Plain-language answer: Surface-wave propagation is the ground-hugging component that follows Earth’s curvature through interaction with the surface.
Why it changes the path
It attenuates with frequency and poor conductivity, so salt water can support it far better than dry rocky ground.
What to observe
Use vertical polarization, record frequency and ground type, and distinguish the path from skywave or elevated direct coverage.
The common mistake
Expecting HF surface-wave range to ignore terrain and conductivity.
Planning boundary
Propagation models and field regions depend on frequency, geometry, terrain, atmosphere, polarization, antenna pattern, and measurement distance. Use them to plan and compare—not to guarantee a contact or installed range.
