In addition to serving as stand-alone primary instrument approaches at airports, NDBs are also used as Locator Outer Markers (LOM) for Instrument landing Systems (ILS). Because of this, NDBs are the most widely used navaid in the world. NDBs are highly reliable, typically provide decades of uninterrupted service, and are extremely low cost to install and operate. Range depends on a number of factors such as output power, antenna, ground conductivity, frequency, site conditions, latitude, and the condition of the ADF receiver. Higher power systems from 500 to 1000 Watts are used for longer range applications. Typically NDBs have output power from 25 to 125 watts for reception up to approx. The main components of an NDB ground station are the Beacon transmitter, Antenna Tuning Unit and Antenna. In North America, the frequency range is typically from 190 to 625 kHz, for offshore operations in the North Sea 500 to 1250 kHz and for offshore Brazil, 1500 to 1800 kHz is used. NDB’s used for aviation are standardized by ICAO, the International Civil Aviation Organization, Annex 10 which specifies that NDB be operated on a frequency between 190 to 1800 kHz. An audible Morse Code call sign of one or more letters or numbers is used to identify the NDB being received. The signal is transmitted on an uninterrupted 24/7 basis. To navigate using the ADF, the pilot enters the frequency of the NDB and the compass card (or arrow) on the ADF will indicate the heading to the station. The pilot uses the ADF to determine the direction to the NDB relative to the aircraft. The NDB transmits an omni-directional signal that is received by the ADF or Automatic Direction Finder, a standard instrument onboard aircraft. An NDB or Non-Directional Beacon is a ground-based, low frequency radio transmitter used as an instrument approach for airports and offshore platforms.
0 Comments
Leave a Reply. |