On the Smith chart shown in Figure E9-3, what is the only straight line shown?

Although the Smith chart is famous for its intricate grid of overlapping circles and arcs, there is only one completely straight line on the entire graph. This straight line runs horizontally straight through the center. This horizontal line is called the resistance axis. Any point plotted exactly on this line has a reactance of zero, meaning it represents a purely resistive impedance. The values on this line start at zero resistance (a dead short) on the far left edge and increase as you move right, approaching infinite resistance (an open circuit) at the far right edge. Because all other lines represent changing reactance or resistance in complex combinations, they curve to fit within the chart's boundaries.