The Smith Chart

is a sophisticated graphic tool for solving transmission line problems. One of the simpler ap-plications is to determine the feed-point impedance of an antenna, based on an impedance measurement at the input of a random length of transmission line. By using the Smith Chart, the impedance measurement can be made with the antenna in place atop a tower or mast, and there is no need to cut the line to an exact multiple of half wavelengths. The Smith Chart may be used for other purposes, too, such as the design of impedance-matching networks. These matching networks can take on any of several forms, such as L and pi networks, a stub matching system, a series-section match, and more. With a knowledge of the Smith Chart, the amateur can eliminate much “cut and try ” work. Named after its inventor, Phillip H. Smith, the Smith Chart was originally described in Electronics for Januar