Heinrich_Hertz_discovering_radio_waves.png
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Summary
Description Heinrich Hertz discovering radio waves.png |
English:
Artist's conception of German scientist
Heinrich Hertz
historic discovery of
radio waves
in 1886. To generate the waves Hertz used a
spark gap radio transmitter
(rear)
consisting of a
spark gap
between two brass balls attached to a
half-wave dipole antenna
consisting of two wires with metal plates at the ends, powered by a
Ruhmkorff coil
with primary current supplied by a set of liquid batteries on the lower table. The Ruhmkorff coil generated pulses of high voltage which caused sparks to jump between the brass balls. Each spark excited oscillating radio frequency currents in the antenna, which were radiated as
electromagnetic waves
(radio waves). For a receiver, Hertz used a simple loop of wire
(in his hands)
with a narrow gap between the ends, forming a narrow
spark gap
(this picture is slightly inaccurate; Hertz actually used a micrometer gap consisting of an adjustable thumbscrew with its end close to the opposite electrode, to precisely measure the spark length). The length of the wire was a quarter wavelength, so the loop formed a resonant
loop antenna
, and the radio waves excited a voltage in the wire. So each spark of the transmitter excited a spark in the receiver loop.
The transmitter shown was one common type Hertz used, but not necessarily the one with which he made his discovery. Hertz experimented with various types of antenna, from a bare spark gap to dipoles 8 feet long, with square metal plates, round metal plates, and metal balls on their ends. Also, the size of the receiver spark gap is exaggerated in the drawing. The gap in the receiving loop was very small, less than a millimeter, to detect the weak voltages induced. Some of his receiving loops used a gap adjusted by a micrometer.
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Date | |
Source | Downloaded September 12, 2013 from Raymond Francis Yates, Louis Gerard Pacent (1922) The Complete Radio Book , The Century Co., New York, p. 32 on Google Books |
Author | Unknown author Unknown author |
Licensing
Public domain Public domain false false |
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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rule of the shorter term
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Wikipedia:Public domain
and
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for more details.
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