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A fundamental limitation of spark-gap transmitters is that they generate a series of brief transient pulses of radio waves called damped waves; they are unable to produce the continuous waves used to carry audio (sound) in modern AM or FM radio transmission. So spark-gap transmitters could not transmit audio, and instead transmitted information ...
Nowadays, this is usually regarded as illegal radio frequency interference and is suppressed, but in the early days of radio communications (1880–1920), this was the means by which radio signals were transmitted, in the unmodulated spark-gap transmitter. Many radio spark gaps include cooling devices, such as the rotary gap and heat sinks ...
The earliest practical use of crystal radio was to receive Morse code radio signals transmitted from spark-gap transmitters by early amateur radio experimenters. As electronics evolved, the ability to send voice signals by radio caused a technological explosion around 1920 that evolved into today's radio broadcasting industry.
The arc converter, sometimes called the arc transmitter, or Poulsen arc after Danish engineer Valdemar Poulsen who invented it in 1903, [1] [2] was a variety of spark transmitter used in early wireless telegraphy. The arc converter used an electric arc to convert direct current electricity into radio frequency alternating current.
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 ...
Diagram of a spark transmitter. As an example, when a person walks over a nylon carpet, the rubbing of shoes on carpet performs the role of a battery and resistor, while the person acts as a capacitor (C1 and C2), and the air between a hand and a door knob is a spark gap. Stray inductance acts as L.
The circuit of a coherer receiver, that recorded the received code on a Morse paper tape recorder. Unlike modern AM radio stations that transmit a continuous radio frequency, whose amplitude (power) is modulated by an audio signal, the first radio transmitters transmitted information by wireless telegraphy (radiotelegraphy), the transmitter was turned on and off (on-off keying) to produce ...