Unguided Media (Wireless)
=> Wireless Transmission media is used when mobility is required for example in mobile phone, data cards connected to personal computer for accessing internet. Wireless Transmission can also be used for fixed devices, in some circumstances where running a wired transmission is difficult due to geographical constraints.
When electrons move their created electro-magnetic waves that can propagate through different transmission media. Example of electro-magnetic waves are Radio waves, micro waves, infrared waves, visible light, ultra visible light, X-ray, gamma rays.
When antenna appropriate size is attached to an electrical circuit, the electro-magnetic waves can be broadcasted efficient and received by a receiver some distance away.
The radio waves, micro waves, infrared waves, visible light, X-ray and gamma rays are not visible and used for transmitting data. Because they are hard to produce and dangerous to living thing.
There are two parts of unguided media
RADIO WAVES
• Radio waves are easy to generate due to their low frequency, the can travel long distance and high penetrating power. They can penetrate building and other rigid things easily. There are widely used for both indoor and outdoor communication, radio waves are multi-directional. They travel in all directions from the source hence transmitter and receiver do not have to be carefully aligned physically.
• At low frequency , radio waves, pass through ovstical very easily but high frequency radio waves travel in strate line and bounce of ovstical in very low frequency(VLF), low frequency(LF), and medium frequency bands follows the ground (earth curvature).
• Radio waves in this band can pass through building very easily in high frequency (HF) and very high frequency (VHF), bands the radio waves tend to be absorbed by the earth surface and the waves that reach the ionosphere are reflected by it and send that back earth.
INFRARED WAVES
• Infrared waves are widely use for short range communication. They are relatively directional cheap and easy to build but major disadvantages is that they do not pass through solid objects (building, walls etc). It means that an infrared system in one room of a building will not interface with similar system in adjustancent room or building. The security of infrared is better therefore no government license is needed to operate an infrared system. e.g. The remote controls used on T.V and V.C.R etc
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