11-09-2013, 12:59 PM
Radio Communication System
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Radio Communication
Radio is the wireless transmission of signals through free space by electromagnetic radiation of a frequency significantly below that of visible light.
The transmission of information from one place using radio waves as carriers, and their reception at another distant place is known as radio communications.
Radio communication employs electromagnetic wave propagation through space.
Electromagnetic Spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation
The electromagnetic spectrum extends from below the low frequencies used for modern radio communication to gamma radiation (high-frequency) end.
Advantages Of Radio Communication
It is very easy to use
It is wireless
•They offer the ability to provide Instant communication over given distances without unpredictable call costs
•They can provide individual calls or group calls to multiple users
Commonly Use
Broadcasting cell phones
Wireless computer networks
Bluetooth enabled devices
Garage door openers
Two-way radios in aircraft, ships, and spacecraft
Radar sets
Radio Receiver
A radio receiver is the opposite of a radio transmitter.
It uses an antenna to capture radio waves
It processes those waves to extract only those waves that are vibrating at the desired frequency, extracts the audio signals that were added to those waves, amplifies the audio signals, and finally plays them on a speaker.
A radio receiver may be a separate piece of electronic equipment, or an electronic circuit within another device.
Elements of block diagram
Antenna: Captures the radio waves. Typically, the antenna is simply a length of wire. When this wire is exposed to radio waves, the waves induce a very small alternating current in the antenna
RF amplifier: A sensitive amplifier that amplifies the very weak radio frequency (RF) signal from the antenna so that the signal can be processed by the tuner.
Tuner: A circuit that can extract signals of a particular frequency from a mix of signals of different frequencies. On its own, the antenna captures radio waves of all frequencies and sends them to the RF amplifier, which dutifully amplifies them all.
Tuned radio frequency receiver (TRF)
A tuned radio frequency receiver (TRF receiver)
is type of a radio receiver that is usually composed of several tuned radio frequency amplifiers followed by circuits to detect and amplify the audio signal.
Prevalent in the early 20th century, it can be difficult to operate because each stage must be individually tuned to the station's frequency. It was replaced by the super heterodyne receiver invented by Edwin Armstrong.