NON DIRECTIONAL BEACON (NDB)

It is a ground based station that emits vertically polarized Low Frequency (LF) and Medium Frequency (MF) signals in all the directions for aiding the aircraft in the range in its navigation towards its destination.

In Aviation charts, it is represented by a single dot surrounded by 3 dotted circles

Transmitter: Non-Directional Beacon (NDB)

Receiver: Automatic Direction Finder (ADF)

CHARACTERISTICS

1. Antenna shape: Large T shaped

2. Antenna type: Omnidirectional Antenna

3. Wave type: Ground Wave

4. Frequency: 190- 1750 kHz

   • Restricted International frequencies:

     1. 255-285 KHz

     2. 315-405 KHz

5. Channel spacing: 0.5 KHz

6. Range: Long Range (500 miles) & Local Navigation (25 miles)

   • To double the range, Quadruple the Power

   • i.e. 2x Range = 4x Power

7. Modulation

   • N0N A1A: High Power & Long Range

   • N0N A2A: Low Power & Short Range

N0N refers to the continuous carrier wave that enables the ADF equipment to establish the direction of the signal

A1A refers to the interrupted carrier wave that continuously replaces the N0N transmission and carries the 3 letter morse code identifier of the NDB

A2A refers to the carrier wave that carries the NDB identifier, which is a keyed single toned amplitude modulated