THE RADIO

The radio is a communication method that sends sound signals by radio waves.

It’s really hard to claim this invention to only one person, but officially it is claimed to Guglielmo Marconi, a Bologna (Italy) physicist who lived in the 19th and 20th centuries.
All radios have an electric circuit than can separate a few current from the antenna and send it to the loudspeaker. I’ve found a diagram about how the radio works.
Radio signals travel by four types of waves:- In 1901 Marconi made the first radio emission, he sent “S” letter in Morse code.
- High frequency waves travel short distances. (They are used in villages).

- Long waves travel to 2.000 km around. (They are used by national radio stations)

- Medium waves can travel around a hundred km. (they are used by national and local radio stations).

- Short waves can travel thousands of km. (they are used by international radio stations).

HISTORY

- In 1924, Radio Barcelona is created, the first Spanish transmitter.

- In 1932, Edwin Armstrong invents frequency modulation that minimizes interferences.

- 1961, the first stereo sounds are emitted in the USA.

- 1988, first car with radio.

Today. radios are used for listening to the news, music or other programs. Everybody has one, on our mobile phone, Mp3 or in our cars. But in the past it was really hard to have a radio.