Category Archives: Popular

Armstrong Papers Open for Research…


The Edwin H. Armstrong Papers are now open to the public. Here is the online finding aid:

Working on Armstrong’s papers for the past year has been a tremendously rewarding experience for me. Not only did I learn a great deal about one of the greatest American inventors of the 20th century, but I had the great pleasure of collaborating with many engineers, most of whom are Columbia Electrical and Computer Engineering faculty. In addition, many radio hams came to my rescue, offering explanations and descriptions of apparatus and technical terminology. I  wish to extend a sincere thanks to all the engineers and radio hams (many of whom are also engineers) who exhibited a tremendous amount of patience in assisting me in understanding all the technical terms and ideas permeating this collection.

For hams, students and those interested in Columbia University history:

Alan Crosswell was kind enough to take me up to the attic in Mudd this past Friday (10th December). It had come to my attention via a Columbia University EE alum that an old piece of Armstrong equipment was living up there. Sure enough, Alan pulled it out of a cabinet.

Armstrong Apparatus: Paper recorder used to record electrical impulses on paper



Armstrong Tag: at one point was attached to box housing device














Armstrong Paper Recorder with carrying case





Armstrong Paper Recorder




The attic in Mudd serves to house W2AEE, Columbia University’s Amateur Radio Club. An abundance of apparatus can be found up there, including a Kenwood HF rig that past Columbia University President William J. McGill bought for the Club after he obtained his Novice Class License in 1977.

Kenwood HF rig, donated by William J. McGill in the 1970s



W2AEE Apparatus












W2AEE Apparatus



The Club history is spotty but a recent article (link: found by a radio ham in Lithuania indicates that Columbia’s Amateur Wireless Club was the earliest college amateur station in the United States. It was founded in 1908, predating Massachusetts Institute of Technology’s Radio Society, W1MX (formerly 1XM) (, in 1909. W1MX should not to be confused with the MIT UHF Repeater Association, W1XM. (

QSL Cards hanging on the wall


W2AEE Station logbook from the 1970s



While on my visit, Alan explained that ham radio can only be legally used for person-to-person contact, broadcasting is illegal. So, in the late 1960s when Columbia University student activists used the Club to broadcast their dissenting sentiments, the FCC cited the Club for illegal transmissions.

W2AEE Banner: created by Alan Crosswell



I have included some pictures here which were taken Friday during my visit to W2AEE. Please see the W2AEE website for further history and information:

WKCR (Columbia University Radio Club) History:


Alpine, New Jersey–My Recent Visit…


W2XMN–Armstrong’s original transmitter building built in 1937, 2010 November 6
W2XMN–Interior of building, 2010 November 6


I had the great pleasure of venturing out to Alpine, New Jersey this past Saturday. I was honored to receive an invitation from Dave Amundsen, the Director of Engineering for CSC Management (the organization who presently owns the Alpine site), to celebrate the 75th anniversary of Major Armstrong’s public demonstration of FM in 1935, through a live radio broadcast.

To be able to stand in close proximity to the original Armstrong tower was truly an incredible experience, and the engaging conversations with the many radio hams in attendance was priceless.

Steve Hemphill was kind enough to serve as a tour guide through the multitude of apparatus, including the one used to transmit the anniversary broadcast. Steve personally built a replica of Armstrong’s 42.8 Mhz FM transmitter, and has lent his helping hand to restore a variety of other instruments on the Alpine site.

The GE BT-1-B 250 watt FM broadcast transmitter that resembles an old refrigerator (photographs immediately below) is Steve’s handiwork. He purchased the GE 250 watt transmitter off Ebay back in August 2002 and refurbished it back to its original shiny and functioning glory.

GE 250 watt transmitter, 2010 November 6
Steve Hemphill with the GE 250 watt transmitter, 2010 November 6








I posted some photographs of the back interior of the GE transmitter to illuminate the amount of work involved in this project. You will see all new wiring–really quite incredible!

GE 250 watt transmitter–backside interior view, 2010 November 6
GE 250 watt transmitter–backside interior view, 2010 November 6










This particular GE transmitter originally belonged to WAVE-FM in the late 1940s and was subsequently sold to the Louisville Free Public Library for use as their transmitter at WFPL-FM, sometime in the 1950s. In 1950, public radio made its debut with WFPL when the Louisville Free Public Library became the first library in the country to obtain a radio license. They started broadcasting using a GE model BT-11-B transmitter (10 watt unit), later upgrading to the model seen here.

GE 250 watt transmitter–backside with "City of Louisville" tag, 2010 November 6


Armstrong’s tower stands as it did decades ago. The bottom of the tower has changed with the construction of a building that serves to house most of the apparatus.

Armstrong Tower, 2010 November 6
Armstrong Tower, 2010 November 6


Armstrong Tower, 2010 November 6







During World War II, Armstrong carried out contract work for the Signal Corps. The tower built for his work on radar still stands (photographs below), albeit with some modifications.

Radar Tower, 2010 November 6
Radar Tower, 2010 November 6







The W2XMN building contains a small museum housing various communications equipment. The photographs below are all from the museum.

Prototype of 30 KHz FM side-channel Multiplex Receiver, 2010 November 6
Prototype of 30KHz FM side-channel Multiplex Receiver, 2010 November 6






The 30 KHz FM side-channel multiplex receiver (photographs above), is a prototype of the receiver designed by John Bose in 1953. The receiver is described in detail in US Patent 2,835,803, issued to Bose in 1958 May 20.

Vacuum Tubes, 2010 November 6
Sample component wiring board–Part of Pulse Generator, Armstrong Experimental Radar, 2010 November 6



David Terwilliger–Radio Ham and textbook of knowledge, 2010 November 6


Double Super-het single knob, 2010 November 6















James O’Neal was kind enough to explain the meaning of Conelrad (CONtrol of ELectronic RADiation) to me. I have seen the CD triangle in a circle emblem on the back of radio apparatus and wondered what it signifies. Mr. O’Neal explained that during the Cold War Conelrad was set up to provide warnings to the public. The system was introduced in 1951, and if an alert was given, radio stations were to go off the air. Chosen stations were to move to either 640 or 1240 KHz, continually alternating so as to avoid enemy direction finding equipment capable of locking into US locations by using radio stations as beacons. In 1963, the Emergency Broadcast System (EMS) replaced Conelrad. Since 1997, the Emergency Alert System (EAS) has been used.

Also in attendance was John Nashmy, who in the aftermath of 9-11, assisted in moving a number of New York television stations to the Alpine site so they could continue broadcasting.



Patent Application…


As can be imagined, there are quite a number of patents to be found within this collection. In addition to Armstrong’s patents, a variety of patents issued to other individuals can be found as well.

Armstrong was issued five patents on December 26, 1933. The first is patent number 1,941,066 titled: "Radio Signaling System," the second is patent 1,941,067:"Radio Broadcasting and Receiving," the third is patent 1,941,068:  "Radiosignaling," the fourth is patent 1,941,069:  "Radiosignaling" (specifically dealing with noise suppression), and the last is patent 1,941,447:  "Radio Telephone Signaling."

I came upon a patent application that appears to have been "dropped". You will see in the documents I have posted here that Armstrong filed for a patent for improvements in "Radio Signaling," through his attorneys Moses & Nolte, on March 26, 1931.

Application for Patent. Armstrong. Radio Signaling. 1931 March 26

Armstrong’s attorney requested an amendment from Armstrong based on an "office action" from the U.S. Patent Office, where they cite patent number 1,797,317. Patent number 1,797,317, titled "Binaural Phase-Discrimination Radio System," was granted on March 24, 1931 to Smart Brand and Pierre Mertz, assignors to American Telephone and Telegraph Company.

Request for Amendment.Radio Signaling. 1932 April 27

Armstrong’s written disclosure (first four pages) for this patent application, along with accompanying figures, can be seen below.

Armstrong.Disclosure Draft.1930 April 21.Page 1


Armstrong.Disclosure Draft.1930 April 21.Page 2












Armstrong.Disclosure Draft.1930 April 21.Page 3




Armstrong.Disclosure Draft.1930 April 21.Page 4











Armstrong.Disclosure Draft. Figure I.1930 August 21



Armstrong.Disclosure Draft. Figure II.1930 August 21











 Instead of making the amendment as requested by his attorney, Armstrong decided to let the application drop.  From reading Armstrong’s patents listed earlier, I can not tell if this dropped application was rewritten into alternate Armstrong patent. Perhaps someone can shed some light on this?

Death Ray?

D. Lippincott to Armstrong, 1942 March 13, page 1
D. Lippincott to Armstrong, 1942 March 13, page 2









No, Armstrong did not invent a death ray, but I did come upon an envelope with "Death Ray" written across the front in the collection. The materials contained within it are incomplete and as a result, there are a variety of holes to this tale. Reading through the documents, let me present a synopsis:

For some years prior to 1942, a Mr. Roberts, residing in New Castle, Delaware, had been trying to sell his death ray to the United States government. He refused to make a disclosure of said invention without a definitive commitment from the government to purchase it.

In 1942, the government engaged in a tentative contract with Roberts for full disclosure of the D.R. invention. The contract called for a disclosure to be made to a board, comprising three individuals. The three would consist of an engineer, a physicist and an Army officer.

Armstrong was contacted by the government through Major Donald Lippincott, who asked if he would be willing to sit on the Board. Armstrong had also been chosen specifically by Roberts attorney, George Finch, as the engineer to fill one of the three spots.  Finch acted as Roberts representative throughout the coming disclosures as Roberts was, at the time, incarcerated. He agreed to serve and signed non-disclosure documents which precluded him from discussing the death ray, at least for the next seventeen years.

Armstrong to Lippincott, 1942 March 21
Lippincott to Armstrong, request for non-disclosure, 1942 July 4

Witnesses were interviewed and gave accounts as to the utility and effectiveness of Roberts creation. The death ray was said to zap ducks out of midair, some thousands of feet high (allegedly, several ducks were retrieved from the road without so much as a mark to indicate cause of death), turn green grass into yellow ribbons, and slice trees horizontally, severing the top from the bottom half.

There are a few notarized witness accounts of the ducks mysterious demise amongst the materials. The following is from William B. Davis, Magistrate at New Castle:

When I saw the ducks and I had them in my possession for a day or two they were dead, their eyes were closed, they were wet, they had not been shot, they had no sign at all as to the cause of their deaths just seemed to be stunned to death.

Walter Borg statement relative to Roberts Death Ray, 1942 August 29, page 1
Walter Borg statement relative to Roberts Death Ray, 1942 August 29, page 2
Walter Borg statement relative to Roberts Death Ray, 1942 August 29, page 3
Walter Borg statement relative to Roberts Death Ray, 1942 August 29, page 4
Walter Borg statement relative toRoberts Death Ray, 1942 August 29, page 5

Walter Borg statement relative to Roberts Death Ray, 1942 August 29, page 6



Major Lippincott investigated the site himself. He visited New Castle to examine any evidence that may remain from supposed death ray invention. His account of the visit is seen in the documents below.

Lippincott memo regarding visit to New Castle, DE, 1942 August 29, page 1



Lippincott memo regarding visit to New Castle, DE, 1942 August 29, page 2













Lippincott memo regarding visit to New Castle, DE, 1942 August 29, page 3

















Lippincott memo regarding visit to New Castle, DE, 1942 August 29, page 4














At some point, either during the disclosure proceedings, or immediately following, Armstrong withdrew from the Board. I can not garner the reason why from the existing documents. Neither can I infer the final outcome or report that was eventually given by the Board. Judging from the last letter in 1943 from Major Lippincott to Armstrong (seen below), the final report was more than likely not in Roberts favor. But the question remains, did the United States government purchase Roberts claimed invention: the death ray?

Lippincott to Armstrong, 1943 February 23


Early Childhood and College Years….

Born in 1890, in the Chelsea district of Manhattan, E. H. Armstrong was the first child of John and Emily Armstrong. He had two younger sisters, Ethel and Edith, and in 1902 the family moved out of New York City to 1032 Warburton Avenue in Yonkers, New York. The house was a large Victorian overlooking the Hudson River.

E. H. Armstrong home at 1032 Warburton Avenue, Yonkers, New York, undated


house at 1032 Warburton Avenue, Yonkers, New York, as seen behind radio pole, undated

During his childhood summers, the family usually left Yonkers and stayed at a farm in upstate New York. John Armstrong was an avid tennis player and set up tennis courts where the young Major quickly honed his talents.

E. H. Armstrong holding a trophy (tennis) with unidentified individual, undated


Edwin’s father gave him a book "The Boys Book of Inventions" which had a huge impact on the young boy. He studied Michael Faraday and Gugliemo Marconi and set out to become an inventor, more specifically, a wireless inventor. He set up wireless apparatus in the attic and soon made friends with numerous boys in and around the neighborhood, all of which had an interest in wireless communications.  His early cohorts, whom he remained friends with for the duration of his life, were Bill Russell, Tom Styles, and Randy Runyon.


E.H. Armstrong with sister’s Edith and Ethel, undated

Armstrong built an antenna mast on his lawn. His youngest sister Edith, or Cricket as Armstrong had nicknamed her, acted as his sole assistant in this project.  


125 foot radio pole at 1032 Warburton Avenue, Yonkers, New York, undated












In 1909, he entered the undergraduate electrical engineering program at Columbia University. He undertook endless experiments, learning from various professors that nothing should be taken for granted. He soon took to Professor Michael Pupin, one of the founders of Columbia’s Department of Electrical Engineering and head of the Marcellus Hartley Research Laboratory.

Pupin had been working on improving wireless transmission, as had Armstrong, up in his attic at 1032 Warburton Avenue. Pupin noticed the young genius in his tireless pursuit of strengthening wireless transmissions. In 1912, Armstrong told his friend and classmate, Herman Burgi, he had discovered a method of amplifying wireless signals. It would not be until 1913, when Armstrong had the money to file for the patent, that he would debut his regenerative circuit.

I came upon many of Armstrong’s undergraduate "labs" for both electrical engineering and mechanical engineering classes. I have included an example of one below.

Armstrong and Burgi undergraduate "lab" for mechanical engineering, 1912, cover page


Armstrong and Burgi undergraduate "lab" for mechanical engineering, 1912, interior page












Armstrong and Burgi undergraduate "lab" for mechanical engineering, 1912, interior page





Armstrong and Burgi undergraduate "lab" for mechanical engineering, 1912, interior page











In addition to a variety of undergraduate "labs", I came upon an early notebook which is unfortunately undated. On the interior of the front cover Armstrong lists himself as the rightful owner and should the notebook get lost, a reward for its return. You will also see some of the interior pages, including the index and his investigation into the audion.

Armstrong Notebook, undated









Armstrong Notebook, interior of cover, undated






Armstrong Notebook, Index, undated


Armstrong Notebook, interior page 51








Armstrong Notebook, page 75


Armstrong Notebook, page 92


Closing of Station KE2XCC…

A. McCormack’s write up for the closing of Alpine, 1954 March 4, page 1

McCormack, closing of Alpine, 1954 March 4, page 2

McCormack, closing of Alpine, 1954 March 4, page 3

McCormack, closing of Alpine, 1954 March 4, page 4

On March 6, 1954, the first experimental FM station, KE2XCC (W2XMN), at Alpine, New Jersey, went off the air. Armstrong’s station had been broadcasting for over fifteen years– it was the end an an era.

I had come across quite a number of letters written to Station KE2XCC from listeners expressing great loss when the station closed. It should be recognized that for all the years Armstrong broadcast from Alpine, not one commercial was heard by his listeners. This was made possible on his own dime, of course.

I think the letters speak for themselves….

Note for documents seen above: Al McCormack was Armstrong’s longtime attorney and friend.

L.T. Alstrup, letter to KE2XCC, 1954 March 10

John Burkhart, letter to KE2XCC, 1954 March 10

D. L. Pace, letter to KE2XCC, 1954 March 9, page 1

D. L. Pace, letter to KE2XCC, 1954 March 9, page 2

Albert Willis, letter to KE2XCC, 1954 March 11, page 1

Albert Willis, letter to KE2XCC, 1954 March 11, page 2

Alan Cunningham, letter to KE2XCC, 1954 March 6

D. B. Lucas, letter to KE2XCC, 1954 March 10

Louise Godley, letter to KE2XCC, 1954 March 9

Carolyn Bedford, letter to KE2XCC, 1954 March 11


Alpine, NJ–Modulator, Transmitter Mixer, Keyer A and Keyer B (left), Receiver (right), undated

When the second World War started in 1939, the United State Signal Corps approached Armstrong for assistance as they wished to use frequency modulation for mobile-military communications. Mobile FM was invaluable during the war and Armstrong allowed the US military use of his frequency modulation system royalty free for the entire war. No company offered such a generous deal and unfortunately, Armstrong’s income was diminishing rapidly and he needed funds to continue support of his Alpine and Columbia University laboratories.

Alpine, NJ–Antenna, close up, undated

Alpine, NJ–Antenna, undated

He accepted contracts to work for the military and began his experiments on radio detection and ranging systems. At the time, the radar employed was of the short wave type (pulse radar). Armstrong was in pursuit of continuous wave FM radar with the help of his chief technical assistants, John Bose and Robert Hull.

When the war ended in 1945, Armstrong had not concluded his radar work. Bose, Hull and Armstrong continued and eventually developed a working radar system. As opposed to pulse radar, the system they produced using continuous wave FM had a searching range far beyond the pulse method.

Alpine, NJ–Transmitter Building-North, Resnatron Cage (right), undated

In December of 1947, John H. Bose, Robert E. Hull and Edwin H. Armstrong filed United States Patent Application No. 794, 608 for Radio Detection and Ranging Systems.The first paragraph of the specification (found in the application) states:

"This invention relates to a new form of radio detection and ranging system for distant objects, commonly known as radar, which utilizes the principles of frequency modulation. It has for its object the provision of a more sensitive and selective system whereby greater sorts is obtained. It has also for its object the provision of means for distinguishing between fixed and moving target relative to the location of the radar station and the sense of motion."

Hull Radar Notes, pp 1, 1944 November 5

Hull Radar Notes, pp 2, 1944 November 5

Hull Radar Notes, pp 3, 1944 November 5

Hull Radar Notes, pp 4, 1944 November 5

Hull Radar Notes, pp 5, 1944 November 5

I have scanned some documents and photographs from Robert Hull’s logbooks (below) and notes (immediately above), which you see here. In addition, I have included the title page of one of the final reports (Contract W28-099-ac14) created at Alpine Laboratory for the US Military (immediately below), along with some photographs (top of post) found within that document. There are many more reports, notes and photographs regarding other US Military contracts held within the Edwin H. Armstrong Papers.

"High Power Frequency Modulation Doppler Radar System", Final Report, Title page, 1952

Logbook–Alpine Lab, Robert Hull, 1947 to 1949, cover

Logbook–Alpine Lab, Robert Hull, 1947 to 1949, index page

Logbook–Alpine Lab, Hull, pp 13, 1947 July 15

Logbook–Alpine Lab, Hull, pp 15, 1947 July 15

Logbook–Alpine Lab, Hull, pp 17, 1947 July 15

Alpine, New Jersey-Part II…

Alpine, NJ-Aerial view of 400 foot

radio tower and transmitter building, undated



As a result of some queries I received with regard to the last post, I decided station W2XMN warrants additional details (photographs and documents).

Alpine,NJ-Unidentified individuals on radio tower, undated

First, Armstrong choose Alpine as the site for his station because of the importance of height as it directly relates to the surrounding landscape, so the chosen site was 500 feet above the Hudson River, facilitating ultra frequency transmissions.

Alpine, NJ-Base of the radio tower, undated

The structure of the antenna of the Alpine station can be seen in many photographs here. Armstrong delineates the details of his tower as follows:

"The height of the tower above grade is 400 feet. The length of the three cross arms is 150 feet and their vertical separation slightly over 80 feet. The radiating members of the antenna consist of a series of seven pairs of crossed rods about 11 feet long which are mounted on a boom supported between the tips of the two upper arms. These crossed rods or ‘turnstiles’ are separated slightly less than half a wave length and are fed by a series of transmission lines which wind around the supporting member. The whole antenna is fed by an open-wire transmission line of about 500 ohms impedance which runs vertically through the center of the tower and horizontally over the transmitter building for a total distance of about 700 feet. The efficiency of transmission appears to be in the order of 90 per cent." 1

Alpine, NJ, Unidentified individuals around the construction site of tower, 1937

Alpine, NJ-Charley Fowler on construction site of radio tower, 1937

Alpine, NJ, original radio mast, 1937 December 4

Following the W2AG’ s many demonstrations by W2AG (Yonkers, New York) to members of the broadcasting industry, the Yankee Network decided to construct a station at Mt. Asnebumskit, Paxton, and Station WDRC (Hartford, Connecticut) management followed with the construction of a station on Meriden Mountain located in Meriden, Connecticut. General Electric was intrigued with Frequency modulation broadcasting and, along with Zenith, began to build FM equipment. Eventually General Electric would build it’s own FM station.

REL turnstile antenna arm correct for 42 to 50 Mc., 1941 March 7

Alpine, NJ-Exterior View of W2XMN building, undated

Skinner, Cook and Babcock builders, estimated costs for lab at Alpine, NJ, 1937 August 7

Immediately following, many more stations were constructed and applications for experimental licenses were flowing into the Federal Communications Commission (FCC).  On December 19, 1939, the FCC finally decided to look into the commercial broadcasting possibilities of FM. The Commission held hearings and as a result released the following advantages of FM:

"1) lack of static; 2) FM operates on low power and gives greater service area than an AM station with similar power; 3) FM stations do not interfere with each other (an FM receiver will accept only the strongest signal when the ratio of the desired to undesired strength is about 2 to 1, whereas in the case of AM, the ratio must at least 20 to 1 for good broadcast service); and 4) FM has definite advantages (technically, economically, quality of service) in operating low power services such as forestry, police, aircraft, etc." 2

On January 1, 1941 the FCC approved commercial FM broadcasting. When the United States entered World War II permits for FM broadcasting would come to a halt. The next battle became postwar frequency allocations.

W2XMN-Special temporary authorization for station from FCC, 1938 June 18


Alpine, NJ-Logbook, Number 2, Cover page, W2XMN, 1939 August 14 through 1940 January 31


Alpine, NJ-Logbook, Number 2, W2XMN, interior page 78, 1939 November 16


Alpine, NJ-Logbook, Number 2, W2XMN, interior page 83, 1939 November 22



Alpine, NJ-Logbook, Number 2, W2XMN, interior 139, 1940 January 22



All of the photographs, documents and logbooks you see here are available within the Edwin H. Armstrong Papers.

1. Armstrong, Edwin H. "Evolution of Frequency Modulation," Electrical Engineering, 1940 December, pp. 490.

2. Erikson, Don V.,  Armstrong’s Fight for FM Broadcasting: One Man vs. Big Business and Bureaucracy, The University of Alabama Press (University, Alabama), 1973, pp. 69.

Alpine, New Jersey…

Subsequent to Armstrong’s frequency modulation system, much of which was patented in 1933, he set out to prove its superiority over AM. He 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 Harry Sadenwater’s (RCA employee) home in Haddonfield, New Jersey, with signals heard loud and crystal clear.

H. Sadenwater Notebook–Memorandum dated 1934 June 22
H. Sadenwater’s Notebook, 1934










Still, RCA would not buy Armstrong’s frequency modulation system. So he attempted to obtain permission to build a high powered FM station in 1935 from the FCC. First, the FCC denied his request. Armstrong then retained an attorney, who was able to get the commissioners to issue an experimental license.

Armstrong began building his station in Alpine, New Jersey. 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.

Amateur Station W2AG Log, Yonkers, New York, 1937-1938
Amateur Station W2AG Log–interior, 1937-1938

Lawrence Lessing describes Armstrong’s creation of  Alpine Station W2XMN in his biography "Man of High Fidelity: Edwin Howard Armstrong" best:

The historic significance of Station W2XMN has never been widely realized. Armstrong lavished all the care and attention to detail of which he was prodigiously capable. With this station, the first full-scale one of its kind, many basic contributions were made to ultra-shortwave communications. In the development of an antenna to operate in this relatively untried region of the radio spectrum, Armstrong spent long days at Alpine making meticulous measurements, observations and modifications in antenna design which added much to the sum of general knowledge in this area. In the development of power tubes and other vacuum tubes to operate at these frequencies, Armstrong acted as a goad. No tubes adequately designed to operate at high power in ultra-shortwaves were available when the Alpine station was contemplated. Armstrong bombarded tube manufacturers with observations, criticisms and suggestions that gradually drew forth adequate tubes. All this was part of the enormous influence which, over the years, Armstrong exercised on the development of radio. 1

Armstrong on the tower at Alpine, NJ station, undated
Interior apparatus, Alpine, NJ, undated

Station W2XMN went on the air with a regular operating schedule in July 1939. Immediately following, various other FM stations were going 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. New battles would be forthcoming with the FCC….

High power amplifier, Alpine, NJ Station, 1938 August
Single unit grid and isolation oscillator set up with solid dielectric feedback cable, Alpine, NJ Station, undated

Harry Sadenwater’s Notebooks, Amateur Station W2AG Log Book, and all photographs of Alpine, NJ Station can be found within the Edwin H. Armstrong Papers in Columbia University’s Rare Book and Manuscript Library.

1 Lessing, Lawrence, Man of High Fidelity: Edwin Howard Armstrong, J.B. Lippencott Company, Philidelphia and New York, 1956, pp. 256.

The Superheterodyne

When the United States entered World War I, Armstrong enlisted in the Signal Corps. In 1917 he was posted to France, 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.                                              

Round, Henry Joseph, 1960

The Major 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. The letter seen here (below), dated 1917 October 28, from Armstrong to his mother, details his visit and recounts his introduction with Henry Joseph Round.

EHA letter to Mother, 1917 October 28, first 2 pages



EHA letter to Mother, 1917 October 28, last 2 pages



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, and would never be, available to the French and the Americans, as these tubes were not appropriate for the task. Armstrong’s attention was captured as 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. As the Major recounts some years later upon receiving the Edison Medal in 1943:

"The third link came months later as I happened to be watching a night bombing raid and wondered at the ineffectiveness of the antiaircraft fire. I may say that night bombing was not very dangerous in those days, either for the man on the ground or the man in the airplane. Thinking of some way of improving the methods of locating the position of airplanes, I conceived the idea that perhaps very short waves sent out from them by the motor ignition systems might be used. The unique nature of the problem, involving the amplification of waves shorter than any ever contemplated and quite insoluble by any conventional means of reception, demanded a radical solution. All three links of the chain suddenly joined up and the superheterodyne method of amplification was practically forced into existence. Not one link in the chain could have been dispensed with. This, I think is the only completely synthetic invention I have ever made." 1

The bombing raid and third link, to which Armstrong refers above, occurred in Paris, March 1918. He had thus sorted out how to use 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 (proposal seen here in 3 pages).

Method of Reception, Disclosed to Major O.E. Buckley, 1918 May-June, page 1


Method of Reception, Disclosed to Major O.E. Buckley, 1918 May-June, page 2










Method of Reception, Disclosed to Major O.E. Buckley, 1918 May-June, page 3

Following Armstrong’s proposed methodology to Major Buckley, experiments would need to be conducted. 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.

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, AT & T purchased Lucien Levy’s patent for essentially, the same invention. Originally Levy’s patent covered a different purpose than did Armstrong’s resulting in the US Patent Office not catching the conflict. Someone eventually noticed this apparent conflict and priority 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 superhet receiver.



1-Armstrong, Edwin H. "Vagaries and Elusiveness of Invention," Electrical Engineering 62 (April 1943).

Additional Information regarding superheterodyne patent:

Schottky, Walter  "On the Origin of the Super-Heterodyne Method," Proceedings if the IRE, Vol. 14, No. 5, 695-698 (October 1926)

Armstrong, Edwin H. "A New System of Short Wave Amplification," Proceedings of the IRE, Vol. 9, No. 1, 3-27 (February 1921)

Douglas, Alan S. "Who Invented the Superheterodyne?," Proceedings of the Radio Club of America, Inc., Vol. 64, No. 3, 123-142 (November 1990)