YAGI-UDA Often one needs to improve reception of a particular radio or television station. One effective way to do this is to build a Yagi-Uda, or Yagi, antenna. This is a traveling-wave structure which, as the number of elements increases, has improved directivity, gain, and front-to-back ratio (and additional sidelobes). The basic antenna is composed of one reflector (in the rear), one driven element, and one or more directors (in the direction of transmission/reception). The "zero-order" version of the Yagi has all elements one-half wavelength long and spaced one-quarter wavelength apart. The two designs presented here - a 3-element and a 6-element antenna - have been optimized for improved all-around performance, so their lengths and spacings are non-uniform.