PROCEEDINGS OF THE IEEE, VOL. 92, NO. 3, MARCH 2004

Digital Object Identifier: 10.1109/JPROC.2003.823150

I.  A NEW YORK ORIGINAL
II.  THE REGENERATIVE RECEIVER
III.  SUPERHETERODYNE PRINCIPLE
IV.  SUPERREGENERATIVE RADIO AND SELECTIVITY
V.  FM: DELAYS AND STRUGGLES
VI.  REGULATION AND LITIGATION

    In 1917, Edwin H. Armstrong (Fig. 1) was selected by the Institute of Radio Engineers (IRE) as the first recipient of its Medal of Honor.

Fig. 1. Edwin H. Armstrong in his later years. (IEEE History Center, Piscataway, NJ).

The young engineer–inventor was cited for his “work and publications dealing with the action of the oscillating and nonoscillating audion.� Only two years earlier, he had presented an influential IRE paper entitled “Some Recent Developments in the Audion Receiver.� In the paper, he had given a comprehensive explanation of regenerative amplifiers and oscillators along with some rather sensational results he had observed with radio receivers. This was only the first of several major contributions to the art of radioelectronics made by Armstrong during his professional career.
    Many years later, in 1942, he also received the Edison Medal from the American Institute of Electrical Engineers (AIEE), thus becoming one of the select group of seven individuals to receive both these awards (prior to the merger of the IRE and AIEE in 1963).

I.  A NEW YORK ORIGINAL

    

Fig. 2. Armstrong regenerative circuit. From Alfred N. Goldsmith, Radio Telephony (New York: The Wireless Press, 1918).

Armstrong was born 18 December 1890 in New York City, where his father was employed by the Oxford University Press. His mother was a former school teacher. The family later moved to Yonkers, NY, where Armstrong attended Yonkers High School. He became an amateur radio enthusiast and engaged in wireless experiments from his home from the age of 14. He enrolled at Columbia University, New York, in 1909, where his mentors included the almost legendary professor–inventor Michael I. Pupin, who had sold the rights to some loading coil patents to the Bell Telephone Company for almost a half million dollars. The University offered not only formal courses and excellent laboratory facilities but also enabled motivated students to learn about the latest developments through attending meetings of the IRE, which frequently were held at the campus.

II.  THE REGENERATIVE RECEIVER

    In the fall of 1912, while still an undergraduate, Armstrong discovered the phenomenon of regenerative amplification (Fig. 2), which could enhance greatly the strength of received wireless signals. He also identified self-excited oscillations in the output of a tuned audion circuit, which meant that the electronic tubes could serve as an alternative source of high-frequency waves. He was encouraged and assisted in this research by the Columbia facility, including Henry Mason and J. H. Morecroft as well as Pupin. Armstrong filed a patent application on the regenerative receiver in October 1913, and Prof. Pupin arranged for the invention to be demonstrated before representatives of several communications companies. He published a paper on his research in the Electrical World in December 1914 and licensed the new receiver to the German Telefunken Company. He graduated in electrical engineering from Columbia in June 1913 but stayed on to teach a course on wireless and continue his research. He and Prof. Pupin filed five joint patent applications during the period from 1915 to 1917. Armstrong began to receive royalties from the American Marconi Company in 1916 for the use of the regenerative receiver.

Fig. 3. Major Armstrong (right), decorated by the French government for his inventions, stands before the Eiffel Tower in Paris, 1919, with (left to right) General Ferrié, chief of French military communications, an unidentified U.S. officer, and Prof. Abraham of the Sorbonne. (IEEE History Center, Piscataway, NJ).

III.  SUPERHETERODYNE PRINCIPLE

    

Fig. 4. Advertisement for the Radiola from the Saturday Evening Post, from the mid-1920s. (IEEE History Center, Piscataway, NJ).

Armstrong's second major invention, the superheterodyne radio receiver, was conceived while he was serving in the U.S. Army Signal Corps during World War I. He received a commission as captain in 1917 and soon afterward was assigned to establish a Signal Corps laboratory in France (Fig. 3). Speculation on whether short-wave radiation from airplane engines might be detected and used to direct anti-aircraft guns served as his inspiration for a superheterodyne receiver early in 1918. He was also aware of the deficiencies of available vacuum tubes at high frequencies, and the superheterodyne principle provided a technique which would permit the use of high-gain amplifiers at lower frequencies. The first prototype design worked well, although the new receivers were not available for wide use until the war had ended. Armstrong applied for a U.S. patent on the receiver in February 1919 and left the Army a few months later to resume his research at Columbia. He presented a paper on the superheterodyne radio at an IRE meeting held in December 1919. The advent of radio broadcasting and its rapid growth during the early 1920s enhanced Armstrong's reputation as well as his personal wealth. He received a reported sum of $335 000 from the Westinghouse Electric Company for rights to his radio patents. The pioneering Westinghouse broadcasting station KDKA went on the air in October 1920, and the number of broadcast stations in the U.S. increased to 580 by the end of 1922. Armstrong helped with the design of a commercial version of his superheterodyne receiver known as the Radiola, which was marketed beginning in 1924 (Fig. 4).

IV.  SUPERREGENERATIVE RADIO AND SELECTIVITY

    Armstrong disclosed the features of a third significant invention, which he called a superregenerative receiver, in 1922. He had discovered the effect while he was constructing a regenerative circuit for use in a patent litigation exhibit. His latest radio receiver proved capable of remarkable sensitivity in a circuit requiring only two tubes in contrast to the superheterodyne receiver, which commonly used six or more. His talk on the superregenerative receiver presented to the IRE in June 1922 attracted what was said to be the largest audience yet to an IRE meeting. When executives at the Radio Corporation of America (RCA) learned of the new receiver, they decided that it might provide a solution to the problem of producing low-cost radio receivers for a growing mass market. Subsequently, RCA paid Armstrong $200 000 in cash and gave him some 80 000 shares of RCA stock for the rights to his superregenerative patents. His holdings of RCA stock eventually became worth about $9 million. Unfortunately for RCA, the superregenerative receiver did not become a commercial success, since it failed to provide sufficient selectivity in the broadcast band. The receiver did achieve some success in specialized high-frequency applications such as test equipment and electronics countermeasures equipment.

V.  FM: DELAYS AND STRUGGLES

    Beginning in the early 1930s, Armstrong devoted much of his energy and personal assets to an effort to introduce and promote his fourth important innovation, frequency-modulated (FM) radio broadcasting. Armstrong then decided to proceed on his own, being convinced that FM broadcasting would prove far superior in quality to the dominant amplitude-modulated (AM) broadcast service. He presented a classic paper entitled “A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation� at an IRE meeting in November 1935. In the paper, he pointed out that several mathematical theorists had been mistaken in their dismissal of FM as offering no advantages. He continued that he was introducing a “new principle� that conflicted “with one which has been a guide to the art for many years.� However, the system he advocated was based on relatively unfamiliar concepts and the response was less enthusiastic than it had been to his earlier inventions. By 1936, he acknowledged that the introduction of FM might be delayed by “intangible forces� originating in “vested interests, habits, customs, and legislation.�
    

Fig. 5. Armstrong, in 1947, delivering a paper before the American Institute of Electrical Engineers. Armstrong strikes a pose familiar to the engineering fraternity for nearly half a century. (IEEE History Center, Piscataway, NJ).

As part of his continuing effort to convince the public of the superiority of FM, Armstrong installed an FM transmitter in Alpine, NJ, and began regular broadcasts during 1939. The same year, the so-called Yankee Network was formed to initiate FM broadcasting from several sites in New England. In 1940, he compared the struggle between FM and AM to the battle between alternating and direct current power systems of the late 19th century. His FM crusade was still gaining momentum when the outbreak of the Second World War intervened. During the war years, he participated in the development of the FM communication systems for military applications, including two-way systems for Army tanks.

VI.  REGULATION AND LITIGATION

    Armstrong's (Fig. 5) personal characteristics made it difficult for him to adapt to an environment of regulation and litigation. The postwar years proved quite frustrating to him as FM broadcasting suffered at least temporary setbacks. He opposed unsuccessfully decisions by the Federal Communications Commission forcing FM to move to a higher frequency band and to operate at lower power than before the war. Also, he brought suit against RCA in 1948 for alleged infringement of his FM patents but “pretrial hearings� dragged on for several years, straining his financial resources. He refused overtures for an out-of-court settlement. The life of this illustrious engineer–inventor ended on the night of 31 January 1954 in a fall from the 13th floor of his River House residence. He was inducted posthumously into the National Inventors Hall of Fame in 1980. He was one of four eminent electrical engineers (including Philo T. Farnsworth, Charles Steinmetz, and Nikola Tesla) to be honored by special stamps issued by the U.S. Postal Service on 21 September 1983.