Also called a beam antenna and parasitic array, the Yagi is very widely used as a high-gain antenna on the HF, VHF and UHF bands. It has moderate to high gain depending on the number of elements present, sometimes reaching as high as 20 dBi, in a unidirectional beam pattern. As an end-fire array, it can achieve a front-to-back ratio of up to 20 dB. It retains the polarization common to its elements, usually linear polarization (its elements being half-wave dipoles). It is relatively lightweight, inexpensive and simple to construct. The bandwidth of a Yagi antenna, the frequency range over which it maintains its gain and feedpoint impedance, is narrow, just a few percent of the center frequency, decreasing for models with higher gain, making it ideal for fixed-frequency applications. The largest and best-known use is as rooftop terrestrial television antennas, but it is also used for point-to-point fixed communication links, in radar antennas, and for long distance shortwave communication by shortwave broadcasting stations and radio amateurs.