Radio As a Media

Radio waves are a type of electromagnetic radiation (also referred to as E-M radiation or EMR) which takes the form of self-mobilizing waves in matter) with wavelengths in the electromagnetic spectrum (the range of all possible frequencies of electromagnetic radiation). These wavelengths are longer than infrared light and invisible to the human eye. They help transmit information, conversations, music, and images through the air. Astronomical objects or lightning naturally cause the creation of radio waves. However artificially produced radio waves are help the stationary and travelling modes f radio broadcasting, communication, and other navigation systems, and other applications.

Today we frequently use radio waves. The transmitting and receiving of waves as that occurs as we take part in the thousands of ways and technologies in everyday life, ultimately help us to communicate with each other.
Listed below are a few familiar things that depend on radio waves:
AM and FM radio broadcasts
Cordless phones

Radio-controlled toys
Microwaves
Garage door openers
Wireless networks
Mobile phones
GPS receivers and navigation satellites
(Satellite communications)
Wireless clocks
Television broadcasts
Police radios
Baby Monitors

Radio's prehistory and Timeline

1820: Hans Christian Orsted discovered the relationship between electricity and magnetism in a very simple experiment. He demonstrated that a wire carrying a current was able to deflect a magnetized compass needle.
1831: Michael Faraday began a series of experiments in which he discovered electromagnetic induction. The relation was mathematically modelled by Faraday's law, which subsequently became one of the four Maxwell equations. Faraday proposed that electromagnetic forces extended into the empty space around the conductor, but did not complete his work involving that proposal.
1861 1865: James Clerk Maxwell made experiments with electromagnetic waves.
July 30, 1872: Mahlon Loomis was issued U.S. Patent 129,971.
1873: Maxwell, as a result of experiments, first described the theoretical basis of the propagation of electromagnetic waves in his paper to the Royal Society A Dynamical Theory of the Electromagnetic Field.
28 November 1875: Thomas Edison announced to the press that while experimenting with the telegraph, he had noted a phenomenon that he termed "etheric force". He abandoned this research when Elihu Thomson, among others, ridiculed the idea.
1878: David E. Hughes was the first to transmit and receive radio waves when he noticed that his induction balance caused noise in the receiver of his homemade telephone.
1880: David Hughes demonstrated his discovery to the Royal Society, but was told it was merely induction.
1884: Temistocle Calzecchi-Onesti at Fermo in Italy invented a tube filled with iron filings, called a coherer.
1884 to 1886: Edouard Branly of France produced an improved version of the coherer.
1885: Edison took out a patent on a system of radio communication between ships, which he then sold to Guglielmo Marconi.
1887 erimental setup of Hertz's apparatus.
1886 to 1888: Heinrich Rudolf Hertz validated Maxwell's theory through experiment. He demonstrated that radio radiation had all the properties of waves (now called Hertzian waves), and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.
1885 to1892: Murray, Kentucky farmer Nathan Stubblefield apparently invented radio, but his devices seem to have worked by induction transmission rather than radio transmission.
1893 to 1894 a Brazilian priest and scientist Roberto Landell de Moura, began his experiments by this year, then came to the UK in 1896 and performed illustrations in London at the General Post Office Building of how his pieces work. He did not publicize his achievement until 1900.
After the opening of the world’s first radio factory in Chelmsford in1898, and the discovery that transmissions could be made over water. Radio just carried on developing until December 1898, saw communication installed up between Queen Victoria’s Royal yacht, off Cowes and Osborne House, where she got regular updates via radio waves.

Marconi made further progress with wireless transmission - a wireless can be tuned to a specific frequency, to remove all other transmissions except the desired one. On 26th April 1900 this idea was patented under the name of ‘Tuned Syntonic Telegraphy’ demand for his product increased, and with it, the number of lives being saved at sea. A famous example is the famous sinking of Titanic - Marconi wireless signalled from the ship, brought help and save a huge amount of passengers.

Not only do the contemporary kind look physically different, the in size and component that form its construction (as demonstrated by the image of a currently high-end transmitter and receiver, Transmitters back in the 19th century could go no higher that 10watts output power and the receivers were mostly crystal sets; extremely insensitive and unselective. A lengthy aerial was needed to work properly and they were connected to a pair of headphones – talk about old school!

Below, An early Marconi transmitter

All radios today, use continuous sine waves to transmit audio, video and data. We use continuous sine waves today because there are so many different people and devices that want to use radio waves at the same time. If you had some way to see them, you would find that there are many varying radio waves (as sine waves) around us.

Radio signal use different sine wave frequencies which some as two parts:
· The transmitter
· The receiver
The transmitter takes some sort of message (it could be the sound of someone's voice, pictures for a TV set, data for a radio modem or whatever), encodes it onto a sine wave and transmits it with radio waves. The receiver receives the radio waves and decodes the message from the sine wave it receives. Both the transmitter and receiver use antennas to radiate and capture the radio signal. Real life examples include a mobile phone.
A typical mobile phone contains both a transmitter and a receiver, and both operate simultaneously on different frequencies. A cell phone communicates with a cell phone tower and can transmit 2 or 3 miles (3-5 km).

To create a simple radio transmitter, what you want to do is create a rapidly changing electric current in a wire. You can do that by rapidly connecting and disconnecting a battery, like this:
When you connect the battery, the voltage in the wire is 1.5 volts, and when you disconnect it, the voltage is zero volts. By connecting and disconnecting a battery quickly, you create a square wave that fluctuates between 0 and 1.5 volts.

A better way is to create a continuously varying electric current in a wire. The simplest (and smoothest) form of a continuously varying wave is a sine wave like the one shown below:

A sine wave fluctuates smoothly between, for example,10 volts and -10 volts.