Radio wave

“ 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.) ”

“ An LRS team that can see everything and report nothing is useless. LRSUs normally use high-frequent radios to report information and receive instructions. Because of the complex nature of using the HF radio spectrum, a LRSU radio operator must have an in-depth knowledge of radios, antennas, and radio wave propagation.
D-1. HIGH-FREQUENCY RADIO FUNDAMENTALS For successful communication, HF radio performance depends on the type of emission (voice or burst device) , transmitter power output, and type of antenna. The challenge facing HF radio operators is tremendous. ”

“ 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. ”

“ This rule challenged the industry, which has only now risen to the occasion, to build a radio that would run at no more than one watt of output power and use a fairly exotic method of modulating the radio wave called spread spectrum. Spread spectrum in fact permits the building of networks so that numerous data communications can occur simultaneously, without interfering with each other, within the same wide radio channel. ”

“ As a frequency is lowered, absorption of the radio wave increases. A wave whose frequency is too low is absorbed to such an extent that it is too weak for reception. Atmospheric noise is also greater at lower frequencies. A combination of higher absorption and atmospheric noise could result in an unacceptable signal-to-noise ratio.
For a given angle ionospheric conditions, of incidence and set of the luf depends on the refraction properties of the ionosphere, absorption considerations, and the amount of noise present. ”

“ 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. ”

“ 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. ”

“ 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 most troublesome and frustrating problem in receiving radio signals is variations in signal strength, most commonly known as FADING. Several conditions can produce fading. When a radio wave is refracted by the ionosphere or reflected from the earth's surface, random changes in the polarization of the wave may occur. ”

“ 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. ”

“ 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.” ”

“ You must have a thorough knowledge of radio-wave propagation to exercise good judgment when selecting transmitting and receiving antennas and operating frequencies. Selecting a usable operating frequency within your given allocations and availability is of prime importance to maintaining reliable communications. ”

“ Here was the powerful short-wave sending and receiving set, an intermediate wave set for communication with near-by cities and other ships of both air and sea, and a radio direction finder. Within this room, a group of mining scouts was carefully taking apart and putting back together one of the Renaud portables, under the watchful eye of Lee. These men must know their radio mechanism. For when the great dirigible dropped these men for scouting in various parts of the Arctic waste, radio would be their only means of communication with the rest of the party. ”

“ 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. ”

“ Antenna construction is limited only by imagination. There are many types and configurations. However, the operator must be careful not to construct an antenna that has a high standing wave ratio, which can damage radio equipment. Standing wave ratio meters should be used when testing or using unfamiliar antennas. In selecting an antenna for an HF circuit, the operator must know the type of propagation.
(1) Ground-wave propagation requires low takeoff angles and vertically polarized antennas. The whip antenna provides good omnidirectional ground-wave radiation. ”

“ And now came the great test for her manifold radio equipment. There was no time to lose. Signals must be sent to all battleships within range to support her by diverting their fire to these fast and powerful ships; signals must be sent to all available destroyers to harass them with torpedo attacks; and still the direction of the fleet as a unit must go on, and all without mutual interference of messages. Signals were flashing out simultaneously on different wave-lengths from three or four separate antennæ, both by radio telephone and by radio telegraph. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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 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. ”

“ 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. ”

“ At present wireless messages are chiefly of service where secrecy is not of such importance as speed; but an enormous number of experiments are being conducted upon beam wireless, directional wireless, and in the combination of the Radio oscillation with some other oscillations such as those of visible or invisible light. By these means secrecy will be obtained when we discover how to use small powers for long distance, but at present Radio is chiefly of value as a time-saver. ”

“ The signal which radiates out from the transmitting antenna carries all the little variations in pitch and loudness of the human voice. When this signal reaches the distant antenna it establishes in that antenna circuit a current of high frequency which has just the same variations as did the current in the antenna at the sending station. The human voice isn’t there. ”

“ In any system of radio-telephony you will always find that there is produced at the transmitting station a high-frequency alternating current and that this current flows in a tuned circuit one part of which is the condenser formed by the antenna and the ground (or something which acts like a ground) . This high-frequency current, or radio-current, as we usually say, is varied in its strength. It is varied in conformity with the human voice. If the human 147voice speaking into the transmitter is low pitched there are slow variations in the intensity of the radio current. ”