Most wireless projects do not fail because RF theory was misunderstood. They fail because a small assumption slipped through late in the build. A connector that looked right, a cable that threaded on smoothly, an extension added after the enclosure layout was already finalized—this is where RP-SMA vs SMA quietly causes trouble. On the surface, the two interfaces appear interchangeable. In practice, they are not. The difference rarely shows up as an obvious fault. Instead, it appears later, when 5 GHz throughput becomes inconsistent, when 6 GHz links lose margin first, or when field returns start coming back with the note “fits but doesn’t work.” This article focuses on practical identification and matching logic rather than formal definitions, with a simple goal: identify the port in seconds, match both ends once, and place orders without rework.