Main content

Edwin H. Armstrong papers


Held at: The Historical and Interpretive Collections of The Franklin Institute [Contact Us]222 N 20th St, Philadelphia, PA, 19103

This is a finding aid. It is a description of archival material held at the The Historical and Interpretive Collections of The Franklin Institute. Unless otherwise noted, the materials described below are physically available in their reading room, and not digitally available through the web.

Overview and metadata sections

Edwin H. Armstrong (1890-1954) was an American electrical engineer and inventor, best known for inventing the regenerative circuit, the super-regenerative circuit, the superheterodyne receiver, and FM (frequency modulation) radio. He spent much of his life battling in court over his patent rights, primarily with Lee De Forest and Radio Corporation of America, and took his own life in 1954.

"Edwin Howard Armstrong was born on December 18, 1890, in the Chelsea District of Manhattan [New York, NY]. He was the first child of John and Emily (Smith) Armstrong. John worked as Vice President of the American branch of Oxford Press, while Emily, a graduate of Hunter College, taught in the New York City public schools. Prior to moving out of Manhattan, Edwin gained two younger sisters, Ethel and Edith. In 1902, the Armstrong family moved north, to 1032 Warburton Avenue, in Yonkers, New York.

"In 1905, Armstrong entered high school. He already sought to emulate Marconi, the Italian inventor responsible for a system of wireless telegraphy. He began to tinker with the telegraph with companions in his neighborhood who were also taken with the invention. Many of these childhood companions would become lasting friends for the balance of [Armstrong's] life. Thomas Styles lived down the block in Yonkers; Randy Runyon was located about a mile away, and William Russell was in the adjacent town of Hastings-on-Hudson. [Armstrong's] uncle, Frank Smith, introduced him to Charles R. Underhill, an engineer and inventor for the American Telegraph Company. He furnished Armstrong with experimental apparatus, and more importantly, a constant mentor. [Armstrong] would join Underhill frequently after school for years, where they would discuss wireless phenomena.

"On June 24, 1909, Armstrong graduated from high school. The following September, he entered Columbia University's Department of Electrical Engineering. Armstrong was constantly in the laboratory, conducting endless experiments. Some professors thought the young student needed discipline, he did not...maintain records of his experiments. But several instructors defended Armstrong, fostering his need for freedom to investigate. [Armstrong] distrusted mathematics as the essential proof of phenomena of the physical world and refused to accept the findings of experts. He continued his experiments both at the Columbia lab and in his attic at home. He was determined to find a method that would strengthen the wireless signal.

"While in his junior year, Armstrong came under the influence of Professor Michael I. Pupin. Pupin was one of the founders of the Columbia University Department of Electrical Engineering, and head of the Marcellus Hartley Research Laboratory. Pupin believed in rigorous scientific experiments, understanding that theory cannot replace results. A successful inventor himself, he soon took notice of Armstrong.

"In 1912, Armstrong joined the Radio Club of America, which his close friends from Yonkers had all joined. The Club, originally called the Junior Wireless Club Ltd., had been organized in 1909, with Reginald A. Fessenden as the advisor. Fessenden had invented and patented the heterodyne principle in 1902. It was an amateur club that would eventually have a large impact on the development of radio and more specifically, Armstrong's career.

The Regenerative Circuit

"In 1906, Lee de Forest created the "audion", an early vacuum tube, by adding a wire grid to the Edison-Fleming diode. Subsequently, in 1912, he accidentally connected the output circuit of one audion to its own input circuit and obtained a loud howling sound, which he later identified as regeneration. Instead of attempting to understand the hissing or howling sound, he tried to abolish it.

"When Armstrong began experimenting with the audion, he took numerous measurements in order to ascertain how this tube functioned, eventually devising a circuit that would operate as a powerful amplifier of incoming radio waves. By the winter of 1912, he had discovered that if part of the plate's output circuit was fed back to the grid in a controlled manner, the incoming signals were remarkably strengthened. In addition, he discovered that when feedback was increased sufficiently the circuit could be used as a transmitter by generating high frequency oscillations, a required element for radio communications. He mentioned his idea to instructors at Columbia University, who advised him to contact William Davis, a patent attorney who had secured patents for many of them. Lacking the necessary funds to file, his uncle advised him to prepare a sketch and have it notarized. He did just that, providing him with a record date of January 31, 1913.

"Armstrong's regenerative circuit led to a nearly twenty year legal battle over patent rights. While the controversy is best known to have been between Armstrong and de Forest, there were actually two other individuals who claimed rights to this invention-- Irving Langmuir and Alexander Meissner.

"In October 1913, Armstrong, along with another inventor, Irving Langmuir of General Electric, filed patent applications disclosing the principle of radio-frequency regeneration and claimed the arrangement of tuned radio frequency circuits, which is characteristic of the invention. Armstrong's patent was issued on October 6, 1914. This patent disclosed the circuit arrangement in its non-oscillating stage, that of an improved receiver of wireless signals. By now his patent attorney, William Davis, recommended he incorporate the transmitting ability into the same patent. Armstrong refused and the regenerative circuits oscillating capacity was disclosed in a separate patent application, filed December 18, 1913.

"A German inventor, Alexander Meissner, filed a United States Patent application on the regenerative circuit on March 16, 1914. Four days later, Lee de Forest filed an application for his "ultra-audion". In De Forest's original claims, he considered his device a detector, not an amplifier (transmitter).

"In November 1913, de Forest delivered a paper to the Institute of Radio Engineers (IRE) on the subject of "The audion, detector and amplifier". He gave an explanation of the action of the audion with regard to circuit change. He made no mention of feedback and this presentation served to reinforce the fact that he did not understand the audion qualities or how it functioned. It was not until after Armstrong's paper "Some Recent Developments in the audion Receiver", was delivered to the IRE in New York on March 3, 1915, and published in September, that de Forest changed his patent disclosure. De Forest filed for patent with oscillating features in September 1915 and was later issued a second patent, claiming a date of invention prior to March 1913, disclosing specifics of regeneration.

"This was the patent that the United States Supreme Court would, on May 21, 1934, decide to sustain in favor of de Forest. The decision of the Supreme Court was the thirteenth pronouncement by a judicial or administrative tribunal with regard to the question of priority between Armstrong and de Forest. These two men fought each other in the courts both as individuals and through the corporations (Westinghouse Electric and American Telephone and Telegraph, respectively) that had purchased rights to their patents. Prior to the Supreme Court decision, six of the tribunals decided in favor of Armstrong and six had decided in de Forest's favor. The scientific community, especially the engineering community, believed that in favoring de Forest's claim the Court had made a large mistake, one based on the justices' lack of technical training and understanding.

"In 1934, the IRE held a convention in Philadelphia. Armstrong indicated that he would like to return the Medal of Honor he had received in 1917 for his discovery of regeneration. He believed that since the United States Supreme Court had decided against him, it was his duty to return what may have been awarded to him in error. The IRE President, along with the Board of Directors unanimously agreed that Armstrong should be reaffirmed as the recipient of the 1917 Medal of Honor, so instead of allowing Armstrong to return his Medal, they restated the award.

The Super-heterodyne

"When the United States entered World War I, Armstrong enlisted in the Signal Corps. In 1917 he was posted in France and placed in charge of the Radio Group of the Research Section of the Division of Research and Inspection. This Division had been created in order to examine any existing equipment manufactured by the Europeans for the American Expeditionary Forces. [Armstrong] set off to France but en route he was delayed in England due to heavy fog. While there, he ventured to London, stopping by the Marconi offices where he met Henry J. Round.

"Round was an engineer with Marconi who, at the time, was in charge of the Admiralty's wireless direction-finding stations. It was here that Armstrong was introduced to Round's short-wave equipment. Round had created these amplifiers by designing his own vacuum tube (V24). These tubes were not of military use to the French or the Americans, but they captured Armstrong's attention and he concluded that this was a problem that required further research.

"Armstrong had studied heterodyne circuitry for quite a while and understood it well. This meeting with Round pushed him further and he continued to examine the problem of receiving weak high frequency signals. In 1918, Harry W. Houck, a sergeant in the United States Army, was sent to Paris to assist Armstrong with his work. They worked together to solve the problem of detecting high frequency waves and converting them to a lower frequency range audible to the human ear. After observing a bombing raid in Paris, Armstrong was inspired to improve the methods of locating aircraft. He used the heterodyne principle to bring short-wave frequencies down to the range of his long-wave amplifier. He worked out the necessary experiments needed to prove his forthcoming invention, writing down the proposed method in June 1918 with Major Buckley signing off as witness.

"Following his proposed methodology to Major Buckley, Armstrong needed assistance to stage these experiments and create the necessary apparatus. With war work taking precedence and his fellow officers tied up in other pressing projects, his work was delayed. The first model was not ready until November. Armstrong first applied for patent in France in December 1918 and for United States patent in February 1919.

"In early 1919, Armstrong was raised to permanent rank of Major. He also received the Chevalier de la Legion d'honneur from General Ferrie, Head of the French Military Communications Division. When Armstrong returned from the war he presented his paper, "A New System of Short Wave Amplification," to the Institute of Radio Engineers in December of 1919, delineating his new receiver.

"In 1920, Westinghouse purchased Armstrong's regeneration and superheterodyne patents. Also, around this time, American Telephone and Telegraph (AT&T) purchased Lucien Levy's patent for essentially the same invention. Levy's patent referred to a different use of the technology than did Armstrong's, resulting in the United States Patent Office not catching the conflict. Someone eventually noticed this apparent conflict and [recognized that it] needed to be resolved.

"The Court of Appeals in the District of Columbia ruled in Levy's favor and his patent was issued on November 5, 1929, with a priority date of August 4, 1917 (he had filed 6 months prior to Armstrong). While Levy, by law, is considered the inventor of the superheterodyne method, Armstrong is recognized as bringing about its commercialization through the single tuning knob superheterodyne receiver.

The Super-regenerative Circuit

"In 1922, Armstrong devised the super-regenerative circuit, a detector with much higher sensitivity. In June, RCA and Armstrong made a deal; Armstrong received two hundred thousand dollars in cash and sixty thousand shares of stock for his super-regeneration invention. It was around this time that he met Marion MacInnis who worked as David Sarnoff's secretary at RCA. In December of 1923, they married at her parents' home in Merrimac. Radio broadcasting was now becoming very popular; what had begun as one station in 1920 had grown to over 500 stations.

Wide-band Frequency Modulation System

"For many years Armstrong and Pupin had been investigating how to eliminate the problem of natural and man-made noise that plagued AM radio, with no success. At the time, the method accepted of reducing noise was in narrowing the band of frequencies used to transmit radio waves. The conventional theories taught that a narrower band of frequencies utilized for broadcasting would allow less noise into the signal. In 1931, Armstrong took the opposite approach and pursued wideband frequency modulation as a remedy for noise.

"On December 26, 1933 about 18 months after he began experimenting with wide-band FM, Armstrong had secured patent number 1,914,069, titled Radio Signaling. In addition, he secured three other patents; patent number 1,941,068 titled Radio Signaling, patent number 1,941,066 titled Radio Signaling System, and the last issued in 1933, patent number 1,941,067 titled Radio Broadcasting and Receiving.

"Armstrong first approached RCA, offering them first option on his new invention. In the spring of 1934 he set up his system in the Empire State building and for the next few years RCA engineers, alongside Armstrong, tested FM. During the summer of 1934, tests were conducted between the Empire State building and Westhampton Beach, Long Island. The results were excellent, but proof was needed from a site located at a further distance. The receiver was moved to the Haddonfield, New Jersey home of Harry Sadenwater, an engineer at RCA. This experiment established that even with longer range, the signals could be heard loud and clear.

Alpine, New Jersey

"Still, RCA would not buy Armstrong's frequency modulation system. So he attempted to obtain permission from the Federal Communications Commission to build a high powered FM station in 1935. First, the FCC denied his request, but he was finally able to secure an experimental license after he hired an attorney to help him. Armstrong began constructing his station in Alpine, New Jersey. In 1936, he poured a large sum of money into it, selling some of his RCA stock to do so. There were no FM broadcast stations in existence (with the exception of W2AG, his longtime childhood friend Randy Runyon's station, operating out of Yonkers, New York), hence all the apparatus would have to be built from scratch. Armstrong oversaw the project from top to bottom.

"Station W2XMN went on the air with a regular operating schedule in July 1939. Immediately following, various other FM stations went on the air, all under experimental licenses. These stations now wanted to go commercial and thus were applying to the FCC to do so. Finally, at the end of 1939, the FCC began to study the commercial possibilities of FM broadcast.

The Federal Communications Commission

"In January 1941, the FCC authorized the commercial development of FM. When the United States entered World War II, there were under one hundred commercial FM stations authorized, but applications were rolling in. The FCC froze the civilian electronics industry; only FM stations already broadcasting could continue. It became clear to the FCC that they would need to establish standards for the post-war electronics industry. A new allocation scheme for the use of frequencies above 30 MHz would become necessary.

"In November 1942, at a joint meeting of the IRE and the electrical engineering department of the Radio Manufacturers Association (RMA), FCC Commissioner James L. Fly encouraged the industry to establish an organization that could provide the FCC with engineering advice for the development of frequency allocation and system standards. Fly's proposal resulted in the establishment of the Radio Technical Planning Board (RTPB), set up in September 1943.

"The RTPB was divided into 13 panels, each responsible for recommendations pertaining to various electronic industry standards. FM broadcasting, including frequency allocations and standards was the responsibility of Panel 5.

"Various hearings were held where a multitude of experts in the field testified. Generally accepted was that the majority of experts, both on the applicable panel, or consulted, agreed that the FM frequency allocations should remain where they were in the 40-50 MHz vicinity. A few experts felt that there was evidence of atmospheric disturbances that could cause interference in the frequency band that was currently being used. The FCC then began to investigate a possible move for FM frequency allocation, to the 100 MHz vicinity.

"In June 1945, after multiple hearings and evidence from an engineer employed by the FCC, Kenneth Norton, the FCC ordered FM stations to broadcast in the 88-106 MHz band. This decision rendered the old FM system, in use since January 1941, obsolete. Engineers, manufacturers and broadcasters had to begin again from scratch.

"A few years prior to the FCC decision to shift frequency allocations, RCA had begun work on FM. Negotiations between Armstrong and RCA for use of his FM System patents had never come to fruition. An engineer employed with RCA, Stuart Seeley, [who] had invented the "radio-detector" for RCA,...claimed that Armstrong's patents were not used. In fact, the Seeley invention did appropriate two of Armstrong's inventions, the limiter and detector. RCA was licensing the rights to what it claimed was its FM invention, to other manufacturers, some of which were Emerson, Motorola and Philco. With the shift in frequency band, RCA was back on a level playing field.

Radar and FM Multiplexing

"Armstrong set out to prove the FCC wrong so he leased a cottage on Westhampton Beach, Long Island and sent John Bose to reside there. Signals were sent from Alpine and the documentation of FM propagation was extensive. He produced incontrovertible evidence that FM could work well in a lower frequency band. At the same time, he also conducted experiments to prove that FM transmission was not limited to short distances. [From Alpine] [h]e transmitted...high powered FM signals that bounced off the ionosphere and [were] received by a mobile receiver in Alabama. The [P]entagon and Bell Labs recognized the importance of this discovery and continued development with Massachusetts Institute of Technology (MIT), REL and Bell Labs. The result was early warning radar.

"At the start of the war, Armstrong offered the United States government use of his FM patents royalty free. Unfortunately, his bills for the Columbia Lab and Alpine station were building so his attorney, Al McCormack, encouraged Armstrong to accept government contract work. At the time, Armstrong was investigating long-range radar. As a result of incoming work, Armstrong hired another assistant, Robert Hull, a recent graduate of Columbia University, to join his investigations of continuous wave radar.

"He had adapted frequency modulation to radar to extend the range of detection far beyond conventional methods. His research provided the basis for long-range radar in use today. Armstrong had still been working on radar and in January 1946, his radar system was tested at the US Army Signal Corps lab in Fort Evans, located in Belmar, New Jersey. Army engineers bounced the first radio signal off the moon and back to earth. His radar system proved that FM waves could penetrate the ionosphere.

"In March 1953, a new invention is announced, FM multiplexing. Armstrong had developed the invention with John Bose, which facilitates a single FM station to transmit simultaneously, two or three different signals over the same FM wave. This invention made stereo broadcasting possible.

Wide-band Frequency Modulation System--Patent Infringement

"On July 22, 1948, Armstrong's attorney, McCormack, filed suit against RCA and NBC in Wilmington, Delaware. The main charge being infringement of his five basic FM patents. In addition, the suit also charged that RCA deliberately set out to retard the production of FM. McCormack was assisted by Dana Raymond (who had worked at Cravath, Swaine & Moore), and the attorney who had filed all of Armstrong's patents since super-regeneration, Albert Nolte, assisted as well.

"The litigation continued and Armstrong began to become not only financially drained, but physically drained as well. At the end of the fifth year of litigation, 1954, Armstrong took his own life.

"His widow Marion would continue the battle against RCA and twenty other companies who had infringed Armstrong's FM patents. It would not be until 1968, when the final pending suit and ruling was made in Armstrong's favor. All twenty-one companies had either settled or were ruled infringers by the courts."

Honors and Awards:

Degree of Doctor of Science Columbia University, 1929

Muhlenberg, 1941

L'Universite Laval, 1948

Medal of Honor, Institute of Radio Engineers, 1917

Chevalier de la Legion d'Honneur, 1919

Armstrong Medal, established by The Radio Club of America, 1935

Egleston Medal, Columbia University, 1939

Holley Medal, American Society of Mechanical Engineers, 1940

National Modern Pioneer Award, National Association of Manufacturers, on the 150th Anniversary of the American Patent System, 1940

Medal of Class on 1989--School of Mines, Columbia University, 1941

Franklin Medal, The Franklin Institute, 1941

John Scott Medal, Awarded by the Board of Directors of City Trusts, City of Philadelphia, 1942

Edison Medal, American Institute of Electrical Engineers, 1942

Medal for Merit (United States) with Presidential Citation, 1947

Radio Club Armstrong Medal along with Ernest V. Amy, George E. Burghard, Milton Cronkhite, Paul F. Godley, John F. Grinan, and Walter P. Inman, for the first shortwave transoceanic signals (1BCG), 1950

Washington Award, Western Society of Engineers, 1951

Lion Award, Columbia University Alumni Club of New Jersey, 1953

Honorary Membership, Institute of Radio Engineers, Australia

Honorary Membership, Franklin Institute

Honorary Membership, American Institute of Electrical Engineers


Quoted text from: Comins, Jennifer S. "Edwin H. Armstrong Papers, 1886-1982 [Bulk Dates: 1912-1954]." (Finding Aid). Rare Book and Manuscript Library, Columbia University Libraries. October 2010. Accessed September 8, 2016.

Edwin H. Armstrong papers, 1909-1956, consist of photographs, lecture notes, letters, certificates, published materials, programs and ephemera, materials from his memorial service, and other documents.

There are several photographs in the collection, many of which show Armstrong speaking and receiving awards.

Lecture notes include some in French, 1919.

Letters include notes of thank you and appreciation to Armstrong; letters related to Armstrong's professional life, circa 1920s; and letters of condolence to his wife after his passing. There are also some materials from Armstrong's memorial.

There are many certificates and citations, 1935-1950, in the collection, including some from the United States military, The Franklin Institute, and other organizations. There are also materials from dinners where Armstrong was honored, including programs and ephemera.

Printed and published materials include Armstrong's high school yearbook from Yonkers High School, 1909; military instruction booklets, 1917; articles by Armstrong, as well as those he may have used for reference; newspaper clippings, 1940; magazines; and several booklets, pamphlets, technical manuals, and other published materials relating to telecommunications, especially to wireless technology from World War I. An inventory is available on-site.

There are objects associated with this collection that were not included as part of this survey.

Summary descriptive information on this collection was compiled in 2014-2016 as part of a project conducted by the Historical Society of Pennsylvania to make better known and more accessible the largely hidden collections of small, primarily volunteer run repositories in the Philadelphia area. The Hidden Collections Initiative for Pennsylvania Small Archival Repositories (HCI-PSAR) was funded by a grant from The Andrew W. Mellon Foundation.

This is a preliminary finding aid. No physical processing, rehousing, reorganizing, or folder listing was accomplished during the HCI-PSAR project.

In some cases, more detailed inventories or finding aids may be available on-site at the repository where this collection is held; please contact The Historical and Interpretive Collections of The Franklin Institute directly for more information.

The Historical and Interpretive Collections of The Franklin Institute
Finding Aid Author
Finding aid prepared by Sarah Leu and Jack McCarthy through the Historical Society of Pennsylvania's Hidden Collections Initiative for Pennsylvania Small Archival Repositories
This preliminary finding aid was created as part of the Historical Society of Pennsylvania's Hidden Collections Initiative for Pennsylvania Small Archival Repositories. The HCI-PSAR project was made possible by a grant from The Andrew W. Mellon Foundation.
Access Restrictions

Contact The Historical and Interpretive Collections of The Franklin Institute for information about accessing this collection.

Collection Inventory

Print, Suggest