Omni
Omni, as used in aviation, typically refers to a VHF Omnidirectional Range (VOR) station — a ground-based navigation facility that transmits bearing information in all directions (omnidirectionally). The term “omni” is colloquial for VOR among pilots and controllers.
VOR Operation
A VOR transmits two signals simultaneously: a reference phase signal (transmitted equally in all directions) and a variable phase signal (whose phase rotates with the direction of transmission). The airborne VOR receiver compares these phases to determine the magnetic bearing FROM the station — the radial the aircraft is on. The OBS (Omni Bearing Selector) is set to the desired course.