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7.6.1 Radio Navigation Aids


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Identify NDB and VOR


Most station NDBs use a modulated carrier wave with an aural identification (a Morse code ident) superimposed over the carrier, broadcasting at roughly ten second intervals to help the pilot identify the correct NDB station is been use for navigation. Some lager airports have the option to broadcast over the carrier voice modulation to pilots allowing them to receive information in flight.

A commercial broadcast stations signal that is use by the public for entertainment can also be used as an NDB, but a word of warning, they are untrustworthy; difficult to identify, unreliable time periods, unknown reliable range coverage and prone to power failure. Often they are networked form another area and listening to them can distract pilots form their responsibilities.

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)

ERC Low 2

VTC Sydney