Detector (radio)

“ I fancy some of your radio experts would gape if they were permitted to see my wave meter. I believe it would cause some excitement in the laboratories of Lodge or Marconi. I—Proctor—I measured these waves which, of course, means that I found a detector for them. Our friend DeForest thinks that he has a monopoly on ultra-sensitive detectors. Proctor's detector is to the audion what a stop watch is to a wheel barrow! ”

“ 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. ”

“ I haven't really put it to the test yet."
"What do you call it?"
"The Universal Detector," replied Jack.
"Just what is that?"
"Well, at present you know a ship can only receive wireless messages from a ship that is 'in tune' with her own radio apparatus. The Universal Detector should make it possible to catch every wireless sound. I am very anxious, if I perfect it, to get it adopted in the navy. It would be of great value in time of war, for by its use every message sent by an enemy, even if they were purposely put 'out of tune,' could be caught." ”

“ I made a crystal receiver and was able to hear the Greek Royal Navy station at Votanikos SXA and the old station at Thiseon in Athens itself, which was still a spark station. There just was nothing else to hear. I acquired a Philips 'E' type valve and built a grid-leak detector circuit, but all I got was silence. The four volt heater drew one amp and I had been trying to get it going with a small torch battery. As I became more experienced I began repairing simple broadcast receivers for my friends and putting up wire antennas for reception for people who had bought broadcast receivers. ”

“ Mirrors, or adding machines? You can't make an audio amplifier of a three million gain."
"I know it—at least not a practical one. But, we can probably use our audio modulator to modulate a radio frequency, and then modulate the driver with the RF. Then we hang a receiver on to the detector gadget here, and collect RF, modulated, just like a standard radio transmission, and amplify it at RF, convert it to IF, and detect it to AF. Catch?" ”

“ 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. ”

“ While oscillator tubes were being experimented with in the research laboratories of the General Electric, the Westinghouse, the Radio Corporation of America, and other big companies, all the youthful amateurs in the country had learned that by using a vacuum tube as a detector they could easily get messages 500 miles away. ”

“ It is remarkable how easy it is to have trouble if the circuits and parts of the detector as a whole are not correct, and this is one of the main reasons why the bulbs are not furnished separately and why all guarantees are immediately dissolved if an Audion bulb is used otherwise than in the Audion Detector made for it. ”

“ 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. ”

“ Crowninshield.
"We are running up our meters in order to catch the higher tuned waves," Bob added. "That is part of the bedlam."
"And the rest?"
"It is static interference."
"What's that?"
"Well, static is the big bugbear of radio," answered Bob, pausing a moment in regulating his tuner and detector. "It is caused by stray waves moving in various directions through the atmosphere, and by electrical conditions. It is the defect all wireless people have to fight. Sometimes it is worse than others and unfortunately to-night it promises to be pretty bad. ”

“ The reason a vacuum tube detector is more sensitive than a crystal detector is because while the latter merely rectifies the oscillating current that surges in the receiving circuits, the former acts as an amplifier at the same time. ”

“ Tim agreed and they made their way out of the hangar and back to the car without detection.
On the trip to New York Tim discussed plans for the capture of Shanghai Sam and Pierre Petard with the young aircraft designer.
“I’ve got something I’ve been fooling with for a long time,” said Giddings. “It’s a sort of radio detector designed for use in time of war. When it is fitted into a plane you can ascertain whether any other ships are in the air and by adjustment of the detector tell how far away they are.” ”

“ Inside was a complete radio receiving set, with vacuum tube detector and batteries in perfect working order. Between the roots of the tree an 182 iron pipe had been driven into the earth to act as a ground. The antenna was strung from top to bottom of the tree on the side away from the path, and there was nothing to differentiate the box from an ordinary wire telephone set, except that it was slightly larger. ”

“ The process of testing Audion Bulbs is one of the most careful and expensive tests in the entire electrical industry. A bulb used in the proper detector may give extremely loud signals from stations twenty or thirty miles away, and yet not be really sensitive to weak signals from great distances, or it may give much weaker response to nearby stations than a crystal detector and still be extremely sensitive to weak signals over long distances. ”

“ All you need for this set are: (1) a crystal detector, (2) a tuning coil and (3) an earphone. You can make a crystal detector out of a couple of binding posts, a bit of galena and a piece of brass wire, or, better, you can buy one all ready to use for 50 cents.
The Crystal Detector.--This is known as the Rasco baby detector and it is made and sold by the Radio Specialty Company, 96 Park Place, New York City. It is shown in Fig. 96. ”

“ For transmitting a 1 kw. transformer is used with an aerial 75 feet long, and 70 feet, high. This station has worked 1ZL, 8NB, 8ZO, 8YL, and has been heard by many stations in the East. The Club has at its disposal an audion detector and for receiving uses an aerial 200 feet long 150 feet high at one end, and 60 feet at the other. ”

“ Make sure that the windings on both coils run in the same direction. If you fail to do this, the set will not work.
For the detector, it is better to purchase a good make of galena detector at any radio supply store. If you are handy with tools, however, you can buy the galena and make your own detector. It will work with more or less satisfaction.
Your next need will be the condenser. The condenser consists of a series of aluminum plates, some of which are movable and the rest stationary. ”

“ The detector was simple, though the tuning had to be precise. A dish-shaped antenna pulled in the signal for the delicately balanced detector. There was a sharp fall-off on both sides of the input so direction could be precisely determined. The resulting signal was fed to an amplifier stage. ”

“ FIG. 63.—Complete receiving set, consisting of two "Perikon" detectors, potentiometer, loose coupler, variable condenser, etc.
There are probably more different forms of detector than any other piece of radiotelegraph apparatus. Those in most common use to-day are the mineral detectors. A small crystal of certain minerals, iron pyrites, silicon, galena, etc., is placed between two contact points which are adjustable so that the pressure may be regulated and the most sensitive portion of the mineral selected. A telephone receiver is shunted across the terminals of the detector. ”

“ With the large condensers and self-inductances employed in modern cable telegraphy, it is easy to get a series of beautifully regular and gradually damped electric oscillations, with a period of two or three seconds, recorded by an ordinary signalling instrument or siphon recorder.
These electromagnetic waves in space have been known on the side of theory ever since 1865, but interest in them was immensely quickened by the discovery of a receiver or detector for them. ”

“ 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. ”

“ According to my theory, upon which the invention is based, the changes produced on or in the sensitive substance of a coherer or detector by electrical disturbances, Hertzian waves, light-waves, and other radiations are due to molecular distortion. In order to obtain the best results with a detector or coherer, it is necessary that this distortion shall be removed before the detector or coherer receives fresh radiations—as, for example, the signals in wireless or other telegraphy. ”

“ He must also see that his detector is adjusted to its greatest degree of sensibility and his tuner to the proper wave length. If your station happens to be near another, or if you are one of a group of ships and other vessels near yours are sending, you must watch out and either weaken the coupling of your detector or open your switch and cut it out altogether when those around you are using powerful currents for transmission ”

“ When used as a receiver for wireless telegraphy Marconi inserted the oscillation coil of this detector in between the earth and a receiving antenna, and this produced one of the most sensitive receivers yet made for wireless telegraphy. Other forms of magnetic detector have been devised by J. A. Fleming, [34] L. H. Walter and J. A. Ewing, [35] H. T. Simon and M. Reich, [36] R. A. Fessenden [37] and others.
A third class of electric wave detector depends upon the power of electric oscillations to annul the electrolytic polarization of electrodes of small surface immersed in an electrolyte. ”

“ After the instruments are connected, place a piece of galena or silicon in the cup of the detector and bring the wire down on it. Then move the sliders on the tuning coil or loose coupler and adjust the detector until you can hear a message buzzing in the telephones. It may require a little patience and practice, but if you persist you will soon learn how to adjust the apparatus so as to receive the signals loudly and clearly with very little trouble. ”

“ 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.) ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”