Plain-language answer: A directional coupler samples forward- and reverse-traveling RF energy while allowing most power to continue toward the load.
Why it matters
It is the sensing element behind many wattmeters, SWR meters, and protection systems. Directivity, frequency range, coupling factor, and power rating determine measurement quality.
Use it well
Install it in the marked direction, use the specified frequency and power range, and calibrate the complete measurement chain.
The common mistake
Using a coupler outside its rated band and trusting the displayed SWR.
Authority and safety boundary
Current regulations, electrical codes, equipment manuals, program authorization, and the served organization’s procedures control. This article is practical orientation, not permission to transmit, alter protective wiring, or self-deploy.
