Scanning the Past: A History of Electrical Engineering from the Past
Submitted by Dick Reiman, Historian
Copyright 1993 IEEE. Reprinted with permission from the IEEE publication, "Scanning the Past" which covers a reprint of an article appearing in the Proceedings of the IEEE Vol. 81, No. 4, April 1993.
Louis Alan Hazeltine
Seventy five years ago this month, the Proceedings of the Institute of Radio Engineers (IRE) included a paper by Alan Hazeltine on audion oscillators. At the time he was teaching electrical engineering at the Stevens Institute of Technology in Hoboken, New Jersey, He later wrote that he could trace "all of my subsequent radio work and what success I have achieved to this paper."
In his paper, Hazeltine explained that the audion consisted of an evacuated tube with three electrodes: an incandescent filament, a grid, and a plate, He stated that he had written the paper in an effort to provide general principles and to show how to determine the criterion for oscillation from the characteristics of the tube and the associated circuit parameters, He pointed out that tube behavior was much more predictable in high-vacuum tubes than in "ordinary bulbs" where ionized gas molecules exerted a significant effect on performance. He introduced the term mutual conductance and showed how it could be determined from the dynamic slope of a characteristic curve of plate current as a function of grid voltage. He included circuit diagrams for a variety of oscillators and discussed applications in radio receivers and in wire telephony. He derived formulas that indicated the necessary values of mutual conductance to initiate and sustain oscillation in different circuits.
Hazeltine was born in 1886 in Morristown, New Jersey, and graduated in mechanical engineering from the Stevens Institute of Technology in 1906. He then spent a little over a year in the testing department of the General Electric Company in Schenectady, New York, He returned to Stevens to teach electrical engineering beginning in 1907 and became department head in 1917, He was stimulated by early papers of Edwin H. Armstrong to begin research on vacuum-tube circuits and became active in both the IRE and the Radio Club of America. He was elected a Fellow of the IRE in 1921 and later served as President of the IRE in 1936. Hazeltine authored a textbook entitled Electrical Engineering, which was published in 1924. He achieved a reputation as an inspiring teacher and his teaching was said to have been "orderly and methodical." .
In 1918, Hazeltine became a radio consultant to the U.S. Navy and designed a receiver for use on destroyers. The receiver, known as the SE 1420, was highly regarded and enjoyed long usage. In 1922, he designed a receiver suitable for broadcast reception that employed neutralization of internal capacitive coupling in high-gain amplifiers. Commercial versions of this receiver, known as the neutrodyne, were introduced in 1923, and, the following year, the Hazeltine Corporation was founded to manage his neutrodyne patents and provide engineering services to clients. Neutrodyne receivers were made by more than 20 firms during the 1920s and Hazeltine received approximately $3,000,000 in royalties from licensees by 1927. The advent of screen-grid tubes beginning in 1926 quickly rendered the neutrodyne obsolete.
Hazeltine ended temporarily his tenure at Stevens in 1925. He lived in Europe for two years in the early 1930s and studied mathematics and art history in France before returning to the United States. In 1933 he resumed his .teaching career at Stevens as Professor of mathematical physics and continued teaching until 1944. During World War II, he served as a consultant to the Office of Scientific Research and Development. After the War, he contributed to the development of television and did consulting work for the Hazeltine Corp.. He received 36 patents during his career. He was a mentor and colleague of Harold Wheeler, who wrote a biography entitled Hazeltine the Professor published in 1978. Hazeltine died in 1964 at the age of 78.
James E. Brittain
School of History, Technology, and Society
Georgia Institute of Technology