Before 1904, many inventors, including Nikola Tesla,
created an alternator to generate an electromagnetic frequency,
but none of these produced a frequency high enough
for radio transmission; they were all under twenty kilohertz.
However, in 1904, Reginald Fessenden, working for
National Electric Signaling Company, contracted with GE
for an alternator to produce up to a hundred kilohertz
for continuous wave radio transmission.
Ernst Alexanderson designed an alternator whose frequency
was controlled by a rotor with hundreds of narrow slots
that caused a variable reluctance to interrupt the flux,
which induced a radio-frequency voltage in a set of coils.
Transoceanic broadcasts
The Alexanderson alternator allowed the installation
of broadcast stations around the world for broadcasting transoceanic
high-power longwave radiotelegraphic messages in Morse code,
which became an urgent requirement during World War I.
Alexanderson Day
The Varberg Radio Station
near Grimeton, Sweden,
celebrates Alexanderson Day
by broadcasting Morse
code messages on 17.2 kHz
using the last working
Alexanderson alternator.
The box
People thought
you needed
a spark-gap transmitter
to make radio waves.
Today we call that
thinking inside the box.
In 1903, Charles Proteus Steinmetz of GE delivered a ten-kilohertz alternator-transmitter,
which Fessenden could not use as a radio transmitter.
Ernst Alexanderson’s effort was far more successful;
however, alternator-transmitters were eventually replaced by vacuum-tube transmitters.
In 1903, Charles Proteus Steinmetz of GE delivered a ten-kilohertz alternator-transmitter, which Fessenden could not use as a radio transmitter. Ernst Alexanderson’s effort was far more successful; however, alternator-transmitters were eventually replaced by vacuum-tube transmitters.
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