What makes HF scatter signals often sound distorted?
The ionospheric region involved is unstable
Ground waves are absorbing much of the signal
The E region is not present
Energy is scattered into the skip zone through several different paths✓Bonne réponse
Explication
Scatter delivers the same transmission over several routes of slightly different length, so copies arrive at slightly different times and phases and add destructively at some audio frequencies and constructively at others. That frequency-selective multipath is what the ear hears as distortion.