"Radio waves" transmit music, conversations, picture and data invisibly through the air, often over million of miles --- it happens every day in thousand of different ways! Even though radio waves are invisible and completely infected table to human, they have totally changed society. Whether we are talking about a cell phone, a baby monitor, a cordless phone or any one of the thousands of the other wireless technology, all of them use radio waves to communicate.

Here are just few of the every day technologies that depends upon on the radio waves:

•AM and FM radio boardcast.

•cordless phone.

•Garage door openers.

•police radio ETC....

The simplest radio.

By tapping the terminal of a 9-volt battery with a coin, you can create radio waves that an AM radio can receive.

Example.

•Take a fresh 9-volt battery and a coin.

•Find an AM radio and tune it to an area of the dial where you hear static.

•you will hear a crackle in the radio that is caused by the connection and disconnection of the coin.

Radio basic parts.

There are two radio basic parts of radio waves.

•The transmitter.

•The receiver.

Radio basics: Real Life example.

A baby monitor is about as simple as radio technology gets. There is a transmitter that's sits in the baby room and a receiver that the parents use to listen to the baby. Some important characteristic of a typical baby monitor.

•Modulation: Amplitude Modulation (AM).

•Frequency range: 49 MHz

•Transmitter power: 0.25 watts

A typical baby monitor, with the receiver on the left and the transmitter on the right: The transmitter sits in the baby room and is essentially a mini "radio station". The parents carry the receiver around the house to the listen to the baby. Typical transmission distance is limited to about 200 feet (61m).

Pulse Modulation.

In pm, you simply turn the sine wave on and off. This is an easy way to send Morse code. PM is not that common, but one good.

Example.

The radio system that sends signals to radio controlled clocks in the united State. One PM transmitter is able to cover the entire United States.

Amplitude Modulation.

Both AM and FM radio station and the picture part's of a TV signals use amplitude Modulation to encode information. The amplitude of the sine wave (its peak -to-peak voltage) changes.

Example.

This sine wave produced by a person voice is overload onto the transmitter sine wave to vary it's amplitude.

Frequency Modulation.

FM radio station and hundred of the other wireless technologies (including the sound portion of the TV signals, cordless phone, cell phone and smart phone, etc). Use frequency Modulation.

Example.

FM is that it is largely immune to statics. In FM the transmitter sine wave frequency change very slightly based on the information signals.

Antenna: Real Life example.

It's a transmitting a sine wave with a frequency of 680,000 hertz. In one cycle of the sine wave, the transmitter is going to move electrons in the antenna in one direction, switch and pull them back, switch and push out and switch and move them back again.