High Quality Content by WIKIPEDIA articles! A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antenna consisting of a driven element (typically a dipole or folded dipole) and additional parasitic elements (usually a so-called reflector and one or more directors). The reflector element is slightly longer (typically 5% longer) than the driven dipole, whereas the so-called directors are a little bit shorter. This design achieves a very substantial increase in the antenna`s directionality and gain compared to a simple dipole.