VHF omnidirectional range
VOR, short for VHF omnidirectional radio range, is a type of radio navigation system for aircraft, enabling them to find their position and stay on course by receiving radio signals emitted by a network of radio beacons. It uses frequencies in very high frequency (VHF) from 108 to 117.95 MHz. Developed in the USA in 1937, VOR is the standard air navigational system in the world, used by both commercial and general aviation. There are about 3000 VOR stations around the world.
A VOR station broadcasts a VHF radio signal including the identifier, voice, and navigation signal. The identifier is in Morse Code. The voice will have information from the station. The navigation signal allows the equipment to find a magnetic bearing from the station to the aircraft. VOR stations in areas of magnetic unreliability are oriented to True North. A line of position is called the "radial" from the VOR. The crossing of two radials from different VOR stations provides the position of the aircraft. VOR signals have a range of about 200 miles.