Radio is the technology of communication and sending information via radiowaves (or microwaves) in the electro-magnetic spectum.
How Radio Works
Radio can store information through the use of
modulation. A
carrier wave is a high-frequency waveform that contains no information and can be modulated by the modulated signal. Think of it as like
a wireless wire. It serves as a medium to transmit information signal over a distance or through a communication frequency. Radio is sent out by a transmitter and received in a receiver. A
transmitter is an
electronic device that produces radiowaves with an antenna while a
receiver receives the radio waves over an antenna as well.
Relevant GIF
In this GIF, the signal goes up and down. In
amplitude modulation (AM), the amplitude is varied (as you can see in the red color). In
frequency modulation (FM), the frequency is varied (as seen in the blue color) while
keeping the same amplitude.
There are also other ways to send information through radiowaves.
Phase modulation (PM) is a modulation that is closely related to FM because phase and frequency are similar. Phase modulation is more relevant in
digital RF unlike FM and AM which is more relevant in analog RF. Both PM and FM radio are a form of
angle modulation in which "angle" is described as a "modification of quantity passed to a sine or cosine".
Compared to FM and AM radio which is mostly used in audio-based transmissions, PM radio is used in satellite telecommunications, GSM, WiFi and other forms of applications that involve digital transmission of information.
PM radio is very relevant in our current world.
How Modulation Works
Radio Waves - All About Circuits
Phase modulation - All About Circuits
Telegraph
The telegraph is one of the first telecommunication network to use radio as its medium. Communication through telegraph is done through Morse Code.
Morse Code
Morse code is still used as one of the official marine, aviation and military mediums of communication.
Morse Code Photo - Liverpool Code Club
Interesting Radio Project