A simplified concept of the ground beacon is that it simultaneously transmits two signals, a constant omni-directional signal called the reference phase and a directional signal which rotates through 360°, during a 0.03 second system cycle, and consistently varies in phase through each rotation. The two signals are only exactly in phase once during each rotation – when the directional signal is aligned to magnetic north.
Imagine a wheel with 360 spokes, at one degree azimuth spacing, with the VOR beacon being the hub. The spokes are numbered clockwise from one to 360 and each spoke or radial represents a magnetic bearing from the VOR beacon. The airborne navigation circuitry measures the phase angle difference between the directional signal phase received and the reference signal phase and interprets that as the angular, or 'radial', indication currently being received. Radials are identified by magnetic bearing – e.g. the 30° radial – and thus form the basis for VOR, and designated air route, navigation. Essentially the system indicates a line of position, from the selected VOR, on which the aircraft is located at any time.
The beacon also transmits a Morse code aural identification signal at about 10 second intervals.
The airborne system utilising the VOR beacon transmissions usually consists of an antenna (probably a V - type dipole mounted horizontally on the fin or fuselage but could be the more expensive 'blade' or 'towel rail' types), a conventional VHF receiver (if combined with the VHF communications transceiver it is then called a NAV / COMM unit), navigation circuitry and the separate panel mounted navigation indicator or 'Omni Bearing Indicator' [OBI].
Some hand held aviation COMMS transceivers can also receive the NAV band VOR transmissions and appear to have some navigation circuitry but, from all reports, their VOR navigation capability, if it exists at all, is limited