VHF navigation signals such as VOR signals generally propagate as quasi-optical waves.

VHF signals generally travel approximately line-of-sight through the atmosphere, a propagation mode described as **quasi-optical**. Their coverage therefore depends strongly on transmitter and receiver altitude and can be limited by terrain or the horizon. This differs from LF/MF propagation, which can include ground-wave and sky-wave components.\n\n**Key takeaway:** VHF range is largely limited by line of sight.\n\n**Glossary:** **Quasi-optical propagation**: direct, approximately line-of-sight radio propagation.