November 1959 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.
Amos E. Dolbear (wikipedia)
I have to confess that I do not recall having heard of Professor Amos Emerson Dolbear (aka A.E. Dolbear) prior to seeing this "Inventors of Radio" piece in a
1959 issue of Radio−Electronics magazine. Per the article, "In 1882,
just 10 years after Loomis' patent was granted, Prof. Amos E. Dolbear
demonstrated what he called an electrostatic telephone before the Society of
Telegraph Engineers and Electricians meeting in London, England. This occasion -
March 23, 1882 - was probably the first time the human voice was transmitted by
radio." Prof. Dolbear was a contemporary of other early electrical
communications pioneers like Alexander Graham Bell and Guglielmo Marconi.
"Inventors of Radio" Prof. A. E. Dolbear
Prof. A. E. Dolbear [1837-1916]
By Eric Leslie
Our April issue told of an American, Dr. Mahloon Loomis, who demonstrated a system
of communications by electromagnetic waves before Marconi was born. In 1882, just
10 years after Loomis' patent was granted, Prof. Amos E. Dolbear demonstrated what
he called an electrostatic telephone before the Society of Telegraph Engineers and
Electricians meeting in London, England. This occasion - March 23, 1882 - was probably
the first time the human voice was transmitted by radio.
Professor Dolbear (Tufts College, Boston, Mass.) was a distinguished researcher
in a number of fields of physics. His microphones and electro-static telephone system
were considered by many superior to Bell's. He also developed a number of instruments
and classroom demonstrations, and investigated so many subjects that it was stated
that a scientist pioneering in almost, any field would be likely to find that Dolbear
had already written something on the subject.
Although Dolbear considered it electrostatic, there is little doubt that his
device would be defined as an induction telephone today. It consisted of an induction
coil with a battery and microphone inserted in the primary. One end of the secondary
was grounded, the other attached to a large elevated capacitor. According to Dolbear's
explanation, a charge on the metal plate of a capacitor induces a charge of opposite
sign on one placed near it. Therefore, another large elevated plate was used as
the collector or antenna of his receiver. The battery in the receiving equipment
demonstrates Dolbear's belief in difference of potential between ground and elevated
point, and was apparently intended to serve a similar purpose as the modern "bias
battery." Probably it was of some use, acting as a chemical rectifier of radio-frequency
currents. The range, as demonstrated in 1882, was only a few feet, from one room
In 1883, Dolbear appears to have broken through into true radio without fully
realizing it. He told the American Association for the Advancement of Science, "Louder
and better results were obtained by using an induction coil having an automatic
break interrupter and with a Morse key in the primary circuit, one terminal of the
secondary grounded, the other in free air, or in a condenser for considerable
At times I have employed a gilt kite, carrying a fine wire from the secondary coil.
The discharges are then apparently nearly as strong as if there was an ordinary
Dolbear's transmitting and receiving circuits.
This equipment, installed at the Electrical Exhibition in Philadelphia, produced
signals that could be received in any part of the large building and immediate neighborhood.
In other experiments, he claimed a range of 13 miles, not an unreasonable figure
for spark telegraphy with his crude apparatus. Though he was transmitting with true
radio waves and no longer was depending on the capacitance effect of his "condensers,"
he apparently never suspected that fact, and always explained his results as a capacitance
It is not quite clear why Dolbear made no attempt to commercialize his telegraph.
Possibly his electrostatic theory, which would have made him pessimistic as to the
maximum range of the equipment, and the poor receiving apparatus, may have been
among the causes. At any rate, he considered his inventions important enough to
patent (US Patents
355,149) and he had in 1883 a wireless transmitter
equal to and almost identical with that which Marconi demonstrated in 1896.
* Hawks, Ellison, Pioneers of Wireless, page 135.
Posted July 15, 2022