Model SWB-3 is SWR & POWER Meter with Directional Coupler installed and its character is to measure the wide frequency range precisely by very easy operation. For SWR measurement, it uses Directional Coupler, comparing the power supplied to and reflected from Antenna and the independent SWR meter indicates the measurement. For power measurement, the power meter indicates the travelling wave power detected by Directional Coupler and its frequency range is determined by the figure of Variable Resistor which is for sensitivity adjustment, Model SWB-3 is a through line power meter in its construction, so RF amount is not directly detected from co-ax line. Accordingly, there is very little loss connecting it between Transmitter and Antenna circuit and QSO is available as it is connected.