Introduction to the return platform

NDB is the abbreviation of Non-Directional Beacon. It is usually a radio transmitting device placed at a known location for positioning in aviation or navigation. Compared with newer navigation stations such as VOR and TACAN, NDB lacks functions such as ranging. At the same time, NDB is also the oldest navigation device in use today. For VOR, because the radio signals emitted by NDB propagate along the radius of curvature of the earth, the range at low altitude is farther than that of VOR. However, the NDB signal is greatly affected by weather, terrain and other factors. The working frequency band of the NDB navigation station is specified in Annex 10 of the ICAO (International Civil Aviation Organization) specification as: from frequency 190kHz to 1750kHz. Each NDB navigation station has an identification of up to 3 letters.