The DDS-1 dual directional coupler measures forward and reflected power of a device in a 50 ohm environment. It is more precise than a simple SWR meter since the reflected and forward power may be observed directly on an oscilloscope.
The RF IN port connects to the HF signal source. This source is normally the transmitter and or linear HF amplifier. The RF OUT connects to a 50 ohm load. This load can be a transmission line, antenna, or a dummy load. When the load completely absorbs the energy from the signal source, little if any power is reflected, thus, the signal output from the REFLECTED port is very low. The signal out of the FWD port indicates the amount of power (– 30 dB) going to the load.