Way Back When
On April 6, 1914, Hiram Percy Maxim and Clarence Tuska founded the American Radio Relay League.
On April 18, 1925, the International Amateur Radio Union (IARU) was founded in Paris [France, not Texas]. April 18 is celebrated each year as World Amateur Radio Day.
Photo by Michael L. Unbricht
In April, 1932, the Hammarlund Manufacturing Co., Inc. introduced the first commercially-produced shortwave superheterodyne receiver, the “Comet Pro.” It was an eight-tube design and covered 14–200 meters with four sets of two coils each. By 1936, the Comet Pro was in use all over the world by thousands of commercial operators, broadcast stations and many amateur radio operators.
Guglielmo Marconi (25 April 1874 – 20 July 1937) was an Italian inventor and electrical engineer, known for his pioneering work on long-distance radio. He shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun “in recognition of their contributions to the development of wireless telegraphy.”
On 12 December 1901, he announced that a message was received at Signal Hill in St John’s, Newfoundland, from the company’s new high-power station at Poldhu, Cornwall. The distance between the two points was about 2,200 miles (3,500 km). Heralded as a great scientific advance, there was—and continues to be—considerable skepticism about this claim. The message was simply the Morse letter S, and there was no independent confirmation.
Nikola Tesla, whose theories on the possibility of the transmission by radio waves go back as far as lectures and demonstrations in 1893, commented that Marconi’s system was done with 17 Tesla patents, though there is little to support this claim.
LEFT British Post Office engineers inspect Guglielmo Marconi’s wireless telegraphy (radio) equipment, during a demonstration on Flat Holm island, 13 May 1897. This was the world’s first demonstration of the transmission of radio signals over open sea, between Lavernock Point and Flat Holm Island, a distance of 3 miles.
In the background is the spark-gap transmitter, an induction coil (right) that generates high voltage pulses that create sparks between the balls of the Righi spark gap (left), which excites oscillating currents in a wire antenna suspended aloft by the pole seen in the center, ratiating radio waves. Information is transmitted by switching the transmitter on and off rapidly using a switch called a telegraph key (not visible), spelling out text messages in Morse code.
Morse photograph by Matthew Brady, 1866
Samuel Finley Breese Morse (27 April 1791 – 2 April 1872) was an American painter and inventor. He was well-established as a painter when he contributed to the invention of a single-wire telegraph system based on European telegraphs. He was a co-developer of the Morse code, and helped to develop the commercial use of telegraphy.
RIGHT Morse’s first telegraph design.
Johann Carl Friedrich Gauss (30 April 1777 – 23 February 1855) was a German mathematician and scientist who contributed significantly to many fields including number theory, analysis, differential geometry, geodesy, magnetism, astronomy and optics. In electrical engineering the gauss, abbreviated as G, is a unit of magnetic flux density or magnetic induction.
LEFT Gauss painting by Christian Albrecht Jensen