IEEE
You are not logged in, please sign in to edit > Log in / create account  

Edwin H. Armstrong

From GHN

(Difference between revisions)
Jump to: navigation, search
 
(16 intermediate revisions by 4 users not shown)
Line 1: Line 1:
<p>[[Image:Edwin Armstrong 0251.jpg|thumb|left]] </p>
+
== Biography ==
  
== Edwin H. Armstrong ==
+
[[Image:Edwin Armstrong 0251.jpg|thumb|right]]
  
<p>Edwin H. Armstrong is widely regarded as one of the foremost contributors to the field of [[Radio|radio-electronics]]. Among his principal contributions were regenerative feedback circuits, the [[Superheterodyne Receiver|superheterodyne radio receiver]], and a [[FM Radio|frequency-modulation radio broadcasting system]]. He was inducted into the National Inventors Hall of Fame in 1980 </p>
+
[[Image:Edison medal.jpg|thumb|right|Edwin H. Armstrong's Edison Medal, awarded in 1942. Photo: Antique Wireless Association Museum, loaned from the Historical and Interpretive Collections of The Franklin Institute, Inc., Philadelphia, PA.]]  
  
<p>[[Image:Edison medal.jpg|thumb|right|Edwin H. Armstrong's Edison Medal, awarded in 1942. Photo: Antique Wireless Association Museum, loaned from the Historical and Interpretive Collections of The Franklin Institute, Inc., Philadelphia, PA. ]] </p>
+
[[Image:3341-armstrong lab at columbia.jpg|thumb|right|Armstrong's Lab at Columbia]]  
  
<p>Armstrong was born on December 18, 1890, in New York City, where he was to spend much of his professional career.He graduated with a degree in electrical engineering from Columbia University in 1913, and observed the phenomenon of regenerative feedback in vacuum-tube circuits while still an undergraduate.At Columbia, he came under the influence of the legendary professor-inventor, [[Michael Pupin|Michael I. Pupin]], who served as a role model for Armstrong and became an effective promoter of the young inventor. In 1915 Armstrong presented an influential paper on regenerative amplifiers and oscillators to the [[IRE History 1912-1963|IRE]]. Subsequently, regenerative feedback was incorporated into a comprehensive engineering science developed by [[Oral-History:Harold S. Black|Harold Black]], [[Harry Nyquist|Harry Nyquist]], [[Hendrik W. Bode|Hendrik Bode]], and others in the period between 1915 and 1940. </p>
+
[[Image:Armstrong regenerative radio 0452.jpg|thumb|right|Armstrong Regenerative Radio]]  
  
<p>Armstrong conceived the superheterodyne radio receiver principle in 1918, while serving in the Army Signal Corps in France.He played a key role in the commercialization of the invention during the early 1920's. [[RCA (Radio Corporation of America)|The Radio Corporation of America (RCA)]] used his superheterodyne patent to monopolize the market for this type of receiver until 1930. The superheterodyne eventually extended its domain far beyond commercial broadcast receivers and, for example, proved ideal for microwave radar receivers developed during World War II. </p>
+
[[Image:Armstrongradiobeach.jpg|thumb|right]]  
  
<p>In 1933 Armstrong was granted patents on a frequency-modulation (FM) system that he promoted as a superior alternative to the established amplitude-modulation (AM) broadcasting service. He drew on his own financial resources in a determined effort to establish FM broadcasting until the War intervened.His crusade for FM received additional setbacks in the post-war years from certain regulatory decisions by the Federal Communications Commission. In 1948 he brought suit against [[RCA (Radio Corporation of America)|RCA]] for patent infringement, but the case was not solved until Armstrong's tragic demise early in 1954. </p>
+
[[Image:Armstrong on WJZ Transmitter 0257.jpg|thumb|right|Armstrong on WJZ Transmitter]]  
  
<p>Armstrong was highly esteemed by a generation of radio-electronics engineers and amateur radio enthusiasts. He received the first [[IEEE Medal of Honor|Medal of Honor of the IRE]] in 1917 "In recognition of his work and publications dealing with the action of the oscillating and non-oscillating audion." In 1942, Armstrong was awarded the [[AIEE History 1884-1963|AIEE]]'s [[IEEE Edison Medal|Edison Medal]] 'For distinguished contributions to the art of electric communication, notably the regenerative circuit, the superheterodyne and frequency modulation.'</p>
+
Edwin H. Armstrong is widely regarded as one of the foremost contributors to the field of [[Radio|radio-electronics]]. Among his principal contributions were regenerative feedback circuits, the [[Superheterodyne Receiver|superheterodyne radio receiver]], and a [[FM Radio|frequency-modulation radio broadcasting system]]. He was inducted into the National Inventors Hall of Fame in 1980
  
<p>The importance of his legacy might be appreciated by means of a thought experiment of imagining what the field of telecommunications would be like without regenerative feedback, the [[Superheterodyne Receiver|superheterodyne receiver]], and [[FM Radio|FM]]. </p>
+
Edwin Howard Armstrong was born in New York City on 18 December 1890, and studied electrical engineering at Columbia University under the celebrated [[Michael Pupin|Michael J. Pupin]]. [[Radio|Radio]] was Armstrong's passion, and about a year before he graduated in 1913, he devised a circuit that revolutionized the radio art. Using a triode as an amplifier, he fed back part of the output to the input, and thereby obtained much greater amplification. Armstrong made a further discovery with this circuit: just when maximum amplification was obtained, the signal changed suddenly to a hissing or a whistling. He realized this meant that the circuit was generating its own oscillations, and thus that the triode could be used as a frequency generator. The first of these discoveries — of a powerful amplifier — vastly increased the sensitivity of radio receivers, while the second — of an oscillator — led to the use of the electron tube in transmitters and also in receivers for an added function, heterodyne reception.  
  
<p></p>
+
In 1901, [[Reginald A. Fessenden|Reginald Fessenden]] had introduced to radio the heterodyne principle: if two tones of frequencies A and B are combined, one may hear a tone with frequency A minus B. Armstrong used this principle in devising what came to be called the [[Superheterodyne Receiver|superheterodyne receiver]]. The essential idea is to convert the high-frequency received signal to one of intermediate frequency by heterodyning it with an oscillation generated in the receiver, then amplifying that intermediate-frequency signal before subjecting it to the detection and amplification usual in receivers. [[RCA (Radio Corporation of America)|RCA]] marketed the superheterodyne beginning in 1924, and soon licensed the invention to other manufacturers. It became — and remains today — the standard type of radio receiver.
  
<p></p>
+
In the early 1920s, Armstrong turned his attention to what seemed to him, and to many other radio engineers, as the greatest problem, namely, the elimination of static. He wrote, "This is a terrific problem. It is the only one I ever encountered that, approached from any direction, always seems to be a stone wall." Armstrong eventually found a solution in frequency modulation, which is a different way of impressing an audio signal on a radio-frequency carrier wave. In the usual technique, known as amplitude modulation (AM), the amplitude of the carrier wave is regulated by the amplitude of the audio signal. With frequency modulation, the audio signal alters instead the frequency of the carrier, shifting it down or up to mirror the changes in amplitude of the audio wave. He soon found it necessary to use a much broader bandwidth than AM stations used (today an [[FM Radio|FM radio]] channel occupies 200 kHz, twenty times the bandwidth of an AM channel), but doing so gave not only relative freedom from static but also much higher sound-fidelity than AM radio offered.
  
<p>[[Category:Communications]] [[Category:Radio_communication]] [[Category:Radio_broadcasting]]</p>
+
With the four patents for his FM techniques that he obtained in 1933, Armstrong set about gaining the support of RCA for his new system. RCA engineers were impressed, but the sales and legal departments saw FM as a threat to RCA's corporate position. [[David Sarnoff|David Sarnoff]], the head of RCA, had already decided to promote television vigorously and believed the company did not have the resources to develop a new radio medium at the same time. Moreover, in the economically distressed 1930s, better sound quality was regarded as a luxury, so there was not thought to be a large market for products offering it.
 +
 
 +
Armstrong did gain some support from [[General Electric (GE)|General Electric]] and Zenith, but it was largely on his own that he carried out the development and field testing of a practical broadcasting system. He gradually gained the interest of engineers, broadcasters, and radio listeners, and in 1939 FM broadcasts were coming from twenty or so experimental stations. These stations could not, according to FCC rules, sell advertising or derive income in any other way from broadcasting, but finally, in 1940, the FCC decided to authorize commercial FM broadcasting, allocating the region of the spectrum from 42 MHz to 50 MHz to forty FM channels. In October of that year, it granted permits for 15 stations. Zenith and other manufacturers marketed FM receivers, and by the end of 1941, nearly 400,000 sets had been sold.
 +
 
 +
U.S. entry into the war brought a halt both to the granting of licenses for FM stations and to the production of FM receivers. After the war, FM broadcasting was dealt a severe blow when the FCC made one of its most unpopular decisions, moving the FM spectrum allocation (to the range from 88 to 108 MHz) and thus making obsolete the 400,000 receivers, as well as the transmitters of dozens of broadcasters. This allocation, however, allowed for two and a half times as many channels, and the FM industry slowly recovered, though it did not enjoy rapid growth until the late 1950s. In the late 1970s, FM broadcasting surpassed AM in share of the radio audience, and by the end of the century, its share had grown to three times that of AM broadcasting.
 +
 
 +
Among the many honors Armstrong received were the [[IEEE Edison Medal|Edison Medal]] of the [[AIEE History 1884-1963|American Institute of Electrical Engineers (AIEE)]] and the [[IEEE Medal of Honor|Medal of Honor]] of the [[IRE History 1912-1963|Institute of Radio Engineers (IRE)]]. These were the highest honors of those two predecessor organizations of the [[IEEE History|IEEE]]. Sadly, the last years of Armstrong's life were darkened by continual patent litigation, and he committed suicide on 31 January 1954.
 +
 
 +
Armstrong's papers are held by Columbia University, where thanks to the efforts of Professor Emeritus (and IEEE Life Fellow) Mischa Schwartz, and a grant from the IEEE Foundation, they were processed in 2010 to make them more accessible to future scholars. [http://www.nytimes.com/2010/04/19/business/media/19archives.html?scp=1&sq=Saving%20the%20Neglected%20History&st=cse A New York Times article] gave this project, and thereby Armstrong's life, well deserved attention. [http://findingaids.cul.columbia.edu/ead/nnc-rb/ldpd_4078687/summary There is a published finding aid to the collection.]
 +
 
 +
== Further Reading ==
 +
 
 +
[[Media:Eitel_Armstrong_817.pdf|Eitel & Armstrong transcript #817.pdf]]
 +
 
 +
[[Category:Radio broadcasting|Armstrong]] [[Category:Receivers|Armstrong]]
 +
 
 +
[[Category:Radio_broadcasting]]

Latest revision as of 15:54, 21 February 2012

Biography

Edwin H. Armstrong's Edison Medal, awarded in 1942. Photo: Antique Wireless Association Museum, loaned from the Historical and Interpretive Collections of The Franklin Institute, Inc., Philadelphia, PA.
Edwin H. Armstrong's Edison Medal, awarded in 1942. Photo: Antique Wireless Association Museum, loaned from the Historical and Interpretive Collections of The Franklin Institute, Inc., Philadelphia, PA.
Armstrong's Lab at Columbia
Armstrong's Lab at Columbia
Armstrong Regenerative Radio
Armstrong Regenerative Radio
Armstrong on WJZ Transmitter
Armstrong on WJZ Transmitter

Edwin H. Armstrong is widely regarded as one of the foremost contributors to the field of radio-electronics. Among his principal contributions were regenerative feedback circuits, the superheterodyne radio receiver, and a frequency-modulation radio broadcasting system. He was inducted into the National Inventors Hall of Fame in 1980

Edwin Howard Armstrong was born in New York City on 18 December 1890, and studied electrical engineering at Columbia University under the celebrated Michael J. Pupin. Radio was Armstrong's passion, and about a year before he graduated in 1913, he devised a circuit that revolutionized the radio art. Using a triode as an amplifier, he fed back part of the output to the input, and thereby obtained much greater amplification. Armstrong made a further discovery with this circuit: just when maximum amplification was obtained, the signal changed suddenly to a hissing or a whistling. He realized this meant that the circuit was generating its own oscillations, and thus that the triode could be used as a frequency generator. The first of these discoveries — of a powerful amplifier — vastly increased the sensitivity of radio receivers, while the second — of an oscillator — led to the use of the electron tube in transmitters and also in receivers for an added function, heterodyne reception.

In 1901, Reginald Fessenden had introduced to radio the heterodyne principle: if two tones of frequencies A and B are combined, one may hear a tone with frequency A minus B. Armstrong used this principle in devising what came to be called the superheterodyne receiver. The essential idea is to convert the high-frequency received signal to one of intermediate frequency by heterodyning it with an oscillation generated in the receiver, then amplifying that intermediate-frequency signal before subjecting it to the detection and amplification usual in receivers. RCA marketed the superheterodyne beginning in 1924, and soon licensed the invention to other manufacturers. It became — and remains today — the standard type of radio receiver.

In the early 1920s, Armstrong turned his attention to what seemed to him, and to many other radio engineers, as the greatest problem, namely, the elimination of static. He wrote, "This is a terrific problem. It is the only one I ever encountered that, approached from any direction, always seems to be a stone wall." Armstrong eventually found a solution in frequency modulation, which is a different way of impressing an audio signal on a radio-frequency carrier wave. In the usual technique, known as amplitude modulation (AM), the amplitude of the carrier wave is regulated by the amplitude of the audio signal. With frequency modulation, the audio signal alters instead the frequency of the carrier, shifting it down or up to mirror the changes in amplitude of the audio wave. He soon found it necessary to use a much broader bandwidth than AM stations used (today an FM radio channel occupies 200 kHz, twenty times the bandwidth of an AM channel), but doing so gave not only relative freedom from static but also much higher sound-fidelity than AM radio offered.

With the four patents for his FM techniques that he obtained in 1933, Armstrong set about gaining the support of RCA for his new system. RCA engineers were impressed, but the sales and legal departments saw FM as a threat to RCA's corporate position. David Sarnoff, the head of RCA, had already decided to promote television vigorously and believed the company did not have the resources to develop a new radio medium at the same time. Moreover, in the economically distressed 1930s, better sound quality was regarded as a luxury, so there was not thought to be a large market for products offering it.

Armstrong did gain some support from General Electric and Zenith, but it was largely on his own that he carried out the development and field testing of a practical broadcasting system. He gradually gained the interest of engineers, broadcasters, and radio listeners, and in 1939 FM broadcasts were coming from twenty or so experimental stations. These stations could not, according to FCC rules, sell advertising or derive income in any other way from broadcasting, but finally, in 1940, the FCC decided to authorize commercial FM broadcasting, allocating the region of the spectrum from 42 MHz to 50 MHz to forty FM channels. In October of that year, it granted permits for 15 stations. Zenith and other manufacturers marketed FM receivers, and by the end of 1941, nearly 400,000 sets had been sold.

U.S. entry into the war brought a halt both to the granting of licenses for FM stations and to the production of FM receivers. After the war, FM broadcasting was dealt a severe blow when the FCC made one of its most unpopular decisions, moving the FM spectrum allocation (to the range from 88 to 108 MHz) and thus making obsolete the 400,000 receivers, as well as the transmitters of dozens of broadcasters. This allocation, however, allowed for two and a half times as many channels, and the FM industry slowly recovered, though it did not enjoy rapid growth until the late 1950s. In the late 1970s, FM broadcasting surpassed AM in share of the radio audience, and by the end of the century, its share had grown to three times that of AM broadcasting.

Among the many honors Armstrong received were the Edison Medal of the American Institute of Electrical Engineers (AIEE) and the Medal of Honor of the Institute of Radio Engineers (IRE). These were the highest honors of those two predecessor organizations of the IEEE. Sadly, the last years of Armstrong's life were darkened by continual patent litigation, and he committed suicide on 31 January 1954.

Armstrong's papers are held by Columbia University, where thanks to the efforts of Professor Emeritus (and IEEE Life Fellow) Mischa Schwartz, and a grant from the IEEE Foundation, they were processed in 2010 to make them more accessible to future scholars. A New York Times article gave this project, and thereby Armstrong's life, well deserved attention. There is a published finding aid to the collection.

Further Reading

Eitel & Armstrong transcript #817.pdf