EDWIN HOWARD ARMSTRONG (December 18, 1890 – January 31, 1954) was
an American electrical engineer and inventor , best known for
developing FM (frequency modulation ) radio. He held 42 patents and
received numerous awards, including the first Medal of Honor awarded
Institute of Radio Engineers (now IEEE), the French Legion of
Honor , the 1941
* 1 Early life
* 2 Early work
* 2.1 Regenerative circuit * 2.2 Superheterodyne circuit * 2.3 Super-regeneration circuit
* 3 Wide-band
Armstrong's boyhood home, 1032 Warburton Avenue, overlooking the Hudson River in Yonkers, New York, c. 1975. It was demolished in November 1982 due to fire damage.
Armstrong was born in the Chelsea district of New York City, the
oldest of John and Emily (Smith) Armstrong's three children. His
father began working at a young age at the American branch of the
Oxford University Press
At the age of eight, Armstrong contracted Sydenham\'s chorea (then known as St. Vitus\' Dance ), an infrequent but serious neurological disorder precipitated by rheumatic fever. For the rest of his life, Armstrong was afflicted with a physical tic exacerbated by excitement or stress. Due to this illness, he withdrew from public school and was home-tutored for two years. To improve his health, the Armstrong family moved to a house overlooking the Hudson River, at 1032 Warburton Avenue in Yonkers . The Smith family subsequently moved next door. Armstrong's tic and the time missed from school led him to become socially withdrawn.
From an early age, Armstrong showed an interest in electrical and mechanical devices, particularly trains. He loved heights and constructed a makeshift backyard antenna tower that included a bosun\'s chair for hoisting himself up and down its length, to the concern of neighbors. Much of his early research was conducted in the attic of his parent's house.
In 1909, Armstrong enrolled at
Armstrong graduated from Columbia in 1913, earning an electrical engineering degree.
World War I
In 1934, he filled the vacancy left by John H. Morecroft's death, receiving an appointment as a Professor of Electrical Engineering at Columbia, a position he held the remainder of his life.
Following college graduation, he received a $600 one-year appointment as a laboratory assistant at Columbia, after which he nominally worked as a research assistant, for a salary of $1 a year, under Professor Pupin. Unlike most engineers, Armstrong never became a corporate employee. He set up a self-financed independent research and development laboratory at Columbia, and owned his patents outright.
Armstrong's "feed back" circuit drawing, from Radio Broadcast vol. 1 no. 1 1922.
Armstrong began working on his first major invention while still an
undergraduate at Columbia. In late 1906,
Lee de Forest
While growing up Armstrong had experimented with the early, temperamental, "gassy" Audions. Spurred by the later discoveries, he developed a keen interest in gaining a detailed scientific understanding of how vacuum-tubes worked. In conjunction with Professor Morecroft he used an oscillograph to conduct comprehensive studies. His breakthrough discovery was determining that employing positive feedback (also known as "regeneration" ) produced amplification hundreds of times greater than previously attained, with the amplified signals now strong enough so that receivers could use loudspeakers instead of headphones. Further investigation revealed that when the feedback was increased beyond a certain level a vacuum-tube would go into oscillation , thus could also be used as a continuous-wave radio transmitter.
Beginning in 1913 Armstrong prepared a series of comprehensive
demonstrations and papers that carefully documented his research, and
in late 1913 applied for patent protection covering the regenerative
circuit . On October 6, 1914, U.S. patent 1,113,149 was issued for his
Lee de Forest
Following the end of
World War I
The United States entered into
World War I
During this period Armstrong's most significant accomplishment was the development of a "supersonic heterodyne" — soon shortened to "superheterodyne" — radio receiver circuit. This circuit made radio receivers more sensitive and selective and is still extensively used today. The key feature of the superheterodyne approach is the mixing of the incoming radio signal with a locally generated, different frequency signal within a radio set. This circuit is typically referred to as the mixer. The end result is a fixed, unchanging intermediate frequency, or I.F. signal which is more easily amplified and detected by subsequent circuit stages that follow the mixer. In 1919, Armstrong filed an application for a U.S. patent of the superheterodyne circuit which was issued the next year. This patent was subsequently sold to Westinghouse. The patent would be challenged, however, triggering yet another patent office interference hearing. Armstrong ultimately lost this patent battle; although the outcome was less controversial than that involving the regeneration proceedings.
The challenger was Lucien Lévy of France who had also worked
developing Allied radio communication during World War I. He had been
awarded French patents in 1917 and 1918 that covered some of the same
basic ideas used in Armstrong's superheterodyne receiver. AT&T, which
was interested in radio development at this time, primarily for
point-to-point extensions of its wired telephone exchanges, purchased
the U.S. rights to Lévy's patent and contested Armstrong's grant. The
subsequent court reviews continued until 1928, when the District of
Columbia Court of Appeals disallowed all nine claims of Armstrong's
patent, assigning priority for seven of the claims to Lévy, and one
Ernst Alexanderson of
Although most early radio receivers used regeneration Armstrong
The regeneration legal battle had one serendipitous outcome for Armstrong. While he was preparing apparatus to counteract a claim made by a patent attorney, he "accidentally ran into the phenomenon of super-regeneration", where, by rapidly "quenching" the vacuum-tube oscillations, he was able to achieve even greater levels of amplification. A year later, in 1922, Armstrong sold his super-regeneration patent to RCA for $200,000 plus 60,000 shares of corporation stock, which was later increased to 80,000 shares in payment for consulting services. This made Armstrong RCA's largest shareholder, and he noted that "The sale of that invention was to net me more than the sale of the regenerative circuit and the superheterodyne combined". RCA envisioned selling a line of super-regenerative receivers until superheterodyne sets could be perfected for general sales, but it turned out the circuit was not selective enough to make it practical for broadcast receivers.
WIDE-BAND FM RADIO
"Static" interference — extraneous noises caused by sources such as thunderstorms and electrical equipment — bedeviled early radio communication using amplitude modulation (AM) and perplexed numerous inventors attempting to eliminate it. Many ideas for static elimination were investigated, with little success. In the mid-1920s, Armstrong began researching whether he could come up with a solution. He initially, and unsuccessfully, attempted to resolve the problem by modifying the characteristics of existing AM transmissions.
One approach considered as a potential solution had been the use of frequency modulation (FM) transmissions, where, in order to encode audio, instead of varying (technically known as "modulating") the amplitude (strength) of a radio signal, as was done for AM transmissions, the frequency was varied. However, in 1922 John Renshaw Carson of AT&T, inventor of Single-sideband modulation (SSB), had published a Proceedings of the IRE paper which included a detailed mathematical analysis which showed that FM transmissions did not provide any improvement over AM. Although the Carson bandwidth rule for FM is still important today, this review turned out to be incomplete, because it analyzed only what is now known as "narrow-band" FM.
In early 1928 Armstrong began researching the capabilities of frequency modulation. Although there were few others involved in FM research at this time, he did have knowledge of a project being conducted by RCA engineers, who were investigating whether FM shortwave transmissions were less susceptible to fading than AM. In 1931 these engineers constructed a successful FM shortwave link transmitting the Schmeling-Stribling fight broadcast from California to Hawaii, and noted at the time that the signals seemed to be less affected by static, but the project made little further progress.
Working in secret in the basement laboratory of Columbia's Philosophy Hall, Armstrong slowly developed what eventually resulted in wide-band FM, in the process discovering significant advantages over the earlier "narrow-band" FM transmissions. He was granted five U.S. patents covering the basic features of new system on December 26, 1933. Initially, the primary claim was that his FM system was effective at filtering out the noise produced in receivers by vacuum tubes.
Armstrong had a standing agreement to give RCA the right of first
refusal to his patents. In 1934 he made a presentation of his new
system to RCA president Sarnoff. Sarnoff was somewhat taken aback by
its complexity, as he had hoped it would be possible to eliminate
static merely by adding a simple device to existing receivers. From
May 1934 until October 1935 Armstrong conducted field tests of his FM
technology from an RCA laboratory located on the 85th floor of the
Empire State Building
Denied the marketing and financial clout that RCA would have brought,
Armstrong decided to finance his own development and form ties with
smaller members of the radio industry, including Zenith and General
Electric , to promote his invention. Armstrong thought that FM had the
potential to replace AM stations within 5 years, which he promoted as
a boost for the radio manufacturing industry, then suffering from the
effects of the
In June 1936, Armstrong gave a formal presentation of his new system at the U.S. Federal Communications Commission (FCC) headquarters in Washington, D.C. For comparison, he played a jazz record using a conventional AM radio, then switched to an FM transmission. A United Press correspondent was present, and recounted in a wire service report that: "if the audience of 500 engineers had shut their eyes they would have believed the jazz band was in the same room. There were no extraneous sounds." Moreover, "Several engineers said after the demonstration that they consider Dr. Armstrong's invention one of the most important radio developments since the first earphone crystal sets were introduced." Armstrong was quoted as saying he could "visualize a time not far distant when the use of ultra-high frequency wave bands will play the leading role in all broadcasting", although the article noted that "A switchover to the ultra-high frequency system would mean the junking of present broadcasting equipment and present receivers in homes, eventually causing the expenditure of billions of dollars."
In the late 1930s, as technical advances made it possible to transmit
on higher frequencies, the FCC investigated options for increasing the
number of broadcasting stations, in addition to ideas for better audio
quality, known as "high-fidelity". In 1937 it introduced what became
known as the Apex band , consisting of 75 broadcasting frequencies
from 41.02 to 43.98 MHz. As on the standard broadcast band these were
AM stations, but with higher quality audio — in one example, a
frequency response from 20 Hz to 17,000 Hz +/- 1 dB — because
station separations were 40 kHz instead of the 10 kHz spacings used on
the original AM band. Armstrong worked to convince the FCC that a
band of FM broadcasting stations would be a superior approach. That
year he financed the construction of the first
FCC studies comparing the Apex station transmissions with Armstrong's FM system concluded that his approach was superior. In early 1940, the FCC held hearings on whether to establish a commercial FM service. Following this review, the FCC announced the establishment of an FM band effective January 1, 1941, consisting of forty 200 kHz-wide channels on a band from 42-50 MHz, with the first five channels reserved for educational stations. Existing Apex stations were notified that they would not be allowed to operate after January 1, 1941 unless they converted to FM.
Although there was interest in the new FM band by station owners, construction restrictions that went into place during World War II limited the growth of the new service. Following the end of World War II, the FCC moved to standardize its frequency allocations. One area of concern was the effects of tropospheric and Sporadic E propagation , which at times reflected station signals over great distances, causing mutual interference. A particularly controversial proposal, spearheaded by RCA, was that the FM band needed to be shifted to higher frequencies in order to avoid this potential problem. This reassignment was fiercely opposed as unneeded by Armstrong, but in the end he lost, and the FM band was reallocated, becoming one hundred channels from 88–108 MHz. After a short period of allowing existing FM stations to broadcast on both their old and new frequencies, the original transmitters had to be shut down, making obsolete the expensive receivers that had been purchased by the public for the original band.
Armstrong felt the FM band reassignment had been inspired primarily by a desire to cause a disruption that would limit FM's ability to challenge the existing radio industry, including RCA's AM radio properties that included the NBC radio network, plus the other major networks including CBS, ABC and Mutual. The change was also thought to have been favored by AT&T, as the elimination of FM relaying stations would require radio stations to lease wired links from that company. Particularly galling was the fact that the FCC then assigned TV channel 1 to the 44-50 MHz segment of the old FM band, despite the fact that in 1941 the FCC had adopted FM sound as part of the NTSC television standard, moreover, the video portions of the standard were even more susceptible to interference than the audio. Channel 1 eventually had to be deleted as well, with all TV broadcasts licensed at frequencies 54 MHz or higher, and in the United States these frequencies are no longer widely used for emergency first responders, those services having moved mostly to UHF.
Although the FM band shift was an economic setback, there was still
reason for optimism, and a book published in 1946 by Charles A.
Siepmann heralded FM stations as "Radio's Second Chance". In late
1945, Armstrong contracted with John Orr Young, founding member of the
public relations firm
Young & Rubicam , to conduct a national campaign
promoting FM broadcasting, especially by educational institutions.
Article placements promoting both Armstrong personally and FM were
made with general circulation publications including
In 1940, RCA offered Armstrong $1,000,000 for a non-exclusive, royalty-free license to use his FM patents. But he refused this offer, primarily because he felt this would be unfair to the other licensed companies, which had to pay 2% royalties on their sales. Over time this impasse with RCA would come to dominate Armstrong's life. RCA countered by conducting its own FM research, eventually developing what it claimed was a non-infringing FM system. The corporation also encouraged other companies to stop paying royalties to Armstrong. Outraged by this turn of events, in 1948 Armstrong filed suit against RCA and the National Broadcasting Company, accusing them of patent infringement and that they had "deliberately set out to oppose and impair the value" of his invention, for which he requested treble damages. Although he was confident that this suit would be successful and result in a major monetary award, the protracted legal maneuvering that followed eventually began to impair his finances, especially after his primary patents expired in late 1950.
Bitter and overtaxed by years of litigation and mounting financial problems, Armstrong lashed out at his wife one day with a fireplace poker, striking her on the arm. She left their apartment to stay with her sister, Marjorie Tuttle, in Granby, Connecticut.
Sometime during the night of January 31/February 1, 1954, with his
wife in Connecticut and three servants having left for the day,
Armstrong removed the air conditioner from a window in his twelve-room
apartment on the thirteenth-floor of River House in Manhattan, New
York City , and jumped to his death. His body—fully clothed, with a
hat, overcoat and gloves—was found in the morning on a third-floor
balcony by a River House employee. The
New York Times
Following her husband's death, Marion Armstrong took charge of pursuing his estate's legal cases. In late December 1954, it was announced that through arbitration an out-of-court settlement of "approximately $1,000,000" had been made with RCA. Dana Raymond of Cravath, Swaine "> Armstrong and his new wife Esther Marion MacInnis in Palm Beach in 1923. The radio is a portable superheterodyne that Armstrong built as a present for her.
In 1923, combining his love for high places with courtship rituals,
Armstrong climbed the WJZ (now WABC) antenna located atop a
twenty-story building in New York City, where he reportedly did a
handstand, and when a witness asked him what motivated him to "do
these damnfool things", Armstrong replied "I do it because the spirit
moves me". Armstrong had arranged to have photographs taken, which he
had delivered to David Sarnoff's secretary, Marion MacInnis.
Armstrong and MacInnis married later that year. Armstrong bought a
He was an avid tennis player until an injury in 1940, and drank an Old Fashioned with dinner. Politically, he was described by one of his associates as "a revolutionist only in technology — in politics he was one of the most conservative of men".
In 1955, Marion Armstrong founded the Armstrong Memorial Research Foundation, and participated in its work until her death in 1979 at the age of 81. She was survived by two nephews and a niece.
In 1917, Armstrong was the first recipient of the IRE 's (now IEEE) Medal of Honor .
For his wartime work on radio, the French government gave him the
Legion of Honor in 1919. He was awarded the 1941
He later received two honorary doctorates, from Columbia in 1929, and Muhlenberg College in 1941.
In 1980, he was inducted into the
National Inventors Hall of Fame
Philosophy Hall , the Columbia building where Armstrong developed FM,
was declared a
National Historic Landmark
Armstrong Hall at Columbia was named in his honor. The hall, located
at the northeast corner of Broadway and 112th Street, was originally
an apartment house but was converted to research space after being
purchased by the university. It is currently home to the Goddard
Institute for Space Studies , a research institute dedicated to
atmospheric and climate science that is jointly operated by Columbia
National Aeronautics and Space Administration . A storefront
in a corner of the building houses Tom\'s Restaurant , a longtime
neighborhood fixture that inspired
Susanne Vega 's song "Tom\'s Diner
" and was used for establishing shots for the fictional "Monk's diner"
in the "
A second Armstrong Hall, also named for the inventor, is located at the United States Army Communications and Electronics Life Cycle Management Command (CECOM-LCMC) Headquarters at Aberdeen Proving Ground, Maryland.
E. H. Armstrong patents:
* U.S. Patent 2,630,497 : "Frequency Modulation Multiplex System"
* U.S. Patent 2,602,885 : "Radio Signaling"
* U.S. Patent 2,540,643 : "Frequency-Modulated Carrier Signal
* U.S. Patent 2,323,698 : "Frequency Modulation Signaling System"
* U.S. Patent 2,318,137 : "Means for Receiving Radio Signals"
* U.S. Patent 2,315,308 : "Method and Means for Transmitting
Frequency Modulated Signals"
* U.S. Patent 2,295,323 : "Current Limiting Device"
* U.S. Patent 2,290,159 : "Frequency Modulation System"
* U.S. Patent 2,276,008 : "Radio Rebroadcasting System"
* U.S. Patent 2,275,486 : "Means and Method for Relaying Frequency
* U.S. Patent 2,264,608 : "Means and Method for Relaying Frequency
* U.S. Patent 2,215,284 : "Frequency Modulation Signaling System"
* U.S. Patent 2,203,712 : "Radio Transmitting System"
* U.S. Patent 2,169,212 : "Radio Transmitting System"
* U.S. Patent 2,130,172 : "Radio Transmitting System"
* U.S. Patent 2,122,401 : "Frequency Changing System"
* U.S. Patent 2,116,502 : "Radio Receiving System"
* U.S. Patent 2,116,501 : "Radio Receiving System"
* U.S. Patent 2,104,012 : "Multplex Radio Signaling System"
* U.S. Patent 2,104,011 : "Radio Signaling System"
* U.S. Patent 2,098,698 : "Radio Transmitting System"
* U.S. Patent 2,085,940 : "Phase Control System"
* U.S. Patent 2,082,935 : "Radio Signaling System"
* U.S. Patent 2,063,074 : "Radio Transmitting System"
* U.S. Patent 2,024,138 : "Radio Signaling System"
* U.S. Patent 1,941,447 : "Radio Telephone Signaling"
* U.S. Patent 1,941,069 : "Radiosignaling"
* U.S. Patent 1,941,068 : "Radiosignaling"
* U.S. Patent 1,941,067 : "Radio Broadcasting and Receiving System"
* U.S. Patent 1,941,066 : "Radio Signaling System"
* U.S. Patent 1,716,573 : "Wave Signaling System"
* U.S. Patent 1,675,323 : "Wave Signaling System"
* U.S. Patent 1,611,848 : "Wireless Receiving System for Continuous
* U.S. Patent 1,545,724 : "Wave Signaling System"
* U.S. Patent 1,541,780 : "Wave Signaling System"
* U.S. Patent 1,539,822 : "Wave Signaling System"
* U.S. Patent 1,539,821 : "Wave Signaling System"
* U.S. Patent 1,539,820 : "Wave Signaling System"
* U.S. Patent 1,424,065 : "Signaling System"
* U.S. Patent 1,416,061 : "Radioreceiving System Having High
* U.S. Patent 1,415,845 : "Selectively Opposing Impedance to
Received Electrical Oscillations"
* U.S. Patent 1,388,441 : "Multiple Antenna for Electrical Wave
* U.S. Patent 1,342,885 : "Method of Receiving High Frequency
* U.S. Patent 1,336,378 : "Antenna with Distributed Positive
* U.S. Patent 1,334,165 : "Electric Wave Transmission" (Note:
U.S. Patent and Tradmark Office Database Search
* Radio portal
* Armstrong oscillator – basic circuit for reception of AM radio signals * Armstrong Tower – tall lattice tower built and used by Edwin Armstrong in 1938 * Armstrong Phase Modulator * Awards named after E. H. Armstrong * Autodyne * Regenerative circuit
* ^ A B Tsividis, Yannis (Spring 2002). "Edwin Armstrong: Pioneer
of the Airwaves". Columbia Magazine. Living Legacies: Great Moments
and Leading Figures in the History of Columbia University. New York:
Columbia University. Retrieved December 12, 2010.
* ^ A B C D E "Armstrong, FM Inventor, Dies In Leap From East Side
Suite". The New York Times. February 2, 1954. p. 1. ISSN 0362-4331 .
Maj. Edwin H. Armstrong, whose inventions provided much of the basis
for modern broadcasting, was found dead yesterday morning on a
third-floor balcony of River House, 435 East Fifty-second Street. The
63-year-old electrical engineer had plunged from a window of his
luxurious thirteenth-floor apartment, apparently late Sunday evening
or during the night.
* ^ Lessing 1956 , p. 22
* ^ Lessing 1956 , p. 23
* ^ Lessing 1956 , p. 26
* ^ Lessing 1956 , p. 24
* ^ A B C D Lessing 1956 , p. 27
* ^ A B Wu 2010 , p. 126
* ^ "What Everyone Should Know About Radio History: Part II" by
Prof. J. H. Morecroft, Radio Broadcast, August, 1922, pages 294-302.
* ^ Empire of the Air by Tom Lewis, 1991, pages 60-61.
* ^ A B C D Who Was Who in American History - the Military.
Chicago: Marquis Who's Who. 1975. p. 15. ISBN 0837932017 .
* ^ "Major Armstrong Goes to Columbia". The New York Times. August
7, 1934. p. 20. ISSN 0362-4331 . The appointment of Major Edwin Howard
Armstrong as Professor of Electrical Engineering at Columbia
University yesterday by Dr. Nicholas Murray Butler, president of the
* ^ The Legacies of Edwin Howard Armstrong, "E. H. Armstrong" by
Thomas Sykes, 1990, page 22.
* ^ DeForest Radio Co. v.
* Erickson, Don V. (1973), Armstrong's fight for FM broadcasting: one man vs big business and bureaucracy, University of Alabama Press, ISBN 0-8173-4818-2 * Frost, Gary L. (2010), Early FM Radio: Incremental Technology in Twentieth-Century America. Baltimore: Johns Hopkins University Press, 2010. ISBN 0-8018-9440-9 , ISBN 978-0-8018-9440-4 . * Lessing, Lawrence (1956), Man of High Fidelity: Edwin Howard Armstrong, a biography, Philadelphia: Lippincott * Lewis, Tom (1991), Empire of the air: the men who made radio, New York: Edward Burlingame Books, ISBN 0-06-098119-9 * Who Was Who in American History - the Military. Chicago: Marquis Who's Who. 1975. ISBN 0837932017 . * Wu, Tim (2010), The Maste