=== Yagi ===

* While monopole and dipole are omnidirectional antennas, yagi is a directional antenna. It's made up of only wires and has only one feed (where you apply signal). It has three elements - feed, directors and reflector. All the three elements are attached to a single long rod which is called “boom”. The feed, directors and reflector are perpendicular to the boom and in the same plane. Their order is - reflector then feed then directors. Feed is the element where signal to be transmitted is applied. The feed is typically a dipole or a folded dipole. The feed is made resonant in the presence of other elements. This length is different from the resonant length of isolated antenna. It is mostly calculated using simulations.

* The other two elements are also called parasitic elements as they are not excited by any signal. The directors are used to increase the directivity of the antenna. Increasing the number of directors increases directivity of the antenna. Their length is slightly less than the feed element and progressively decreases when we move further away from feed. The number of directors can be as large as 20-30. The reflector, as the name suggests, seem to reflect radiation thus decreasing its radiation in unwanted direction. Usually only one reflector is used but antennas having more than one reflectors have been designed. They are physically longer than feed element. Its theory of operation is quite interesting, so do give it a [https://en.wikipedia.org/wiki/Yagi%E2%80%93Uda_antenna#Theory_of_operation read].