Why does my SWR change when I increase power output?

SWR (Standing Wave Ratio) is primarily a function of the antenna system, not the radio itself. However, increasing power can reveal problems in that system that weren’t as obvious before. Here’s what’s happening:

• SWR is based on how well your antenna system is matched, including the antenna, coax, mount, and especially the ground plane.
• When you increase power, you’re sending more energy into that same system.
• If something isn’t ideal (poor ground, bad coax, weak mount, etc.), that extra energy has a harder time being properly radiated.
• Instead, more of it gets reflected back — which shows up as a higher SWR reading.

Simple way to think about it:

Increasing power doesn’t cause high SWR — it exposes existing flaws in the antenna system.

Bottom line:

If SWR changes when power increases, it’s a strong sign that something in the antenna system (usually grounding) needs improvement — not that the radio is the problem.