Wireless Transmission and Microwaves.

Microwaves use line of sight propagation. Microwaves frequency ranges from 1 to 300 GHz. Microwaves are used in cellular phones, satellite networks and wireless LANs. Microwaves are unidirectional. It is useful in unicasting i.e. one to one communication. To travel longer distances, the antennas must be taller. There should not be any obstacle in between. Usually mountain tops are the preferred positions for the antennas to avoid obstacles. Microwave can travel for one direction at a time. Fro two way communication two frequencies need to be allocated. At both ends a transceiver for operating two different frequencies. Repeaters are used along with antennas to generate the signal. Microwave is inexpensive and it allows you to communicate from anywhere.
Microwave is commonly used for both voice and television transmission.
There are two types of  antennas used for microwave communications, 
1. The parabolic dish and 
2. The horn.
The Parabolic dish is 3m in diameter and its shape is like a parabola. It focuses a narrow beam to achieve line of sight transmission. The parabolic dish acts a funnel, catching wide range of waves and directing to a common point.

In horn antenna, the outgoing transmission is broadcast up a stem and deflected outward in series of narrow parallel beams by the curved head. The scooped shape of the horn collects the received transmissions and deflected down into the stem.

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