AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a signal and is still widely used today. Commercial and public AM broadcasting is authorized in the wave band worldwide. Commercial AM broadcasting developed from amateur broadcasts around 1920, and was the commercially important form of radio broadcasting until FM broadcasting began after World War II. This period is known as the Golden Age of Radio, today, AM competes with FM, as well as with various digital radio broadcasting services distributed from terrestrial and satellite transmitters. AM broadcasting was the first broadcasting technology invented, the technology of amplitude modulation radio transmission was developed between 1900 and 1920. This was used for private communication and message traffic, such as telegrams. The entrepreneurs who developed AM radiotelephone transmission did not anticipate broadcasting voice, the term broadcasting, borrowed from agriculture, was applied to this new activity around 1920. Prior to 1920 there was no concept of broadcasting, or that radio listeners could be a market for entertainment. Although there were a number of broadcasts during this period. True radio broadcasting didnt begin until around 1920, when it sprang up spontaneously among amateur stations, AM remained the dominant method of broadcasting for the next 30 years, a period called the Golden Age of Radio, until FM broadcasting started to become widespread in the 1950s. AM remains a popular, profitable entertainment medium today and the dominant form of broadcasting in some such as Australia. The first AM voice transmission was made by Canadian researcher Reginald Fessenden on 23 December 1900, Fessenden is a significant figure in the development of AM radio. He helped develop one of the first – the Alexanderson alternator, the first practical continuous wave AM transmitters were based on versions of the Poulsen arc transmitter invented in 1903, and the huge, expensive Alexanderson alternator, developed 1906–1910. The modifications necessary to transmit AM were clumsy and resulted in low audio quality. Modulation was usually accomplished by a carbon microphone inserted directly in the antenna wire, the limited power handling ability of the microphone severely limited the power of the first radiotelephones, in powerful transmitters water-cooled microphones had to be used. At the receiving end, the crystal radio receivers then in use could not drive loudspeakers, only earphones. The discovery in 1912 of the ability of the Audion vacuum tube, invented in 1906 by Lee De Forest
One of the earliest radio broadcasts, French soprano Mariette Mazarin singing into Lee de Forest's arc transmitter in New York City on February 24, 1910.
Lee de Forest used an early vacuum-tube transmitter to broadcast returns for the Hughes-Wilson presidential election returns on November 7, 1916, over 2XG in New York City. Pictured is engineer Charles Logwood
Nellie Melba making a broadcast over the Marconi Chelmsford Works radio station in England on 15 June 1920
Farmer listening to U.S. government weather and crop reports using a crystal radio. Public service government time, weather, and farm broadcasts were the first radio "broadcasts".