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Low-power inductively coupled spark-gap transmitter on display in Electric Museum, Frastanz, Austria. The spark gap is inside the box with the transparent cover at top center. A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark.
This new, more-refined method for generating continuous-wave radio signals was initially developed by Danish inventor Valdemar Poulsen.The spark-gap transmitters in use at that time produced damped wave which wasted a large portion of their radiated power transmitting strong harmonics on multiple frequencies that filled the RF spectrum with interference.
A spark plug.The spark gap is at the bottom. A spark plug uses a spark gap to initiate combustion.The heat of the ionization trail, but more importantly, UV radiation and hot free electrons (both cause the formation of reactive free radicals) [citation needed] ignite a fuel-air mixture inside an internal combustion engine, or a burner in a furnace, oven, or stove.
The primitive spark-gap transmitters used until 1920 transmitted by a modulation method called damped wave. As long as the telegraph key was pressed, the transmitter would produce a string of transient pulses of radio waves which repeated at an audio rate, usually between 50 and several thousand hertz. [33]
The Alexanderson alternator followed Fessenden's rotary spark-gap transmitter as the second radio transmitter to be modulated to carry the human voice. Until the invention of vacuum-tube (valve) oscillators in 1913 such as the Armstrong oscillator , the Alexanderson alternator was an important high-power radio transmitter , and allowed ...
Appleby's overall conclusion was that Loomis had successfully made multiple wireless telegraphic transmissions beginning in 1866, and, based on his analysis of Loomis notebooks, he had inadvertently created a "spark-gap" radio transmitter, similar to what early radio inventors would employ a few decades later.
He hired an electric power expert, Prof. John Ambrose Fleming, who designed and built a complex spark transmitter with three cascaded tuned circuits and two spark gaps, powered by a 25 kW generator turned by a combustion engine. This fed an inverted conical wire antenna consisting of 200 wires suspended from a circle of wooden masts.
One of the first antennas that used this design was the tubular 420 foot (130 m) mast erected in 1905 by Reginald Fessenden for his experimental spark gap transmitter at Brant Rock, Massachusetts with which he made the first two-way transatlantic transmission, communicating with an identical antenna in Machrihanish, Scotland. [10]