The simplest answer may be that a radio is a device that either emits radio waves or responds to them. You may already know that radio waves are part of a larger group of electromagnetic waves, which also includes light, X-rays, and even gamma rays. These waves can travel through materials such as air, wood, glass or concrete, or even through the empty vacuum of space. In fact, they travel best through empty space. Some waves, such as light, X-rays and gamma rays, can travel quite well through varying amounts of water or metal. The radio waves of interest don’t penetrate water very well at all, and only a small amount of metal will stop them.
If all radio does is simply emit radio waves or respond to them, it would be a very exciting scientific curiosity, but probably no more than that. It is radio’s ability to provide communication that makes it so vital to modern society. Try to make a list of as many different ways as possible that one person can communicate with another person. How many of these ways require two people to be near each other? For what kinds of communication can people be away from each other? What will happen immediately and what might take hours or even days or weeks? Which ones should have a wire connecting the places where people are? What can happen without wires?
A radio transmitter (some just call it a transmitter) is a device that can take some information (it could be voice, music, or computer data) and convert it to the right kind of radio waves, which can travel through the air or through space, without any wires. The waves are launched into space by an antenna . Elsewhere, a radio receiver (often referred to simply as a receiver ) intercepts the radio waves from the air or space (using its own antenna) and converts the radio waves back into the information people need. A receiver does not “use” radio waves; in fact, many receivers can “listen” to radio waves generated by a single transmitter.
For two-way communication (two-way radio communication), there must be a transmitter and a receiver at each location. Sometimes the transmitter and receiver are combined into a single unit, which can then be called a transceiver. The modern cell phone is an example of a transceiver.
In the early days, before the word ” radio” was commonplace, the most important use was to be able to send telegraphic messages over long distances without having to use wires to connect the places that wanted to communicate. This was very important for ships at sea that could not be connected by wires to land. Once out of sight of a ship in distress, it could no longer call for help. Thus, one of the earliest forms of radio was actually called wireless telegraphy . It wasn’t long before it was shortened simply to wireless communication . the movie Titanicdal is a pretty accurate depiction of how wireless communication was used by ships in distress. In fact, in this movie, even the Morse code you hear is authentic. It correctly sends the actual message that the Titanic’s communications operator relayed as a call for help.
Pretty soon people began to think how nice it would be if a fairly new invention called the telephone could be made to work without wires. Soon scientists and engineers invented the radio telephone. They quickly realized that more than one person could listen at the same time, and broadcasting began . Soon after that, advertising was invented , and modern civilization has changed since then.
About the same time another inventor figured out how to press the letters on a typewriter in one place, convert the identity of the keys pressed into radio waves and make another typewriter far away print the same letters. The radio teletype was born . I bet you can see what happens next.
It would be great if moving images could be transmitted through the air so that lots of people could watch the same movie at the same time without even leaving the house. Well, say hello to television , just another form of radio. We’ve come full circle now, and most of us get our TV pictures over the wire (cable), rather than ripping them off the airwaves with an antenna like in the “good old days. But how many of you have seen a television dish to receive television signals from satellites. A dish is just an antenna to which a special kind of radio receiver is connected, recreating picture and sound.