What type of propagation allows signals to be heard in the transmitting station's skip zone?
Why The skip zone is the dead region between the end of ground wave coverage and the point where the first ionospheric hop returns to Earth, so normal refraction puts no signal there. Scatter propagation, where a small part of the signal is scattered in the ionosphere (or off terrain, aircraft, or meteor trails) in directions other than the main refracted path, spills weak energy back into that gap. Scatter signals are typically weak, distorted, and have a watery or fluttery sound because the energy arrives over multiple slightly different paths.
Watch out Short-path is just the shorter of the two great-circle routes to a distant station and still lands beyond the skip zone; chordal hop describes signals refracting between ionospheric layers without touching the ground, which extends long-distance range rather than filling the skip zone.
Skip zone isn't totally dead: weak, watery, fluttery signals sneak in by scatter.