An antenna is a device that radiates and receives electromagnetic waves.
Helical antenna: It has a conducting wire wound in the form of a helix. They are mounted over ground plane and are used at earth base stations in satellite communication systems.
Yagi antenna: It is an array of parallel, straight antenna elements, one or more driven and one or more parasitic. Yagi, the Japanese antenna expert researched how parasitic elements effects the directional properties of an antenna.
Loop antenna: It receives radio signals more efficiently. The loop is wound on a form, which may be box or spiral wound. The core may be air or powdered iron compound. Its gain is less but it has less noise pick up.
Horn antenna: It has a flaring metal wave guide shaped like a horn to direct radio waves in a beam. These are used at UHF and microwave frequencies above 300 MHx. The maximum radiation is along the axis of the horn.
