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15 Goniometric Radio Navigation Systems
• at altitudes from 1000 ft (300 m) up to 14,500 ft (about 4400 m) at a distance up
to 40 nautical miles (74 km);
• at altitudes from 14,500 ft up to 60,000 ft (about 18,300 m)—at a distance up to
100 nautical miles (185 km);
• at altitudes from 18,000 ft up to 45,000 ft (about 13,700 m) at a distance up to
130 nautical miles (240 km).
It may cause consternation the fact that in accordance with mentioned above
figures, the distance at altitudes of more than 45,000 ft is less than this altitude (100
nautical miles instead of 130). In fact, it should seem that the more altitude the
more should be a distance. However, the mentioned distances are far from maximum
distances at which a signal receiving is possible. As a rule, a signal can be received
at large distances. These distances, besides ensuring of signal receiving, additionally
guarantee that, being within its limits, AV will not be in operation zone of another
RB, operating at the same or at a close frequency. Thus, a determined distance in
100 miles (for high altitudes) just guarantees that at smaller distances this will not
happen.
Nowadays, the three main types of azimuthal RB of VOR system are used in civil
aviation:
• RB with envelope phase measuring of amplitude-modulated (AM) oscillations
(VOR);
• RB with two-stage phase measurement (PVOR);
• RB with use of Doppler effect (DVOR).
VOR radio beacons have two transmitting antennas: omnidirectional (nondirectional) A 1 with directional pattern in horizontal plane F 1 (α) = 1; directional
(beamed) antenna A 2 with directional pattern in horizontal plane F 2 (α) = cos α. In
any azimuthal direction θ , a directional pattern magnitude A 2 is characterized by a
value F 2 (α − θ ) = cos(α − θ).
Antenna A 1 sets a field with strength (density):
e 1 (t) = E 1M cos(ω 0 t),
(15.1)
with amplitude E 1M .
Antenna A 2 sets a field in any azimuthal direction
e 2 (t) = E 2M cos(α − θ) cos(ω 0 t),
(15.2)
with amplitude E 2M cos(α − θ).
Usually for VOR RB, the following condition is fulfilled: E 1M > E 2M .
Antennas’ radiation patterns of VOR radio beacon are shown on Fig. 15.1a. Highfrequency signals are formed by one transmitter and radiated by antennas, having a
common phase (electric) center. During field summation in air space, a resultant field
of all-directional azimuthal VOR RB is formed e (t) = e 1 (t) + e 2 (t) (Fig. 15.1b).
15 Goniometric Radio Navigation Systems
• at altitudes from 1000 ft (300 m) up to 14,500 ft (about 4400 m) at a distance up
to 40 nautical miles (74 km);
• at altitudes from 14,500 ft up to 60,000 ft (about 18,300 m)—at a distance up to
100 nautical miles (185 km);
• at altitudes from 18,000 ft up to 45,000 ft (about 13,700 m) at a distance up to
130 nautical miles (240 km).
It may cause consternation the fact that in accordance with mentioned above
figures, the distance at altitudes of more than 45,000 ft is less than this altitude (100
nautical miles instead of 130). In fact, it should seem that the more altitude the
more should be a distance. However, the mentioned distances are far from maximum
distances at which a signal receiving is possible. As a rule, a signal can be received
at large distances. These distances, besides ensuring of signal receiving, additionally
guarantee that, being within its limits, AV will not be in operation zone of another
RB, operating at the same or at a close frequency. Thus, a determined distance in
100 miles (for high altitudes) just guarantees that at smaller distances this will not
happen.
Nowadays, the three main types of azimuthal RB of VOR system are used in civil
aviation:
• RB with envelope phase measuring of amplitude-modulated (AM) oscillations
(VOR);
• RB with two-stage phase measurement (PVOR);
• RB with use of Doppler effect (DVOR).
VOR radio beacons have two transmitting antennas: omnidirectional (nondirectional) A 1 with directional pattern in horizontal plane F 1 (α) = 1; directional
(beamed) antenna A 2 with directional pattern in horizontal plane F 2 (α) = cos α. In
any azimuthal direction θ , a directional pattern magnitude A 2 is characterized by a
value F 2 (α − θ ) = cos(α − θ).
Antenna A 1 sets a field with strength (density):
e 1 (t) = E 1M cos(ω 0 t),
(15.1)
with amplitude E 1M .
Antenna A 2 sets a field in any azimuthal direction
e 2 (t) = E 2M cos(α − θ) cos(ω 0 t),
(15.2)
with amplitude E 2M cos(α − θ).
Usually for VOR RB, the following condition is fulfilled: E 1M > E 2M .
Antennas’ radiation patterns of VOR radio beacon are shown on Fig. 15.1a. Highfrequency signals are formed by one transmitter and radiated by antennas, having a
common phase (electric) center. During field summation in air space, a resultant field
of all-directional azimuthal VOR RB is formed e (t) = e 1 (t) + e 2 (t) (Fig. 15.1b).