Yagi antenna

A Yagi-Uda antenna. From left to beam right, the elements mounted on the boom are called the reflector, driven element, and director. The reflector is easily identified as being a bit (5%) longer than the driven element, and the director a bit (5%) shorter.

A Yagi-Uda Antenna, commonly known simply as a Yagi antenna or Yagi, is a directional antenna system^[1] consisting of an array of a dipole and additional closely coupled parasitic elements (usually a reflector and one or more directors). The dipole in the array is driven, and another element, 10% longer, operates as a reflector. Other shorter parasitic elements are typically added in front of the dipole as directors. This arrangement gives the antenna directionality that a single dipole lacks. Yagis are directional along the axis perpendicular to the dipole in the plane of the elements, from the reflector through the driven element and out via the director(s). If one holds out one's arms to form a dipole and has the reflector behind oneself, one would receive signals with maximum gain from in front of oneself.

Directional antennas, such as the Yagi-Uda, are also commonly referred to as beam antennas^[2] or high-gain antennas (particularly for transmitting).