Plain-language answer: Flat fading changes the whole occupied signal bandwidth by roughly the same amount when the channel response is nearly uniform across it.
Why it changes the path
The signal becomes stronger or weaker without major frequency-selective distortion, though noise and decoding margin still change.
What to observe
Watch the entire passband or multiple tones and compare position, polarization, and time.
The common mistake
Calling every fade flat without checking the signal spectrum.
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.
