Radio waves

“ In almost the same way that a large truck can carry a bigger load than a small one, the greater number of cycles per second in a high frequency wave permits it to carry more information than a low frequency wave.
However, high frequencies must be generated in different ways than low frequency waves are; they require special equipment to handle them. Radio waves are transmitted by causing masses of free electrons to oscillate or swing back and forth in the transmitting antenna. (Any time electrons are made to change their speed or direction they radiate electromagnetic energy.) ”

“ A lot of the little facts I knew had not been picked up in the Corps. One fact—normally of interest only to warpdrive technicians—concerns the curious propagation of radiation in warpspace. Radio waves in particular. They just don't go anyplace. If you broadcast on one frequency you get a strong return signal on all frequencies, as if the radio waves had been squeezed out thin and bounced right back. ”

“ In radio communication it is advantageous and has long been the practice to use a directive antenna by which the waves of radio activity emanating from it are projected as a beam in the direction of the receiving station. In practice the beam is directed at an angle from the earth's surface toward the ionized layer of the stratosphere, or Heaviside layer, from which the beam is deflected toward the earth's surface in the compass direction of the receiving station. In more recent years it has been the practice to use relatively short wave lengths for radio communication. ”

“ They should think that the man coming in was one of their own. The radio contact between the men outside had been limited to a few micromilliwatts of power—necessarily, since radio waves of very small wattage can be decoded at tremendous distances in open space. ”

“ I guess the human race will never have power by radio. Probably we will be able to get along without it. Atomic power seems to be coming along, and it's safe.
I took Fradin to the hospital. That slug through his shoulder had cost him a lot of blood, but he recovered all right, only to discover that the Institute of Radio Engineers had booted him right out of their organization, for making the preposterous claim that radio waves are transmitted through the fourth dimension instead of through the ether. ”

“ On Mars we received all your radio waves. We heard all the languages used on your earth. But try as we would, we were not able to send our radio waves to your earth. There is a strange, strong interference. Your earth has a protective shell of electrically charged gases, some sixty miles thick, clinging to it. This shell seriously disturbs the travels of our radio waves in your atmosphere. It prevented us from making communications. That is one of the reasons we captured your plane; we wished to analyze your radio transmitter and find the metal or element which would help us pierce through. ”

“ When a radio wave encounters a layer of the ionosphere, that wave is returned to earth at the same angle (roughly) as its angle of incidence. Figure 1-6 shows three radio waves of the same frequency entering a layer at different incidence angles. The angle at which wave A strikes the layer is too nearly vertical for the wave to be refracted to earth, However, wave B is refracted back to earth. The angle between wave B and the earth is called the critical angle. Any wave, at a given frequency, that leaves the antenna at an incidence angle greater than the critical angle will be lost into space. ”

“ Serge Olinski, and myself.
"For some time, mysterious radio waves, which appeared to come from some definite source in space, have been puzzling men of science engaged in radio research work. We know that infra-red radiation and short radio waves make it theoretically possible to communicate with other planets. They can penetrate the upper atmosphere, and may be directed toward any planet with accuracy and power, as well as penetrating the planets without scattering. ”

“ They mixed radio and audio, modulated the radio with the audio and hurled both continuous waves and pulsed waves, and mixed complex combinations of both. Then they modulated the subradio with radio, which was modulated with audio and they bombarded it with that. Rejecting the radiation bands entirely, they went after it, exploring the quasi-optical region just below the infra-red in the same complete manner. They fired at it constantly, climbing up into the heat waves, up into visible light and out into the ultra-violet. ”

“ How do you figure to locate that wreck with radio waves?”
“It’s not so complicated as it seems,” said Phil. “This set is equipped with unusually sensitive vacuum tubes, and with certain condenser arrangements, radio waves affected by metal deposits are received through the water. Now, in the receivers of this set I can hear the incoming radio waves, and the second that they vary in strength I know that we are near some large quantity of metal. That’s simple enough, isn’t it?”
“Well, yes, but this was a wooden ship, remember,” objected Benton. ”

“ 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. ”

“ The range of intermediate wave receptors is such that they will receive amateur, broadcasting, ship and shore Navy, commercial, Arlington's time and all other stations using spark telegraph damped waves or arc or vacuum tube telephone continuous waves but not continuous wave telegraph signals, unless these have been broken up into groups at the transmitting station. ”

“ 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. ”

“ Don't--no never--connect one side of the spark gap to the aerial wire and the other side of the spark gap to the ground. The Government won't have it--that's all.
Don't try to tune your transmitter to send out waves of given length by guesswork. Use a wavemeter.
Don't use hard fiber for panels. It is a very poor insulator where high frequency currents are used.
Don't think you are the only one who doesn't know all about wireless. Wireless is a very complex art and there are many things that those experienced have still to learn. ”

“ 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.” ”

“ 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." ”

“ When a tuning fork is made to vibrate it sends out waves in the air, or sound waves, in all directions and just so when high frequency currents surge in an oscillation circuit they send out waves in the ether, or electric waves, that travel in all directions. For this reason electric waves from a transmitting station cannot be sent to one particular station, though they do go further in one direction than in another, according to the way your aerial wire points. ”

“ With this spectacular demonstration he administered the deathblow to all plans for high power ultra-long-wavelength transmitters, and from then on the commercial companies concentrated their efforts on developing equipment for international communications on the short waves.
With present-day electronic news gathering and world-wide satellite links, the problems faced by broadcasting organisations fifty years ago when transmitting programmes which did not originate in a studio were thought to be very complex. ”

“ 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 ”

“ Since the electric waves travel out in all directions any receiving set properly tuned to the wave length of the sending station will receive the waves and the only limit on your ability to receive from high-power stations throughout the world depends entirely on the wave length and sensitivity of your receiving set. ”

“ At night we use those lights or blinkers and make ’em wink by electricity. It’s really sending wireless messages with lights instead of sound waves.”
“And how does a fellow become a first-class radio man?”
“To become a first-class man, you’d have to have a good knowledge of all parts of the ship, and all radio laws and regulations and general radio procedure. You could take your examination nine months after you entered the service, but there are mighty few radio men who are ready to take it so soon.”
“What about Mr. Sharp here? He is chief electrician. ”

“ Thus sound is converted into waves, and the receiving station, as you see here, with its aërial on the roof, its detector, its 'phone and its tuner, gets these waves and turns them again into sound. That is the outline of the thing, which you will understand better 'after' than 'before using.'
"The technical construction of the radio receiving set is neither difficult nor expensive ”

“ 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. ”

“ If wireless had really been selective in the first instance, broadcasting would not have been its initial phase.
Wireless at present is excessively inefficient; a few yards from a large broadcasting station the power is measured in millionths of a horse-power, is disseminated in all directions, and is almost without definite selectivity.
When the day comes when we can tune with absolute accuracy; when we can combine waves with accuracy and obtain a directional beam with the shortest waves for re-broadcasting purposes, then we shall obtain real happiness from the results. ”

“ The propagation media, including the Earth, atmosphere, and ionosphere, as well as physical and electrical characteristics of transmitters and receivers, influence the stability and accuracy of received radio signals, dependent upon the frequency of the transmission and length of signal path. ”

“ 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. ”

“ Because the radio signal travels in the air, any obstruction (such as a mountain) between the antennas can block or reduce the signal. For an antenna 10 feet above the ground, 8 kilometers (5 miles) is the maximum line-of-sight distance. (2) The reflected wave reflects off the earth in going from the transmitting antenna to the receiving antenna. Together, the reflected wave and the direct wave are called the space wave. (3) The surface wave travels along the surface of the earth. It is the usual means of ground-wave communication. ”

“ 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. ”