VHF Direction Finder (VDF) Service

VDF equipment is available at selected airports across Canada. The purpose of the VDF is to provide navigation assistance to VFR aircraft. This equipment is not intended as a substitute for normal VFR navigation, but rather as an aid in times of difficulty.

VDF information is electronically derived from radio signals transmitted from the aircraft. Since VHF transmissions are restricted to line-of-sight, the altitude and location of the aircraft may limit the provision of the service. Information may be obtained from either a modulated signal (speech transmission) or an unmodulated signal (microphone button pressed – no speech). The length of the transmission is not critical since information can be obtained from a very short transmission (2 seconds).

VDF navigation assistance is provided when requested by the pilot or when suggested by the VDF operator (either an airport controller or a flight service specialist) and accepted by the pilot. The VDF operator will provide the pilot with heading and bearing information relevant to the VDF site. Pilots planning to use the direction indicator as a heading reference during VDF navigation assistance should reset the direction indicator to the magnetic compass before requesting VDF navigation assistance. Thereafter, the direction indicator should not be reset without advising the VDF operator.

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