VOR

Very High Frequency Omni- Range System (VOR)

 

Function:

   The VOR determines the entrance angle of the A/C to the VOR station.

The fundamental task of a VOR receiver. This task is to compare the phases of the detected 30 Hz AM and 30 Hz FM signals, in order to discover on which radial the receiver is located. The VOR system can give no information without having accomplished this task.

Once the AM and FM signals have been sepa­rately detected, they can be compared for phase difference by the phase detector section. When the phase detector section establishes the phase dif­ference between these signals, it has established the radial on which the receiver is located.

Once this fundamental knowledge has been derived, it can be used in a deviation indicator by comparing it to the radials which have been selected. It can also be used in a needle-pointing RMI by adding compass information to it.

When we select a VOR course with the course select knob, we are telling the VOR receiver the radials on which we intend to travel. The VOR receiver can compare the selected radial with the actual radial on which the receiver is located.

The deviation indicator shows the difference between the selected and the actual. One dot is 5˚ and two dots is 10˚. The maximum indicating of the deviation indicator is limited to about 10˚ or 15˚ difference between selected and actual.

When the compass system tells the VOR receiver the heading of the airplane, the VOR RMI needle can point at the VOR station.

Operating Frequency Range:

From 108 to 118 MHz with 50 KHz channel spacing.

 108. x 0 or 108. x 5.         ( even tenth)

Antenna Location:

On the vertical stabilizer.

 

 Transmitted Wave

      •The antenna isn’t physically rotated.

      •It transmits a directional beam and rotates with 30 rpm. This is  the same effect of the rotating antenna.

•When the antenna points to north, the phase of the 30 Hz FM is (+). When the antenna points to south, the phase of the 30 Hz FM is (-).

•The VOR signal  & VOR receiver don’t tell anything about the VOR station location w.r.t A/C but it determines the receiver location w.r.t the magnetic north and VOR station.

  

   This is the A/C bearing.

 VOR Received Signals

1.30 Hz AM.

2.30 Hz FM.

3.Radio frequency signal.

4.Station identification tone.