Tag Archives: antenna


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.