Bird® offers a wide selection of portable insertion-type instruments for measuring forward and reflected power in coaxial transmission lines. Thruline® instruments can be left in the line for continuous monitoring of either the transmitter power output or the amount reflected by the antenna.

​

These two quantities are actually the most important transmission parameters: Tuning for the minimum reflected power results in a good match of the load (antenna) to the line, and adjusting the transmitter for maximum forward power into a matched antenna approaches ideal design goals, These optimum system adjustments result in a low Voltage Standing Wave Ratio.