Plain-language answer: Selective fading changes some frequencies within a signal more than others because multipath components arrive with different delay and phase.
Why it changes the path
It can distort voice or data even when average signal strength remains adequate, especially on wide or multi-tone signals.
What to observe
Compare modes and bandwidths, use receiver equalization or diversity where available, and observe whether distortion moves with frequency.
The common mistake
Treating selective distortion as simple flat signal loss.
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.
