The communication device and navigation satellite can work without the radio wave. It's also the case in the navigation field. The aircraft can work based on various different radio systems. The popular radio network also makes use of the radio. It indicates that we will enjoy a more convenient future life.
It's interesting that the core technology – radio is an unbelievably simple technology. Some electronic components are enough to creat the simple radio transmitter and receiver. Why such a simple thing can become the world technical foundation stone?
It's an interesting thing to explore it. The radio is unbelievablely simple. Take a new 9V battery, a coin and a muting AM radio first. Then approach the antena with the battery and hit the ends of the battery with the coin strongly. They can be connected at that instant. You can hear the noise from the radio which is produced by the connecting and cut of the coin.
The receivable radio is produced by hitting the ends of the battery with a coin. It can't transmitt any useful message and long distance can't be realized. But you can take advantage of the primary device to make communications within several centimeters by using the produced Morse code.
However, in the modern society the radio delievers messages (audio, video and data) through the continous sine. The reason why we use the continuous sine is that there are too many people and devices share the radio. If the radio is visible, you will find kinds of different radio around – television broadcast, AM and FM broadcast, fire radio broadcasting, satellite transmitting, mobile talking and GPS signals. Each different radio signal uses each sine wave frequency.
Each radio device constitutes two parts: transmitter and receiver. The transmitter carries some information like the voice, image and data and encodes it to sine wave. The receiver will receive the radio and decode the sine wave message. Both of the transmitter and the receiver transmitt or capture the radio signal through the antena.
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The mobile phone is also a kind of radio receiving device. It's a more complicated device. The cell phone contains both the transmitter and receiver at the same time. The transmitter and receiver can work together. They can recognize hundreds of different frequencies. A typical mobile phone contains transmitter and receiver which can work simutaneously at different frequency.