Edwin Howard Armstrong

- a summary of the life of Edwin Armstrong, the man credited with several radio inventions including the superhet or superheterodyne radio, the regenerative receiver, and wideband FM.

Edwin Armstrong was a man who gave much to the development of radio or wireless technology. Starting at a very young age, he developed the first regenerative radio receiver, was the first to develop and construct a superhet or superheterodyne receiver, and he also saw the benefits of wideband FM which he again pioneered. Without Edwin Armstrong, radio technology would have not developed as fast as it did.

Armstrong's early years

Edwin Howard Armstrong was born on 18 December 1890 and became one of the foremost inventors in radio technology. However he was primarily a scientist and not a businessman and as a result he did not gain as much financial reward from his inventions as might have done. His name is well known to vintage wireless enthusiasts as a man who brought the developed the regenerative radio receiver as well as the superhet and wideband FM.

Armstrong had a keen interest in radio, building early radio sets while still at high school. On graduating from high school he moved to Columbia University to study engineering. It was while he was here that he made his first discovery. He investigated the action of de Forest's Audion triode valve that in these early days of wireless was not well understood. In the summer of 1912 he devised a circuit that fed part of its output back into the input to give what is called a regenerative circuit. So successful was this that he could hear distant stations without the need for headphones. Although others came up with the idea around the same time as Armstrong, he is normally credited with the invention of the regenerative receiver. He received his degree in 1913 and filed a patent for his idea.

Armstrong's war service

When the USA joined the war in Europe, Armstrong was commissioned as an officer in the Army Signals Corps. He was sent to Paris and started work on receivers for detecting enemy transmissions. This work resulted in the development in 1918 of a new type of receiver that used the heterodyne principle to convert the incoming signals down to a fixed intermediate frequency where they could be more effectively amplified and filtered. This new type of receiver was called the supersonic heterodyne or superhet receiver, because it used heterodynes above the audible range for its operation.

The end of hostilities the need for his new type of receiver dwindled. Broadcasting was in its infancy and the small number of stations meant the need for the selectivity provided by his new set was not needed. As valves (tubes) were very expensive it was not until the late 1920s that the rise in broadcasting meant that superhet receivers were needed.

FM development

After the war Armstrong continued his researches. One of the major problems of the time was that of static noise that reduced the quality of transmissions. Rather than using the normal amplitude modulated signals, Armstrong devised a system of using wideband frequency modulation. Unfortunately in the 1930s of the depression, there was little enthusiasm for a new style of transmission. Undaunted, Armstrong managed to gain permission to set up an FM station at his own cost in 1940. It then took two further years before new frequency allocations were given for this new mode that was proving popular.

Legal battles

Armstrong faced many legal battles over royalties and payments. Facing another legal battle, Armstrong took his life on 31st January 1954, jumping from his apartment window in New York. By the 1960s FM was firmly established as the method to be used for high fidelity broadcast transmissions, and he was posthumously elected to the line of electrical leaders by the International Telecommunications Union in Geneva.