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Radio

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What is Radio?

Radio is a way to send electromagnetic signals over a long distance, to deliver information from one place to another. A machine that sends radio signals is called a transmitter, while a machine that "picks up" the signals is called a receiver. A machine that does both jobs is a "transceiver". When radio signals are sent out to many receivers at the same time, it is called a broadcast. Television also uses radio signals to send pictures and sound. Radio signals can start engines moving so that gates open on their own from a distance. Radio signals can be used to lock and unlock the doors in a car from a distance. Sound can be sent by radio, sometimes through Frequency Modulation (FM) or Amplitude Modulation (AM).

Today, radio is used in such technologies as cellular telephones, global positioning systems (GPS), satellite radio, broadcast television, microwave ovens, some remote controls, and radar.

Millions of people listen to the radio every day in their car, on their smartphones, and over the Internet.

 

History of Radio:-

In 1864 James Clerk Maxwell showed mathematically that electromagnetic waves could propagate through free space. The effects of electromagnetic waves (then-unexplained "action at a distance" sparking behavior) were actually observed before and after Maxwell's work by many inventors and experimenters including Luigi Galvani (1791), Peter Samuel Munk (1835), Joseph Henry (1842), Samuel Alfred Varley (1852), Edwin Houston, Elihu Thomson, Thomas Edison (1875) and David Edward Hughes (1878). Edison gave the effect the name "etheric force" and Hughes detected a spark impulse up to 500 yards (460 m) with a portable receiver, but none could identify what caused the phenomenon and it was usually written off as electromagnetic induction. In 1886 Heinrich Rudolf Hertz noticed the same sparking phenomenon and, in published experiments (1887-1888), was able to demonstrate the existence of electromagnetic waves in an experiment confirming Maxwell's theory of electromagnetism.

Early 20th century radio systems transmitted messages by continuous wave code only. Early attempts at developing a system of amplitude modulation for voice and music were demonstrated in 1900 and 1906, but had little success. World War I accelerated the development of radio for military communications, and in this era the first vacuum tubes were applied to radio transmitters and receivers. Electronic amplification was a key development in changing radio from an experimental practice by experts into a home appliance. After the war, commercial radio broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. After the war, the experiments in television that had been interrupted were resumed, and it also became an important home entertainment medium.

 

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How Radio work?

External, telescopic FM antenna: The one on this radio extends to about 30 cm, which is plenty long enough to catch a good range of FM broadcasts. You can extend and swivel the telescopic antenna for better reception. Generally speaking, the longer the antenna, the more signals you can pick up.

Battery compartment: This radio is either battery or AC powered. When you plug in an AC lead, a switch automatically cuts out the battery power.

Loudspeaker: There is only one loudspeaker, so this radio can reproduce only mono sounds. Generally, the bigger the loudspeaker the louder the radio.

AC power input: A cable plugs into this socket so you can run the radio economically from a domestic power supply.

Transformer: The radio's electronic components operate on very small voltages, but the power that comes in from the AC outlet is typically 110 volts, 240 volts, or similar. The transformer's job is to scale down the AC voltage so it's safe and appropriate for the radio's delicate components.

Internal AM antenna: When you're listening to an AM broadcast, the external FM antenna is redundant. Instead, signals are picked up by this tightly coiled AM antenna concealed inside the case. If you're listening on AM, you have to turn the entire radio to reorient the built-in antenna and improve your signal reception.

Transformer: A series of smaller transformers help the radio hone in on just the station you want by blocking out other, nearby stations.

Amplifier: This small chip boosts the signal strength so it's powerful enough to drive the loudspeaker. The amplifier is based on transistors, electronic components that take in a small current and put out a much larger one—scaling it up in size. Small radios are often called "transistor radios": it was the development of the tiny transistor, from the late 1940s onward that made it possible to pack all the components of a radio into a small portable unit. Before transistors came along, radios were typically huge wooden boxes that stood in the corner of your home, as big as an old-fashioned TV

Earphone socket: You can plug a small mono earphone in here to listen in privacy. If you plug stereo headphones into the mono socket, you'll hear sound in only one of the two earpieces.

Volume control: This is the back of the volume knob. Turning the volume knob adjusts an electronic component called a variable resistor or potentiometer, which increases or decreases the electric current flowing to the loudspeaker. A bigger current makes a louder sound with more volume; a smaller current makes a quieter sound with less volume.

Tuning control: This is a variable capacitor that tunes the radio in to a specific station.

 

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Use of Radio:-

Radio waves are still use to send messages between people.

Radio telescopes receive radio waves from the sky to study astronomical objects.

Amplitude Modulation is used so that multiple stations on the same channel can be received.

Radar detects objects at a distance by bouncing radio waves off them.

 

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