An antenna is an electromagnetic device that collects or emits radio waves. It consists of material that conducts electricity arranged in such a way that it is in tune with the frequency of a radio signal. Like a tuning fork in the presence of a sound of the same pitch, an antenna tuned to a particular frequency will resonate to a radio signal of the same frequency.
Yagi Antenna Example
Yagi is the name of the Japanese man who designed this type of antenna. It is very easy for the amateur to build using materials such as clothes hangers or copper wire used for house wiring.
The Yagi antenna consists of 2 parts:
the antenna elements
the antenna boom
There are three types of elements:
the Reflector (REFL)
the Driven Element (DE)
the Directors (DIR)
http://www.skyscan.ca/Antennas.htm#6 Element Yagi Antenna