Domanda 122, Comunicazioni in inglese - PPL(A) - Licenza Pilota Privato (Aerei)

The waves are reflected at the ionosphere at the height of about 100 km and reach the earth surface in the form of sky-waves
The waves travel along the surface of the earth and penetrate into valleys in a way that topographical obstacles have no influence
Similar to short waves with practically no atmospheric disturbance
Practically straight-line similar to light waves