Ernst Alexanderson

Ernst Frederick Werner Alexanderson (January 25, 1878 – May 14, 1975) was a Swedish-American electrical engineer, who was a pioneer in radio and television development. He invented the Alexanderson alternator, an early radio transmitter used between 1906 and the 1930s for longwave long distance radio transmission.

Background

Alexanderson was born at Uppsala, Sweden, and educated at the Royal Institute of Technology in Stockholm and the Technische Hochschule (Technical University) in Berlin, Germany. He emigrated to the U.S. in 1902 and spent much of his life working for the General Electric company.

Engineering work

Alexanderson designed the Alexanderson alternator, an early longwave radio transmitter, one of the first devices which could transmit modulated audio (sound) over radio waves. He had been employed at General Electric for only a short time when GE received an order from Canadian-born professor and researcher Reginald Fessenden, then working for the US Weather Bureau, for a specialized alternator with much higher frequency than others in existence at that time, for use as a radio transmitter. Fessenden had been working on the problem of transmitting sound by radio waves, and had concluded that a new type of radio transmitter was needed, a continuous wave transmitter. Designing a machine that would rotate fast enough to produce radio waves proved a formidable challenge. Alexanderson's family were convinced the huge spinning rotors would fly apart and kill him, and he set up a sandbagged bunker from which to test them. In the summer of 1906 Mr. Alexanderson's first effort, a 50 kHz alternator, was installed in Fessenden's radio station in Brant Rock, Massachusetts. By fall its output had been improved to 500 watts and 75 kHz. On Christmas Eve, 1906, Fessenden made an experimental broadcast of Christmas music, including him playing the violin, that was heard by Navy ships and shore stations down the East Coast as far as Arlington. This is considered the first AM radio entertainment broadcast.

Alexanderson and G.E. continued improving his machine, and the Alexanderson alternator became widely used in high power very low frequency commercial and Naval wireless stations to transmit radiotelegraphy traffic at intercontinental distances, until by the 1930s it was replaced by vacuum tube transmitters. The only surviving transmitter in a working state is at the Grimeton radio station outside Varberg, Sweden. It is a prime example of pre-electronic radio technology and was added to UNESCO's World heritage list in 2004.

Alexanderson also created the amplidyne, a direct current amplifier.

Mr. Alexanderson was also instrumental in the development of television. The first television broadcast in the United States was to his GE Plot home at 1132 Adams Rd, Schenectady, NY, in 1927. Over his lifetime, Mr. Alexanderson received 345 US patents, the last filed in 1968 at age 89. The inventor and engineer remained active to an advanced age, working as a consultant to GE and RCA in the 1950s. He died in 1975 and was buried at Vale Cemetery in Schenectady, New York.

Legacy

In 1983, he was inducted into the National Inventors Hall of Fame and in 2002 the Consumer Electronics Hall of Fame.

Patents

• U.S. Patent 1,008,577 – High frequency alternator (100 kHz), filed April, 1909; issued, November, 1911
• U.S. Patent 1,173,079 – Selective Tuning System (Tuned RF Circuit, filed October, 1913; issued February, 1916
• U.S. Patent 1,723,908 – Ignition system, (RFI suppressor), filed June, 1926; issued August, 1929
• U.S. Patent 1,775,801 – Radio signaling system (directional antenna), filed November 1927, issued September 1930

See also

• Amplidyne
• Tuned radio frequency receiver

References

• David E. Fisher and Marshall J. Fisher, Tube, the Invention of Television Counterpoint, Washington D.C. USA, (1996) ISBN 1-887178-17-1
• E.F.W. Alexanderson. General Electric Review, January, 1913
• E.F.W. Alexanderson, "Transatlantic Radio Communication", Trans. AIEE, (1919), pp. 1077–1093
• J.E. Brittain, Electrical Engineering Hall of Fame: Ernst F. W. Alexanderson, Proc. of the IEEE, Volume 92, July 2004, pp. 1216–1219.

External links

• Consumer Electronics Hall of Fame
• Inventor's Hall of Fame citation accessed April 10, 2006
• Biography at IEEE History Center accessed July 8th, 2011
• Biography at Oldradio.com accessed April 10, 2006
• Illustrated biography at prof. Eugenii Katz website accessed April 10, 2006
• Fessenden and Marconi – their technologies and transatlantic experiments compared. Accessed April 10, 2006
• Transoceanic Radio Communication in 1920, by E.F.W. Alexanderson accessed April 10, 2006
• "A Historical Review of Continuous Wave Radio Frequency Power Generators" accessed April 10, 2006
• Ernst Alexanderson at Find a Grave