1. RADIO NAVIGATION

2. The Exam! Time: 1hr 30min 59 questions Day 3, i.e. Wednesday, 11:15
75% pass mark

3. DIRECTION FINDING
General Principles

4. VHF Direction Finding (VDF)
Service available to aircraft using VHF A/G Comms
Frequency range = MHz
Uses line-of-sight transmission from the aircraft to the ground station

5. DF - General Principles
Radio waves travel along great circle routes

6. 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

7. LOOP ANTENNA
NULL
Maximum
Signal Strength
Maximum
Signal Strength
NULL

8. Adcock VDF Aerial

9. Doppler Direction Finder

10. Ground Station

11. VDF CRT Display

12. Magnetic bearing to the station True bearing from the station
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

13. Classification of Bearings
Class A
Class B
Class C
Class D
± 2º
± 5º
± 10º
accuracy less than Class C

14. 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

15. VDF Approach = Pilot interpreted procedure
QGH procedure = Controller interpreted

16. Range & Errors VHF propagation = Line of Sight Terrain
Approximate MTR = FL x 12
Terrain
Atmospheric Refraction:
Super-refraction
Sub-refraction
Transmitter Power
Multi-path reflections

17. Synchronous Transmissions
Vector addition of signals

18. Range & Errors Adverse polarisation:
Ground transmissions are vertically polarised
Best results obtained when aircraft is flying straight and level

19. 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

20. Questions Is a QGH procedure pilot or 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