|
October 1962 Radio-Electronics
 [Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Electronics,
published 1930-1988. All copyrights hereby acknowledged.
|
Heinrich Rudolf Hertz,
a pioneering physicist whose name became eponymously associated with the unit of
frequency numbering cycles per second, was born on February 22, 1857, in
Hamburg, Germany. His father, Gustav Ferdinand Hertz, was a prominent lawyer and
senator, while his mother, Anna Elisabeth Pfefferkorn, came from a cultured and
intellectual family. Heinrich was raised in an environment that valued education
and intellectual inquiry, shaping his future pursuits in science. This entry in
the 1962 Radio-Electronics magazine "Inventors of Radio" series
features Hertz. He excelled in academics, showing particular talent in
mathematics and science, but he also pursued a wide range of interests,
including languages and engineering. Hertz initially studied engineering at the
Polytechnic School in Dresden, but his fascination with theoretical science soon
led him to shift his focus to physics.
Inventors of Radio: Heinrich Rudolf Hertz
 By Dexter S. Bartlett
Heinrich Rudolf Hertz, born at Hamburg on Feb. 22, 1857, began to attend the
lectures of Kirchoff and Von Helmholtz at Berlin in October 1878 and was able to
plunge into original research on a problem of electric inertia. For the best solution,
a prize was offered by the philosophy faculty of the university. He succeeded in
winning with his paper on the "Kinetic Energy of Electricity in Motion." His next
investigation, on "Induction in Rotating Spheres," was offered as his dissertation
for the doctor's degree, which he obtained with the rare distinction in those days
of Summa Cum Laude. Later in the same year he was assistant to Helmholtz in the
physical laboratory of the Berlin Institute. During the 3 years he held this position,
he carried out researches on elastic solids, hardness, evaporation and the electric
discharge in gases. In 1883 he went to Kiel, and there began the studies in Maxwell's
electromagnetic theories that made him famous.
James Clerk Maxwell, who was always saying, "What's t' go o' that," sowed the
seed with his mathematical theorems:
1. If electric waves could ever be generated, they would travel at the speed
of light.
2. Light is essentially electro-magnetic and not a mechanical phenomenon.
3. The refractive index of a substance is intimately related to its dielectric
coefficient.
4. Conductors of electricity must be opaque to light.
Hertz' oscillator and resonator.
It remained for Hertz to prove these 20 years later. Hertz actually made these
experiments between 1885 and 1889, when he was professor of physics at the Carlsruhe
Polytechnic. He used an oscillator and resonator, as shown in the diagram. With
the resonator held in his hand he moved about the laboratory, and, within certain
distances from the oscillator, he found that a small spark would jump across the
gap in his resonator, or wire loop. The latter was tuned to be in resonance with
the frequency of the waves radiated from the oscillator by varying its diameter.
This was the very first spark-gap transmitter and receiver.
In this way Hertz verified the opinion of Maxwell and, for probably the first
time in history, determined the wavelength of the electric waves he was using. He
also established the close relation between those waves and light waves. He found
that when electric waves, radiated from his oscillator, were directed against a
metal mirror connected to the resonator, there would be a spark across the resonator
gap. But, if he held sheet iron between the oscillator and the resonator, there
would be no spark. This he considered as a shadow. He believed that the iron absorbed
the waves because it was opaque to them as it was to light. He also claimed that
the electric waves each have a North and South polarity which causes them to proceed
in a given direction by the laws of attraction and repulsion. He checked diffraction
with a prism and lenses of pitch. Polarization was checked with a screen composed
of parallel wires placed between oscillator and resonator and rotated.
Hertz' best known discoveries were not his only ones. He contributed eighteen
papers on various subjects to German periodicals. He also found that, if the spark
gap is made of certain appropriate substances, ordinary light would cause the spark
to jump more easily. This was the beginning of photoelectric cells.
In 1875, Prof. Elihu Thomson, also, experimentally discovered electric-magnetic
waves. On the first floor of a Philadelphia high school, he had a grounded induction
coil connected to an insulated still for an antenna and drew long sparks between
his pencil and door knobs, even on the sixth floor. This was 12 years prior to Hertz.
Although Thomson was a brilliant inventor and scientist, he did not pursue his research
further. Even earlier than this, in 1869, Dr. Mahlon Loomis had described electric
vibrations, but without any clear knowledge of the theory behind them. See "Radio
Telegraphy in 1866," Radio-Electronics, April 1959.
In 1889, Hertz was appointed Professor of Physics at the University of Bonn.
There he continued his researches on the discharge of electricity in rarefied gases,
only just missing the discovery of X-rays, and produced his treatise Principles
of Mechanics, which is still in print. This was his last work, for after a long
illness he died at Bonn on Jan. 1, 1894, a month before his 37th birthday.
Helmholtz thought him the one of all his pupils who had penetrated farthest into
his own circle of scientific thought, and looked to him with the greatest confidence
for the further extension and development of his work.
Bibliography
Encyclopaedia Britannica, 11th edition.
Sir Oliver Lodge, Signalling Through
Space Without Wires, 1906.
Orrin E. Dunlap, Radio's 100 Men of Science, 1944.
Mary Texanna Loomis, Radio Theory and Operating, 1926.
Ellison Hawks, The
Book of Electrical Wonders, 1935.
G. G. Blake, History of Radio Telegraphy and
Telephony, 1926.
Heinrich Hertz, Principles of Mechanics, Dover, 1956.
|
