Spark-gap transmitter

978: 1988: 2419:. Since without the spark no current could flow in the primary circuit, this effectively uncoupled the secondary from the primary circuit, allowing the secondary resonant circuit and antenna to oscillate completely free of the primary circuit after that (until the next spark). This produced output power centered on a single frequency instead of two frequencies. It also eliminated most of the energy loss in the spark, producing very lightly damped, long "ringing" waves, with decrements of only 0.08 to 0.25 (a Q of 12-38) and consequently a very "pure", narrow bandwidth radio signal. Another advantage was the rapid quenching allowed the time between sparks to be reduced, allowing higher spark rates of around 1000 Hz to be used, which had a musical tone in the receiver which penetrated radio static better. The quenched gap transmitter was called the "singing spark" system. 2609: 1671: 2004: 1799: 1786: 2121: 2088: 2593: 2497: 2482: 2828: 966: 931: 2113: 2581: 2100: 1770: 2036: 911: 2273: 2514:: In the earlier rotary gaps, the motor was not synchronized with the frequency of the AC transformer, so the spark occurred at random times in the AC cycle of the voltage applied to the capacitor. The problem with this was the interval between the sparks was not constant. The voltage on the capacitor when a moving electrode approached the stationary electrode varied randomly between zero and the peak AC voltage. The exact time when the spark started varied depending on the gap length the spark could jump, which depended on the voltage. The resulting random phase variation of successive damped waves resulted in a signal that had a "hissing" or "rasping" sound in the receiver. 2305: 2359: 2470: 3003:, slowly replaced the spark transmitter in high-power radiotelegraphy stations. However spark transmitters remained popular in two way communication stations because most continuous wave transmitters were not capable of a mode called "break in" or "listen in" operation. With a spark transmitter, when the telegraph key was up between Morse symbols the carrier wave was turned off and the receiver was turned on, so the operator could listen for an incoming message. This allowed the receiving station, or a third station, to interrupt or "break in" to an ongoing transmission. In contrast, these early CW transmitters had to operate continuously; the 2293: 2329: 896: 1834: 2016: 3020: 2261: 1098: 2824:

so that a round-the-clock radio watch could be kept. US President Taft and the public heard reports of chaos on the air the night of the disaster, with amateur stations interfering with official naval messages and passing false information. In response Congress passed the 1912 Radio Act, in which licenses were required for all radio transmitters, maximum damping of transmitters was limited to a decrement of 0.2 to get old noisy non-syntonic transmitters off the air, and amateurs were mainly restricted to the unused frequencies above 1.5 MHz and output power of 1 kilowatt.

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until the stored energy is dissipated, permitting practical operation only up to around 60 signals per second. If active measures are taken to break the arc (either by blowing air through the spark or by lengthening the spark gap), a much shorter "quenched spark" may be obtained. A simple quenched spark system still permits several oscillations of the capacitor circuit in the time taken for the spark to be quenched. With the spark circuit broken, the transmission frequency is solely determined by the antenna resonant circuit, which permits simpler tuning.

1340: 1571: 2458: 1296: 1617: 759:, the capacitor was charged by AC from a high-voltage transformer as above, and discharged by a spark gap consisting of electrodes spaced around a wheel which was spun by an electric motor, which produced sparks as they passed by a stationary electrode. The spark rate was equal to the rotations per second times the number of spark electrodes on the wheel. It could produce spark rates up to several thousand hertz, and the rate could be adjusted by changing the speed of the motor. The rotation of the wheel was usually synchronized to the AC 705:

contact, opening the switch and cutting off the primary current. Then the magnetic field collapses, creating a pulse of high voltage in the secondary winding, and the interrupter arm springs back to close the contact again, and the cycle repeats. Each pulse of high voltage charged up the capacitor until the spark gap fired, resulting in one spark per pulse. Interrupters were limited to low spark rates of 20–100 Hz, sounding like a low buzz in the receiver. In powerful induction coil transmitters, instead of a vibrating interrupter, a

2383:. The oscillating radio frequency energy was passed rapidly back and forth between the primary and secondary resonant circuits as long as the spark continued. Each time the energy returned to the primary, some was lost as heat in the spark. In addition, unless the coupling was very loose the oscillations caused the transmitter to transmit on two separate frequencies. Since the narrow passband of the receiver's resonant circuit could only be tuned to one of these frequencies, the power radiated at the other frequency was wasted. 1352: 2186:, which lost funding and was abandoned unfinished after Marconi's success). Marconi's original round 400-wire transmitting antenna collapsed in a storm 17 September 1901 and he hastily erected a temporary antenna consisting of 50 wires suspended in a fan shape from a cable between two 160 foot poles. The frequency used is not known precisely, as Marconi did not measure wavelength or frequency, but it was between 166 and 984 kHz, probably around 500 kHz. He received the signal on the coast of St. John's, 1735:(coil) between the sides of his dipole antennas, which resonated with the capacitance of the antenna to make a tuned circuit. Although his complicated circuit did not see much practical use, Lodge's "syntonic" patent was important because it was the first to propose a radio transmitter and receiver containing resonant circuits which were tuned to resonance with each other. In 1911 when the patent was renewed the Marconi Company was forced to buy it to protect its own syntonic system against infringement suits. 1465: 726:, when the capacitor was fully charged. Since the AC sine wave has two peaks per cycle, ideally two sparks occurred during each cycle, so the spark rate was equal to twice the frequency of the AC power (often multiple sparks occurred during the peak of each half cycle). The spark rate of transmitters powered by 50 or 60 Hz mains power was thus 100 or 120 Hz. However higher audio frequencies cut through interference better, so in many transmitters the transformer was powered by a 2446: 1001: 1485: 1445: 1016: 7949: 2047:

of the above prior patents, Marconi in his 26 April 1900 "four circuit" or "master tuning" patent on his system claimed rights to the inductively coupled transmitter and receiver. This was granted a British patent, but the US patent office twice rejected his patent as lacking originality. Then in a 1904 appeal a new patent commissioner reversed the decision and granted the patent, on the narrow grounds that Marconi's patent by including an antenna

7959: 357: 7938: 20: 2783:. In the US prior to 1912 there was no government regulation of radio, and a chaotic "wild west" atmosphere prevailed, with stations transmitting without regard to other stations on their frequency, and deliberately interfering with each other. The expanding numbers of non-syntonic broadband spark transmitters created uncontrolled congestion in the airwaves, interfering with commercial and military wireless stations. 2628:, one of the most powerful spark transmitters ever built. During World War I it transmitted telegram traffic at 200 words per minute on 21.5 kHz to receivers in Belmar, New Jersey. The roar of the spark could reportedly be heard a kilometer away. On 22 September 1918 it transmitted the first wireless message from Britain to Australia, a distance of 15,200 km (9,439 miles). In 1921 it was replaced by 1138:, and largely failed to foresee its possibilities as a communication technology. Due to the influence of Maxwell's theory, their thinking was dominated by the similarity between radio waves and light waves; they thought of radio waves as an invisible form of light. By analogy with light, they assumed that radio waves only traveled in straight lines, so they thought radio transmission was limited by the visual 7969: 666:. As long as the key is pressed the spark gap fires repetitively, creating a string of pulses of radio waves, so in a receiver the keypress sounds like a buzz; the entire Morse code message sounds like a sequence of buzzes separated by pauses. In low-power transmitters the key directly breaks the primary circuit of the supply transformer, while in high-power transmitters the key operates a heavy duty 3069:

equipment that was still being used on older ships. The Convention prohibited licensing of new land spark transmitters after 1929. Damped wave radio emission, called Class B, was banned after 1934 except for emergency use on ships. This loophole allowed shipowners to avoid replacing spark transmitters, which were kept as emergency backup transmitters on ships through World War II.

1751:. The energy in each spark, and thus the power output, was no longer limited by the capacitance of the antenna but by the size of the capacitor in the resonant circuit. In order to increase the power very large capacitor banks were used. The form that the resonant circuit took in practical transmitters was the inductively-coupled circuit described in the next section. 1593:). During each spark the energy stored in the antenna was quickly radiated away as radio waves, so the oscillations decayed to zero quickly. The radio signal consisted of brief pulses of radio waves, repeating tens or at most a few hundreds of times per second, separated by comparatively long intervals of no output. The power radiated was dependent on how much 977: 4360:, Applied: 2 June 1896, full specification: 2 March 1897, accepted: 2 July 1897. British patents allowed the full specification to be submitted after the application. Marconi's monopole antenna did not appear in his initial June 1896 application but in his March 1897 specification. Corresponding US patent 586193, Marconi, Guglielmo, 2132:. This would require a major scale-up in power, a risky gamble for his company. Up to that time his small induction coil transmitters had an input power of 100 - 200 watts, and the maximum range achieved was around 150 miles. To build the first high power transmitter, Marconi hired an expert in electric power engineering, Prof. 1785: 4909:"Crookes’s article was read very widely—and more than that, attended to and remembered—both in Europe and in the United States; there is hardly one figure important in the early days of radio who does not at some point in his memoirs or correspondence refer to the article of 1892 as having made a difference." 1798: 6532:

George Fitzgerald as early as 1892 described a spark oscillator as similar to the oscillations produced when a cork pops out of a winebottle, and said what was needed was a continuous electromagnetic "whistle". He realized that if the resistance of a tuned circuit were made zero or negative it would

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s call as its radio operator had gone to bed. This was held responsible for most of the 1500 deaths. Existing international regulations required all ships with more than 50 passengers to carry wireless equipment, but after the disaster subsequent regulations mandated ships have enough radio officers

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gap. A quenched gap consisted of a stack of wide cylindrical electrodes separated by thin insulating spacer rings to create many narrow spark gaps in series, of around 0.1–0.3 mm (0.004–0.01 in). The wide surface area of the electrodes terminated the ionization in the gap quickly by cooling

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Marconi at first paid little attention to syntony, but by 1900 developed a radio system incorporating features from these systems, with a two circuit transmitter and two circuit receiver, with all four circuits tuned to the same frequency, using a resonant transformer he called the "jigger". In spite

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used also had no resonant circuits, so they had no way of selecting one signal from others besides the broad resonance of the antenna, and responded to the transmissions of all transmitters in the vicinity. An example of this interference problem was an embarrassing public debacle in August 1901 when

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of the transmitter, which is the number of sinusoidal oscillations per second in each damped wave. Since the transmitter produces one pulse of radio waves per spark, the output power of the transmitter was proportional to the spark rate, so higher rates were favored. Spark transmitters generally used

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to zero. When the oscillating electric current in the primary circuit has decreased to a point where it is insufficient to keep the air in the spark gap ionized, the spark stops, opening the resonant circuit, and stopping the oscillations. In a transmitter with two resonant circuits, the oscillations

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for deep body heating. High oscillating voltages of hundreds of thousands of volts at frequencies of 0.1 - 1 MHz from a Tesla coil were applied directly to the patient's body. The treatment was not painful, because currents in the radio frequency range do not cause the physiological reaction of

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Knowledgeable sources today doubt whether Marconi actually received this transmission. Ionospheric conditions should not have allowed the signal to be received during the daytime at that range. Marconi knew the Morse code signal to be transmitted was the letter 'S' (three dots). He and his assistant

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provided the means for tuning the four circuits to the same frequency, whereas in the Tesla and Stone patents this was done by adjusting the length of the antenna. This patent gave Marconi a near monopoly of syntonic wireless telegraphy in England and America. Tesla sued Marconi's company for patent

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of the circuit so the oscillations were less damped. Another advantage was the frequency of the transmitter was no longer determined by the length of the antenna but by the resonant circuit, so it could easily be changed by adjustable taps on the coil. The antenna was brought into resonance with the

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The transmitter works in a rapid repeating cycle in which the capacitor is charged to a high voltage by the transformer and discharged through the coil by a spark across the spark gap. The impulsive spark excites the resonant circuit to "ring" like a bell, producing a brief oscillating current which

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in synchronism with the cycles of the AC voltage to the transformer, so the spark occurred at the same points of the voltage sine wave each cycle. Usually it was designed so there was one spark each half cycle, adjusted so the spark occurred at the peak voltage when the capacitor was fully charged.

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Marconi's achievement received worldwide publicity, and was the final proof that radio was a practical communication technology. The scientific community at first doubted Marconi's report. Virtually all wireless experts besides Marconi believed that radio waves traveled in straight lines, so no one

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The inductively coupled or "syntonic" spark transmitter was the first type that could communicate at intercontinental distances, and also the first that had sufficiently narrow bandwidth that interference between transmitters was reduced to a tolerable level. It became the dominant type used during

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so the moving electrode passed by the stationary one at the peak of the sine wave, initiating the spark when the capacitor was fully charged, which produced a musical tone in the receiver. When tuned correctly in this manner, the need for external cooling or quenching airflow was eliminated, as was

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steps the input voltage up to the high voltage needed. The sinusoidal voltage from the transformer is applied directly to the capacitor, so the voltage on the capacitor varies from a high positive voltage, to zero, to a high negative voltage. The spark gap is adjusted so sparks only occur near the

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audiences and aviation authorities were complaining of the disruption to radio reception that noisy legacy marine spark transmitters were causing. But shipping interests vigorously fought a blanket prohibition on damped waves, due to the capital expenditure that would be required to replace spark

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can only have low damping (high Q, narrow bandwidth) if it is a "closed" circuit, with no energy dissipating components. But such a circuit does not produce radio waves. A resonant circuit with an antenna radiating radio waves (an "open" tuned circuit) loses energy quickly, giving it high damping

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The speed at which signals may be transmitted is naturally limited by the time taken for the spark to be extinguished. If, as described above, the conductive plasma does not, during the zero points of the alternating current, cool enough to extinguish the spark, a 'persistent spark' is maintained

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waves (CW), had theoretical advantages over damped waves for radio transmission. Because their energy is essentially concentrated at a single frequency, in addition to causing almost no interference to other transmitters on adjacent frequencies, continuous wave transmitters could transmit longer

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and reinforced each other. The result was essentially a continuous sinusoidal wave, whose amplitude varied with a ripple at the spark rate. This system was necessary to give Marconi's transoceanic stations a narrow enough bandwidth that they didn't interfere with other transmitters on the narrow

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repeatedly breaks the circuit that provides current to the primary winding, causing the coil to generate pulses of high voltage. When the primary current to the coil is turned on, the primary winding creates a magnetic field in the iron core which pulls the springy interrupter arm away from its

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This troublesome backflow of energy to the primary circuit could be prevented by extinguishing (quenching) the spark at the right instant, after all the energy from the capacitors was transferred to the antenna circuit. Inventors tried various methods to accomplish this, such as air blasts and

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were developed, which were less expensive and produced continuous waves which had a greater range, produced less interference, and could also carry audio, making spark transmitters obsolete by 1920. The radio signals produced by spark-gap transmitters are electrically "noisy"; they have a wide

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and others. It consisted of multiple electrodes equally spaced around a disk rotor spun at high speed by a motor, which created sparks as they passed by a stationary electrode. By using the correct motor speed, the rapidly separating electrodes extinguished the spark after the energy had been

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of the radiated signal, it would occupy a smaller range of frequencies around its center frequency, so that the signals of transmitters "tuned" to transmit on different frequencies would no longer overlap. A receiver which had its own resonant circuit could receive a particular transmitter by

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of the coil when the capacitor voltage reaches zero the current doesn't stop but keeps flowing, charging the capacitor plates with an opposite polarity, until the charge is stored in the capacitor again, on the opposite plates. Then the process repeats, with the charge flowing in the opposite

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to carry sound. The problem was no techniques were known for generating them. The efforts described above to reduce the damping of spark transmitters can be seen as attempts to make their output approach closer to the ideal of a continuous wave, but spark transmitters could not produce true

1905:. The advantage of the inductively coupled circuit was that the "loosely coupled" transformer transferred the oscillating energy of the tank circuit to the radiating antenna circuit gradually, creating long "ringing" waves. A second advantage was that it allowed a large primary capacitance 402:

The cycle begins when current from the transformer charges up the capacitor, storing positive electric charge on one of its plates and negative charge on the other. While the capacitor is charging the spark gap is in its nonconductive state, preventing the charge from escaping through the

846:". Maxwell proposed that light consisted of electromagnetic waves of short wavelength, but no one knew how to confirm this, or generate or detect electromagnetic waves of other wavelengths. By 1883 it was theorized that accelerated electric charges could produce electromagnetic waves, and 2496: 205:

Pictorial diagram of a simple spark-gap transmitter from a 1917 boy's hobby book, showing examples of the early electronic components used. It is typical of the low-power transmitters homebuilt by thousands of amateurs during this period to explore the exciting new technology of

930: 2304: 1769: 1946:) attached to an elevated wire monopole antenna transmitted radio waves, which were received across the room by a similar wire antenna attached to a receiver consisting of a second grounded resonant transformer tuned to the transmitter's frequency, which lighted a 2249:("static") in their earphones for the clicks of the transmitter. Marconi made many subsequent transatlantic transmissions which clearly establish his priority, but reliable transatlantic communication was not achieved until 1907 with more powerful transmitters. 1282:, mainly by combining and tinkering with the inventions of others. Starting at age 21 on his family's estate in Italy, between 1894 and 1901 he conducted a long series of experiments to increase the transmission range of Hertz's spark oscillators and receivers. 1392:. The length of the antenna determined the wavelength of the waves produced and thus their frequency. Longer, lower frequency waves have less attenuation with distance. As Marconi tried longer antennas, which radiated lower frequency waves, probably in the 854:. Fitzgerald in a brief note published in 1883 suggested that electromagnetic waves could be generated practically by discharging a capacitor rapidly; the method used in spark transmitters, however there is no indication that this inspired other inventors. 379: 2916:

gas, eroded the spark electrodes, and could be a fire hazard. Despite its drawbacks, most wireless experts believed along with Marconi that the impulsive "whipcrack" of a spark was necessary to produce radio waves that would communicate long distances.

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The first application of radio was on ships, to keep in touch with shore, and send out a distress call if the ship were sinking. The Marconi Company built a string of shore stations and in 1904 established the first Morse code distress call, the letters

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to carry sound. Due to the development of the first high-power transmitting tubes by the end of World War I, in the 1920s tube transmitters replaced the arc converter and alternator transmitters, as well as the last of the old noisy spark transmitters.

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and capacitor in the primary circuit of the induction coil produced a continuous string of damped waves. Hertz often just used a pushbutton switch, which created a single spark and pulse of radio waves when pushed, resulting in a single spark in his

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the "spark" era. A drawback of the plain inductively coupled transmitter was that unless the primary and secondary coils were very loosely coupled it radiated on two frequencies. This was remedied by the quenched-spark and rotary gap transmitters

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The energy in the resonant circuit is limited to the amount of energy originally stored in the capacitor. The radiated radio waves, along with the heat generated by the spark, uses up this energy, causing the oscillations to decrease quickly in

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The largest spark transmitters were powerful transoceanic radiotelegraphy stations with input power of 100 - 300 kW. Beginning about 1910, industrial countries built global networks of these stations to exchange commercial and diplomatic

1950:. This system, patented by Tesla 2 September 1897, 4 months after Lodge's "syntonic" patent, was in effect an inductively coupled radio transmitter and receiver, the first use of the "four circuit" system claimed by Marconi in his 1900 patent 1380:

He was unable to communicate beyond a half-mile until 1895, when he discovered that the range of transmission could be increased greatly by replacing one side of the Hertzian dipole antenna in his transmitter and receiver with a connection to

1582:(also called LC circuits, tank circuits, or tuned circuits), the spark gap was in the antenna, which functioned as the resonator to determine the frequency of the radio waves. These were called "unsyntonized" or "plain antenna" transmitters. 5376: 3632: 1661:

attempted to report the New York Yacht Race to newspapers from ships with their untuned spark transmitters. The Morse code transmissions interfered, and the reporters on shore failed to receive any information from the garbled signals.

2558:. These were discharged sequentially by multiple rotary discharger wheels on the same shaft to create overlapping damped waves shifted progressively in time, which were added together in the oscillation transformer so the output was a 6533:

produce continuous oscillations, and tried to make an electronic oscillator by exciting a tuned circuit with negative resistance from a dynamo, what would today be called a parametric oscillator, but was unsuccessful. G. Fitzgerald,

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sinking 14 April 1912 increased public appreciation for the role of radio, but the loss of life brought attention to the disorganized state of the new radio industry, and prompted regulation which corrected some abuses. Although the

5013:(1) the idea of inductive coupling between the driving and the working circuits (2) the importance of tuning both circuits, i.e. the idea of an 'oscillation transformer' (3) the idea of a capacitance loaded open secondary circuit 1505:

funded his experiments. Marconi applied for a patent on his radio system 2 June 1896, often considered the first wireless patent. In May 1897 he transmitted 14 km (8.7 miles), on 27 March 1899 he transmitted across the

1000: 2771:", many of them teenage boys, who used their homebuilt sets recreationally to contact distant amateurs and chat with them by Morse code, and relay messages. Low-power amateur transmitters ("squeak boxes") were often built with " 1609:" antennas characteristic of the "spark" era. The only other way to increase the energy stored in the antenna was to charge it up to very high voltages. However the voltage that could be used was limited to about 100 kV by 965: 700:(Ruhmkorff coil) was used in low-power transmitters, usually less than 500 watts, often battery-powered. An induction coil is a type of transformer powered by DC, in which a vibrating arm switch contact on the coil called an 301:. The advantage of this circuit was that the oscillating current persisted in the antenna circuit even after the spark stopped, creating long, ringing, lightly damped waves, in which the energy was concentrated in a narrower 1069:

were applied between the two sides of the antenna. Each pulse stored electric charge in the capacitance of the antenna, which was immediately discharged by a spark across the spark gap. The spark excited brief oscillating

1248:, limiting their power output. Therefore, these devices were not capable of long distance transmission; their reception range with the primitive receivers employed was typically limited to roughly 100 yards (100 meters). 806:

had come close to discovering radio in 1875; he had generated and detected radio waves which he called "etheric currents" experimenting with high-voltage spark circuits, but due to lack of time did not pursue the matter.

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around 1896. One of the first uses for spark-gap transmitters was on ships, to communicate with shore and broadcast a distress call if the ship was sinking. They played a crucial role in maritime rescues such as the 1912

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The inductively-coupled transmitter had a more complicated output waveform than the non-syntonic transmitter, due to the interaction of the two resonant circuits. The two magnetically coupled tuned circuits acted as a

297:. The antenna and ground were connected to the secondary winding. The capacitance of the antenna resonated with the secondary winding to make a second resonant circuit. The two resonant circuits were tuned to the same 789:

signals without wires. Experiments by a number of inventors had shown that electrical disturbances could be transmitted short distances through the air. However most of these systems worked not by radio waves but by

3882:. The text in full: "This is by utilizing the alternating currents produced when an accumulator is discharged through a small resistance. It would be possible to produce waves of ten meters wavelength, or even less" 377: 2541:

of 15 or greater). Virtually the only spark transmitters which could satisfy this condition were the quenched-spark and rotary gap types above, and they dominated wireless telegraphy for the rest of the spark era.

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It became clear that for multiple transmitters to operate, some system of "selective signaling" had to be devised to allow a receiver to select which transmitter's signal to receive, and reject the others. In 1892

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of damped waves. The speed of the discharger wheel was controlled so that the time between sparks was equal to an integer multiple of the wave period. Therefore, oscillations of the successive wave trains were

1086:, which radiated waves roughly twice the length of the antenna (for example a dipole 1 meter long would generate 150 MHz radio waves). Hertz detected the waves by observing tiny sparks in micrometer spark gaps 1917:. The receiver in most systems also used two inductively coupled circuits, with the antenna an "open" resonant circuit coupled through an oscillation transformer to a "closed" resonant circuit containing the 1514:

communication at increasingly long distances convinced the world that radio, or "wireless telegraphy" as it was called, was not just a scientific curiosity but a commercially useful communication technology.

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of the transmitter, the number of sparks and resulting damped wave pulses it produces per second, which determines the tone of the signal heard in the receiver. The spark rate should not be confused with the

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toy trucks, boats and robots called Radicon, which used a low-power spark transmitter in the controller as an inexpensive way to produce the radio control signals. The signals were received in the toy by a

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Standard Marconi inductively coupled transmitter on ship 1902. Spark gap is in front of induction coil, lower right. The spiral oscillation transformer is in the wooden box on the wall above the Leyden

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Beginning about 1904, continuous wave transmitters were developed using new principles, which competed with spark transmitters. Continuous waves were first generated by two short-lived technologies:

2003: 819:. Neither of these individuals are usually credited with the discovery of radio, because they did not understand the significance of their observations and did not publish their work before Hertz. 3307:

Individual nations enforce this prohibition in their communication laws. In the United States, Federal Communications Commission (FCC) regulations make it a felony to operate a spark transmitter:

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used to receive them were simple enough that they were widely built by hobbyists. During the first decades of the 20th century this exciting new high tech hobby attracted a growing community of "

1510:, 46 km (28 miles), in fall 1899 he extended the range to 136 km (85 miles), and by January 1901 he had reached 315 km (196 miles). These demonstrations of wireless 1225:

of radio waves. He also measured the speed of radio waves, showing they traveled at the same speed as light. These experiments established that light and radio waves were both forms of Maxwell's

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is radiated as electromagnetic waves by the antenna. The transmitter repeats this cycle at a rapid rate, so the spark appeared continuous, and the radio signal sounded like a whine or buzz in a

198:; the charge flows rapidly back and forth through the spark gap for a brief period, charging the conductors on each side alternately positive and negative, until the oscillations die away. 1146:, and therefore was not capable of longer distance communication. As late as 1894 Oliver Lodge speculated that the maximum distance Hertzian waves could be transmitted was a half mile. 2502:

US Navy 100 kW rotary gap transmitter built by Fessenden in 1913 at Arlington, Virginia. It transmitted on 113 kHz to Europe, and broadcast the US's first radio time signal.

2490:'s 35 kW synchronous rotary spark transmitter, built 1905 at Brant Rock, Massachusetts, with which he achieved the first 2 way transatlantic communication in 1906 on 88 kHz. 2872:

Co. which was dominant outside the British Empire. Marconi transmitters used the timed spark rotary discharger, while Telefunken transmitters used its quenched spark gap technology.

268:. However, this meant that the electromagnetic energy produced by the transmitter was dissipated across a wide band, thereby limiting its effective range to a few kilometers at most. 226:

to 75-100 kilovolts in powerful transmitters) to jump across the spark gap. The transformer charges the capacitor. In low-power transmitters powered by batteries this was usually an

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invalidated the inductive coupling claims of Marconi's patent due to the prior patents of Lodge, Tesla, and Stone, but this came long after spark transmitters had become obsolete.

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The 1927 International Radiotelegraph Convention in Washington, D.C. saw a political battle to finally eliminate spark radio. Spark transmitters were obsolete at this point, and

2035: 1830:(low Q, wide bandwidth). There was a fundamental tradeoff between a circuit which produced persistent oscillations which had narrow bandwidth, and one which radiated high power. 1712:

to the frequency of the desired transmitter, analogously to the way one musical instrument could be tuned to resonance with another. This is the system used in all modern radio.

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in the secondary circuit and antenna may continue some time after the spark has terminated. Then the transformer begins charging the capacitor again, and the whole cycle repeats.

1644:, which made it impossible for other transmitters to be heard. When multiple transmitters attempted to operate in the same area, their broad signals overlapped in frequency and 1416:

propagation. Marconi did not understand any of this at the time; he simply found empirically that the higher his vertical antenna was suspended, the further it would transmit.

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To reduce interference caused by the "noisy" signals of the burgeoning numbers of spark transmitters, the 1912 US Congress "Act to Regulate Radio Communication" required that "

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direction through the coil. This continues, resulting in oscillating currents flowing rapidly back and forth between the plates of the capacitor through the coil and spark gap.

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In 1912 in his high-power stations Marconi developed a refinement of the rotary discharger called the "timed spark" system, which generated what was probably the nearest to a

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Hertz's first oscillator: a pair of one meter copper wires with a 7.5 mm spark gap between them, ending in 30 cm zinc spheres. When 20,000 volt pulses from an induction coil

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was also experimenting with spark oscillators at this time and came close to discovering radio waves before Hertz, but his focus was on waves on wires, not in free space.

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The resonant circuit is connected to the antenna, so these oscillating currents also flow in the antenna, charging and discharging it. The current creates an oscillating

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between two conductors was the first device known which could generate radio waves. The spark itself doesn't produce the radio waves, it merely serves as a fast acting

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Quenched spark gap from transmitter, left. The handle turns a screw which puts pressure on the stack of cylindrical electrodes, allowing the gap widths to be adjusted.

2852:, radio became a strategic defensive technology, as it was realized a nation without long distance radiotelegraph stations could be isolated by an enemy cutting its 4560: 881:, which were called "Hertzian waves" until about 1910. Hertz was inspired to try spark excited circuits by experiments with "Reiss spirals", a pair of flat spiral 3904:

Translated from German by A. E. Selig. Zenneck describes the Marconi, Braun, and Wien transmitters on p. 173, and the early "lineal" or Hertz oscillators on p. 41.

1757: 370: 2163:, which generated the output. The spark rate was low, perhaps as low as 2 - 3 sparks per second. Fleming estimated the radiated power was around 10 - 12 kW. 1601:

of the antenna. To increase their capacitance to ground, antennas were made with multiple parallel wires, often with capacitive toploads, in the "harp", "cage", "

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The high frequencies produced by Hertzian oscillators could not travel beyond the horizon. The dipole resonators also had low capacitance and couldn't store much

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band. Timed spark transmitters achieved the longest transmission range of any spark transmitters, but these behemoths represented the end of spark technology.

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were used to transmit Morse code text at high speed. To achieve a maximum range of around 3000 – 6000 miles, transoceanic stations transmitted mainly in the

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of the transformer made one resonant circuit, which generated the oscillating current. The oscillating current in the primary winding created an oscillating

2217:(including Marconi) understood how the waves had managed to propagate around the 300 mile high curve of the Earth between Britain and Newfoundland. In 1902 7213: 4666: 2529:

with the line frequency. The synchronous gap was said to produce a more musical, easily heard tone in the receiver, which cut through interference better.

857:

The division of the history of spark transmitters into the different types below follows the organization of the subject used in many wireless textbooks.

1408:

that followed the contour of the Earth. Under certain conditions they could also reach beyond the horizon by reflecting off layers of charged particles (

3011:

could not operate as long as the transmitter was powered up. Therefore, these stations could not receive messages until the transmitter was turned off.

2912:, which due to their large bandwidth caused interference between transmitters. The spark also made a very loud noise when operating, produced corrosive 1271:

was one of the first people to believe that radio waves could be used for long distance communication, and singlehandedly developed the first practical

802:

claimed to have transmitted an electrical signal through the atmosphere between two 600 foot wires held aloft by kites on mountaintops 14 miles apart.

1530:

throughout the spark era. Inspired by Marconi, in the late 1890s other researchers also began developing competing spark radio communication systems;

6575: 5440: 1404:

waves produced by Hertz's horizontal antennas. These longer vertically polarized waves could travel beyond the horizon, because they propagated as a

2469: 2434:

A second type of spark gap that had a similar quenching effect was the "rotary gap", invented by Tesla in 1896 and applied to radio transmitters by

2411:

it after the current stopped. In the inductively coupled transmitter, the narrow gaps extinguished ("quenched") the spark at the first nodal point (

6560: 3356: 325:, a metal conductor such as an elevated wire, that radiates the power in the oscillating electric currents from the resonant circuit into space as 3386: 1201:

bands. In his various experiments, Hertz produced waves with frequencies from 50 to 450 MHz, roughly the frequencies used today by broadcast

1057:

a common lab power source which produced pulses of high voltage, 5 to 30 kV. In addition to radiating the waves, the antenna also acted as a

4983: 662:

in the primary circuit of the transformer, producing sequences of short (dot) and long (dash) strings of damped waves, to spell out messages in

3794: 1731:, who had been researching electrical resonance for years, patented the first "syntonic" transmitter and receiver in May 1897 Lodge added an 3562: 59:

built the first experimental spark-gap transmitters in 1887, with which he proved the existence of radio waves and studied their properties.

3413: 7921: 7893: 7888: 6913: 5615:. Proceedings of the 1995 International Conference on 100 Years of Radio. London: Institute of Engineering and Technology. pp. 32–34. 1670: 4148:

Signor Marconi's Magic Box: The Most Remarkable Invention Of The 19th Century & The Amateur Inventor Whose Genius Sparked A Revolution

3109:

discovered that RF currents applied to a scalpel could cut and cauterize tissue in medical operations, and spark oscillators were used as

2608: 2445: 462:

The cycle is very rapid, taking less than a millisecond. With each spark, this cycle produces a radio signal consisting of an oscillating

6546: 4811: 3197: 5922: 2136:

of University College, London, who applied power engineering principles. Fleming designed a complicated inductively-coupled transmitter

1909:

to be used which could store a lot of energy, increasing the power output enormously. Powerful transoceanic transmitters often had huge

4845: 4503: 4476: 3088:

The spark gap oscillator was also used in nonradio applications, continuing long after it became obsolete in radio. In the form of the

709:

was used. This could break the current at rates up to several thousand hertz, and the rate could be adjusted to produce the best tone.

1490:

French non-syntonic transmitter used for ship-to-shore communication around 1900. It had a range of about 10 kilometres (6.2 mi).

613:

The transmitter repeats this cycle rapidly, so the output is a repeating string of damped waves. This is equivalent to a radio signal

4543: 2128:

Marconi decided in 1900 to attempt transatlantic communication, which would allow him to dominate Atlantic shipping and compete with

6865: 5961:

Improvements relating to the production, regulation, and utilization of electric currents of high frequency, and apparatus therefore

1825:

In developing these syntonic transmitters, researchers found it impossible to achieve low damping with a single resonant circuit. A

1257:

I could scarcely conceive it possible that application to useful purposes could have escaped the notice of such eminent scientists.

2120: 1522:. and radio communication began to be used commercially around 1900. His first large contract in 1901 was with the insurance firm 557: 122:(RFI) that can disrupt other radio transmissions. This type of radio emission has been prohibited by international law since 1934. 4927: 4865:

Wireless telegraphy and wireless telephony: An understandable presentation of the science of wireless transmission of intelligence

4705:

Wireless Telegraphy and Wireless Telephony: An understandable presentation of the science of wireless transmission of intelligence

264:

The earliest spark-gap transmitters before 1897 did not have a resonant circuit; the antenna performed this function, acting as a

62:

A fundamental limitation of spark-gap transmitters is that they generate a series of brief transient pulses of radio waves called

5411: 7915: 5770: 2896:

antennas up to several miles long with large capacitive toploads, to achieve adequate efficiency. The antenna required a large

2093:

Marconi's transmitting station at Poldhu, Cornwall, showing the original 400-wire vertical inverted cone aerial which collapsed

2654:

was agreed on. The first significant marine rescue due to radiotelegraphy was the 23 January 1909 sinking of the luxury liner

2087: 7910: 7900: 7880: 7682: 6093: 6043: 5308: 3309: 3224: 2592: 1396:

band around 2 MHz, he found that he could transmit further. Another advantage was that these vertical antennas radiated

2457: 2334:

A powerful quenched-spark transmitter in Australia. The 6 cylinders in front of the Leyden jars are the quenched spark gaps.

1613:

which caused charge to leak off the antenna, particularly in wet weather, and also energy lost as heat in the longer spark.

869:

in 1887 built the first experimental spark gap transmitters during his historic experiments to demonstrate the existence of

7993: 6853: 5854: 7047: 4025: 187:

in the conductors of the attached circuit. The conductors radiate the energy in this oscillating current as radio waves.

7972: 7905: 7751: 6728: 5613:

Fessenden and Marconi: Their differing technologies and transatlantic experiments during the first decade of this century

3251: 1921:. A radio system with a "two circuit" (inductively coupled) transmitter and receiver was called a "four circuit" system. 654:

In order to transmit information with this signal, the operator turns the transmitter on and off rapidly by tapping on a

6886: 6371: 4528: 3281: 2554:

that sparks could produce. He used several identical resonant circuits in parallel, with the capacitors charged by a DC

2439:

transferred to the secondary. The rotating wheel also kept the electrodes cooler, important in high-power transmitters.

1715:

During the period 1897 to 1900 wireless researchers realized the advantages of "syntonic" or "tuned" systems, and added

1329:

Marconi's first monopole antenna transmitter, 1895. One side of spark gap grounded, the other attached to a metal plate

8008: 7677: 6612: 6517: 5884: 5830: 5803: 5550: 5421: 5281: 5190: 5160: 5120: 5093: 4623:. Proceedings of the 1995 International Conference on 100 Years of Radio. London: Institute of Engineering Technology. 4570: 4513: 4486: 4450: 4418: 4334: 4307: 4190: 4156: 4129: 4067: 4035: 3853: 3804: 3774: 3457: 3423: 3396: 3366: 3234: 3207: 2827: 2415:) when the primary current momentarily went to zero after all the energy had been transferred to the secondary winding 4910: 2112: 7771: 4636: 4097: 4005: 706: 5708: 5298: 4774: 1932:

in 1891. At a March 1893 St. Louis lecture he had demonstrated a wireless system that, although it was intended for

1849:

The solution found by a number of researchers was to use two resonant circuits in the transmitter, with their coils

1585:

The average power output of these transmitters was low, because due to its low capacitance the antenna was a highly

1074:

of current between the sides of the antenna. The antenna radiated the energy as a momentary pulse of radio waves; a

7556: 7104: 6906: 6701: 2909: 2535:

the logarithmic decrement per oscillation in the wave trains emitted by the transmitter shall not exceed two tenths

1075: 475: 63: 6765: 2580: 971:

Hertz's 450 MHz transmitter; a 26 cm dipole with spark gap at focus of a sheet metal parabolic reflector

7667: 4408: 4324: 4057: 1222: 6667: 3128:

Spark gap oscillators are still used to generate high-frequency high voltage needed to initiate welding arcs in

2880:(VLF) band, from 50 kHz to as low as 15 – 20 kHz. At these wavelengths even the largest antennas were 2099: 1369:

Later researchers found that multiple parallel wires were a better way to increase capacitance. "Cage antennas"

7662: 2116:

Circuit of Poldhu transmitter. Fleming's curious dual spark gap design was not used in subsequent transmitters.

82:

radio transmission. So spark-gap transmitters could not transmit audio, and instead transmitted information by

3868:

Fitzgerald, George "On a method of producing electromagnetic disturbances of comparatively short wavelength",

3339: 7687: 6315: 5820: 5793: 2857: 1936:, had many of the elements of later radio communication systems. A grounded capacitance-loaded spark-excited 1727:(coils of wire) to transmitters and receivers, to make resonant circuits (tuned circuits, or tank circuits). 1704: 1629: 1519: 302: 115: 97:

The first practical spark gap transmitters and receivers for radiotelegraphy communication were developed by

6848: 4650: 4440: 7962: 7723: 7620: 7163: 6958: 6930: 2234: 1645: 119: 5482: 5083: 4592: 3662: 1385:

and the other side with a long wire antenna suspended high above the ground. These antennas functioned as

738:, that produced AC at a higher frequency, usually 500 Hz, resulting in a spark rate of 1000 Hz. 47:. Spark-gap transmitters were the first type of radio transmitter, and were the main type used during the 7952: 7459: 6899: 6650: 5661: 5180: 5110: 4214:

Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity Through Space

3925:

Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity Through Space

2358: 1933: 1531: 271:

Most spark transmitters had two resonant circuits coupled together with an air core transformer called a

194:

of circuit conductors, the discharge of a capacitor through a low enough resistance (such as a spark) is

6077: 5443:, filed: 26 April 1900, granted: 13 April 1901. Corresponding US Patent no. 763,772, Guglielmo Marconi, 3081:

were regularly nicknamed "Sparky" long after the devices ceased to be used. Even today, the German verb

2426:

Co., Marconi's rival, acquired the patent rights and used the quenched spark gap in their transmitters.

7998: 7811: 7733: 7672: 7379: 3843: 2809:

which rescued 705 survivors, the rescue operation was delayed four hours because the nearest ship, the

2210: 1977:

in February 1900. Braun made the crucial discovery that low damping required "loose coupling" (reduced

1658: 6406: 6026: 5580: 222:

electricity from the power source, a battery or electric outlet, to a high enough voltage (from a few

7583: 7544: 7389: 7289: 7218: 7151: 6978: 5994: 2856:. Most of these networks were built by the two giant wireless corporations of the age: the British 2853: 2832: 2129: 1805: 1119: 847: 816: 795: 5621: 2201:. Marconi announced the first transatlantic radio transmission took place on 12 December 1901, from 1889:) formed a "closed" resonant circuit which generated the oscillations, while the secondary winding ( 1833: 764:

the loss of power directly from the charging circuit (parallel to the capacitor) through the spark.

7942: 7184: 7119: 7072: 7032: 3129: 2586:

Transmitter building, showing the 36 feedlines feeding power to the 3,600 ft. flattop wire antenna.

2187: 6187: 5065: 4893: 4761: 4218: 3764: 3598: 2525:

Thus the spark had a steady frequency equal to a multiple of the AC line frequency, which created

936:

Hertzian spark oscillator, 1902. Visible are antenna consisting of 2 wires ending in metal plates

7781: 7766: 7610: 7561: 7484: 7384: 7062: 6948: 6943: 6635: 5902: 5691: 4869: 4087: 3929: 3899: 3532: 2972: 2861: 2629: 2559: 1775:

Amateur inductively coupled spark transmitter and receiver, 1910. The spark gap is in glass bulb

1620:

Emission bandwidth of a spark gap transmitter showing signal strength versus wavelength in meters

1401: 1313:

Marconi first tried enlarging the dipole antenna with 6×6 foot metal sheet "capacity areas"

791: 361: 5975: 4963: 3019: 3007:

was not turned off between Morse code symbols, words, or sentences but just detuned, so a local

1458:

during a demonstration 1897. The pole supporting the vertical wire antenna is visible at center.

1361:

Marconi found suspending the metal plate "capacity area" high above the ground increased range.

8003: 7703: 7489: 7304: 7249: 7244: 7057: 7022: 5938: 5616: 2908:

Although their damping had been reduced as much as possible, spark transmitters still produced

2238: 2071: 1202: 831: 782:

The invention of the radio transmitter resulted from the convergence of two lines of research.

429:

The charge on the capacitor discharges as a current through the coil and spark gap. Due to the

257:

or tuning coil, connected together. The values of the capacitance and inductance determine the

110: 6604: 6540: 6507: 6426: 5874: 5540: 5271: 5150: 4297: 3875: 3826: 7605: 7409: 7374: 7294: 7274: 7196: 7084: 7005: 6264: 5205: 4797: 4702: 4234: 4146: 3133: 3056:. Vacuum tube oscillators were a far cheaper source of continuous waves, and could be easily 3034: 2179: 1397: 1234: 1135: 1111: 1110:

Hertz and the first generation of physicists who built these "Hertzian oscillators", such as

983: 419: 6938: 6881: 6778:...the number one maintenance item on a TIG machine is cleaning and adjusting the spark gap. 5381:, applied: 3 November 1899, complete specification: 30 June 1900, granted: 22 September 1900 4119: 3447: 2598:

5 ft diameter primary coil of oscillation transformer, consisting of 3 turns of specialized

2229:

atoms in the upper atmosphere, enabling them to return to Earth beyond the horizon. In 1924

889:

capacitor discharged through one spiral, would cause sparks in the gap of the other spiral.

7519: 7479: 7449: 7206: 7141: 6963: 6438: 5720: 2885: 2133: 1970: 1937: 1929: 1854: 1547: 1523: 1386: 1382: 1226: 1218: 1194: 1097: 870: 843: 625: 614: 446: 273: 253:) which stores high-voltage electricity from the transformer, and a coil of wire called an 130: 6492: 5498: 4719: 2344: 2105:

The temporary antenna used in the transatlantic transmission, a fan-shaped 50-wire aerial.

1497:

After failing to interest the Italian government, in 1896 Marconi moved to England, where

1323: 678:

The circuit which charges the capacitors, along with the spark gap itself, determines the

8: 8013: 7529: 7469: 7228: 7190: 6988: 6973: 6869: 6795: 6535:

On the Driving of Electromagnetic Vibrations by Electromagnetic and Electrostatic Engines

6015:, July 27, 1914 edition, Department of Commerce, United States government printing office 3819:

Fitzgerald, George "On the energy lost by radiation from alternating electric currents",

3592: 2953: 2655: 1502: 1424: 1307: 1190: 1186: 1058: 874: 827: 808: 727: 48: 6819: 6629: 6442: 6181: 5724: 4887: 4863: 4755: 4357:

Improvements in transmitting electrical impulses and signals, and in apparatus therefore

4212: 3923: 2839:, Germany was the most powerful radio transmitter in the world when it was built in 1911 1065:) which generated the oscillating currents. High-voltage pulses from the induction coil 501:

of the oscillations, which is the frequency of the emitted radio waves, is equal to the

7756: 7713: 7644: 7514: 7444: 7419: 7354: 7201: 6922: 6843: 6554: 6464: 5746: 5642: 5042: 4939: 3893: 3150: 3065: 3042: 2992: 2980: 2976: 2881: 2877: 2873: 2569: 2487: 2435: 2230: 2183: 1902: 1850: 1709: 1539: 1079: 777: 534: 511: 502: 484: 298: 1897:) and ground, forming an "open" resonant circuit with the capacitance of the antenna ( 1616: 1535: 1339: 1010:

in 1894. Its 5-inch resonator ball produced waves of around 12 cm or 2.5 GHz

201: 157:

flowing through a conductor which suddenly change their velocity, thus accelerating.

7796: 7718: 7632: 7615: 7578: 7424: 7254: 7223: 7089: 6983: 6608: 6598: 6513: 5880: 5826: 5799: 5646: 5634: 5546: 5417: 5304: 5277: 5240: 5186: 5156: 5116: 5089: 5034: 4791: 4632: 4566: 4509: 4482: 4446: 4414: 4330: 4303: 4186: 4152: 4125: 4093: 4063: 4031: 4001: 3849: 3800: 3770: 3453: 3419: 3392: 3362: 3310:"Section 2.201: Emission, modulation, and transmission characteristics, footnote (f)" 3230: 3203: 3031: 2521: 1978: 1570: 1464: 1295: 1268: 1123: 812: 773: 471: 407: 294: 98: 7464: 5046: 27:, Austria. The spark gap is inside the box with the transparent cover at top center. 7801: 7761: 7741: 7708: 7637: 7595: 7509: 7364: 7349: 7324: 7299: 7259: 7109: 6968: 6953: 6815: 6509:

The Tentacles of Progress: Technology Transfer in the Age of Imperialism, 1850-1940

6468: 6459: 6454: 6446: 6383: 5934: 5750: 5741: 5736: 5728: 5626: 5026: 4624: 4593:

The Science of Radio: with MATLAB and Electronics Workbench demonstrations, 2nd Ed.

4246: 3663:

The Science of Radio: with MATLAB and Electronics Workbench demonstrations, 2nd Ed.

3145: 3106: 2965: 2949: 2889: 2648:, used until the Second International Radiotelegraphic Convention in 1906 at which 2526: 2392: 2222: 2056: 1974: 1918: 1826: 1700: 1610: 1602: 1579: 1574:

Circuit of Marconi's monopole transmitter and all other transmitters prior to 1897.

1393: 1389: 1241:

of 12 and 60 GHz respectively, using small metal balls as resonator-antennas.

1083: 823: 632: 628: 234: 184: 150: 23:

Low-power inductively coupled spark-gap transmitter on display in Electric Museum,

2848:

traffic with other countries and communicate with their overseas colonies. During

1965:

In addition to Tesla's system, inductively coupled radio systems were patented by

1628:

was that the radio transmissions were electrically "noisy"; they had a very large

7429: 7284: 7052: 7027: 7015: 5413:

Semiconductors and the Information Revolution: Magic Crystals that made IT Happen

3995: 3314:

Code of Federal Regulations, Title 47, Chapter I, Subchapter A, Part 2, Subpart C

3038: 2988: 2921: 2551: 2218: 2070:

In recognition of their achievements in radio, Marconi and Braun shared the 1909

1874: 1688: 1594: 1518:

In 1897 Marconi started a company to produce his radio systems, which became the

1507: 1272: 1245: 987: 644: 322: 286: 238: 180: 134: 83: 79: 75: 67: 6486: 2667:

Radio frequencies used by spark transmitters during the wireless telegraphy era

2144:

firing at different rates, and three resonant circuits, powered by a 25 kW

1597:

could be stored in the antenna before each spark, which was proportional to the

811:

in 1879 had also stumbled on radio wave transmission which he received with his

7627: 7499: 7474: 7434: 7404: 7279: 7114: 7067: 7042: 7000: 6127: 5462:

Tesla: Master of Lightning - companion site for 2000 PBS television documentary

5457: 3117: 3110: 3102: 3078: 3008: 2865: 2810: 2377: 2194: 1955: 1649: 1641: 1555: 1498: 1351: 1279: 1166: 1050: 1032: 866: 839: 835: 731: 697: 442: 438: 415: 350: 290: 227: 165: 56: 44: 4618: 4250: 1841:

is not an actual capacitor but represents the capacitance between the antenna

1049:

attached to the outer ends. The two sides of the antenna were connected to an

994:

generated 60 GHz (5 mm) waves using 3 mm metal ball resonators.

7987: 7776: 7549: 7539: 7454: 7344: 7339: 7329: 7314: 7136: 6995: 6537:, read at the January 22, 1892 meeting of the Physical Society of London, in 6286: 5638: 5444: 5394: 5324: 5225: 5038: 4362: 3170: 3160: 3155: 3053: 2945: 2803: 2776: 2772: 2768: 2764: 2520:: In this type, invented by Fessenden around 1904, the rotor was turned by a 2388: 2055:

infringement but didn't have the resources to pursue the action. In 1943 the

1947: 1703:(also called tuned circuit or tank circuit) in transmitters would narrow the 1654: 1625: 1586: 1543: 1230: 1206: 1182: 1170: 1127: 1115: 1071: 953: 803: 799: 659: 636: 333: 87: 5378:

Improvements in or related to telegraphy without the use of continuous wires

5030: 1763:

Demonstration inductively coupled spark transmitter 1909, with parts labeled

7654: 7494: 7439: 7369: 7334: 7269: 7168: 7158: 7010: 4235:"On a complete apparatus for the study of the properties of electric waves" 3004: 2957: 2933: 2897: 2780: 2175: 2048: 1966: 1925: 1748: 1728: 1527: 1174: 1131: 1091: 1007: 851: 618: 138: 71: 6427:"Wireless Telegraphy, with special reference to the quenched-spark system" 6237: 6154: 5923:"The New Telefunken Telegraph: A combination of the arc and spark systems" 5709:"Wireless Telegraphy, with special reference to the quenched-spark system" 5630: 5241:"Misreading the Supreme Court: A Puzzling Chapter in the History of Radio" 4628: 3845:

The Science of Radio: with MATLAB and Electronics Workbench demonstrations

3796:

The Science of Radio: with MATLAB and Electronics Workbench demonstrations

3415:

The Science of Radio: with MATLAB and Electronics Workbench demonstrations

2614:

The three 5 ft rotary spark discharger wheels of the "timed spark" system.

2310:

Cross section of portion of quenched spark gap, consisting of metal disks

1808:, Nauen, Germany, showing large 360 Leyden jar 400 μF capacitor bank 445:. These oscillating fields radiate away from the antenna into space as an 7854: 7504: 7414: 7399: 7359: 7319: 7178: 6655:(5th ed.). Philadelphia: Lea and Febiger. pp. 187–188, 197–200. 5347: 5009:

Tesla is entitled to either distinct priority or independent discovery of

3116:

In the 1950s a Japanese toy company, Matsudaya, produced a line of cheap

3049: 3028: 2900:

at the base, 6 – 10 feet tall, to make it resonant with the transmitter.

2849: 2663: 2373: 2246: 1739: 1637: 1598: 1551: 1526:

to equip their ships with wireless stations. Marconi's company dominated

1438:, which recorded the Morse code symbols with an ink line on a paper tape. 1405: 1275: 1214: 1162: 1043: 1015: 718: 701: 506: 242: 215: 195: 161: 36: 6322:. San Francisco, California: Charles Shortridge. 7 July 1912. p. 22 5905:

Wireless Telegraphy, with special reference to the quenched-spark system

5694:

Wireless Telegraphy, with special reference to the quenched-spark system

5017:

Wheeler, L. P. (August 1943). "Tesla's contribution to high frequency".

2620:

Marconi 300 kW transatlantic timed spark transmitter built 1916 at

2151:

turned by a combustion engine. The first spark gap and resonant circuit

1484: 1444: 7859: 7566: 7264: 7173: 7129: 7099: 7077: 4089:

Radio's Conquest of Space: The experimental rise of radio communication

3093: 3089: 2984: 2929: 2924: 2869: 2621: 2423: 2226: 2145: 1942: 1910: 1720: 1559: 1511: 1210: 1154: 1150: 886: 878: 735: 663: 529: 463: 430: 411: 385: 337: 326: 250: 191: 142: 91: 40: 6858: 6205: 2987:) driven by an electric motor at a high enough speed that it produced 2266:

Ship radio room with 1.5 kW Telefunken quenched-spark transmitter

2225:

independently theorized that radio waves were reflected by a layer of

1691:

had given an influential lecture on radio in which he suggested using

7844: 7309: 7124: 6891: 6450: 5856:

Text-book on Wireless Telegraphy, Vol. 1: General Theory and Practice

5732: 3418:(2nd ed.). Springer Science and Business Media. pp. 27–28. 3097: 3057: 2893: 2599: 1924:

The first person to use resonant circuits in a radio application was

1716: 1692: 1633: 1606: 1238: 1198: 1143: 1062: 1036: 1024: 786: 760: 723: 640: 622: 479: 467: 454: 389: 311: 265: 258: 246: 169: 146: 6824:. Translated by Alfred E. Seelig. New York: McGraw-Hill Book Company 318:

in the resonant circuit, discharging the capacitor through the coil.

7839: 7829: 7746: 7571: 7394: 3505: 3000: 2999:

These transmitters, which could produce power outputs of up to one

2961: 2920:

From the beginning, physicists knew that another type of waveform,

2845: 2564: 2538: 2399: 2398:

In 1906, a new type of spark gap was developed by German physicist

2206: 2171: 1779:

next to tuning coil, on top of box containing glass plate capacitor

1743: 1732: 1724: 1590: 1373:

distributed current more equally between wires, reducing resistance

1288:

Evolution of Marconi's monopole antenna from Hertz's dipole antenna

882: 648: 356: 254: 223: 177: 154: 24: 6351:. New York, NY: James Gordon Bennett, Jr. 17 April 1912. p. 2 5825:(2nd ed.). Springer Science and Business Media. p. 972. 2888:(often below 1 ohm), so these transmitters required enormous wire 2831:

Telefunken 100 kW transoceanic quenched spark transmitter at

2178:

was building his own transatlantic radiotelegraphy transmitter on

1101:

Circuit of Hertz's spark oscillator and receiver. The interrupter

1090:

in loops of wire which functioned as resonant receiving antennas.

1082:

of the antenna, which was determined by its length; it acted as a

647:

range, typically 50 to 1000 sparks per second, so in a receiver's

7834: 7819: 7037: 5499:"No. 369 (1943) Marconi Wireless Co. of America v. United States" 3848:(2nd ed.). Springer Science and Business Media. p. 18. 3165: 3132:. Powerful spark gap pulse generators are still used to simulate 3122: 2787: 2191: 2041:

Marconi's inductively coupled transmitter patented 26 April 1900.

1699:) to reduce the bandwidth of transmitters and receivers. Using a 1413: 1139: 1035:

made of a pair of collinear metal rods of various lengths with a

901:

Heinrich Hertz discovering radio waves with his spark oscillator

219: 103: 19: 6180:

Moorcroft, John Harold; Pinto, A.; Curry, Walter Andrew (1921).

5066:

The Inventions, Researches and Writings of Nikola Tesla, 2nd Ed.

4329:(2nd ed.). UK: Cambridge University Press. pp. 37–39. 4062:(2nd ed.). UK: Cambridge University Press. pp. 34–36. 3870:

Report of the British Association for the Advancement of Science

3821:

Report of the British Association for the Advancement of Science

3799:(2nd ed.). Springer Science and Business Media. p. 7. 2009:

Braun's inductively coupled transmitter patented 3 November 1899

1205:. Hertz used them to perform historic experiments demonstrating 336:

to switch the transmitter on and off to communicate messages by

7864: 7824: 7146: 5795:

Communications: An International History of the Formative Years

4777:

The Design of CMOS Radio-Frequency Integrated Circuits, 2nd Ed.

4562:

Communications: An International History of the Formative Years

3085:, literally, "to spark", also means "to send a radio message". 3046: 2555: 2202: 2167: 1178: 1158: 834:. Maxwell's theory predicted that a combination of oscillating 655: 315: 173: 90:, creating pulses of radio waves to spell out text messages in 6583:. Hartford, CN: American Radio Relay league. pp. 123–124. 6128:"The first direct wireless messages from England to Australia" 5958:

British patent GB189620981 Henry Harris Lake for Nikola Tesla

1804:

Telefunken 25 kW long distance transmitter built 1906 at

1682:

of the first "syntonic" radio system, from Lodge's 1897 patent

1636:, but a continuous band of frequencies. They were essentially 1450:

British Post Office officials examining Marconi's transmitter

822:

The other was research by physicists to confirm the theory of

426:). This closes the circuit between the capacitor and the coil. 7849: 7786: 7094: 6542:

The Scientific Writings of the late George Francis Fitzgerald

3877:

The Scientific Writings of the Late George Francis Fitzgerald

3828:

The Scientific Writings of the Late George Francis Fitzgerald

3449:

The Continuous Wave: Technology and American Radio, 1900-1932

2913: 2836: 2625: 1157:

high-frequency waves with which they could duplicate classic

815:

detector, however he was persuaded that what he observed was

667: 603:{\displaystyle f={\frac {1}{2\pi }}{\sqrt {\frac {1}{LC}}}\,} 441:

around the antenna, while the voltage creates an oscillating

52: 6600:

The History of Communications - Electronics in the U.S. Navy

6266:

The History of Communications - Electronics in the U.S. Navy

4793:

The History of Communications - Electronics in the U.S. Navy

785:

One was efforts by inventors to devise a system to transmit

245:

when excited by the spark. A resonant circuit consists of a

7791: 6876: 3763:

Sarkar, T. K.; Mailloux, Robert; Oliner, Arthur A. (2006).

3286:(2nd ed.). New York: McGraw-Hill Book Co. pp. 6–9 2198: 210:

A practical spark gap transmitter consists of these parts:

6280: 6278: 6276: 5777:. This author misspells the word "quenched" as "squenched" 3341:

Contact at Sea: A History of Maritime Radio Communications

2233:

demonstrated the existence of this layer, now called the "

1365:

He found that a simple elevated wire worked just as well.

285:

transmitter. The spark gap and capacitor connected to the

86:; the operator switched the transmitter on and off with a 4862:

Ashley, Charles Grinnell; Hayward, Charles Brian (1912).

3316:. US Government Publishing Office website. 1 October 2007 2650: 2451:

A typical rotary spark gap used in low-power transmitters

2077: 1409: 1031:

See circuit diagram. Hertz's transmitters consisted of a

423: 4968:. London: The Electrician Publishing Co. pp. 50–58. 4846:

Improvements in Syntonized Telegraphy without Line Wires

4239:

The London, Edinburgh, and Dublin Philosophical Magazine

2928:

distances with a given output power. They could also be

1742:, storing oscillating electrical energy, increasing the 55:, from 1887 to the end of World War I. German physicist 6512:. New York: Oxford University Press. pp. 126–130. 6273: 5798:. Institute of Electrical Engineers. pp. 361–362. 4960:

Lodge's explanation of his syntonic radio system is in

4565:. Institute of Electrical Engineers. pp. 313–329. 4502:

Dosi, Giovanni; Teece, David J.; Chytry, Josef (2004).

4030:. Springer Science and Business Media. pp. 51–53. 4027:

Heinrich Hertz: Classical Physicist, Modern Philosopher

2884:, a tiny fraction of a wavelength tall, and so had low 1632:. These transmitters did not produce waves of a single 1317:, 1895 Metal sheets and spark balls not shown to scale. 1042:

between their inner ends and metal balls or plates for

798:, which had too short a range to be practical. In 1866 5819:

Bard, Allen J.; Inzelt, György; Scholz, Fritz (2012).

5152:

Intellectual Property Law for Engineers and Scientists

4326:

The Design of CMOS Radio-Frequency Integrated Circuits

4059:

The Design of CMOS Radio-Frequency Integrated Circuits

3355:

Serway, Raymond; Faughn, Jerry; Vuille, Chris (2008).

1149:

To investigate the similarity between radio waves and

651:

the signal sounds like a steady tone, whine, or buzz.

6044:"The Marconi Timed-Spark Continuous-Wave Transmitter" 3499: 3497: 3495: 3493: 3491: 3489: 2983:, was a huge rotating alternating current generator ( 2166:

The transmitter was built in secrecy on the coast at

560: 537: 514: 487: 6545:. London: Longmans, Green and Co. pp. 277–281. 6310: 6308: 6199: 6197: 6134:. VK2DYM's military radio and radar information site 5464:. PBS.org, Public Broadcasting Service website. 2000 5371: 5369: 3762: 3487: 3485: 3483: 3481: 3479: 3477: 3475: 3473: 3471: 3469: 3195: 3096:

it was used until the 1940s in the medical field of

3027:

All these early technologies were superseded by the

1189:. Their short antennas generated radio waves in the 1153:, these researchers concentrated on producing short 6179: 5964:

filed: 22 September 1896, granted: 21 November 1896

5375:British patent no. 189922020 Karl Ferdinand Braun, 4804: 4209:, Vol. 36, December 13, 1988, p. 769, reprinted in 4023: 3831:. London: Hodges, Figgis, and Co. pp. 128–129. 3226:

Academic Press Dictionary of Science and Technology

2159:powering the second spark gap and resonant circuit 2155:generated the high voltage to charge the capacitor 1589:oscillator (in modern terminology, it had very low 1345:

Re-creation of Marconi's first monopole transmitter

305:, creating less interference to other transmitters. 6411:. New York: Wireless Press, Inc. pp. 288–307. 6031:. New York: Wireless Press, Inc. pp. 274–275. 5859:. London: Longmans Green and Co. pp. 200–204. 5585:. London: Longmans Green and Co. pp. 449–454. 5397:, filed: 8 February 1900, granted: 2 December 1902 3916:Hertz, H., "On very rapid electric oscillations", 3354: 2507:There were two types of rotary spark transmitter: 2197:with a 400 ft. wire antenna suspended from a 1640:sources radiating energy over a large part of the 673: 602: 543: 520: 493: 6305: 6194: 5447:, filed: 10 November 1900, granted: 28 June 1904. 5441:Improvements in apparatus for wireless telegraphy 5366: 5348:"Nikola Tesla: The Guy Who DIDN'T "Invent Radio"" 5327:, filed: 1 February 1898, granted: 16 August 1898 5229:, filed: 2 September 1897; granted: 20 March 1900 4812:"Reporting the yacht races by wireless telegraph" 3466: 3023:Marconi 2 kilowatt ship spark transmitter, 1920. 1738:The resonant circuit functioned analogously to a 1430:Marconi in 1901 with his early spark transmitter 1142:like existing optical signalling methods such as 916:Hertz's drawing of one of his spark oscillators. 7985: 6849:Fessenden and the Early History of Radio Science 6764:. Lincoln Electric website. 2006. Archived from 6754: 6082:. New York: Wireless Press, Inc. pp. 73–75. 5980:. London: Ernst Benn, Ltd. pp. 25, 138–148. 5818: 4350: 4348: 4346: 3997:Wireless: From Marconi's Black-box to the Audion 3537:. London: Longmans Green and Co. pp. 15–16. 2975:transmitter, developed between 1906 and 1915 by 2213:, a distance of 2100 miles (3400 km). 1578:The primitive transmitters prior to 1897 had no 6480: 6478: 5989: 5987: 5435: 5433: 5389: 5387: 5219: 5217: 5115:. Barnes and Noble Publishing. pp. 65–70. 4501: 4366:, filed 7 December 1896, accepted: 13 July 1897 3361:(8th ed.). Cengage Learning. p. 714. 3196:Hempstead, Colin; Worthington, William (2005). 2545: 2237:" or "E-layer", for which he received the 1947 1478:Induction coil, telegraph key, and battery box. 237:(tuned circuits or tank circuits) which create 6866:"The Sounds of a Spark Transmitter with audio" 6491:. Scientific American Publishing Co. pp. 6342:"President Moves to Stop Mob Rule of Wireless" 6334: 5185:. Greenwood Publishing Group. pp. 21–23. 4868:. American School of Correspondence. pp. 4839: 4837: 4711: 4402: 4400: 4398: 4396: 4394: 4392: 4291: 4289: 4287: 4024:Baird, D.; Hughes, R.I.; Nordmann, A. (2013). 3880:. London: Hodges, Figgis, and Co. p. 129. 3391:. Cambridge University Press. pp. 16–17. 3229:. Gulf Professional Publishing. p. 2045. 2252: 1993:Tesla's inductively coupled power transmitter 1078:. The frequency of the waves was equal to the 885:with their conductors ending in spark gaps. A 717:In higher power transmitters powered by AC, a 406:When the voltage on the capacitor reaches the 6907: 6887:Spark gap transmitter history & operation 6238:"Section 12: Pioneering Amateurs (1900-1912)" 6086: 6013:Radio Communication Laws of the United States 6001:. United States Congress. 1912. pp. 6–14 5868: 5866: 5766: 5764: 5762: 5760: 5534: 5532: 5530: 5528: 5526: 5524: 5522: 5520: 4861: 4849:filed: May 10, 1897, granted: August 10, 1898 4505:Understanding Industrial and Corporate Change 4434: 4432: 4430: 4390: 4388: 4386: 4384: 4382: 4380: 4378: 4376: 4374: 4372: 4343: 4285: 4283: 4281: 4279: 4277: 4275: 4273: 4271: 4269: 4267: 3441: 3439: 3437: 3435: 3113:generators or "Bovies" as late as the 1980s. 3077:One legacy of spark-gap transmitters is that 1134:, were mainly interested in radio waves as a 639:used during the wireless telegraphy era. The 6559:: CS1 maint: multiple names: authors list ( 6475: 6420: 6418: 5984: 5439:British patent no. 7777, Guglielmo Marconi, 5430: 5384: 5317: 5214: 4660: 4658: 4354:British patent 189612039 Marconi, Guglielmo 4174: 4172: 4170: 4168: 2638: 1251: 7922:Global telecommunications regulation bodies 6592: 6590: 6526: 6484: 6372:"Marconi´s 200kW transatlantic transmitter" 5952: 5898: 5896: 5848: 5846: 5844: 5842: 5773:The Worldwide History of Telecommunications 5687: 5685: 5683: 5323:US Patent no. 609,154 Oliver Joseph Lodge, 5226:System of transmission of electrical energy 5085:Biographical Encyclopedia of American Radio 5077: 5075: 5061:On light and other high frequency phenomena 4977: 4975: 4892:. New York: Moffat, Yard, and Co. pp. 4889:Wireless Telegraphy: An Elementary Treatise 4834: 4546:The Worldwide History of Telecommunications 4442:The Worldwide History of Telecommunications 4185:. The Rosen Publishing Group. p. 159. 3862: 3813: 3380: 3378: 3333: 3331: 3190: 3188: 3186: 2174:, UK. Marconi was pressed for time because 1981:) between the primary and secondary coils. 1006:Microwave spark oscillator demonstrated by 755:In a transmitter with a "rotary" spark gap 505:of the resonant circuit, determined by the 422:to a very low level (usually less than one 51:or "spark" era, the first three decades of 7958: 6914: 6900: 6762:"TIG Welding Series: The Power to Perform" 6363: 6231: 6229: 6227: 6173: 5999:Public 264 S. 6412 approved 13 August 1912 5939:10.1038/scientificamerican06191909-390supp 5863: 5757: 5606: 5604: 5602: 5600: 5598: 5596: 5594: 5592: 5582:The Principles of Electric Wave Telegraphy 5574: 5572: 5570: 5568: 5566: 5564: 5562: 5517: 5144: 5142: 5140: 5138: 5136: 5134: 5132: 4857: 4855: 4760:. New York: McGraw-Hill Book Co. pp. 4749: 4747: 4745: 4743: 4741: 4698: 4696: 4694: 4692: 4612: 4610: 4608: 4606: 4604: 4602: 4537: 4470: 4468: 4466: 4464: 4462: 4427: 4369: 4264: 4081: 4079: 3898:. New York: McGraw Hill Book Co. pp. 3873: 3824: 3758: 3756: 3754: 3752: 3750: 3748: 3746: 3744: 3742: 3740: 3738: 3736: 3734: 3732: 3730: 3728: 3726: 3724: 3722: 3720: 3718: 3716: 3714: 3712: 3710: 3708: 3706: 3704: 3702: 3700: 3698: 3696: 3694: 3692: 3597:. New York: John Wiley and Sons. pp. 3556: 3554: 3552: 3550: 3548: 3546: 3544: 3534:The Principles of Electric Wave Telegraphy 3432: 2816:, only a few miles away, did not hear the 2475:1 kilowatt rotary spark transmitter, 1914. 2429: 2314:separated by thin insulating mica washers 1954:. However, Tesla was mainly interested in 6882:Radio Technology in common use circa 1914 6861:The new England Wireless and Steam Museum 6793: 6702:"Flotsam & Jetsam – Control by Radio" 6499: 6458: 6415: 6369: 6125: 6119: 6075: 6069: 5872: 5787: 5785: 5783: 5740: 5620: 5538: 5341: 5339: 5337: 5335: 5333: 5155:. John Wiley and Sons. pp. 196–199. 4954: 4655: 4586: 4584: 4582: 4445:. John Wiley and Sons. pp. 207–209. 4438: 4295: 4178: 4165: 4144: 4138: 3912: 3910: 3788: 3786: 3690: 3688: 3686: 3684: 3682: 3680: 3678: 3676: 3674: 3672: 3590: 3584: 3384: 3337: 3249: 1624:A more significant drawback of the large 599: 6720: 6587: 6505: 6398: 6256: 5995:"An act to regulate radio communication" 5920: 5893: 5839: 5700: 5680: 5659: 5653: 5405: 5403: 5393:US Patent no. 714,756, John Stone Stone 5174: 5172: 5081: 5072: 4972: 4885: 4879: 4843:British patent GB189711575 Lodge, O. J. 4664: 4019: 4017: 3989: 3987: 3985: 3983: 3981: 3979: 3977: 3975: 3973: 3971: 3969: 3967: 3965: 3963: 3892:Zenneck, Jonathan Adolf Wilhelm (1915). 3626: 3624: 3622: 3620: 3618: 3616: 3614: 3612: 3610: 3608: 3524: 3375: 3328: 3275: 3273: 3252:"The spark era - the beginning of radio" 3243: 3183: 3018: 2826: 2350:Ordinary inductively coupled transmitter 2318:to make multiple microscopic spark gaps 2119: 2111: 2021:Stone's inductively coupled transmitter 1901:). Both circuits were tuned to the same 1873:" transmitter. See circuit diagram. The 1832: 1669: 1665: 1615: 1569: 1412:) in the upper atmosphere, later called 1096: 1014: 986:in 1894 was the first person to produce 617:with a steady frequency, so it could be 355: 200: 18: 6814: 6727:Findlay, David A. (September 1, 1957). 6726: 6693: 6642: 6621: 6424: 6284: 6224: 6203: 6146: 6041: 6035: 6018: 5916: 5914: 5706: 5610: 5589: 5578: 5559: 5491: 5199: 5148: 5129: 5053: 5016: 5001: 4981: 4925: 4919: 4913:Syntony and Spark: The origins of radio 4852: 4783: 4738: 4717: 4689: 4616: 4599: 4481:. John Wiley and Sons. pp. 30–33. 4459: 4410:Syntony and Spark: The Origins of Radio 4233:Bose, Jagadish Chandra (January 1897). 4182:The Britannica Guide to Sound and Light 4113: 4111: 4109: 4076: 4051: 4049: 4047: 3961: 3959: 3957: 3955: 3953: 3951: 3949: 3947: 3945: 3943: 3891: 3885: 3560: 3541: 3530: 3503: 3199:Encyclopedia of 20th-Century Technology 2964:atmosphere to excite oscillations in a 2948:(Poulsen arc) transmitter, invented by 1837:Inductively coupled spark transmitter. 860: 826:proposed in 1864 by Scottish physicist 7986: 6921: 6699: 6648: 6627: 6596: 6567: 6538: 6404: 6262: 6155:"Section 12: Radio at Sea (1891-1922)" 6042:Coursey, Phillip R. (September 1919). 6024: 5967: 5852: 5780: 5476: 5330: 5238: 5232: 5063:", in Thomas Cummerford Martin (1894) 5011:" three concepts in wireless theory: " 4903: 4789: 4753: 4720:"Aerials, Attachments, and Audibility" 4579: 4552: 4522: 4474: 4406: 4199: 4085: 3907: 3835: 3783: 3669: 3654: 3570:The history of QST Vol. 1 - Technology 3445: 3279: 3222: 2078:First transatlantic radio transmission 1958:and never developed a practical radio 688:one of three types of power circuits: 466:wave that increases rapidly to a high 371:Audio of Massie spark gap transmission 125: 6895: 6729:"Radio Controlled Toys Use Spark Gap" 6659: 6573: 6235: 6152: 5973: 5791: 5660:Margolis, Laurie (11 December 2001). 5611:Belrose, John S. (5 September 1995). 5409: 5400: 5345: 5296: 5290: 5182:Radio: The Life Story of a Technology 5178: 5169: 4965:Signaling through space without wires 4961: 4926:Crookes, William (February 1, 1892). 4558: 4478:Array and Phased Array Antenna Basics 4210: 4014: 3921: 3920:, Vol. 31, p. 421, 1887 reprinted in 3841: 3792: 3630: 3605: 3411: 3405: 3348: 3303: 3301: 3270: 3216: 2182:, in a bid to be first (this was the 1893:) was connected to the wire antenna ( 1820: 850:had calculated the output power of a 741: 643:of repetition (spark rate) is in the 410:of the spark gap, the air in the gap 7968: 6665: 6577:The Radio Amateur's Handbook, 1st Ed 6094:"Great Wireless Stations: Carnarvon" 5911: 5812: 5505:. Findlaw.com website. June 21, 1943 5503:United States Supreme Court decision 5346:White, Thomas H. (1 November 2012). 5263: 5223:US Patent No. 645576, Nikola Tesla, 4768: 4495: 4316: 4232: 4226: 4223:translated to English by D. E. Jones 4106: 4044: 3993: 3940: 3937:translated to English by D. E. Jones 3642:. American Radio Relay League: 29–32 2463:Small rotary spark transmitter, 1918 2286:oscillation transformer, Leyden jars 1470:Marconi's transmitter in July 1897. 1161:experiments with radio waves, using 1023:was applied, it produced waves at a 722:maximum voltage, at peaks of the AC 6802:. New York: Wiley. pp. 275–363 5450: 5269: 5108: 5102: 4982:Marconi, Guglielmo (May 24, 1901). 4928:"Some Possibilities of Electricity" 4617:Thrower, K. R. (5 September 1995). 4322: 4117: 4055: 2903: 2779:from early automobiles such as the 2661:, in which 1500 people were saved. 750: 360:Demonstration of the restored 1907 314:which acts as a voltage-controlled 149:, can be generated by time-varying 13: 6787: 6370:Pickworth, George (January 1994). 5239:Wunsch, A. David (November 1998). 3344:. The Gregg Press. pp. 26–30. 3298: 1851:inductively (magnetically) coupled 1558:in Germany who in 1903 formed the 1520:Marconi Wireless Telegraph Company 842:could travel through space as an " 343: 14: 8025: 6837: 6800:Principles of Radio Communication 6242:United States Early Radio History 6183:Principles of Radio Communication 6159:United States Early Radio History 5445:Apparatus for wireless telegraphy 5352:United States Early Radio History 5082:Sterling, Christopher H. (2013). 4667:"United States Radio Development" 4665:Marriott, Robert H. (June 1917). 3594:Principles of Radio Communication 3512:. C. F. Codella's private website 3280:Terman, Frederick Emmons (1937). 712: 691: 670:that breaks the primary circuit. 145:, electromagnetic waves of radio 66:; they are unable to produce the 7967: 7957: 7948: 7947: 7936: 7557:Free-space optical communication 6652:Electrotherapy and Light Therapy 6628:Strong, Frederick Finch (1908). 6549:from the original on 2014-07-07. 6285:Codella, Christopher F. (2016). 6204:Codella, Christopher F. (2016). 6186:. John Wiley and Sons. pp. 6161:. T. H. White's personal website 6132:Australian Amateur Radio History 5921:von Arco, Georg (19 June 1909). 5579:Fleming, John Archibald (1906). 5354:. T. H. White's personal website 4754:Jansky, Cyril Methodius (1919). 4718:Codella, Christopher F. (2016). 3531:Fleming, John Archibald (1906). 3504:Codella, Christopher F. (2016). 3250:Champness, Rodney (April 2010). 2607: 2591: 2579: 2495: 2480: 2468: 2456: 2444: 2357: 2343: 2327: 2303: 2291: 2271: 2259: 2245:could have mistaken atmospheric 2098: 2086: 2034: 2014: 2002: 1986: 1877:of the oscillation transformer ( 1797: 1784: 1768: 1756: 1565: 1483: 1463: 1443: 1423: 1350: 1338: 1322: 1306: 1294: 999: 976: 964: 929: 909: 894: 877:in 1864, in which he discovered 375: 6877:The Sparks Telegraph Key Review 6794:Morecroft, John Harold (1921). 6700:Parker, John (September 2017). 6634:. New York: Rebman Co. p. 6485:Lescarboura, Austin C. (1922). 5276:. McFarland. pp. 111–113. 5088:. Routledge. pp. 382–383. 4886:Kennelly, Arthur Edwin (1906). 4822:(15): 596–597. October 12, 1901 4363:Transmitting electrical signals 4217:. Dover Publications. pp. 4124:. McFarland. pp. 4–6, 13. 3928:. Dover Publications. pp. 3223:Morris, Christopher G. (1992). 3202:. Routledge. pp. 649–650. 3194:"Radio Transmitters, Early" in 3014: 2864:to link the possessions of the 1229:, differing only in frequency. 674:Charging circuit and spark rate 249:(in early days a type called a 6574:Handy, Frances Edward (1926). 6425:Leggett, Bernard John (1921). 6269:. U.S. Navy. pp. 69, 117. 5927:Scientific American Supplement 5707:Leggett, Bernard John (1921). 5416:. Academic Press. p. 37. 4984:"Syntonic Wireless Telegraphy" 3631:Hyder, Harry R. (March 1992). 3452:. Princeton University Press. 2278:Tuned circuit of transmitter. 1913:capacitor banks filling rooms 1: 6408:Practical Wireless Telegraphy 6107:(78): 301–307. September 1919 6076:Goldsmith, Alfred N. (1918). 6028:Practical Wireless Telegraphy 4757:Principles of Radiotelegraphy 4151:. Da Capo Press. p. 52. 3633:"The final days of ham spark" 3572:. American Radio Relay League 3563:"How spark transmitters work" 3385:Ellingson, Steven W. (2016). 3176: 2140:with two cascaded spark gaps 261:of the radio waves produced. 109:disaster. After World War I, 7943:Telecommunication portal 7724:Telecommunications equipment 6666:Carr, Joseph J. (May 1990). 6539:Larmor, Joseph, Ed. (1902). 6506:Headrick, Daniel R. (1988). 5395:Method of electric signaling 5303:. Dockside Consultants Inc. 5300:Lightning: Fire from the Sky 4439:Huurdeman, Anton A. (2003). 3872:, 1883, p.405, reprinted in 3338:Schroeder, Peter B. (1967). 2802:distress calls summoned the 2546:Marconi's timed spark system 1562:Co., Marconi's chief rival. 293:that induced current in the 120:radio frequency interference 7: 7994:History of radio technology 7460:Alexander Stepanovich Popov 6316:"To Check Wireless Anarchy" 6293:. Codella's private website 6212:. Codella's private website 5149:Rockman, Howard B. (2004). 4726:. Codella's private website 4508:. OUP Oxford. p. 251. 4475:Visser, Hubregt J. (2006). 4205:Hertz, H., "On radiation", 3874:Fitzgerald, George (1902). 3825:Fitzgerald, George (1902). 3591:Morecroft, John H. (1921). 3139: 2763:Spark transmitters and the 2734:Moderate size land stations 2537:" (this is equivalent to a 2253:Quenched-spark transmitters 1934:wireless power transmission 707:mercury turbine interrupter 10: 8030: 7164:Telecommunications history 6668:"Early radio transmitters" 5822:Electrochemical Dictionary 5792:Burns, Russell W. (2004). 5112:Tesla, Master of Lightning 4559:Burns, Russell W. (2004). 4407:Aitken, Hugh G.J. (1985). 4092:. Murray Hill Books, Inc. 3446:Aitken, Hugh G.J. (2014). 2854:submarine telegraph cables 2691: 2422:The German wireless giant 2364:Quenched-spark transmitter 2130:submarine telegraph cables 2124:View of Poldhu transmitter 771: 767: 734:with its shaft turning an 8009:Electric power conversion 7931: 7873: 7810: 7772:Public Switched Telephone 7732: 7696: 7653: 7594: 7584:telecommunication circuit 7545:Fiber-optic communication 7528: 7290:Francis Blake (telephone) 7237: 7085:Optical telecommunication 6929: 6844:Alternator, Arc and Spark 6405:Bucher, Elmer E. (1917). 6236:White, Thomas H. (2003). 6153:White, Thomas H. (2003). 6126:MacKinnon, Colin (2004). 6025:Bucher, Elmer E. (1917). 5977:Radio: Beam and Broadcast 5879:. IET. pp. 194–197. 5545:. IET. pp. 192–194. 5485:Radio: Beam and Broadcast 5273:Wireless Radio: A History 4938:: 174–176. Archived from 4531:Radio: Beam and Broadcast 4413:. Princeton Univ. Press. 4302:. IET. pp. 186–190. 4251:10.1080/14786449708620959 4145:Weightman, Gavin (2009). 4121:Wireless Radio: A History 3388:Radio Systems Engineering 3072: 2833:Nauen Transmitter Station 2666: 2211:Signal Hill, Newfoundland 1997:patented 2 September 1897 1806:Nauen Transmitter Station 1357:Early vertical antennas. 1301:Hertz's dipole oscillator 1252:Non-syntonic transmitters 796:electromagnetic induction 621:in a radio receiver by a 528:of the capacitor and the 16:Type of radio transmitter 7683:Orbital angular-momentum 7120:Satellite communications 6959:Communications satellite 6859:Massie Spark Transmitter 6649:Kovács, Richard (1945). 5853:Rupert, Stanley (1919). 5771:Huurdeman, Anton (2003) 5297:Smith, Craig B. (2008). 5206:Cheney, Margaret (2011) 4671:Proceedings of the I.R.E 4544:Huurdeman, Anton (2003) 4211:Hertz, Heinrich (1893). 4179:Gregersen, Erik (2011). 4086:Donald, McNicol (1946). 3922:Hertz, Heinrich (1893). 3130:gas tungsten arc welding 2860:, which constructed the 2235:Kennelly–Heaviside layer 2029:patented 8 February 1900 1973:, in November 1899, and 1812:and vertical spark gaps 1474:4 ball Righi spark gap, 160:An electrically charged 111:vacuum tube transmitters 7562:Molecular communication 7385:Gardiner Greene Hubbard 7214:Undersea telegraph line 6949:Cable protection system 6631:High Frequency Currents 6460:2027/mdp.39015063598398 6287:"The first regulations" 5903:Bernard Leggett (1921) 5873:Beauchamp, Ken (2001). 5742:2027/mdp.39015063598398 5692:Bernard Leggett (1921) 5539:Beauchamp, Ken (2001). 5410:Orton, John W. (2009). 5031:10.1109/EE.1943.6435874 4703:Ashley, Hayward (1912) 4323:Lee, Thomas H. (2004). 4296:Beauchamp, Ken (2001). 4056:Lee, Thomas H. (2004). 3842:Nahin, Paul J. (2001). 3793:Nahin, Paul J. (2001). 3769:. John Wiley and Sons. 3412:Nahin, Paul J. (2001). 2973:Alexanderson alternator 2862:Imperial Wireless Chain 2630:Alexanderson alternator 2430:Rotary gap transmitters 1861:); this was called an " 1859:oscillation transformer 1203:television transmitters 990:; his spark oscillator 792:electrostatic induction 364:spark gap transmitter 362:Massie Wireless Station 279:oscillation transformer 218:, to transform the low- 35:is an obsolete type of 7704:Communication protocol 7490:Charles Sumner Tainter 7305:Walter Houser Brattain 7250:Edwin Howard Armstrong 7058:Information revolution 6854:Brief history of spark 6708:. MyTimeMedia Ltd., UK 6603:. U.S. Navy. pp. 6597:Howeth, L. S. (1963). 6382:(1718). Archived from 6263:Howeth, L. S. (1963). 6244:. earlyradiohistory.us 5208:Tesla: Man Out Of Time 5019:Electrical Engineering 4962:Lodge, Oliver (1900). 4932:The Fortnightly Review 4796:. U.S. Navy. pp. 4790:Howeth, L. S. (1963). 4590:Nahin, Paul J. (2001) 3994:Hong, Sungook (2010). 3660:Nahin, Paul J. (2001) 3037:, invented in 1912 by 3024: 2840: 2239:Nobel Prize in Physics 2125: 2117: 2072:Nobel Prize in physics 1881:) with the capacitor ( 1846: 1683: 1621: 1605:", "inverted-L", and " 1575: 1402:horizontally polarized 1400:waves, instead of the 1267:Italian radio pioneer 1265: 1237:around 1894 generated 1107: 1028: 604: 545: 522: 495: 398: 207: 164:discharged through an 28: 7678:Polarization-division 7410:Narinder Singh Kapany 7375:Erna Schneider Hoover 7295:Jagadish Chandra Bose 7275:Alexander Graham Bell 7006:online video platform 5974:Morse, A. H. (1925). 5876:History of Telegraphy 5542:History of Telegraphy 5458:"Who invented radio?" 5179:Regal, Brian (2005). 4942:on September 29, 2018 4299:History of Telegraphy 3823:, 1883, reprinted in 3561:Kennedy, Hal (1990). 3035:electronic oscillator 3022: 2830: 2748:Transoceanic stations 2180:Long Island, New York 2123: 2115: 1836: 1673: 1666:Syntonic transmitters 1648:with each other. The 1619: 1573: 1434:and coherer receiver 1255: 1235:Jagadish Chandra Bose 1227:electromagnetic waves 1136:scientific phenomenon 1112:Jagadish Chandra Bose 1100: 1018: 984:Jagadish Chandra Bose 871:electromagnetic waves 772:Further information: 605: 546: 523: 496: 359: 281:. This was called an 204: 131:Electromagnetic waves 33:spark-gap transmitter 22: 7520:Vladimir K. Zworykin 7480:Almon Brown Strowger 7450:Charles Grafton Page 7105:Prepaid mobile phone 7033:Electrical telegraph 5109:Uth, Robert (1999). 4911:Aitken, Hugh (2014) 4898:selective signaling. 4874:selective signaling. 4775:Lee, Thomas H. 2004 3052:invented in 1906 by 2886:radiation resistance 2134:John Ambrose Fleming 2052:(J in circuit above) 1971:Karl Ferdinand Braun 1938:resonant transformer 1930:resonant transformer 1915:(see pictures above) 1855:resonant transformer 1747:tuned circuit using 1548:Karl Ferdinand Braun 1398:vertically polarized 1187:diffraction gratings 861:Hertzian oscillators 844:electromagnetic wave 558: 535: 512: 485: 447:electromagnetic wave 274:resonant transformer 190:Due to the inherent 7470:Johann Philipp Reis 7229:Wireless revolution 7191:The Telephone Cases 7048:Hydraulic telegraph 6821:Wireless Telegraphy 6706:Model Boats website 6675:Popular Electronics 6488:Radio for Everybody 6443:1921Natur.107..390. 5725:1921Natur.107..390. 5631:10.1049/cp:19950787 5325:Electric Telegraphy 5270:Coe, Lewis (2006). 4629:10.1049/cp:19950799 4207:Wiedemann's Annalen 4118:Coe, Lewis (2006). 3918:Wiedemann's Annalen 3895:Wireless Telegraphy 3766:History of Wireless 3256:Silicon Chip Online 2954:negative resistance 2874:Paper tape machines 1928:, who invented the 1863:inductively coupled 1503:General Post Office 1165:components such as 1059:harmonic oscillator 875:James Clerk Maxwell 832:Maxwell's equations 828:James Clerk Maxwell 809:David Edward Hughes 615:amplitude modulated 283:inductively-coupled 126:Theory of operation 49:wireless telegraphy 7668:Frequency-division 7645:Telephone exchange 7515:Charles Wheatstone 7445:Jun-ichi Nishizawa 7420:Innocenzo Manzetti 7355:Reginald Fessenden 7090:Optical telegraphy 6923:Telecommunications 6796:"Spark Telegraphy" 6320:San Francisco Call 5662:"Faking the waves" 3151:Invention of radio 3043:Alexander Meissner 3025: 2993:very low frequency 2981:Ernst Alexanderson 2977:Reginald Fessenden 2937:continuous waves. 2882:electrically short 2878:very low frequency 2841: 2436:Reginald Fessenden 2374:coupled oscillator 2231:Edward V. Appleton 2184:Wardenclyffe Tower 2126: 2118: 1969:in February 1898, 1903:resonant frequency 1847: 1821:Inductive coupling 1710:resonant frequency 1684: 1622: 1576: 1540:Reginald Fessenden 1108: 1080:resonant frequency 1029: 1027:of roughly 50 MHz. 778:Invention of radio 742:Quenched spark gap 600: 541: 518: 503:resonant frequency 491: 474:to zero, called a 399: 299:resonant frequency 208: 74:(sound) in modern 29: 7999:Radio electronics 7981: 7980: 7719:Store and forward 7714:Data transmission 7628:Network switching 7579:Transmission line 7425:Guglielmo Marconi 7390:Internet pioneers 7255:Mohamed M. Atalla 7224:Whistled language 6872:on July 18, 2011. 6816:Zenneck, Jonathan 6437:(2691): 299–305. 6376:Electronics World 6291:Ham Radio History 6210:Ham Radio History 5310:978-0-615-24869-1 4724:Ham Radio History 4620:History of tuning 3510:Ham Radio History 3283:Radio Engineering 3045:, which used the 2952:in 1904 used the 2868:, and the German 2798:radio operator's 2765:crystal receivers 2761: 2760: 2522:synchronous motor 2417:(see lower graph) 2190:using an untuned 1979:mutual inductance 1885:) and spark gap ( 1580:resonant circuits 1524:Lloyd's of London 1390:monopole antennas 1269:Guglielmo Marconi 1262:Guglielmo Marconi 1124:Frederick Trouton 1120:George Fitzgerald 1053:(Ruhmkorff coil) 944:, induction coil 865:German physicist 848:George Fitzgerald 813:carbon microphone 774:Timeline of radio 597: 596: 580: 544:{\displaystyle L} 521:{\displaystyle C} 494:{\displaystyle f} 408:breakdown voltage 380: 295:secondary winding 235:resonant circuits 230:(Ruhmkorff coil). 185:electric currents 151:electric currents 99:Guglielmo Marconi 37:radio transmitter 8021: 7971: 7970: 7961: 7960: 7951: 7950: 7941: 7940: 7939: 7812:Notable networks 7802:Wireless network 7742:Cellular network 7734:Types of network 7709:Computer network 7596:Network topology 7510:Thomas A. Watson 7365:Oliver Heaviside 7350:Philo Farnsworth 7325:Daniel Davis Jr. 7300:Charles Bourseul 7260:John Logie Baird 6969:Data compression 6964:Computer network 6916: 6909: 6902: 6893: 6892: 6873: 6868:. Archived from 6833: 6831: 6829: 6811: 6809: 6807: 6781: 6780: 6775: 6773: 6758: 6752: 6751: 6749: 6747: 6733: 6724: 6718: 6717: 6715: 6713: 6697: 6691: 6690: 6688: 6686: 6672: 6663: 6657: 6656: 6646: 6640: 6639: 6625: 6619: 6618: 6594: 6585: 6584: 6582: 6571: 6565: 6564: 6558: 6550: 6530: 6524: 6523: 6503: 6497: 6496: 6482: 6473: 6472: 6462: 6451:10.1038/107390b0 6422: 6413: 6412: 6402: 6396: 6395: 6393: 6391: 6367: 6361: 6360: 6358: 6356: 6346: 6338: 6332: 6331: 6329: 6327: 6312: 6303: 6302: 6300: 6298: 6282: 6271: 6270: 6260: 6254: 6253: 6251: 6249: 6233: 6222: 6221: 6219: 6217: 6206:"The Squeak Box" 6201: 6192: 6191: 6177: 6171: 6170: 6168: 6166: 6150: 6144: 6143: 6141: 6139: 6123: 6117: 6116: 6114: 6112: 6098: 6090: 6084: 6083: 6073: 6067: 6066: 6064: 6062: 6048: 6039: 6033: 6032: 6022: 6016: 6010: 6008: 6006: 5991: 5982: 5981: 5971: 5965: 5956: 5950: 5949: 5947: 5945: 5918: 5909: 5900: 5891: 5890: 5870: 5861: 5860: 5850: 5837: 5836: 5816: 5810: 5809: 5789: 5778: 5768: 5755: 5754: 5744: 5733:10.1038/107390b0 5704: 5698: 5689: 5678: 5677: 5675: 5673: 5657: 5651: 5650: 5624: 5608: 5587: 5586: 5576: 5557: 5556: 5536: 5515: 5514: 5512: 5510: 5495: 5489: 5480: 5474: 5473: 5471: 5469: 5454: 5448: 5437: 5428: 5427: 5407: 5398: 5391: 5382: 5373: 5364: 5363: 5361: 5359: 5343: 5328: 5321: 5315: 5314: 5294: 5288: 5287: 5267: 5261: 5260: 5258: 5256: 5236: 5230: 5221: 5212: 5203: 5197: 5196: 5176: 5167: 5166: 5146: 5127: 5126: 5106: 5100: 5099: 5079: 5070: 5057: 5051: 5050: 5005: 4999: 4998: 4996: 4994: 4979: 4970: 4969: 4958: 4952: 4951: 4949: 4947: 4923: 4917: 4907: 4901: 4900: 4883: 4877: 4876: 4859: 4850: 4841: 4832: 4831: 4829: 4827: 4816:Electrical World 4808: 4802: 4801: 4787: 4781: 4772: 4766: 4765: 4751: 4736: 4735: 4733: 4731: 4715: 4709: 4700: 4687: 4686: 4684: 4682: 4662: 4653: 4649: 4647: 4645: 4614: 4597: 4588: 4577: 4576: 4556: 4550: 4541: 4535: 4526: 4520: 4519: 4499: 4493: 4492: 4472: 4457: 4456: 4436: 4425: 4424: 4404: 4367: 4352: 4341: 4340: 4320: 4314: 4313: 4293: 4262: 4261: 4259: 4257: 4230: 4224: 4222: 4203: 4197: 4196: 4176: 4163: 4162: 4142: 4136: 4135: 4115: 4104: 4103: 4083: 4074: 4073: 4053: 4042: 4041: 4021: 4012: 4011: 3991: 3938: 3936: 3934:heinrich hertz . 3914: 3905: 3903: 3889: 3883: 3881: 3866: 3860: 3859: 3839: 3833: 3832: 3817: 3811: 3810: 3790: 3781: 3780: 3760: 3667: 3658: 3652: 3651: 3649: 3647: 3637: 3628: 3603: 3602: 3588: 3582: 3581: 3579: 3577: 3567: 3558: 3539: 3538: 3528: 3522: 3521: 3519: 3517: 3501: 3464: 3463: 3443: 3430: 3429: 3409: 3403: 3402: 3382: 3373: 3372: 3352: 3346: 3345: 3335: 3326: 3325: 3323: 3321: 3305: 3296: 3295: 3293: 3291: 3277: 3268: 3267: 3265: 3263: 3247: 3241: 3240: 3220: 3214: 3213: 3192: 3146:History of radio 3107:William T. Bovie 2966:resonant circuit 2956:of a continuous 2950:Valdemar Poulsen 2904:Continuous waves 2822: 2664: 2611: 2595: 2583: 2499: 2484: 2472: 2460: 2448: 2414: 2393:magnetic blowout 2381:(see top graphs) 2361: 2347: 2331: 2307: 2295: 2275: 2263: 2223:Oliver Heaviside 2102: 2090: 2057:US Supreme Court 2038: 2018: 2006: 1990: 1975:John Stone Stone 1827:resonant circuit 1801: 1788: 1772: 1760: 1701:resonant circuit 1611:corona discharge 1546:in America, and 1487: 1467: 1447: 1427: 1354: 1342: 1326: 1310: 1298: 1263: 1084:half-wave dipole 1003: 988:millimeter waves 980: 968: 933: 913: 898: 824:electromagnetism 751:Rotary spark gap 728:motor–alternator 633:crystal detector 609: 607: 606: 601: 598: 595: 584: 583: 581: 579: 568: 550: 548: 547: 542: 527: 525: 524: 519: 500: 498: 497: 492: 382: 381: 153:, consisting of 135:electric charges 133:are radiated by 68:continuous waves 39:which generates 8029: 8028: 8024: 8023: 8022: 8020: 8019: 8018: 7984: 7983: 7982: 7977: 7937: 7935: 7927: 7869: 7806: 7728: 7692: 7649: 7598: 7590: 7531: 7524: 7430:Robert Metcalfe 7285:Tim Berners-Lee 7233: 7053:Information Age 6925: 6920: 6864: 6840: 6827: 6825: 6805: 6803: 6790: 6788:Further reading 6785: 6784: 6771: 6769: 6760: 6759: 6755: 6745: 6743: 6731: 6725: 6721: 6711: 6709: 6698: 6694: 6684: 6682: 6670: 6664: 6660: 6647: 6643: 6626: 6622: 6615: 6595: 6588: 6580: 6572: 6568: 6552: 6551: 6531: 6527: 6520: 6504: 6500: 6483: 6476: 6423: 6416: 6403: 6399: 6389: 6387: 6368: 6364: 6354: 6352: 6349:New York Herald 6344: 6340: 6339: 6335: 6325: 6323: 6314: 6313: 6306: 6296: 6294: 6283: 6274: 6261: 6257: 6247: 6245: 6234: 6225: 6215: 6213: 6202: 6195: 6178: 6174: 6164: 6162: 6151: 6147: 6137: 6135: 6124: 6120: 6110: 6108: 6096: 6092: 6091: 6087: 6079:Radio Telephony 6074: 6070: 6060: 6058: 6046: 6040: 6036: 6023: 6019: 6004: 6002: 5993: 5992: 5985: 5972: 5968: 5957: 5953: 5943: 5941: 5919: 5912: 5901: 5894: 5887: 5871: 5864: 5851: 5840: 5833: 5817: 5813: 5806: 5790: 5781: 5769: 5758: 5719:(2691): 51–55. 5705: 5701: 5690: 5681: 5671: 5669: 5658: 5654: 5622:10.1.1.205.7281 5609: 5590: 5577: 5560: 5553: 5537: 5518: 5508: 5506: 5497: 5496: 5492: 5481: 5477: 5467: 5465: 5456: 5455: 5451: 5438: 5431: 5424: 5408: 5401: 5392: 5385: 5374: 5367: 5357: 5355: 5344: 5331: 5322: 5318: 5311: 5295: 5291: 5284: 5268: 5264: 5254: 5252: 5237: 5233: 5222: 5215: 5204: 5200: 5193: 5177: 5170: 5163: 5147: 5130: 5123: 5107: 5103: 5096: 5080: 5073: 5058: 5054: 5006: 5002: 4992: 4990: 4988:The Electrician 4980: 4973: 4959: 4955: 4945: 4943: 4924: 4920: 4908: 4904: 4884: 4880: 4860: 4853: 4842: 4835: 4825: 4823: 4810: 4809: 4805: 4788: 4784: 4773: 4769: 4752: 4739: 4729: 4727: 4716: 4712: 4701: 4690: 4680: 4678: 4663: 4656: 4643: 4641: 4639: 4615: 4600: 4589: 4580: 4573: 4557: 4553: 4542: 4538: 4527: 4523: 4516: 4500: 4496: 4489: 4473: 4460: 4453: 4437: 4428: 4421: 4405: 4370: 4353: 4344: 4337: 4321: 4317: 4310: 4294: 4265: 4255: 4253: 4231: 4227: 4204: 4200: 4193: 4177: 4166: 4159: 4143: 4139: 4132: 4116: 4107: 4100: 4084: 4077: 4070: 4054: 4045: 4038: 4022: 4015: 4008: 3992: 3941: 3915: 3908: 3890: 3886: 3867: 3863: 3856: 3840: 3836: 3818: 3814: 3807: 3791: 3784: 3777: 3761: 3670: 3659: 3655: 3645: 3643: 3635: 3629: 3606: 3589: 3585: 3575: 3573: 3565: 3559: 3542: 3529: 3525: 3515: 3513: 3502: 3467: 3460: 3444: 3433: 3426: 3410: 3406: 3399: 3383: 3376: 3369: 3358:College Physics 3353: 3349: 3336: 3329: 3319: 3317: 3308: 3306: 3299: 3289: 3287: 3278: 3271: 3261: 3259: 3248: 3244: 3237: 3221: 3217: 3210: 3193: 3184: 3179: 3142: 3079:radio operators 3075: 3066:broadcast radio 3039:Edwin Armstrong 3017: 2991:current in the 2989:radio frequency 2906: 2858:Marconi Company 2820: 2686: 2681: 2676: 2641: 2639:The "spark" era 2636: 2635: 2634: 2633: 2617: 2616: 2615: 2612: 2604: 2603: 2596: 2588: 2587: 2584: 2552:continuous wave 2548: 2503: 2500: 2491: 2485: 2476: 2473: 2464: 2461: 2452: 2449: 2432: 2412: 2369: 2368: 2367: 2366: 2365: 2362: 2353: 2352: 2351: 2348: 2335: 2332: 2323: 2308: 2299: 2296: 2287: 2276: 2267: 2264: 2255: 2219:Arthur Kennelly 2110: 2109: 2108: 2107: 2106: 2103: 2095: 2094: 2091: 2080: 2042: 2039: 2030: 2019: 2010: 2007: 1998: 1991: 1875:primary winding 1867:coupled circuit 1823: 1816: 1802: 1793: 1789: 1780: 1773: 1764: 1761: 1689:William Crookes 1668: 1650:radio receivers 1595:electric charge 1568: 1536:Eugène Ducretet 1532:Alexander Popov 1508:English Channel 1501:of the British 1495: 1494: 1493: 1492: 1491: 1488: 1480: 1479: 1468: 1460: 1459: 1448: 1440: 1439: 1428: 1378: 1377: 1376: 1375: 1374: 1355: 1347: 1346: 1343: 1335: 1334: 1327: 1319: 1318: 1311: 1303: 1302: 1299: 1290: 1289: 1273:radiotelegraphy 1264: 1261: 1254: 1011: 1004: 995: 992:(in box, right) 981: 972: 969: 960: 948:, auto battery 934: 925: 914: 905: 899: 863: 840:magnetic fields 780: 770: 753: 744: 715: 694: 676: 588: 582: 572: 567: 559: 556: 555: 536: 533: 532: 513: 510: 509: 486: 483: 482: 449:; a radio wave. 418:, reducing its 397: 396: 395: 394: 393: 383: 376: 373: 346: 344:Operation cycle 287:primary winding 239:radio frequency 214:A high-voltage 181:radio frequency 128: 84:radiotelegraphy 43:by means of an 17: 12: 11: 5: 8027: 8017: 8016: 8011: 8006: 8001: 7996: 7979: 7978: 7976: 7975: 7965: 7955: 7945: 7932: 7929: 7928: 7926: 7925: 7918: 7913: 7908: 7903: 7898: 7897: 7896: 7891: 7883: 7877: 7875: 7871: 7870: 7868: 7867: 7862: 7857: 7852: 7847: 7842: 7837: 7832: 7827: 7822: 7816: 7814: 7808: 7807: 7805: 7804: 7799: 7794: 7789: 7784: 7779: 7774: 7769: 7764: 7759: 7754: 7749: 7744: 7738: 7736: 7730: 7729: 7727: 7726: 7721: 7716: 7711: 7706: 7700: 7698: 7694: 7693: 7691: 7690: 7685: 7680: 7675: 7670: 7665: 7663:Space-division 7659: 7657: 7651: 7650: 7648: 7647: 7642: 7641: 7640: 7635: 7625: 7624: 7623: 7613: 7608: 7602: 7600: 7592: 7591: 7589: 7588: 7587: 7586: 7576: 7575: 7574: 7564: 7559: 7554: 7553: 7552: 7542: 7536: 7534: 7526: 7525: 7523: 7522: 7517: 7512: 7507: 7502: 7500:Camille Tissot 7497: 7492: 7487: 7482: 7477: 7475:Claude Shannon 7472: 7467: 7465:Tivadar Puskás 7462: 7457: 7452: 7447: 7442: 7437: 7435:Antonio Meucci 7432: 7427: 7422: 7417: 7412: 7407: 7405:Charles K. Kao 7402: 7397: 7392: 7387: 7382: 7380:Harold Hopkins 7377: 7372: 7367: 7362: 7357: 7352: 7347: 7342: 7337: 7332: 7327: 7322: 7317: 7312: 7307: 7302: 7297: 7292: 7287: 7282: 7280:Emile Berliner 7277: 7272: 7267: 7262: 7257: 7252: 7247: 7241: 7239: 7235: 7234: 7232: 7231: 7226: 7221: 7219:Videotelephony 7216: 7211: 7210: 7209: 7204: 7194: 7187: 7182: 7176: 7171: 7166: 7161: 7156: 7155: 7154: 7149: 7144: 7134: 7133: 7132: 7122: 7117: 7115:Radiotelephone 7112: 7107: 7102: 7097: 7092: 7087: 7082: 7081: 7080: 7070: 7065: 7060: 7055: 7050: 7045: 7040: 7035: 7030: 7025: 7020: 7019: 7018: 7013: 7008: 7003: 7001:Internet video 6993: 6992: 6991: 6986: 6981: 6976: 6966: 6961: 6956: 6951: 6946: 6941: 6935: 6933: 6927: 6926: 6919: 6918: 6911: 6904: 6896: 6890: 6889: 6884: 6879: 6874: 6862: 6856: 6851: 6846: 6839: 6838:External links 6836: 6835: 6834: 6812: 6789: 6786: 6783: 6782: 6768:on 16 May 2006 6753: 6719: 6692: 6658: 6641: 6620: 6614:978-1365493225 6613: 6586: 6566: 6525: 6519:978-0198021780 6518: 6498: 6474: 6414: 6397: 6362: 6333: 6304: 6272: 6255: 6223: 6193: 6172: 6145: 6118: 6101:Wireless World 6085: 6068: 6051:Wireless World 6034: 6017: 5983: 5966: 5951: 5910: 5892: 5886:978-0852967928 5885: 5862: 5838: 5832:978-3642295515 5831: 5811: 5805:978-0863413278 5804: 5779: 5756: 5699: 5679: 5652: 5588: 5558: 5552:978-0852967928 5551: 5516: 5490: 5475: 5449: 5429: 5423:978-0080963907 5422: 5399: 5383: 5365: 5329: 5316: 5309: 5289: 5283:978-0786426621 5282: 5262: 5231: 5213: 5198: 5192:978-0313331671 5191: 5168: 5162:978-0471697398 5161: 5128: 5122:978-0760710050 5121: 5101: 5095:978-1136993756 5094: 5071: 5052: 5025:(8): 355–357. 5000: 4971: 4953: 4918: 4902: 4878: 4851: 4833: 4803: 4782: 4767: 4737: 4710: 4688: 4654: 4637: 4598: 4578: 4572:978-0863413278 4571: 4551: 4536: 4521: 4515:978-0191533457 4514: 4494: 4488:978-0470871188 4487: 4458: 4452:978-0471205050 4451: 4426: 4420:978-1400857883 4419: 4368: 4342: 4336:978-0521835398 4335: 4315: 4309:978-0852967928 4308: 4263: 4225: 4198: 4192:978-1615303007 4191: 4164: 4158:978-0786748549 4157: 4137: 4131:978-0786426621 4130: 4105: 4098: 4075: 4069:978-0521835398 4068: 4043: 4037:978-9401588553 4036: 4013: 4006: 3939: 3906: 3884: 3861: 3855:978-0387951508 3854: 3834: 3812: 3806:978-0387951508 3805: 3782: 3776:978-0471783015 3775: 3668: 3653: 3604: 3583: 3540: 3523: 3465: 3459:978-1400854608 3458: 3431: 3425:978-0387951508 3424: 3404: 3398:978-1316785164 3397: 3374: 3368:978-0495386933 3367: 3347: 3327: 3297: 3269: 3242: 3236:978-0122004001 3235: 3215: 3209:978-1135455514 3208: 3181: 3180: 3178: 3175: 3174: 3173: 3168: 3163: 3158: 3153: 3148: 3141: 3138: 3118:remote control 3111:electrosurgery 3103:electric shock 3074: 3071: 3016: 3013: 2997: 2996: 2969: 2905: 2902: 2866:British Empire 2777:ignition coils 2769:radio amateurs 2759: 2758: 2755: 2752: 2749: 2745: 2744: 2741: 2738: 2735: 2731: 2730: 2727: 2724: 2721: 2717: 2716: 2713: 2710: 2709:500, 660, 1000 2707: 2703: 2702: 2699: 2696: 2693: 2689: 2688: 2683: 2678: 2673: 2669: 2668: 2640: 2637: 2619: 2618: 2613: 2606: 2605: 2602:one foot thick 2597: 2590: 2589: 2585: 2578: 2577: 2576: 2575: 2574: 2547: 2544: 2531: 2530: 2515: 2512:Nonsynchronous 2505: 2504: 2501: 2494: 2492: 2486: 2479: 2477: 2474: 2467: 2465: 2462: 2455: 2453: 2450: 2443: 2431: 2428: 2363: 2356: 2355: 2354: 2349: 2342: 2341: 2340: 2339: 2338: 2337: 2336: 2333: 2326: 2324: 2309: 2302: 2300: 2297: 2290: 2288: 2282:quenched gap, 2277: 2270: 2268: 2265: 2258: 2254: 2251: 2104: 2097: 2096: 2092: 2085: 2084: 2083: 2082: 2081: 2079: 2076: 2044: 2043: 2040: 2033: 2031: 2020: 2013: 2011: 2008: 2001: 1999: 1992: 1985: 1956:wireless power 1822: 1819: 1818: 1817: 1803: 1796: 1794: 1790: 1783: 1781: 1777:(center right) 1774: 1767: 1765: 1762: 1755: 1667: 1664: 1642:radio spectrum 1567: 1564: 1556:Georg von Arco 1499:William Preece 1489: 1482: 1481: 1469: 1462: 1461: 1449: 1442: 1441: 1429: 1422: 1421: 1420: 1419: 1418: 1356: 1349: 1348: 1344: 1337: 1336: 1328: 1321: 1320: 1312: 1305: 1304: 1300: 1293: 1292: 1291: 1287: 1286: 1285: 1284: 1259: 1253: 1250: 1207:standing waves 1072:standing waves 1051:induction coil 1033:dipole antenna 1013: 1012: 1005: 998: 996: 982: 975: 973: 970: 963: 961: 935: 928: 926: 924:induction coil 915: 908: 906: 900: 893: 867:Heinrich Hertz 862: 859: 769: 766: 752: 749: 743: 740: 732:electric motor 714: 713:AC transformer 711: 698:induction coil 693: 692:Induction coil 690: 675: 672: 631:, such as the 611: 610: 594: 591: 587: 578: 575: 571: 566: 563: 540: 517: 490: 470:and decreases 460: 459: 450: 443:electric field 439:magnetic field 435: 427: 416:electric spark 414:, starting an 404: 384: 374: 369: 368: 367: 366: 365: 351:radio receiver 345: 342: 341: 340: 330: 319: 308: 307: 306: 291:magnetic field 269: 231: 228:induction coil 166:electric spark 137:when they are 127: 124: 70:used to carry 57:Heinrich Hertz 45:electric spark 15: 9: 6: 4: 3: 2: 8026: 8015: 8012: 8010: 8007: 8005: 8004:Electric arcs 8002: 8000: 7997: 7995: 7992: 7991: 7989: 7974: 7966: 7964: 7956: 7954: 7946: 7944: 7934: 7933: 7930: 7923: 7919: 7917: 7914: 7912: 7909: 7907: 7904: 7902: 7899: 7895: 7892: 7890: 7887: 7886: 7884: 7882: 7879: 7878: 7876: 7872: 7866: 7863: 7861: 7858: 7856: 7853: 7851: 7848: 7846: 7843: 7841: 7838: 7836: 7833: 7831: 7828: 7826: 7823: 7821: 7818: 7817: 7815: 7813: 7809: 7803: 7800: 7798: 7795: 7793: 7790: 7788: 7785: 7783: 7780: 7778: 7775: 7773: 7770: 7768: 7765: 7763: 7760: 7758: 7755: 7753: 7750: 7748: 7745: 7743: 7740: 7739: 7737: 7735: 7731: 7725: 7722: 7720: 7717: 7715: 7712: 7710: 7707: 7705: 7702: 7701: 7699: 7695: 7689: 7688:Code-division 7686: 7684: 7681: 7679: 7676: 7674: 7673:Time-division 7671: 7669: 7666: 7664: 7661: 7660: 7658: 7656: 7652: 7646: 7643: 7639: 7636: 7634: 7631: 7630: 7629: 7626: 7622: 7619: 7618: 7617: 7614: 7612: 7609: 7607: 7604: 7603: 7601: 7599:and switching 7597: 7593: 7585: 7582: 7581: 7580: 7577: 7573: 7570: 7569: 7568: 7565: 7563: 7560: 7558: 7555: 7551: 7550:optical fiber 7548: 7547: 7546: 7543: 7541: 7540:Coaxial cable 7538: 7537: 7535: 7533: 7527: 7521: 7518: 7516: 7513: 7511: 7508: 7506: 7503: 7501: 7498: 7496: 7493: 7491: 7488: 7486: 7483: 7481: 7478: 7476: 7473: 7471: 7468: 7466: 7463: 7461: 7458: 7456: 7455:Radia Perlman 7453: 7451: 7448: 7446: 7443: 7441: 7438: 7436: 7433: 7431: 7428: 7426: 7423: 7421: 7418: 7416: 7413: 7411: 7408: 7406: 7403: 7401: 7398: 7396: 7393: 7391: 7388: 7386: 7383: 7381: 7378: 7376: 7373: 7371: 7368: 7366: 7363: 7361: 7358: 7356: 7353: 7351: 7348: 7346: 7345:Lee de Forest 7343: 7341: 7340:Thomas Edison 7338: 7336: 7333: 7331: 7330:Donald Davies 7328: 7326: 7323: 7321: 7318: 7316: 7315:Claude Chappe 7313: 7311: 7308: 7306: 7303: 7301: 7298: 7296: 7293: 7291: 7288: 7286: 7283: 7281: 7278: 7276: 7273: 7271: 7268: 7266: 7263: 7261: 7258: 7256: 7253: 7251: 7248: 7246: 7243: 7242: 7240: 7236: 7230: 7227: 7225: 7222: 7220: 7217: 7215: 7212: 7208: 7205: 7203: 7200: 7199: 7198: 7195: 7193: 7192: 7188: 7186: 7183: 7180: 7177: 7175: 7172: 7170: 7167: 7165: 7162: 7160: 7159:Smoke signals 7157: 7153: 7150: 7148: 7145: 7143: 7140: 7139: 7138: 7137:Semiconductor 7135: 7131: 7128: 7127: 7126: 7123: 7121: 7118: 7116: 7113: 7111: 7108: 7106: 7103: 7101: 7098: 7096: 7093: 7091: 7088: 7086: 7083: 7079: 7076: 7075: 7074: 7071: 7069: 7066: 7064: 7061: 7059: 7056: 7054: 7051: 7049: 7046: 7044: 7041: 7039: 7036: 7034: 7031: 7029: 7026: 7024: 7021: 7017: 7014: 7012: 7009: 7007: 7004: 7002: 6999: 6998: 6997: 6996:Digital media 6994: 6990: 6987: 6985: 6982: 6980: 6977: 6975: 6972: 6971: 6970: 6967: 6965: 6962: 6960: 6957: 6955: 6952: 6950: 6947: 6945: 6942: 6940: 6937: 6936: 6934: 6932: 6928: 6924: 6917: 6912: 6910: 6905: 6903: 6898: 6897: 6894: 6888: 6885: 6883: 6880: 6878: 6875: 6871: 6867: 6863: 6860: 6857: 6855: 6852: 6850: 6847: 6845: 6842: 6841: 6828:September 14, 6823: 6822: 6817: 6813: 6806:September 12, 6801: 6797: 6792: 6791: 6779: 6767: 6763: 6757: 6741: 6737: 6730: 6723: 6707: 6703: 6696: 6680: 6676: 6669: 6662: 6654: 6653: 6645: 6637: 6633: 6632: 6624: 6616: 6610: 6606: 6602: 6601: 6593: 6591: 6579: 6578: 6570: 6562: 6556: 6548: 6544: 6543: 6536: 6529: 6521: 6515: 6511: 6510: 6502: 6494: 6490: 6489: 6481: 6479: 6470: 6466: 6461: 6456: 6452: 6448: 6444: 6440: 6436: 6432: 6428: 6421: 6419: 6410: 6409: 6401: 6386:on 2002-10-20 6385: 6381: 6377: 6373: 6366: 6350: 6343: 6337: 6321: 6317: 6311: 6309: 6292: 6288: 6281: 6279: 6277: 6268: 6267: 6259: 6243: 6239: 6232: 6230: 6228: 6211: 6207: 6200: 6198: 6189: 6185: 6184: 6176: 6160: 6156: 6149: 6133: 6129: 6122: 6106: 6102: 6095: 6089: 6081: 6080: 6072: 6057:(78): 310–316 6056: 6052: 6045: 6038: 6030: 6029: 6021: 6014: 6000: 5996: 5990: 5988: 5979: 5978: 5970: 5963: 5962: 5955: 5940: 5936: 5933:(1746): 390. 5932: 5928: 5924: 5917: 5915: 5908: 5906: 5899: 5897: 5888: 5882: 5878: 5877: 5869: 5867: 5858: 5857: 5849: 5847: 5845: 5843: 5834: 5828: 5824: 5823: 5815: 5807: 5801: 5797: 5796: 5788: 5786: 5784: 5776: 5774: 5767: 5765: 5763: 5761: 5752: 5748: 5743: 5738: 5734: 5730: 5726: 5722: 5718: 5714: 5710: 5703: 5697: 5695: 5688: 5686: 5684: 5667: 5663: 5656: 5648: 5644: 5640: 5636: 5632: 5628: 5623: 5618: 5614: 5607: 5605: 5603: 5601: 5599: 5597: 5595: 5593: 5584: 5583: 5575: 5573: 5571: 5569: 5567: 5565: 5563: 5554: 5548: 5544: 5543: 5535: 5533: 5531: 5529: 5527: 5525: 5523: 5521: 5504: 5500: 5494: 5488: 5486: 5483:Morse (1925) 5479: 5463: 5459: 5453: 5446: 5442: 5436: 5434: 5425: 5419: 5415: 5414: 5406: 5404: 5396: 5390: 5388: 5380: 5379: 5372: 5370: 5353: 5349: 5342: 5340: 5338: 5336: 5334: 5326: 5320: 5312: 5306: 5302: 5301: 5293: 5285: 5279: 5275: 5274: 5266: 5250: 5246: 5242: 5235: 5228: 5227: 5220: 5218: 5211: 5209: 5202: 5194: 5188: 5184: 5183: 5175: 5173: 5164: 5158: 5154: 5153: 5145: 5143: 5141: 5139: 5137: 5135: 5133: 5124: 5118: 5114: 5113: 5105: 5097: 5091: 5087: 5086: 5078: 5076: 5068: 5067: 5062: 5056: 5048: 5044: 5040: 5036: 5032: 5028: 5024: 5020: 5014: 5010: 5004: 4989: 4985: 4978: 4976: 4967: 4966: 4957: 4941: 4937: 4933: 4929: 4922: 4916: 4914: 4906: 4899: 4895: 4891: 4890: 4882: 4875: 4871: 4867: 4866: 4858: 4856: 4848: 4847: 4840: 4838: 4821: 4817: 4813: 4807: 4799: 4795: 4794: 4786: 4780: 4778: 4771: 4763: 4759: 4758: 4750: 4748: 4746: 4744: 4742: 4725: 4721: 4714: 4707: 4706: 4699: 4697: 4695: 4693: 4676: 4672: 4668: 4661: 4659: 4652: 4640: 4638:0-85296-649-0 4634: 4630: 4626: 4622: 4621: 4613: 4611: 4609: 4607: 4605: 4603: 4595: 4594: 4587: 4585: 4583: 4574: 4568: 4564: 4563: 4555: 4549: 4547: 4540: 4534: 4532: 4529:Morse (1925) 4525: 4517: 4511: 4507: 4506: 4498: 4490: 4484: 4480: 4479: 4471: 4469: 4467: 4465: 4463: 4454: 4448: 4444: 4443: 4435: 4433: 4431: 4422: 4416: 4412: 4411: 4403: 4401: 4399: 4397: 4395: 4393: 4391: 4389: 4387: 4385: 4383: 4381: 4379: 4377: 4375: 4373: 4365: 4364: 4359: 4358: 4351: 4349: 4347: 4338: 4332: 4328: 4327: 4319: 4311: 4305: 4301: 4300: 4292: 4290: 4288: 4286: 4284: 4282: 4280: 4278: 4276: 4274: 4272: 4270: 4268: 4252: 4248: 4244: 4240: 4236: 4229: 4220: 4216: 4215: 4208: 4202: 4194: 4188: 4184: 4183: 4175: 4173: 4171: 4169: 4160: 4154: 4150: 4149: 4141: 4133: 4127: 4123: 4122: 4114: 4112: 4110: 4101: 4099:9780405060526 4095: 4091: 4090: 4082: 4080: 4071: 4065: 4061: 4060: 4052: 4050: 4048: 4039: 4033: 4029: 4028: 4020: 4018: 4009: 4007:9780262514194 4003: 4000:. MIT Press. 3999: 3998: 3990: 3988: 3986: 3984: 3982: 3980: 3978: 3976: 3974: 3972: 3970: 3968: 3966: 3964: 3962: 3960: 3958: 3956: 3954: 3952: 3950: 3948: 3946: 3944: 3935: 3931: 3927: 3926: 3919: 3913: 3911: 3901: 3897: 3896: 3888: 3879: 3878: 3871: 3865: 3857: 3851: 3847: 3846: 3838: 3830: 3829: 3822: 3816: 3808: 3802: 3798: 3797: 3789: 3787: 3778: 3772: 3768: 3767: 3759: 3757: 3755: 3753: 3751: 3749: 3747: 3745: 3743: 3741: 3739: 3737: 3735: 3733: 3731: 3729: 3727: 3725: 3723: 3721: 3719: 3717: 3715: 3713: 3711: 3709: 3707: 3705: 3703: 3701: 3699: 3697: 3695: 3693: 3691: 3689: 3687: 3685: 3683: 3681: 3679: 3677: 3675: 3673: 3665: 3664: 3657: 3641: 3634: 3627: 3625: 3623: 3621: 3619: 3617: 3615: 3613: 3611: 3609: 3600: 3596: 3595: 3587: 3571: 3564: 3557: 3555: 3553: 3551: 3549: 3547: 3545: 3536: 3535: 3527: 3511: 3507: 3506:"Spark Radio" 3500: 3498: 3496: 3494: 3492: 3490: 3488: 3486: 3484: 3482: 3480: 3478: 3476: 3474: 3472: 3470: 3461: 3455: 3451: 3450: 3442: 3440: 3438: 3436: 3427: 3421: 3417: 3416: 3408: 3400: 3394: 3390: 3389: 3381: 3379: 3370: 3364: 3360: 3359: 3351: 3343: 3342: 3334: 3332: 3315: 3311: 3304: 3302: 3290:September 14, 3285: 3284: 3276: 3274: 3257: 3253: 3246: 3238: 3232: 3228: 3227: 3219: 3211: 3205: 3201: 3200: 3191: 3189: 3187: 3182: 3172: 3171:Crystal radio 3169: 3167: 3164: 3162: 3161:Antique radio 3159: 3157: 3156:Amateur radio 3154: 3152: 3149: 3147: 3144: 3143: 3137: 3135: 3131: 3126: 3124: 3119: 3114: 3112: 3108: 3104: 3099: 3095: 3091: 3086: 3084: 3080: 3070: 3067: 3062: 3059: 3055: 3054:Lee de Forest 3051: 3048: 3044: 3040: 3036: 3033: 3030: 3021: 3012: 3010: 3006: 3002: 2994: 2990: 2986: 2982: 2978: 2974: 2970: 2967: 2963: 2959: 2955: 2951: 2947: 2946:arc converter 2943: 2942: 2941: 2938: 2935: 2931: 2926: 2923: 2918: 2915: 2911: 2901: 2899: 2895: 2891: 2887: 2883: 2879: 2875: 2871: 2867: 2863: 2859: 2855: 2851: 2847: 2838: 2834: 2829: 2825: 2819: 2815: 2814: 2808: 2807: 2801: 2797: 2792: 2791: 2784: 2782: 2778: 2774: 2770: 2766: 2756: 2754:20,000 - 1600 2753: 2750: 2747: 2746: 2742: 2739: 2736: 2733: 2732: 2728: 2725: 2722: 2719: 2718: 2714: 2712:600, 450, 300 2711: 2708: 2705: 2704: 2700: 2697: 2694: 2690: 2685:Typical power 2684: 2679: 2674: 2671: 2670: 2665: 2662: 2660: 2659: 2653: 2652: 2647: 2632:transmitters. 2631: 2627: 2623: 2610: 2601: 2594: 2582: 2573: 2571: 2566: 2561: 2560:superposition 2557: 2553: 2543: 2540: 2536: 2528: 2523: 2519: 2516: 2513: 2510: 2509: 2508: 2498: 2493: 2489: 2483: 2478: 2471: 2466: 2459: 2454: 2447: 2442: 2441: 2440: 2437: 2427: 2425: 2420: 2418: 2409: 2405: 2402:, called the 2401: 2396: 2394: 2390: 2389:Elihu Thomson 2384: 2382: 2379: 2375: 2360: 2346: 2330: 2325: 2321: 2317: 2313: 2306: 2301: 2294: 2289: 2285: 2281: 2274: 2269: 2262: 2257: 2256: 2250: 2248: 2242: 2240: 2236: 2232: 2228: 2224: 2220: 2214: 2212: 2208: 2204: 2200: 2196: 2193: 2189: 2185: 2181: 2177: 2173: 2169: 2164: 2162: 2158: 2154: 2150: 2147: 2143: 2139: 2138:(see circuit) 2135: 2131: 2122: 2114: 2101: 2089: 2075: 2073: 2068: 2066: 2060: 2058: 2053: 2050: 2037: 2032: 2028: 2025:and receiver 2024: 2017: 2012: 2005: 2000: 1996: 1989: 1984: 1983: 1982: 1980: 1976: 1972: 1968: 1963: 1961: 1960:communication 1957: 1953: 1949: 1948:Geissler tube 1945: 1944: 1939: 1935: 1931: 1927: 1922: 1920: 1916: 1912: 1908: 1904: 1900: 1896: 1892: 1888: 1884: 1880: 1876: 1872: 1868: 1864: 1860: 1856: 1852: 1844: 1840: 1835: 1831: 1828: 1815: 1811: 1807: 1800: 1795: 1787: 1782: 1778: 1771: 1766: 1759: 1754: 1753: 1752: 1750: 1749:loading coils 1745: 1741: 1736: 1734: 1730: 1726: 1722: 1718: 1713: 1711: 1708:"tuning" its 1706: 1702: 1698: 1695:(then called 1694: 1690: 1681: 1678:and receiver 1677: 1672: 1663: 1660: 1659:G. W. Pickard 1656: 1655:Lee de Forest 1651: 1647: 1643: 1639: 1635: 1631: 1627: 1618: 1614: 1612: 1608: 1604: 1600: 1596: 1592: 1588: 1583: 1581: 1572: 1566:Disadvantages 1563: 1561: 1557: 1553: 1549: 1545: 1544:Lee de Forest 1541: 1537: 1533: 1529: 1525: 1521: 1516: 1513: 1509: 1504: 1500: 1486: 1477: 1473: 1466: 1457: 1454:and receiver 1453: 1446: 1437: 1433: 1426: 1417: 1415: 1411: 1407: 1403: 1399: 1395: 1391: 1388: 1384: 1372: 1368: 1364: 1360: 1353: 1341: 1332: 1325: 1316: 1309: 1297: 1283: 1281: 1277: 1274: 1270: 1258: 1249: 1247: 1242: 1240: 1236: 1232: 1231:Augusto Righi 1228: 1224: 1220: 1216: 1212: 1208: 1204: 1200: 1196: 1192: 1188: 1184: 1180: 1176: 1172: 1168: 1164: 1160: 1156: 1152: 1147: 1145: 1141: 1137: 1133: 1129: 1128:Augusto Righi 1125: 1121: 1117: 1116:Lord Rayleigh 1113: 1104: 1099: 1095: 1093: 1089: 1085: 1081: 1077: 1073: 1068: 1064: 1060: 1056: 1052: 1048: 1045: 1041: 1038: 1034: 1026: 1022: 1017: 1009: 1002: 997: 993: 989: 985: 979: 974: 967: 962: 958: 955: 954:telegraph key 951: 947: 943: 939: 932: 927: 923: 919: 912: 907: 904: 897: 892: 891: 890: 888: 884: 880: 876: 873:predicted by 872: 868: 858: 855: 853: 849: 845: 841: 837: 833: 830:, now called 829: 825: 820: 818: 814: 810: 805: 804:Thomas Edison 801: 800:Mahlon Loomis 797: 793: 788: 783: 779: 775: 765: 762: 758: 748: 739: 737: 733: 729: 725: 720: 710: 708: 703: 699: 689: 686: 681: 671: 669: 665: 661: 660:telegraph key 657: 652: 650: 646: 642: 638: 637:Fleming valve 634: 630: 627: 624: 620: 616: 592: 589: 585: 576: 573: 569: 564: 561: 554: 553: 552: 551:of the coil: 538: 531: 515: 508: 504: 488: 481: 477: 473: 472:exponentially 469: 465: 456: 451: 448: 444: 440: 436: 432: 428: 425: 421: 417: 413: 409: 405: 401: 400: 391: 387: 372: 363: 358: 354: 352: 339: 335: 334:telegraph key 331: 328: 324: 320: 317: 313: 309: 304: 300: 296: 292: 288: 284: 280: 276: 275: 270: 267: 263: 262: 260: 256: 252: 248: 244: 240: 236: 232: 229: 225: 221: 217: 213: 212: 211: 203: 199: 197: 193: 188: 186: 182: 179: 175: 171: 167: 163: 158: 156: 152: 148: 144: 140: 136: 132: 123: 121: 117: 112: 108: 107: 100: 95: 93: 89: 88:telegraph key 85: 81: 77: 73: 69: 65: 60: 58: 54: 50: 46: 42: 38: 34: 26: 21: 7655:Multiplexing 7530:Transmission 7495:Nikola Tesla 7485:Henry Sutton 7440:Samuel Morse 7370:Robert Hooke 7335:Amos Dolbear 7270:John Bardeen 7189: 7169:Telautograph 7073:Mobile phone 7028:Edholm's law 7011:social media 6944:Broadcasting 6870:the original 6826:. Retrieved 6820: 6804:. Retrieved 6799: 6777: 6770:. Retrieved 6766:the original 6756: 6746:November 11, 6744:. Retrieved 6739: 6735: 6722: 6710:. Retrieved 6705: 6695: 6683:. Retrieved 6678: 6674: 6661: 6651: 6644: 6630: 6623: 6599: 6576: 6569: 6541: 6534: 6528: 6508: 6501: 6487: 6434: 6430: 6407: 6400: 6388:. Retrieved 6384:the original 6379: 6375: 6365: 6353:. Retrieved 6348: 6336: 6324:. Retrieved 6319: 6295:. Retrieved 6290: 6265: 6258: 6246:. Retrieved 6241: 6214:. Retrieved 6209: 6182: 6175: 6163:. Retrieved 6158: 6148: 6136:. Retrieved 6131: 6121: 6109:. Retrieved 6104: 6100: 6088: 6078: 6071: 6059:. Retrieved 6054: 6050: 6037: 6027: 6020: 6012: 6011:included in 6003:. Retrieved 5998: 5976: 5969: 5959: 5954: 5942:. Retrieved 5930: 5926: 5904: 5875: 5855: 5821: 5814: 5794: 5775:, p. 271-272 5772: 5716: 5712: 5702: 5693: 5670:. Retrieved 5666:The Guardian 5665: 5655: 5612: 5581: 5541: 5507:. Retrieved 5502: 5493: 5484: 5478: 5466:. Retrieved 5461: 5452: 5412: 5377: 5356:. 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