AVIONICS Training by OSTROUMOV Ivan
Chapter 7. Navigation and surveillance systems

7.3. Very high frequency Omnidirectional Range equipment

VOR (Very high frequency Omnidirectional Range beacon) determines azimuth of aircraft relative to point located point this radio beacon. Radio beacons VOR works in the range frequency 108–117,975 MHz. In this range allocated 200 channels (from 50 kHz), 160 of which are assigned VOR, and 40 channels in the frequency range 108-112 MHz (the odd tenths MHz) – directional radio beacon ILS.

With the help antennas system radio beacons generates two direction diagrams: direct and non direct. Through non direct antanna radiated referebce signals modulated with a frequincies 30 Hz [26]. Directed diagram ratated with a frequencies 30 revolutions per seconds.

Fig. 72. The principle of operations VOR

On the board aircrafts accepted signals, where a signals from direction antenna detected amplitude-modulated ( max signals – if the direction of antanna on the aircraft). The phase of the reference signal is combined with the phase of the envelope of the amplitude-modulated signal when the azimuth is zero. It is a measure of the current azimuth. The range of the beacon, depending on the power of radiation is 50-370 km. The appearance of VOR ground equipment shown on Fig. 73.


Fig. 73. VOR Radio beacon

For identification beacons VOR emitted signal is modulated Morse code or language callsign. Callsign broadcast receiver VOR equipment intercom and the pilot can control them through listening

VOR receiver also receives signals from marked radio beacons. This radio beacons installed near runway (RNW) at a distance from 75m to 4 km from the runway cut (Fig. 74). Depends from this distance marked beacons devided by: near intermediate and far. Marked radio beacons emit a a signal at a frequency of 75 MHz Morse code.

The signal emitted directed upwards so that it is taken on an aircraft only at the time of flight of beacon. The signals are modulated low-frequency oscillations 400, 1300 or 4000 Hz respectively at near, intermediate and far beacons.

The signal emitted directed upwards so that it is taken on an aircraft only at the time of flight of beacon. The signals are modulated low-frequency oscillations 400, 1300 or 4000 Hz respectively at near, intermediate and distant beacons.

VOR receiver receives a signal beacon and sends messages in this indication and, in addition, produces a characteristic sound signal. This signal together with the notice simply indicate the pilot, how far from the runway he is.


Fig. 74. Мarker radio beacon

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Interested in learning Avionics system in detail.
(26th of September, 2016)
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Avionics training in details by
Ostroumov IvanOSTROUMOV Ivan, PhD
Associate Professor, www.sciary.com/ostroumov