RF Field Guide · reviewed reference
Real-world path-loss estimation
Free-space loss is a transparent baseline; a deployable prediction adds the environmental effects that the baseline deliberately excludes.
Question
What belongs in a real path-loss estimate?
Inputs
- Distance and frequency
- Terrain and curvature
- Clutter, diffraction, atmospheric conditions, and availability target
Answer
Working
FSPL(dB) = 92.45 + 20 log10(distance km) + 20 log10(frequency GHz). Terrain obstruction, diffraction, foliage, gaseous loss, rain, and reflections are separate terms; they must not be silently folded into an unexplained ‘extra loss’ number.
Visual explanation
- Free-space baseline
- Terrain / diffraction
- Clutter
- Atmosphere
- Rain
- Uncertainty margin
Interpretation
A documented model is more useful than a precise-looking undocumented number. Keep the inputs and model revision so a path can be re-evaluated when site facts change.