Radio waves are used for a wide range of applications, including AM and FM radio broadcasts, satellite communications, cordless phones, baby monitors, television broadcasts, wireless networks, cell phones, GPS receivers, ham radios, police radios, garage door openers, radio-controlled toys, and wireless clocks.
To transmit audio, video, or data, all of today's radios use continuous sine waves. Each sine-wave uses a different frequency to distinguish between the types of devices using the radio waves.
First, the transmitter converts the information into a sine wave and then transmits it along with a radio signal. Then, the receiver obtains the signal and decodes the information from the sine-wave. A battery provides a good working example of a radio transmitter. Messages are encoded into sine waves through modulation. There are three types of modulation: pulse modulation, amplitude modulation, and frequency modulation. In pulse modulation, the sine wave is turned on and off to transmit information. Using frequency modulation, the frequency of the wave is changed slightly to transmit information.
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