1896 - Guglielmo Marconi invents the radio beside the father's farm near Bologna.
These devices were elementary with only any vacuum tube (due to the cost)
Tune the device wasn't simple, the sound was full of interference and disturbance

1920 - Arrive the Supereterodina circuitry which use the frequency conversion concept, conceived by Lucien Levy in 1917, but patented by E.W. Armstrong in 1918, after commercialized the RCA company
The device improve the listening quality, currently yet used inside the radios, televisions and mobile phones

1935 - Bear the frequency modulation

1960 - Bear in America the stereophonic frequency modulation

1974 - Bear in Sweden the Radio Data System and subsequently introduced in USA RBDS

1980 - Bear the Phase Looked Loop circuitry (PLL) inside the analogic radios to improve the demodulation of the signal.

1990 - Begins the researches about the digital radio in frequency modulation (DAB)

1996 -Begins the researches about the digital radio in amplitude modulation (DRM)

1996 - Begins the planning of Interactive Radio System