NDB Polar Diagram RNAV

The NDBNDB —Non-Directional Beacon, which is the ground element of the NDBNDB —Non-Directional Beacon/ADFADF —Automatic Direction Finder setup, is a very simple dipole aerial that transmits equally in all directions, and is therefore circular.

The work to determine the signal direction is done by the ADFADF —Automatic Direction Finder equipment in the aircraft. Do not get this answer confused with the ADFADF —Automatic Direction Finder (which has a cardioid diagram) or the VORVOR —VHF Omnidirectional Range (which is a limacon.)