions used to be so slight that almost any one could set up and use a radio set, both for receiving and for transmitting. ”