He used a thermocouple bridge and voltmeter to make the measurements.

Smith developed the first graphical solution in the form of a rectangular plot from his measurements of the maxima and minima voltages along the transmission line. Phillip Smith - Inventor of the Smith Chart. He relished the problem of matching the transmission line to the antenna a component he considered matched the line to space. Although Smith did a great deal of work with antennas, his expertise and passion focused on transmission lines. In 1928, he joined Bell Labs, where he became involved in the design of antennas for commercial AM broadcasting. Smith attended Tufts College and was an active amateur radio operator with the callsign 1ANB. The Smith Chart was invented by Phillip Smith, who was born in Lexington, MA on April 29, 1905. After reading this, you will have a better understanding of impedance matching and VSWR - common parameters in a radio station. The purpose of this article is to introduce you to the basics of the Smith Chart. The Smith Chart is one of the most useful tools in radio communications, but it is often misunderstood.