Basics of Radio Communications
Radio communication is the process by which radio signals are produced, processed, and then transmitted to a radio unit. Radio communication derives its roots from the telegraph machine, when in 1887 Heinrich Hertz discovered the process of transmitting electromagnetic signals through the atmosphere. The process was eventually patented by Guglielmo Marconi in 1895.
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Sound Wave
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When a radio announcer or disc jockey speaks, the voice produces a sound wave within a frequency range of 5 Hz to 20kHz. Hz and kHz are the frequency bands that are assigned to particular radio station, and help the listener determine where to find the station on the radio dial.
Microphone
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When a microphone picks up the sound of the spoken voice, it converts the sound wave into an electrical signal that is similar to the original sound wave. In this way, an electronic wave is now ready for the modulation process.
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Modulation
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The electrical wave modulates a "carrier" wave, which is a hi-frequency radio wave that can either be amplitude modulated (AM) or frequency modulated (FM). Modulation is the process of encoding sound on the carrier wave so that it can be picked up by a radio receiver. With AM, the strength of a transmitted signal fluctuates for the reproduction of sound, while with FM, the frequency of the signal fluctuates.
Transmission
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The waves are then picked up by the radio station's transmitter which converts them into electromagnetic waves at the station's assigned frequency. A radio tower broadcasts the waves from the transmitter out into the atmosphere.
Reception
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A radio unit then receives the signal, often through the use of an antenna. The radio's tuner determines the necessary broadcast frequency, then a demodulator extracts the sound wave from the signal. Finally, the signal is transmitted to the speakers by an amplifier, and the sound can then be heard by the human ear.
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