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KF4LLF > TODAY 22.02.12 21:34l 73 Lines 3813 Bytes #999 (0) @ WW
BID : 110033KF4LLF
Read: GUEST IV3JER
Subj: Happy Birthday Heinrich Hertz
Path: IZ3LSV<IW0QNL<IK6ZDE<I0OJJ<VE3UIL<N9PMO<AC4ZR
Sent: 120222/1926Z 17609@AC4ZR.#LCS.SC.USA.NOAM [Lancaster, SC] FBB7.00e
From: KF4LLF@AC4ZR.#LCS.SC.USA.NOAM
To : TODAY@WW
We wouldn't be where we are... Born today:
Heinrich Rudolf Hertz (Born 22 February 1857 - Died 1 January 1894) was a
German physicist who clarified and expanded the electromagnetic theory of
light that had been put forth by James Clerk Maxwell. He was the first to
conclusively prove the existence of electromagnetic waves by engineering
instruments to transmit and receive radio pulses using experimental procedures
that ruled out all other known wireless phenomena. The scientific unit of
frequency—one cycle per second—was named the "hertz" in his honor.
Hertz was born in Hamburg, then a sovereign state of the German Confederation,
into a prosperous and cultured Hanseatic family. His father, Gustav Ferdinand
Hertz, was a writer and later a senator. His mother was the former Anna
Elisabeth Pfefferkorn. His paternal grandfather David Wolff Hertz (1757–1822),
fourth son of Benjamin Wolff Hertz, moved to Hamburg in 1793 where he made his
living as a jeweler. He and his wife Schone Hertz (1760–1834) were buried in
the former Jewish cemetery in Ottensen. Their first son Wolff Hertz
(1790–1859), was chairman of the Jewish community. His brother Hertz Hertz
(1797–1862) was a respected businessman. He was married to Betty Oppenheim,
the daughter of the banker Salomon Oppenheim, from Cologne. Hertz converted
from Judaism to Christianity and took the name Heinrich David Hertz.
In 1885, Hertz became a full professor at the University of Karlsruhe where he
discovered electromagnetic waves.
The most dramatic prediction of Maxwell's theory of electromagnetism,
published in 1865, was the existence of electromagnetic waves moving at the
speed of light, and the conclusion that light itself was just such a wave.
This challenged experimentalists to generate and detect electromagnetic
radiation using some form of electrical apparatus.
The first clearly successful attempt was made by Heinrich Hertz in 1886. For
his radio wave transmitter he used a high voltage induction coil, a condenser
(capacitor, Leyden jar) and a spark gap—whose poles on either side are formed
by spheres of 2 cm radius-to cause a spark discharge between the spark gap's
poles oscillating at a frequency determined by the values of the capacitor and
the induction coil.
To prove there really was radiation emitted, it had to be detected. Hertz used
a piece of copper wire, 1 mm thick, bent into a circle of a diameter of 7.5
cm, with a small brass sphere on one end, and the other end of the wire was
pointed, with the point near the sphere. He bought a screw mechanism so that
the point could be moved very close to the sphere in a controlled fashion.
This "receiver" was designed so that current oscillating back and forth in the
wire would have a natural period close to that of the "transmitter" described
above. The presence of oscillating charge in the receiver would be signaled by
sparks across the (tiny) gap between the point and the sphere (typically, this
gap was hundredths of a millimeter).
In more advanced experiments, Hertz measured the velocity of electromagnetic
radiation and found it to be the same as the light’s velocity. He also showed
that the nature of radio waves’ reflection and refraction was the same as
those of light and established beyond any doubt that light is a form of
electromagnetic radiation obeying the Maxwell equations.
Hertz's experiments would soon trigger the invention of the wireless
telegraph, radio, and later television. In 1930 the International
Electrotechnical Commission (IEC) recognized his work by naming the unit of
frequency-one cycle per second-the "hertz".
Refrences: http://en.wikipedia.org/wiki/Heinrich_Hertz
73, KF4LLF @ AC4ZR
Message timed: 14:24 on 2012-Feb-22
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