Home Table of Contents

7.6.2 Radio Navigation Aids


Back Next

Frequency and Range

A Non Directional Beacon (NDB) sends out a signal in all directions to help aircraft navigate. It is a medium range navigational aid using frequencies from 200 kHz to 400 kHz with a few operating up to 1700 kHz. This frequency range is within the LF (low frequency) and MF (medium frequency) bands, although the NDB is primary described as a MF aid.

They provide short distance surface wave signal propagation over ranges of 200nm or less. There are a few higher powered non directional beacons at large airports that range up to 500nm. Low powered non directional beacons are often used by aircraft on their final approach to an airport. These are known as locators and have a small coverage range around 30nm. The majority of non directional beacons are connected with a second standby system should the primary beacon stop working.

A NDBs location, frequency, range and ident code is published in a number of publications; Enroute Supplement Australia (ERSA), Visual Terminal Chart (VTC) and Enroute Low Chart (ERC).


Above is a part extract from an ERSA for Sydney airport, we see:

  • The ident - GLF (GLENFIELD)
  • The frequency - 317 kHz
  • The Latitude and Longitude for the NDB location - S33 59.2 E150 58.6
  • The range over land by day 75 nm and 50 nm at night. The range over water by day 200 nm and 110 nm at night - (*1) Range 75 (HN 50) OW 200 (HN 110)

Distance Measuring Equipment

  1. The DME system uses the channels designated in ICAO Annex 10 for operation with the VOR FREQ selected for the same AD. This 'pairing of the VOR and the DME thus permits airborne equipment suitably designed, to display both DME and VOR INFO by the selection of only the VOR FREQ.
  2. TACAN has also been installed at a number of MIL and joint user AD and the DME element of these instillations is AVBL to civil ACFT equipped with 1000 DME. This element will normally be paired with VOR where both faculties are establisher at a joint user AD/WI the ICAO Annex 10 collocation DIST RQMNTS.
  3. The amiability of associated VOR and DME INFO is shown in ERSA, ERC, AC and on FLIP Terminal charts in one of the FLW forms.
    • VOR/DME 112.7
    • VOR 113.7
    • DME 112.7/74X
    • TACAN 84

Bearings, Distance and Hours or Aids

Bearings and distance given is from the aid to the ARP, (shown DEG MAG and NM) unless noted that the bearing and distance is to the appropriate RWY THR. Navigation aids HR of OPS H24 unless otherwise shown.

ERC Low 2

VTC Sydney