Who invent radio and MP3?

For radio:

The identity of the original inventor of radio, at the time called wireless telegraphy, is contentious. The controversy over who invented the radio, with the benefit of hindsight, can be broken down as follows:

1. Nikola Tesla developed means to reliably produce radio frequencies, publicly demonstrated the principles of radio, and transmitted long-distance signals. He holds the US patent for the invention of the radio, as defined as "wireless transmission of data."
2. Alexander Stepanovich Popov, in 1894, built his first radio receiver, which contained a coherer. Further refined as a lightning detector, he presented it to the Russian Physical and Chemical Society on May 7, 1895.
3. Guglielmo Marconi was an early radio experimenter and founded the first commercial organization devoted to the development and use of radio.
4. Reginald Fessenden [1] and Lee de Forest invented amplitude-modulated (AM) radio, so that more than one station can send signals (as opposed to spark-gap radio, where one transmitter covers the entire bandwidth of the spectrum).
5. Edwin H. Armstrong invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics.

Early radios ran the entire power of the transmitter through a carbon microphone. While some early radios used some type of amplification through electric current or battery, until the mid 1920s the most common type of receiver was the crystal set. In the 1920s, amplifying vacuum tube radio receivers and transmitters came into use.


For MP3:

It was invented by a team of European engineers who worked in the framework of the EUREKA 147 DAB digital radio research program, and it became an ISO/IEC standard in 1991.