Radio transmitter

“ Don unwrapped something that looked like a flat cigarette case with two appendages, one a disk of perforated hard rubber the size of a half dollar, and the other a three-quarter-inch-wide ribbon of opaque plastic. "I've got it, sir."
"Good. What you see is a highly advanced radio transmitter and receiver. You can imagine its value in the field. It's a pilot model you were bringing back from the contractor for tests here. ”

“ 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. ”

“ A TRANSMISSION LINE is a device designed to guide electrical energy from one point to another. It is used, for example, to transfer the output rf energy of a transmitter to an antenna. This energy will not travel through normal electrical wire without great losses. Although the antenna can be connected directly to the transmitter, the antenna is usually located some distance away from the transmitter. On board ship, the transmitter is located inside a radio room, and its associated antenna is mounted on a mast. A transmission line is used to connect the transmitter and the antenna. ”

“ The detector, sometimes known to users of the radio as a “cat’s whisker,” is a thin wire with a point attached to it, extending from the sounding posts to a piece of galena or silicon. This detector is used for this reason: The voice waves that are sent out through a radio transmitter are too faint to be heard by the human ear unaided by a mechanical apparatus. ”

“ Electromechanical protection circuits ensure that a transmitter can only be connected to an antenna that is tuned to the same frequency. The change of antennas and transmitting frequencies is made during the ten-minute interval between programmes, which always begin on the hour, preceded by the now familiar signature tune of a shepherd playing his flute with the tinkling of sheep-bells in the background, recorded in 1936, followed by the Greek National Anthem. ”

“ 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. ”

“ 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. ”

“ Operators thus know when and where to expect degraded performance. Of course, strong solar activity can virtually make over-the-horizon HF radar unusable.
A Spectrum Analyser display shows all the frequencies between 5 and 28 MHz. In order to avoid possible interference to other services, those frequencies which are known to be permanently allocated to fixed broadcasting and telecommunication stations are locked out, as well as frequencies which happen to be used at any instant so that they can also be avoided by the OTHR transmitter. ”

“ Its application has also been suggested for wireless transmission, and although with any system using continuous waves this would not be very difficult, it could hardly be adapted to work with the ordinary spark system. The apparatus for receiving from this type of transmitter would, on the other hand, necessarily be more elaborate than the methods that are described in the next chapter, and as far as the writer's experience goes, experiments along these lines would not prove very profitable, as simplicity is the keynote of success in any radio-photographic system. ”

“ The aerial wire is precisely the same for either wireless telegraphy or wireless telephony. The transmitter of a wireless telegraph set generally uses a spark gap for setting up the electric oscillations, while usually for wireless telephony a vacuum tube is employed for this purpose. The receptor for wireless telegraphy and telephony is the same and may include either a crystal detector or a vacuum tube detector, as will be explained presently. ”

“ RADIATION RESISTANCE—The resistance, which if inserted in place of an antenna, would consume the same amount of power as that radiated by the antenna.
RADIO FREQUENCIES—Electromagnetic frequencies that fall between 3 kilohertz and 300 gigahertz and are used for radio communications.
RADIO HORIZON—The boundary beyond the natural horizon in which radio waves cannot be propagated over the earth’s surface.
RADIO WAVE— (1) A form of radiant energy that can neither be seen nor felt; (2) An electromagnetic wave generated by a transmitter. ”

“ Where set up by spark discharges the spark frequency must be above twenty thousand per second. This unbroken wave train does not affect the telephone and is not audible in a telephone receiver inserted in the radio receiving circuit. But when a microphone transmitter is inserted in the sending circuit, instead of the make-and-break key used for telegraphy, the waves of the voice, thrown against the transmitter in speaking, break up the waves so that the telephone receiver in the receiving circuit will reproduce sound. ”

“ The peak envelope power is the average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the highest crest of the modulation envelope, taken under conditions of normal operation. The mean power is the power supplied to the antenna transmission line by a transmitter during normal operation, averaged over a time sufficiently long compared with the period of the lowest frequency encountered in the modulation. ”

“ Transceivers are light weight units capable of operation with or without headsets. Each transceiver has a removeable, rechargable battery, capable of seven hours of operation based upon 10% transmitter operation, 10% receive and 80% standby operation. External, heliflex antennas are located at the top of each transceiver. There are two types of portable transceivers. The aluminum faced Type 1 transceivers are stored in the control center and will react to the Radio Net Override signal generated by either the LCCFC, ALOC or an operational PTS control trailer. ”

“ The receiver has an open antenna circuit which is electrically responsive to the transmitted waves and is capable of using those responses to actuate by means of a relay or amplifier any convenient form of signalling apparatus for making audible an electrically transmitted signal, such as a telegraph sounder or a loud speaker. In brief, signals at the transmitter are utilized to control high frequency electrical oscillations which are radiated by an antenna through the ether to the distant receiver and there produce an audible or visible signal. ”

“ 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. ”

“ Just like any -- anything that we own, like a car or a microwave oven, after some time, transmitters may degrade or fail in ways that cause them to transmit on incorrect frequencies or have incorrect characteristics, and when that occurs, there is a potential in -- in any radio-type system for other systems to be affected. ”

“ A telephone receiver is connected across the terminals of the detector. When the electromagnetic waves from the transmitting station strike the aerial of the receiving station, they set up therein a series of high frequency oscillations, corresponding to the Morse signals emitted from the transmitter. The oscillations flow back and forth through the aerial and ground, striking the mineral detector on their journey. The high frequency oscillations are alternating currents, because they reverse their direction many thousand times per second. ”

“ The "impulses" generated in the receiving aerial are exceedingly weak and in order to produce an effect must be timed so as to follow one another in proper succession. Tuning devices are for this purpose and by their means the receiving circuits and instruments may be carefully adjusted to the same wave length or "note" as the transmitter so that the high frequency currents in the aerial will arrive at the proper time to oscillate or surge back and forth to produce the maximum results. ”

“ 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. ”

“ The circuits are so constructed that the electrical impulses in the antenna circuit of the transmitter vibrate longer with the application to the transmitter of a given amount of electrical energy than had been the case in the previous structures known to the art, and the selectively and sensitivity of the receiver is likewise enhanced. Thus increased efficiency in the transmission and reception of signals is obtained. ”

“ Since the radio frequency transformer has no iron core the high frequency, or radio frequency oscillating currents, as they are called, surge through it and are not changed into low frequency, or audio frequency pulsating currents, until they flow through the detector. Since the diagram shows only one amplifier and one radio frequency transformer, it is consequently a one step amplifier; however, two, three or more, amplifying tubes can be connected up by means of an equal number of radio frequency transformers when you will get wonderful results. ”

“ The adapter C-band radar beacon is a transponder, which employs the same basic operating principles as the re-entry C-band beacon to provide spacecraft location data upon receipt of a properly coded interrogation signal. The interrogation signal is fed from the antenna to the duplexer. The duplexer is a ferrite circulator which couples the received signal to the rf filter preselector and also isolates the receiver from the transmitter to permit use of a common antenna for reception and transmission. ”

“ 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. ”

“ 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.) ”

“ In an emergency, any wire of sufficient length can be used for an antenna; for example, barbed wire, electrical wire, fence wire, and metal-cored clothesline. Communication has been successful using metal house gutters and even metal bed springs. A radio operator's mission is not completed until communication is established. f. Grounding. A good electrical ground is needed for two reasons: first, to protect the operator and his equipment; and second, as a radio frequency ground needed by some antennas to function properly. ”

“ By connecting a telephone transmitter to the arc in the same manner that it is connected to the speaking arc, the oscillations can be varied in accordance with the vibrations of the voice. The apparatus is connected to the aerial and the earth through the medium of a loose-coupled helix, formed by providing the helix in series with the arc and condenser, with a secondary winding.
FIG. 148.—The Majorana wireless telephone transmitter.
The ordinary carbon transmitter, in its common form, is unsuited for wireless telephonic work, on account of its inability to handle large amounts of power. ”