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RADIO NAVIGATION. The Exam!. Time: 1hr 30min 59 questions Day 3, i.e. Wednesday, 11:15. 75% pass mark. DIRECTION FINDING. General Principles. VHF Direction Finding (VDF). Service available to aircraft using VHF A/G Comms Frequency range = 118.00 - 137.00 MHz

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Presentation Transcript

The exam
The Exam!

  • Time: 1hr 30min

  • 59 questions

  • Day 3, i.e. Wednesday, 11:15

  • 75% pass mark


Direction finding

DIRECTION FINDING

General Principles


Vhf direction finding vdf
VHF Direction Finding (VDF)

  • Service available to aircraft using VHF A/G Comms

  • Frequency range = 118.00 - 137.00 MHz

  • Uses line-of-sight transmission from the aircraft to the ground station


Df general principles
DF - General Principles

  • Radio waves travel along great circle routes


Df general principles1
DF - General Principles

  • An aerial used to detect the direction of a radio wave is known as a loop antenna

  • With an AM transmission, the antenna is energised by the Carrier Wave portion of the signal

  • The polar diagram for a loop antenna is a figure of eight


LOOP ANTENNA

NULL

Maximum

Signal Strength

Maximum

Signal Strength

NULL






Types of Bearings

Red = Magnetic

Blue = True

QDR

QTE

QDM

QUJ

  • QDM

  • QTE

  • QDR

  • QUJ

  • Magnetic bearing to the station

  • True bearing from the station

  • Magnetic bearing from the station

  • True bearing to the station


Classification of bearings

Class A

Class B

Class C

Class D

± 2º

± 5º

± 10º

accuracy less than Class C

Classification of Bearings


Example of r t phraseology
Example of R/T Phraseology

  • “Walden Homer G-ABCD Request QDM G-ABCD”

  • “G-ABCD Walden Homer QDM 245 degrees, Class Bravo”

  • “245 degrees, Class Bravo, G-ABCD”

Refer to Communications notes


Vdf approach
VDF Approach

= Pilot interpreted procedure

QGH procedure = Controller interpreted


Range errors
Range & Errors

  • VHF propagation = Line of Sight

    • Approximate MTR = FLx 12

  • Terrain

  • Atmospheric Refraction:

    • Super-refraction

    • Sub-refraction

  • Transmitter Power

  • Multi-path reflections


  • Synchronous transmissions
    Synchronous Transmissions

    Vector addition of signals


    Range errors1
    Range & Errors

    • Adverse polarisation:

    • Ground transmissions are vertically polarised

    • Best results obtained when aircraft is flying straight and level


    Questions
    Questions

    • In which frequency range is VHF DF available?

    • 118 – 137 MHz

    • What part of the aircraft transmission does the ground equipment respond to?

    • The carrier wave

    • What is the accuracy of a Class A bearing?

    • ± 2º


    Questions1
    Questions

    • Is a QGH procedure pilot or controller interpreted?

    • Controller interpreted

    • A true bearing to the aircraft from the station is a Q..?

    • QTE

    • A magnetic bearing to the aircraft from the station is a Q..?

    • QDR


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