vacuum tube
vacuum tube
A vacuum tube is an electron tube or valve or device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons such as signal amplification and current rectification.
Non-thermionic types, such as a vacuum photo tube however, achieve electron emission through the photoelectric effect, and are used for such as the detection of light levels. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube.
The simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, it contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device- from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode to the anode to be controlled by the voltage on he grid or grids. They were crucial to the development of radio, television, radar, sound recording and reproduction., long-distance telephone networks, and analogue and early Digital computer.
vacuum tube also used in spark gap transmitter for radio. A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark. German physicist Heinrich Hertz built the first experimental spark-gap transmitters in 1887, with which he discovered radio waves and studied their properties.
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 by radiotelegraphy; the operator switched the transmitted on and off with a telegraph key, creation pulses of radio waves to spell out ext messages in Morse code.
After World War 1, transmitters based on vacuum tubes were developed, which were cheaper and produced continuous waves which had a greater range, produced less interference, and it 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 bandwidth, and creating radio frequency interference (RF I) that can disrupt other radio transmissions. This type of radio emission has been prohibited by international law since 1934.
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| Vacuum tube |
A vacuum tube is an electron tube or valve or device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons such as signal amplification and current rectification.
Non-thermionic types, such as a vacuum photo tube however, achieve electron emission through the photoelectric effect, and are used for such as the detection of light levels. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube.
The simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, it contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device- from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode to the anode to be controlled by the voltage on he grid or grids. They were crucial to the development of radio, television, radar, sound recording and reproduction., long-distance telephone networks, and analogue and early Digital computer.
vacuum tube also used in spark gap transmitter for radio. A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark. German physicist Heinrich Hertz built the first experimental spark-gap transmitters in 1887, with which he discovered radio waves and studied their properties.
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 by radiotelegraphy; the operator switched the transmitted on and off with a telegraph key, creation pulses of radio waves to spell out ext messages in Morse code.
After World War 1, transmitters based on vacuum tubes were developed, which were cheaper and produced continuous waves which had a greater range, produced less interference, and it 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 bandwidth, and creating radio frequency interference (RF I) that can disrupt other radio transmissions. This type of radio emission has been prohibited by international law since 1934.
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