Heinrich Hertz - first to detect radio waves in 1887 by causing a spark to leap across a gap that generated electromagnetic waves - built oscillator and resonator by 1893
Oliver Lodge in Britain, Alexander Popov in Russia, Edward Brauley in France - filled a glass tube with metal filings that would cohere under electromagnetic waves and when the tube was tapped, the filings would collapse to break the circuit - built coherer to detect radio waves by 1894
Guglielmo Marconi invented his spark transmitter with antenna at his home in Bologna, Italy, in December 1894. He took his "Black Box" to Britain in Feb. 1896 and although it was broken by custom officials, he filed for British Patent number 12039 on June 2, 1896. He formed his first Wireless Telegraph and Signal Company in Britain in 1897 at age 23 and the world's first radio factory on Hall Street in Dec. 1898. The American Marconi Co. was formed in 1899. Marconi controlled patents for the Lodge tuner of 1900 with dial, and Fleming valve of 1904 that acted as a diode tube to amplify electrical current in one direction. His company sold spark transmitters to the U.S. Navy for point-to-point transmission.
Reginald Fessenden of Canada invented a continuous-wave voice transmitter 1905 using a high-frequency alternator developed by Charles Steinmetz at GE 1903, made voice broadcast over North Atlantic Christmas Eve 1906; this broadcast was heard by wireless operators on banana boats of the United Fruit Company that developed crystal receivers for its ships; Fessenden sold to Westinghouse in 1910 the patent for a heterodyne receiver that used the joint operation of two AC currents for a third frequency.
Lee de Forest patented his audion tube 1906, had visited the Fessenden lab in 1903 and stole the design for a "spade detector," promoted idea of multi-point broadcasting, sold patents to AT&T.
Harold D. Arnold at AT&T developed the amplifying vacuum tube in 1913 that made possible the first coast-to-coast telephony and the first transatlantic radio transmission in 1915.
Edwin Armstrong patented the regenerative circuit in 1913 that fed a radio signal through an audion tube 20,000 times per second to caused stronger oscillations in the tube that generated radio waves. He made long-distance voice transmissions 1914, developed superheterodyne circuit during World War I that combined high and low frequency waves, was promoted to Major in the Signal Corps, sold patents to RCA 1920, discovered FM transmission 1933 but rejected by Sarnoff at RCA who was trying to develop television. ...continued