Chièvres

A VOR (VHF Omnidirectional Range) is the workhorse of ground-based navigation. It broadcasts on a VHF frequency (108.0–117.95 MHz) and effectively projects 360 radials outward like spokes of a wheel. The aircraft receiver compares two signal phases to determine which radial you are on, and a course-deviation indicator (CDI) with an omni-bearing selector (OBS) shows the selected course and whether you are flying TO or FROM the station.

VOR is far more precise than an NDB and is immune to night effect and thunderstorm error. Because VHF is line-of-sight, usable range grows with altitude — roughly 40–130 nm depending on how high you are and the station's service volume. VORs define the Victor airways low-altitude route structure and back many instrument approaches. As satellite navigation matures, the network is being thinned to a resilient Minimum Operational Network (MON) that keeps VOR coverage available if GPS is lost.