What is a characteristic of HF scatter?

Scatter propagation happens when radio waves bounce off small, irregular patches of ionization in the ionosphere, rather than reflecting cleanly off a uniform, solid layer. Because these patches are scattered, parts of the radio signal take slightly different paths and take different amounts of time to reach the receiving antenna. These multiple signal paths arrive in and out of phase, causing rapid fading and phase distortion at the receiver. As a result, HF scatter signals have a very distinct, distorted "fluttering" sound, making them significantly less intelligible than cleanly refracted skywave signals.