Tyskland NOTES > Radio Navigation > Flashcards

Radio Navigation Flashcards

(56 cards)

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1
Q

What two characteristics define electromagnetic waves?

A
  • Amplitude (is the magnitude of change in the electric field intensity)
  • Frequency (f) (is the number of oscillations per second, measured in Hertz (Hz).
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2
Q

What is wavelength?

A

The distance between beginning and the end of one oscillation. Given en metres.

Wavelength = speed of light/frequency

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3
Q

Name all 3 propagation types

A
  • Ground wave
  • Sky wave
  • Line of sight
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4
Q

Phenomena of propagation

  • Reflection
A

electromagnetic waves may be reflected by ionized air layers of the ionosphere, mountains, buildings metal surfaces or the ground.

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5
Q

Phenomena of propagation

  • Refraction
A

is an alteration in speed and direction of propagation which is caused by a change of the air density or conductivity e.g. changes of humidity (coastline) or ionization (ionosphere).

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6
Q

Phenomena of propagation

  • Diffraction
A

bending of waves around obstacles e.g. at the edges of mountains, buildings or layers of the ionosphere.

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7
Q

Phenomena of propagation

  • Dispersion
A

separation of waves caused by particles in the air e.g. rain, fog or dust.

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8
Q

Phenomena of propagation

  • Absorption
A

electromagnetic energy is transformed to other forms of energy, for example to heat, especially near the ground (rain, fog, haze, dust) and the lower layers of the ionosphere.

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9
Q

Phenomena of propagation

  • Interference
A

interaction of two waves which have the same source or nearly the same frequency, it results in increased or decreased amplitude.

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10
Q

Phenomena of propagation

  • Polarization
A

is the change of the orientation (e.g. vertical / horizontal) of the oscillation.

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11
Q

What propagations characteristics has these frequency bands?

  • VLF/LF
  • MF
  • HF
  • VHF/UHF
A
  • VLF/LF = only ground wave
  • MF = generally ground wave (up to 50km).
    Additionally sky wave component at night (from 50 km).
  • HF = Generally sky wave
  • VHF/UHF = propagate direct and straight (Line of Sight)
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12
Q

What are the 3 basic types of modulation called?

A
  1. Frequency modulation (FM)
  2. Amplitude modulation (AM)
  3. Pulse modulation (PM)
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13
Q

NDB abbreviation:

A

Non Directional Beacon

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14
Q

To a NDB facility belongs:

A
  • a radio antenna
  • a transmitting unit
  • monitoring unit
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15
Q

NDB monitoring unit monitors what?

A
  • transmitting power
  • deviation of frequency
  • identifier transmission
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16
Q

Two types of antenna are in use for the NDB:

A
  • high (35 m), vertical pole (radio tower)
  • T-type antenna between to vertical poles (T-antenna)
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17
Q

What is an NDB station?
- principle
- what equipment
- what propagation
- what errors

A

Principle: it transmits a continuous low/medium frequency signal (200 – 1750 kHz).
Aircraft use an Automatic Direction Finder (ADF) to detect the direction of the signal.

Equipment: NDB transmitter antenna

Propagation: Works in low and medium frequency (LF/MF) bands. usually ground wave.

Errors: Night effect, Dip error, mountain effect.

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18
Q

ADF abbreviation

A

Automatic Direction Finder

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19
Q

On board ADF equipment contains:

A
  • antenna unit (loop and sense antenna)
  • reciever
  • control panel
  • indication instrument
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20
Q

Explain the error (Differences in Range)

A

Differences in Range: Signal takes multiple paths of different lengths, causing bearing errors.

The Book:
“NDB signals propagate mostly as ground waves which have smaller ranges over dry surfaces and longer ranges over wet surfaces and water.”

Countermeasures: Identify tuned in NDB.

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21
Q

Explain the error (Fading)

A

Interference between ground waves and sky waves, or multiple sky waves, may lead to errors up to total annihilation of the signal.

Countermeasures: Use low frequency NDB

Example:
🎯 Imagine you’re standing in a field with your friend shouting directions to you:

  • Your friend represents the NDB station.
  • You are the aircraft with the ADF.
  • Their voice is the radio signal.

Now, suppose:

  1. Your friend shouts directly at you (this is the direct signal).
  2. At the same time, their voice also bounces off a nearby wall or hill (this is the reflected signal).
  3. The reflected voice reaches you a tiny bit later than the direct one.

🌀 Sometimes, the two voices add up (get louder) → stronger signal.
💤 Other times, they cancel each other out (go quiet) → weaker signal or fading.

That up-and-down in loudness is what your ADF experiences as fading.

And because the ADF relies on a stable signal to point accurately, fading makes the needle wander or swing, causing errors in direction.

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22
Q

Explain the error (Night effect/twilight)

A

Night effect: Skywave reflection at night interferes with ground wave, causing bearing errors on the ADF.

The Book:
“NDB radio waves are reflected at the layers of the ionosphere especially during sunset and night. This process causes a change in polarization of the sky wave.”

Countermeasures: Use low frequency NDB

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23
Q

Explain the error (statics and thunderstorm effect)

Study These Flashcards
A

Lightning and static electricity produce noise on NDB frequencies, causing ADF needle deflections and unreliable bearings.

Countermeasures: Turn off instrument if possible

Example:
⚡ Statics and Thunderstorm (Electrical) Effect
When you’re flying near a thunderstorm or around heavy electrical activity in the atmosphere, the air gets full of electrical noise — kind of like static on a radio.

This static is caused by:

  • Lightning, which gives off strong bursts of radio waves.
  • Other electrical disturbances in the atmosphere.

Now, your ADF is trying to lock onto a steady signal from an NDB station. But all this static can:

  • Overwhelm or interfere with that signal.
  • Make the ADF needle jump, wander, or even point in the wrong direction.

Imagine trying to listen to a friend in a quiet room (easy), versus trying to hear them during a loud thunderstorm with static crackling all around (hard!).

24
Q

Explain the error (Mountain effect / Terrain effect)

Study These Flashcards
A

NDB signals reflect off mountains, causing signal distortion and incorrect ADF indications.

Countermeasures: Climb to higher altitude.

Example:
⛰️ Mountain Effect — Simple Explanation
Radio signals from NDBs usually travel in straight lines close to the ground. But when they hit mountains or hilly terrain, they can bounce or get distorted.

The ADF doesn’t know the signal is reflected — it just follows whatever signal it picks up. So if it locks onto a bounced signal instead of the direct one, the needle can point in the wrong direction.

25
Explain the error (Dip error)
During turns, the ADF needle tilts due to bank angle, giving a false bearing indication.
26
Explain the error (Shoreline effect)
NDB signals bend when crossing coastlines at an angle, causing bearing errors on the ADF. Countermeasures: Choose NBSs closer to the shoreline
27
Explain the error (Quadrantal error)
Caused by aircraft structure distorting NDB signals, leading to slight bearing errors, especially at 45°, 135°, 225°, and 315° relative bearings. Maximum deviation is plus/minus 6.2 degrees.
28
VOR abbreviation:
VHF Omnidirectional Radio Range (Very High Frequency Omnidirectional Radio Range)
29
VOR ground station contains:
- Transmitting unit - Antenna unit - Monitoring unit
30
What is a DVOR (Doppler VOR)?
Instead of physically rotating anything, the DVOR has a circle of antennas on the ground. It turns the signal on and off around the circle in a pattern that mimics motion, creating a virtual rotation — and using the Doppler effect to make the signal more stable.
31
VOR monitoring unit monitors:
- Transmitting power - Deviation of frequency and phase - Identifier and voice transmission
32
The VOR onboard equipment contains:
- VOR onboard antenna unit (handle bars) - VOR reciever - VOR control panel - VOR indication instrument
33
What is a VOR? - principle - what equipment - what propagation - what errors
- principle: Lighthouse principle. A reference light signal appears every minute and can be seen from all directions. a rotating light can also be seen every minute. - what equipment: On the ground VOR has a ground station with rotating signal system. On the aircraft we have a VOR receiver. - what propagation: Uses VHF band (108.0 – 117.95 MHz) Signal travels in line-of-sight - what errors: Cone of silence, Needle fluctuation due to reflections.
34
ILS abbreviation:
Instrument Landing System
35
The ILS ground components are:
Localizer (108.10 - 111.95 MHz only odd tenth e.g. 109.35) (VHF) Glideslope antenna (329.15 - 335.00 MHz) (UHF) Marker beacons (75 MHz)
36
What does the ILS Localizer send out?
Transmit two different signals with exact the same strength. The left signal toward the runway is amplitude modulated with 90 Hz and the right signal is modulated with 150 Hz to make them distingusihable. The ILS receiver on board compares the intensity of both signals. The aircraft is death on centerline when the 90 Hz and the 150 Hz field have the same intensity.
37
What does the ILS glideslope send out?
The signal is transmitted by several antennas, it contains a 90 Hz beam above the glide slope and a 150 Hz beam below the glide slope. The glide slope reciever recieves the signal and compares the field intensity. When the two signals do not have the same intensity, the aircraft is below or above the glide slope.
38
ILS onboard equipment:
ILS antennas (handle bars) ILS reciever ILS control panel ILS indicator
39
What is an ILS? - principle - what equipment - what propagation - what errors
- principle: Signals are transmitted from fixed ground antennas, and aircraft receive them to stay on the correct approach path. - what equipment: On the ground: Localizer antenna (at far end of runway) Glideslope antenna (beside runway near touchdown zone) Marker beacons. On board: ILS antennas ILS reciever ILS control panel ILS indicator - what propagation: Localizer: VHF band (108.1–111.95 MHz) Glideslope: UHF band (329.15–335.00 MHz) Marker beacon (75MHz) Line-of-sight propagation - what errors: Terrain blockage
40
DME abbreviation:
Distance Measuring Equipment
41
What is a DME? - principle - what equipment - what propagation - what errors
- principle: The system measures the time delay between send and receive to calculate slant range. - what equipment: on ground: Receiver/transmitter and antenna. on board: Receiver/interrogator, antenna and DME indication. - what propagation: Uses UHF band (962–1213 MHz) - Line-of-sight only - what errors: Slant range error, Signal blockage.
42
RADAR abbreviation:
Radio Detection and Ranging
43
What is the working principle of the primary radar and what does it consist of?
Primary radar sends out radio pulses that reflect off objects. By measuring the time and direction of the echo, it determines the object's distance and bearing. Consists of: Radar Transmitter Radar antenna Radar Receiver Display unit
44
What propagation does the primary radar have?
Frequency is GHZ Line of sight
45
Types of primary radar facilities: - SRE - RSR - ASR - PAR - ASDE - Weather Radar...
SRE - Surveillance Radar Element RSR - En Route Surveillance Radar ASR - Airport Surveillance Radar PAR - Precision Approach Radar ASDE - Airport Surface Detection Equipment Weather Radar...
46
What is the working principle of the secondary radar and what does it consist of?
Principle: Secondary radar sends an interrogation signal to the aircraft, which replies using a transponder. Interrogator is the radar on ground with a carrier frequency of 1030 Hz. - interrogation transmitter and encoder - reciever and decoder - radar antenna - control and display unit - monitoring unit Transponder is in the aircraft with a carrier frequency of 1090 Hz. - receiver and decoding unit - transmitter and encoder - antenna - control panel
47
What modes does the civil (SSR - Secondary Surveillance Radar) transponders provide?
Mode A = aircraft identification Mode C = pressure altitude Mode S = selective information
48
What modes does the military transponders provide?
Mode 1 = mission identifier Mode 2 = military unit code and type of aircraft Mode 3 = aircraft identification (like mode A) Mode 4 = coded identifier Mode C = pressure altitude Mode S = selective information
49
GNSS abbreviation:
Global Navigation Satellite System
50
What is the operating principle of the GNSS?
- Satellites transmit a signal including their position and time - as the signal is received the elapsed time will be computed - Requires min. 3 signals to compute 3 coordinates (x, y, z)
51
What information does the receiver provide?
- Current position - Exact time - Velocity and direction of movement - Altitude information
52
What are the 3 segments of the GNSS?
Space segment = satellite Control segment = on ground User segment = aircraft, watch and etc.
53
What is GBAS?
Ground based augmentation system A ground station at the airport that provides very accurate corrections for GPS signals. - DGPS principle used --> enabling precision approaches
54
What is SBAS
Satellite Based Augmentation System - Regional augmentation by using additional geostationary satellites
55
What is ABAS?
Aircraft Based Augmentation System - A system inside the aircraft that checks the GPS data using its own sensors. - when neither GBAS or SBAS are available
56
What are the two functionalities of the ABAS?
1. Receiver Autonomous Integrity Monitoring (RAIM) 2. Aircraft Autonomous Integrity Monitoring (AAIM)
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