HAM Radio 101

What is a Smith Chart?

Look through the 2019 DX Engineering Fall/Winter Catalog and you’ll run across a handful of Smith Charts—a graphic display of how RF parameters behave at certain frequencies. Invented by Phillip H. Smith (1905-1987), the chart is used as a problem-solving tool to assist Hams in calculating the feed-point impedance of an antenna. It can also be employed to help build accurate impedance-matching systems along with other functions. A description of the Smith Chart was first published in 1939. Today’s impedance measuring equipment and RF circuit analysis software commonly come with a Smith Chart display option. Here is an instructive article from the ARRL Antenna Handbook about how to use the Smith Chart.

Antenna analyzers, such as those from RigExpert, enable you to connect to a PC to plot Smith Charts. DX Engineering also carries Michael Toia, K3MT’s book, “You, Coax, and Smith,” which contains instructions on how to draw a Smith Chart, what it means, and how to use it.

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