Radiophone

“ He aimed his gun carefully at the base of the snout and pulled the trigger; on the side of the monster there appeared a flash of flame as the shell exploded, then a bright smear of metal—a direct hit, and not the slightest damage!
Ben Ruby's voice came through the radiophone, cool and masterful. “Pull out, folks, our guns are no good against that baby. I'm cutting off; radio positions back to the heavy artillery. Put the railroad guns on.”
Murray glanced through the side peep-hole again—one, two, three, four, five—all the American tanks seemed undamaged. ”

“ The radio-telephone does not transmit the human voice. It reproduces near the ears of the listener similar motions of the air molecules and hence causes in the ears of the listener the same sensations of sound as if he were listening directly to the speaker. This reproduction takes place almost instantaneously so great is the speed with which the electrical effects travel outward from the sending antenna. If you wish to understand radio-telephony you must know something of the mechanism by which the voice is produced and something of the peculiar or characteristic properties of voice sounds. ”

“ A means of producing and radiating a stream of undampened electrical waves sufficiently continuous to transmit the upper harmonics of the voice, on which the quality and recognition of the speech depends. Means for varying or modulating the stream of electrical waves in accordance with the sound waves. A receiver, continuously responsive and capable of corresponding with sufficient rapidity to the speech harmonics.
In order to obtain the desired result, recourse is had to an arc lamp as a generator of undamped high frequency oscillations. ”

“ Giddings.
"Practically the same, dad. The wireless transmitter, like that of the wire telephone, contains a sensitive diaphragm which your voice strikes and sets to vibrating. These vibrations compress and release a capsule of carbon granules which agitate and set in motion an electrical current in two magnets connecting with them. The magnets convey the sound-waves in the form of electrical waves, along wires out to the tip of each wing, where the wires hang down a little way. When a message comes in it is caught by a webbing of antennae wires in our wings." ”

“ 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. ”

“ We send sound, music by radio waves across half the world from our broadcasting stations. We send light, pictures, across the world from our television stations. We do that by changing the wave length of the light-vibrations to make them radio vibrations, flashing them out thus over the world, to receivers which alter their wave-lengths again and change them back into light-vibrations. ”

“ The telephone philosophically considered is an instrument for the conversion of a sound-wave into electrical motion, and its reconversion into sound at a distance. The sound is, as it were, committed to the electrical current and is thus sent to the end of the journey, and there discharged with its message. The possibility of this result lies first of all in the fact of electrical transmission by wire, and in the second place to the mounting of a sound-rider on the electrical saddle for an instantaneous journey with important despatches! ”

“ To get music by radio, a microphone converts sound into electrical modulation, which, carried by radio to distant places, is then changed back into sound and we hear the music.
To get pictures by radio, a sensitive cell converts light into electrical current, and at radio distances changes these currents back into light values, and one may see the distant scene; for light is the thing of which pictures are made, as music is made of sound. ”

“ 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. ”

“ How, therefore, dare we neglect the dreadful sounds we hear in the name of radio music?
If a piece of silvering, one thirty-secondth of an inch, be scraped from the back of a mirror and fastened to the outer part of a celluloid diaphragm (made by water-floating a drop of amyl acetate in which celluloid has been dissolved) , it only requires a horn and a beam of light to render visible the waves of sound. A diaphragm movement of a millionth of a millionth of an inch is sometimes audible.
It is the science of wireless that is [Pg 34] beautiful; it is the possibilities that are wonderful ”

“ If a telephone-receiver diaphragm can be made to vibrate in accordance with the variations in signal intensity then the air adjacent to that diaphragm will be set into vibration and these vibrations will be just like those which the human voice set up in the air molecules near the mouth of the speaker. All the different systems of receiving radio-telephone signals are merely different methods of getting a current which will affect the telephone receiver in conformity with the variations in signal strength. ”

“ When it is remembered that the principle of the telephone is that the sound-caused vibrations in the filmy diaphragm at one end create similar but magnetically-caused vibrations in the diaphragm at the other end, and so reproduce the sound, it will be obvious why the rapid roll of the ABC currents, or the swift sending of the fast-speed transmitter, when brought by induction into the telephone-wire, cause disturbances in the sound-vibrations, and thereby cripple the instrument. ”

“ Not only is the vacuum tube a detector of electric wave signals and speech and music but it can also be used to amplify them, that is, to make them stronger and, hence, louder in the telephone receiver and further its powers of amplification are so great that it will reproduce them by means of a loud speaker, just as a horn amplifies the sounds of a phonograph reproducer, until they can be heard by a room or an auditorium full of people. ”

“ The minutest vibrations conveyed to the stand are perceived at the receiver as loud noises. The tread of a fly walking over the board, S, is heard like the tramp of a horse, and the ticks of a watch are audible in the receiver when the ear is several inches away from it. The slight touch of a feather on the stand is distinctly audible, and a current of air impinging upon it is reproduced as the noise of a stream of water. The microphone is, in fact, the most sensitive detector of vibrations that is known, and its employment as a transmitter has brought the telephone to its present perfection. ”

“ A single receiver can be used but a pair of receivers connected with a head-band gives far better results. Then again the higher the resistance of the receivers the more sensitive they often are and those wound to as high a resistance as 3,200 ohms are made for use with the best sets. To make the incoming signals, conversation or music, audible to a room full of people instead of to just yourself you must use what is called a loud speaker. In its simplest form this consists of a metal cone like a megaphone to which is fitted a telephone receiver. ”

“ Tom wanted to know.
"Because, up to the present, no way has been found of utilizing in radio telephony the entire energy of the electric waves sent out," replied Professor Chadwick. "Only the variations in the waves can be detected, or transformed into sound at the receiving end of a radio telephone system. Therefore an immense amount of electrical energy has to be manufactured in order that the voice vibrations may register their variations as powerfully as possible." ”

“ With modern machines in that ice hangar, this little band of explorers could tap the air of the civilized latitudes and bring its music across thousands of miles of snow barrens. A turn of the dial in the ship’s radio-room, and the long arm of radio reached forth and plucked music out of the air, the latest news from America’s metropolitan cities, tunes from Broadway and personal messages from well-wishers. ”

“ That night when I fell off the roof I was running a wire from my room to the aerial on the roof. I’ve been working for a long time with a dear old man who’s a real genius. He invented a special kind of radio and he gave me two of them to try out.”
“I see. That’s what you’re doing now. Did the outside aerial help?”
“Oh, yes, a whole lot. The ‘put-puts’ come in a whole lot more distinctly.”
“The what?” He stared.
“The ‘put-puts’. That’s what we call them. I suppose it’s some special form of code, but it’s not like any I’ve ever heard on the short wave section of our radio.” ”

“ Audio radio engineers have been working in the very limited audio-frequency band below, say, ten thousand cycles, whereas the workable range where light instead of sound is employed goes away up to millions of cycles. It is confidently predicted that the next great development in radio is in this area. ”

“ To serve as an ear, the telephone must be able to take up quickly and nicely the sound-waves of the air. A tightened drum-head will do that; or better, a strip of goldbeaters'-skin drawn tightly over a ring or the end of a tube. But these would not help Professor Bell, the inventor of the telephone we shall describe, since he wanted an ear that would translate the waves of sound into waves of electricity, which would travel farther and faster than sound-waves could. ”

“ With a long wave autodyne, or self-heterodyne receptor, as this type is called, and a two-step audio-frequency amplifier you can clearly hear many of the cableless stations of Europe and others that send out long waves. For receiving long wave stations, however, you must have a long aerial--a single wire 200 or more feet in length will do--and the higher it is the louder will be the signals. Where it is not possible to put the aerial up a hundred feet or more above the ground, you can use a lower one and still get messages in International Morse fairly strong. ”

“ From the telephone to radio constituted but another such step, and we are now enjoying radio broadcast from stations thousands of miles away. Every time you have an Xray photograph taken you are bombarded, not by rays, but by actual particles that go right through the walls of the tube, which particles are just as real as if they were bullets or bricks, the only difference being that they are smaller. Thus our scientists lead up to the way of sending solids through space. ”

“ We ask in vain for an answer to the question which is upon the lips of every one-What next? The microphone has proved itself highly useful in strengthening the sounds given out by the telephone, and it is probable that we shall soon see those three inventions working unitedly; for the microphone might make the telephone sounds so powerful as to enable them to be printed by phonograph as they are received, and thus a durable record of telephonic messages would be obtained. We can now transmit sound by wire, but it may yet be possible to transmit light, and see by telegraph. ”

“ I told him about my visitor and the repair job. "What I did was add a modulator-oscillator-power amplifier, and a few feet of wire for an antenna, coiled around inside the case."
"So what does that make it?"
"Simple. It makes it a radio transmitter. Not only will he hear what the horses are saying, but anyone in town with a radio tuned to that frequency will, too."
"And where does that get you?" The sergeant was still puzzled but not bored now. ”

“ When a telephone is placed in circuit with a telegraph line, the telephone is found seemingly to emit sounds on its own account. The most extraordinary noises are often produced, the causes of which are at present very obscure. One class of sounds is produced by the inductive influence of neighbouring wires and by leakage from them, the signals of the Morse alphabet passing over neighbouring wires being audible in the telephone, and another class can be traced to earth currents upon the wire, a curious modification of this sound revealing the presence of defective joints in the wire. ”

“ Finally, the ladies withdrew, and Myles Cabot, the radio man, began the first discussion of radio that he had undertaken since his return to Poros.
VIII
BUT WHY RADIO?
Three fields of “magic” were open to him, rifle-fire, aviation, and radio. The opportunity for building a workable airplane among people who knew no metal arts was obviously slight. To make a radio set should be possible, if he could find certain minerals and other natural products, which ought to be available in almost any country. ”

“ The remarkable growth of the radio-phone has, of course, been due to the radio broadcasting stations which have been established in all parts of the country, and from which concerts, speeches, market reports, baseball reports, news reports, children's stories and religious services are sent out. ”

“ The parlor was red in the fading light, and the hall beyond the sliding doors was deeply shadowed. In the sewing room, he remembered, in the drawers of the treadle machine the radio was captured. The rings and secret manuals of the days when radio had been alive. ”

“ When a sub is heard and located, the listeners call the net-layers by radio, and they go to the spot at a thirty-knot speed. As they approach they soon drown out the sound of the sub, but their speed and number enables them to surround the area in which she is known to be, for she won’t have time to go far from where she was last heard. Paying out their nets, they hem her in and keep the ring of nets closed round her till the area is raked with trailing wires and other electromagnetic detectors which will enable the chasers to concentrate their depth charges with the certainty of a kill. ”