ABERDEEN PROVING GROUND, Md. — In 1938, the director of the Signal Corps Laboratories at Fort Monmouth, New Jersey, Col. Roger B. Colton, transformed the face and future of Army communications. War was on the horizon, and the Army and the Signal Corps were not prepared for the scope of what would erupt as World War II. The Army was moving towards preparations for a more mobile war than was experienced with the static-front warfare of World War I. The Signal Corps was working on equipping light automobiles with radios, but little had been done to integrate communications into larger, combined arms mobile formations.
Edwin Howard Armstrong, who had served with the American Expeditionary Forces Signal Corps in World War I and then went on to a position at Columbia University in New York City, had filed a series of patents in 1934. After years of painstaking experiments, he proved that wideband frequency modulation, or FM, evidenced a drastic reduction of noise and static in a demonstration at Columbia University in 1935. During this demonstration, he turned on his FM receiver in front of the audience, and an FM transmission from a friend's house in Yonkers, New York, came in strong, clear, and static-free. The stunned audience listened to a live music performance and a series of sounds, such as a glass of water being poured or a piece of paper being torn, which would have been unrecognizable over amplitude modulation, or AM, radio.
The Signal Corps Laboratories had been experimenting with FM transceivers since 1936, but they had continued developing AM radios. However, the vibrations from airplane and tank engines generated static that interfered with AM radio transmissions. FM eliminated noise and static interference and could transmit a wider range of sounds than AM radio.
Armstrong frequently visited the Signal Corps Labs beginning in 1938. A 1946 letter acknowledges that he served in an advisory capacity, was under contract at various times, and attended conferences and field demonstrations at the behest of the Signal Corps.
Colton made the historic decision to employ FM in all future military radios with the support of research that supported its feasibility. In a letter from Armstrong to Colton dated June 29, 1944, Armstrong listed the problems to be overcome.
"Only the very limited number of people who knew about FM in those early days can have any conception of the magnitude of the problems which confronted the Signal Corps in that period,” Armstrong said. “I do not think I will ever forget how impossible of fulfillment seemed the demands for systems of a hundred separate channels, with push-button selection between any chosen ten of them, together with the requirement of meeting most severe frequency stability tolerances and not enough quartz in sight to make the crystals to do it. All these problems were, of course, overlaid with the necessity of providing adequately rugged construction for field use."
Armstrong called this decision, "the most difficult decision of the history of radio which anyone was ever called upon to make…I most sincerely hope that when this war is over what your organization accomplished here can be duly laid before the world and properly acknowledged."
An oral history interview with World War II veteran John J. "Jack" Kelleher talked about why this decision was important for the future of signal communications. From late 1940 until spring 1941, Kelleher was assigned to the Vehicular Radio Section at Fort Monmouth, which was kept busy overseeing the development of new very high frequency, or VHF, equipment designed for use in tactical vehicles and tanks.
"It used the new frequency modulation (FM) technique invented in 1933 by E. H. Armstrong, and Major Armstrong was a frequent visitor to our facility [at the Signal Corps Laboratories]," Kelleher recalled. "The upshot of this work, was that War Department orders for VHF AM equipment were changed to call for FM instead."
This change was partly made possible by Armstrong offering free use of his FM patents during wartime to the War Department.
"I feel every Soldier who lived through the war with an armored unit owes a debt he does not even realize to Colton," said Col. Grant Williams, a signal officer in the 1st U.S. Army.
The Army's conversion to FM gave Soldiers a tactical advantage over the enemy, one which was adopted in the field by other branches of the military. Armstrong explained adopting this new equipment in a second letter from Oct. 12, 1945.
"After the action at Tarawa, the Marine Corps discarded the equipment on which they had been depending for amphibious operations and adopted the FM equipment produced by General Colton for the use in the Armored Force, the Field Artillery and the Advanced Infantry units of the Army," Armstrong wrote.
Armstrong concluded his letter with the following accolades for Colton. "I know of no one in the Armed Forces whose achievements have so completely the respects and confidence of the technical man in the radio art."
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