File:Hertz spark gap transmitter and parabolic antenna.png
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Summary
DescriptionHertz spark gap transmitter and parabolic antenna.png |
English: Drawing of early 450 MHz spark-gap radio transmitter and parabolic antenna used by German physicist Heinrich Hertz in 1888 during his historic first researches on radio waves (Hertzian waves), from his 1893 book. This is the earliest example of a parabolic antenna. The antenna is described on p. 175 of the source as a 2 m x 2 m sheet of zinc attached to a wooden frame to make a cylindrical parabolic reflector with aperture 2 m high by 1.2 m wide, with focal length of 12.5 cm. Along the focal line is suspended a Hertzian dipole antenna consisting of two 1 cm dia. brass rods about 13 cm long, with metal balls attached to its adjacent ends to make a spark gap about 3 mm wide. The drawing on the left shows a closeup of the dipole. The dipole elements were attached to an induction coil powered by a battery on a table behind the antenna, which applied high voltage pulses which caused sparks in the spark gap, exciting high frequency oscillations in the dipole. The wavelength of the waves produced was measured by Hertz at 66 cm, making the corresponding frequency 454 MHz. Hertz used a similar parabolic antenna with a spark gap for receiving. With these he performed historic experiments demonstrating standing waves, diffraction, refraction and polarization of radio waves, proving that radio waves are electromagnetic waves like light waves, thus confirming the 1867 theory of James Clerk Maxwell. |
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Source | Downloaded 7 December 2011 from Heinrich Hertz, Daniel Evan Jones (1893) Electric Waves, 2nd Ed., McGraw-Hill, New York, p. 183, fig. 35 and 36 on Google Books. Combined fig. 36, a detail drawing of the dipole, with fig. 35, a drawing of the entire transmitter. | |||||||||||||||||||||||
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creator QS:P170,Q41257 |
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Permission (Reusing this file) |
Public domain - Hertz died in 1894 |
Licensing
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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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Annotations InfoField | This image is annotated: View the annotations at Commons |
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English: Parabolic reflector made of zinc sheet metal attached to wooden frame focuses radio waves from dipole into beam
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English: Dipole antenna made of two 13 cm brass rods with spark gap between them. When high voltage from coil jumps the gap it creates a pulse of radio waves
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English: Induction coil (Ruhmkorff coil) powered by battery creates pulses of high voltage electricity
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English: Battery to power induction coil
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English: Induction coil (Ruhmkorff coil) generates pulses of high voltage electricity from the low voltage provided by battery
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English: Parabolic reflector made of zinc sheet metal attached to wooden frame focuses radio waves from dipole antenna into a beam
Items portrayed in this file
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1893
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File history
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 22:03, 19 June 2018 | 816 × 926 (130 KB) | wikimediacommons>Chetvorno | Added closeup of the dipole antenna which was part of the original drawing |
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