Hertz_spark_gap_transmitter_and_parabolic_antenna.png
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Summary
Description Hertz 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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Date | ||||||||||||||||||||||||
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. | |||||||||||||||||||||||
Author |
creator QS:P170,Q41257
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Permission
( Reusing this file ) |
Public domain - Hertz died in 1894 |
Licensing
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This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights. |
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Public domain Public domain false false |
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. This applies to U.S. works where the copyright has expired, often because its first
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Annotations
InfoField
|
This image is annotated: View the annotations at Commons |
231
63
181
477
506
926
English:
Parabolic reflector
made of zinc sheet metal attached to wooden frame focuses radio waves from dipole into beam
249
234
57
130
506
926
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
77
327
125
51
506
926
English:
Induction coil
(Ruhmkorff coil) powered by battery creates pulses of high voltage electricity
105
652
107
46
506
926
English:
Battery to power induction coil
96
706
116
79
506
926
English:
Induction coil
(Ruhmkorff coil) generates pulses of high voltage electricity from the low voltage provided by battery
244
601
167
286
506
926
English:
Parabolic reflector
made of zinc sheet metal attached to wooden frame focuses radio waves from dipole antenna into a beam