The Advent of AM Radio
The development of the technique is attributed to Lee de Forest and Reginald Fessenden.
A number of inventions are attributed to Lee de Forest, including the triode amplifier, the space telegraphy and the Audion, another type of vacuum tube. The use of the term "radio" is also attributed to him. His work had to do with the amplification of very weak signals that needed to be picked up by the antenna before application to the receiver detector. This work is thought to have significantly contributed to the development of the amplitude modulation technique.
The first transmission however, took place in 1906 from a garage in Brant Rock, Massachusetts. After six years of hard work, Reginald Fessenden, a Canadian inventor transmitted the world's first voice message by using an Alexanderson alternator and a rotary spark-gap transmitter. His message was heard by radio-equipped ships within a range of several hundred miles away from the transmission point
The use of AM broadcasting became more extensive in the years before World War I. Back in 1909, Charles David Herrold founded the first radio station in San Jose, California, known as KQW. Radio station KCBS from San Francisco, is believed to be the descendant of this first broadcast station. After World War I, the number of radio experimentalists increased dramatically and so did the use of AM radio.
The year 1920 was the year of the first "commercial" AM broadcasting by XWA in Montreal, Quebec, Canada. The station is now called CINW. Correspondingly, the first commercial broadcasting in the US took place in Pennsylvania by Frank Conrad, who was also responsible for the founding of the first licensed broadcast station in the world, KDKA. Conrad was an Assistant Chief Engineer in the Westinghouse Electric Corporation that created KDKA on November 2, 1920. The station is now owned by the CBS Radio and its transmitter is located in Allison Park.