Radio is
the radiation (wireless transmission) of
electromagnetic energy through space. The biggest use of radio waves is to carry information, such as
sound, by systematically changing (modulating)
some property of the radiated waves, 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, 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. Theelectrical 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 atransmitter and a receiver, each having an antenna
and appropriate terminal equipment such as a microphone at the transmitter and aloudspeaker at the receiver in the case of a
voice-communication system.
No comments:
Post a Comment