1. VOR VHF Omnidirectional Range
With the help of CAAP navaids ANS staffs davao branch

2. WHAT IS VOR?
VOR or VHF Omnidirectional Range is a navigational aid equipment designed to provide bearing information to aircraft.

3. WHAT IS BEARING?
Bearing refers to the direction from a certain place towards another. In VOR application, this refers to the bearing from an airplane to a VOR station.

4. The VOR System

5. ALL DIRECTIONS ASSOCIATED WITH A VOR STATION ARE RELATED TO MAGNETIC NORTH.
These are shown in the figures below:

6. How is the bearing information produced by the VOR ?
This is done by radiating two signals from two sets of antenna, the central or reference antenna and the variable or sideband antennas surrounding the central antenna.

8. The phase of the signal received from the reference or central antenna is the same regardless of aircraft position.
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360°
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° N

9. However, the signal received from the sideband or variable antennas depend on the aircraft’s position.
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° N

10. The aircraft’s VOR receiver then processes these two signals to obtain its angular position with respect to magnetic north.
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360°
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° N

11. Supposed the aircraft is in the east (or 90°) radial.
The phase difference between the two signals would then be:
90 degrees
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° 90
0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° N

12. In practice the aircraft’s VOR receiver has three dials:
one of which can be set manually to any desired course,
the second of which tells whether the plane is to the left or right of the course, and
the third of which resolves 180° ambiguity by indicating either “from” or “to” .

13. Tells whether the airplane is to the LEFT or RIGHT of desired course
Indicates desired course
COURSE
“TO or “FROM” ARROW N 3 6 E 33 S W 24 12 15 21 30

14. VOR Deviation - “Left” Or “Right” Sense (Selected Course 90)

15. VOR “TO” or “FROM” Sense (Selected Course 90)

16. a Selected Course - 000 (N) c b a N N 3 33 30 6 W E 24 12 21 15 S N 3 6 E 33 S W 24 12 15 21 30 b
VOR a
Selected Course - 000 (N)

17. b Selected Course - 000 (N) c b a N N 3 33 6 30 W E 24 12 21 15 S N 3 6 E 33 S W 24 12 15 21 30 b
VOR a
Selected Course - 000 (N)

18. c Selected Course - 000 (N) c b a N N 33 3 6 30 W E 24 12 21 15 S N 3 6 E 33 S W 24 12 15 21 30 b
VOR a
Selected Course - 000 (N)

19. These VOR stations radiate at different frequencies.18 27 9 A
113.9MHz
These VOR stations radiate at different frequencies.
An aircraft may pass through several VOR stations in travelling from one place to another (Point A to B) . 18 27 9
115.1MHz 18 27 9 18 27 9 B
112.7MHz
116.3MHz N

21. Simplified Block Diagram of DVOR SIDEBAND ANTENNAS ( X 48 )
CARRIER ANTENNA
MONITOR ANTENNA 1 2 48
30Hz
OUTDOOR
INDOOR
DISTRIBUTOR UNIT
MONITOR
RECEIVER
ANTENNA CHANGEOVER UNIT
MONITOR 1
MONITOR 2
AFC
CONTROL
UNIT
CARRIER POWER
AMP MODULE
(fo)
UPPER SIDEBAND
MODULE
(fo Hz)
LOWER SIDEBAND
MODULE
(fo Hz)
MONITOR & CONTROL UNIT
9960Hz
30 Hz (REF)
ALC
720 Hz (SIN)
1020 Hz (ID)
720 Hz (COS)
Simplified Block
Diagram of DVOR
MOD SIG GEN Module
TRANSMITTER UNIT

22. Block Diagram of a VOR Receiver ( Airborne)
30 Hz VAR
LPF
PHASE
COMP O O O O O O TO
OBS
0-360° RF IF AM
DET
OBS LO
CDI
9960 Hz
filter FM
DET
LPF
30 Hz REF

23. The DVOR Training Equipment
Specification:
Model : TW 2158A (Toshiba)
Frequency Range : Mhz
Modulating Freq. : Hz
Identification Freq. : 1020Hz