Ernst Alexanderson

Alexanderson circa 1920

Swedish-American electrical engineer, who was a pioneer in radio and television development.

- Ernst Alexanderson

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Alexanderson alternator

200 kW Alexanderson alternator preserved at the Grimeton radiotelegraphy station, Sweden, the only remaining example of an Alexanderson transmitter.
Alexanderson 200-kW motor-alternator set installed at the US Navy's New Brunswick, NJ station, 1920.
Rotor of 200 kW alternator
Closeup of above rotor. It has 300 narrow slots cut through the rotor. The "teeth" between the slots are the magnetic poles of the machine.

An Alexanderson alternator is a rotating machine invented by Ernst Alexanderson in 1904 for the generation of high-frequency alternating current for use as a radio transmitter.

General Electric

American multinational conglomerate founded in 1892, and incorporated in New York State and headquartered in Boston.

General Electric in Schenectady, New York, aerial view, 1896
Plan of Schenectady plant, 1896
General Electric Building at 570 Lexington Avenue, New York
Carmen Miranda in a 1945 advertisement for a General Electric FM radio in The Saturday Evening Post
GE Global Operations Center in Downtown Cincinnati, Ohio
A General Electric neon sign.
GE gauges to control a railway locomotive at a museum near Saskatoon, Canada
GE facility in Schenectady, New York
A General Electric EV charging station in North America
Linear GE stock price graph 1962–2013
GE trading volume graph

In 1927, Ernst Alexanderson of GE made the first demonstration of television broadcast reception at his General Electric Realty Plot home at 1132 Adams Rd, Schenectady, New York.

KTH Royal Institute of Technology

Public research university in Stockholm, Sweden.

Main building in winter
Main courtyard in summer
KTH "Courtyard" ("borggården") 2005
Kerberos guarding the entrance to the courtyard
Royal Institute of Technology 2012
The R1 nuclear reactor.

Ernst Alexanderson, inventor

IEEE Medal of Honor

Highest recognition of the Institute of Electrical and Electronics Engineers .

IEEE Human logo

Eleven persons with an exceptional career in electrical engineering received both the IEEE Edison Medal and the IEEE Medal of Honor, namely Edwin Howard Armstrong, Ernst Alexanderson, Mihajlo Pupin, Arthur E. Kennelly, Vladimir K. Zworykin, John R. Pierce, Sidney Darlington, James L. Flanagan, Nick Holonyak, Robert H. Dennard, Dave Forney, and Kees Schouhamer Immink.

IEEE Edison Medal

Presented by the Institute of Electrical and Electronics Engineers "for a career of meritorious achievement in electrical science, electrical engineering or the electrical arts."

Eleven persons with an exceptional career in electrical engineering received both the IEEE Edison Medal and the IEEE Medal of Honor, namely Edwin Howard Armstrong, Ernst Alexanderson, Mihajlo Pupin, Arthur E. Kennelly, Vladimir K. Zworykin, John R. Pierce, Sidney Darlington, James L. Flanagan, Nick Holonyak, Robert H. Dennard, Dave Forney, and Kees Schouhamer Immink.

Reginald Fessenden

Canadian-born inventor, who did a majority of his work in the United States and also claimed U.S. citizenship through his American-born father.

Portrait photograph of Reginald Fessenden from Harper's Weekly Magazine, 1903
Whitney Institute in Bermuda, founded in 1881, of which Fessenden was headmaster
Cobb Island on the Potomac River, scene of the first successful radio transmission of speech in the fall of 1900.
April 1904 company advertisement
Gravesite in St. Mark's church cemetery in Bermuda

Fessenden's request for a faster, more powerful unit was assigned to Ernst F. W. Alexanderson, who in August 1906 delivered an improved model which operated at a transmitting frequency of approximately 50 kHz, although with far less power than Fessenden's rotary-spark transmitters.


Three amplidynes, from a 1951 General Electric advertisement (not to same scale). (top left) 1 kW amplidyne motor-generator, (bottom left) 3 kW amplidyne motor-generator, (right) 5 kW amplidyne generator.
Figure 1 of the patent drawing
Amplidyne circuit as used in U.S. Navy naval gun control. This is a high-power position servo system.

An amplidyne is an obsolete electromechanical amplifier invented prior to World War II by Ernst Alexanderson.

Tuned radio frequency receiver

Type of radio receiver that is composed of one or more tuned radio frequency (RF) amplifier stages followed by a detector (demodulator) circuit to extract the audio signal and usually an audio frequency amplifier.

This 1920s TRF radio manufactured by Signal is constructed on a breadboard
Tuning a TRF receiver, like this 5 tube Neutrodyne set from 1924 with two stages of RF amplification, was a complicated process. The three tuned circuits, controlled by the 3 large knobs, had to be tuned in unison to the new station. So tuning in a station was a process of successive approximation. Once a station was found, the numbers on the dials were written down, so it could be found again.
Tuning all 3 stages of a TRF set in unison. This 1925 Grebe Synchrophase receiver has thumbwheels instead of knobs which can be turned with a finger, so a third hand is not needed.
Typical tube layout of a TRF radio
Typical Dial Layout of Tuned Radio Frequency Receiver
Typical Tuned Radio Frequency receiver component layout
Block diagram of TRF receiver
Leutz 9-tube receiver from 1927 clearly shows the component parts of a TRF set. Each RF stage is in a separate compartment. Within each compartment can be seen (from top): the triode tube, the interstage coupling coil, and the capacitor attached to its front panel tuning dial. The compartments contain (from left): the 4 RF stages, the detector stage, and the 4 tube audio amplifier. The capacitors could be linked to a common shaft and tuned together, or tuned separately.
Schematic of Six Tube Design using Triode Tubes – Two Radio Frequency Amplifiers, One Grid-Leak Detector, Three Class ‘A’ Audio Amplifiers
The ZN414; almost a whole TRF radio on a single chip

The TRF receiver was patented in 1916 by Ernst Alexanderson.

Vale Cemetery and Vale Park

Historic rural cemetery and the largest cemetery in Schenectady, New York.

Vale Cemetery, October 2003
Veterans plot, February 2007
Westinghouse Family memorial, February 2007
State Street entrance sign, February 2007
Vale Park entrance, November 2010

Ernst Alexanderson — came to the United States in 1901 to meet electrical wizard Charles Steinmetz. Developed the Alexanderson alternator, the first radio transmitter used to broadcast the human voice. Dr. Alexanderson was also instrumental in the development of television. Over his lifetime, Dr. Alexanderson received 344 patents, the last awarded in 1973 at age 94.

Grimeton Radio Station

Early longwave transatlantic wireless telegraphy station built in 1922–1924, that has been preserved as a historical site.

VLF transmitter Grimeton
Alexanderson alternator in the Grimeton VLF transmitter. The drive motor is at the extreme right; the speed-increaser gearbox is just to its left. Note the bronze-colored shaft coupling.
Principle of a multipole generator for creating radio frequencies
1900 meter (1.2 mile) flattop antenna
Interior of Grimeton radio station
Log-periodic shortwave antenna beside the transmitter building
Interior of transmitter hall showing control panel for alternator
Interior of transmitter hall showing Alexanderson alternator
Grimeton World Heritage entrance hall
A warning sign at the entrance

The transmitter chosen was the Alexanderson alternator, invented around 1906 by Swedish-American Ernst Alexanderson and manufactured by RCA.