Guglielmo Marconi RADIO

Radio is the use of radio waves to carry information, such as sound, by systematically modulating some property of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

Radio systems need a transmitter to modulate (change) some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation (which can be frequency modulation or phase modulation). Radio systems also need an antenna to convert electric currents into radio waves, and vice versa. An antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected. The electromagnetic wave is intercepted by a tuned receiving antenna. A radio receiver receives its input from an antenna and converts it into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc. Radio frequencies occupy the range from a 3 kHz to 300 GHz, although commercially important uses of radio use only a small part of this spectrum.

A radio communication system sends signals by radio. The radio equipment involved in communication systems includes a transmitter and a receiver, each having an antenna and appropriate terminal equipment such as a microphone at the transmitter and a loudspeaker at the receiver in the case of a voice-communication system.

Radio owes its development to two other inventions, the telegraph and the telephone, all three technologies are closely related. Radio technology began as "wireless telegraphy".

Radio can refer to either the electronic appliance that we listen with or the content listened to. However, it all started with the discovery of "radio waves" - electromagnetic waves that have the capacity to transmit music, speech, pictures and other data invisibly through the air.

Many devices work by using electromagnetic waves including: radio, microwaves, cordless phones, remote controlled toys, television broadcasts, and more

Many people were involved in the invention of radio in its current form. Experimental work on the connection between electricity and magnetism began around 1820 with the work of Hans Christian Ørsted, and continued with the work of André-Marie Ampère, Joseph Henry, and Michael Faraday. These investigations culminated in a theory of electromagnetism developed by James Clerk Maxwell, which predicted the existence of electromagnetic waves.

Maxwell published A Treatise on Electricity and Magnetism in 1873, stimulating many people to experiment with wireless communication. Others experimented without the benefit of his theories. It is considered likely that the first intentional transmission of a signal by means of electromagnetic waves was performed by David Edward Hughes around 1880, although this was considered to be induction at the time. The first systematic and unequivocal transmission of EM waves was performed by Heinrich Rudolf Hertz and described in papers published in 1887 and 1890. Hertz famously considered these results as being of little practical value.