A Radio beacon is non-direction transmitter that usually transmits a constant signal on a specified radio frequency.

Before the days of VOR, GPS, LORAN. Beacons were used with direction finding equipment to find ones relative bearing to a known location (the beacon).

There are several different kinds of beacons. In aviation there is a beacon called NDB or Non-directional Beacon. These are used to help find airports and conduct instrument approaches. These beacons will be decommissioned over the next few years as they have been replaced with newer better technologies. There also in the past were marine beacons for use at sea, but most cases these no longer are in service. There are also HAM radio beacons that are used to test propagation of radio signals. Any AM, VHF, or UHF radio station can also be used as a beacon with Direction_finding equipment.