In this ATPL summary will you find all you need both for cadet pilot to study for exams and for pilot who want to brush up some Radio Navigation topics:
- Theory for studying,
- Tips for exams.
Contains both summary of Oxford CAE ATPL books and personal reworked elements.
(This summaries ...
06 Navigation 2 - Radio Navigation
Basics
Symbol / Formula Definition Formula / Unit
Period τ Time to generate one cycle of a radio wave µs
1
𝟏 𝑓= = 𝐻𝑧
𝒇= 𝑠
𝝉
Frequency Number of cycles produced in one second
𝑚𝑠 −1
𝒄 𝑓= = 𝑠 −1 =𝐻𝑧
𝒇= 𝑚
𝛌
Speed of radio 300 000 000 ms-1 (= 300 × 106 ms-1), or 162 000 𝑚
waves c NM/s 𝑠
Cycle A complete series of values of a periodical process (EASA)
Wavelength 𝑚
𝛌 = c. τ λ= ∗𝑠=𝑚
The physical distance travelled by a radio wave 𝑠
𝒄 during one cycle of transmission (EASA) 𝑚𝑠 −1
𝛌= λ= =𝑚
𝒇 𝑠 −1
Range
(Surface wave) 𝑹𝒂𝒏𝒈𝒆 𝒐𝒏 𝒔𝒆𝒂 ≈ 𝟑 ∗ √𝑷𝒐𝒘𝒆𝒓
𝑹𝒂𝒏𝒈𝒆 𝒐𝒏 𝒍𝒂𝒏𝒅 ≈ 𝟐 ∗ √𝑷𝒐𝒘𝒆𝒓
Line of sight
Range 𝑅𝑎𝑛𝑔𝑒 = 1.23 ∗ (√ℎ𝑡𝑥 + √ℎ𝑟𝑥 ) 𝟏. 𝟐𝟑 ∗ (√𝒇𝒕 + √𝒇𝒕) = 𝑁𝑀
(Space wave)
Phase The fraction of one wavelength expressed in degrees from 0° to 360° (EASA)
Phase The angular difference/shift between the corresponding points of two cycle of EQUAL WAVELENGTH,
comparison which is measurable in degrees (EASA)
Attenuation The loss of signal strength in a radio wave, main reasons are:
• Spreading of available RF energy over a greater area
• RF energy is absorbed by the Earth, atmosphere or ionized layers
Absorption Energy is absorbed or scattered by ground or atmosphere and is transformed in other forms of energy.
This affect increases as frequency increases and is very significant over 1000 MHz (except ionospheric)
Diffraction The wave bends round the surface of the earth or bends around an object which size is comparable to
the wavelength.
,Reflection Change in direction of the radio wave when interfacing with a different media so that the radio wave
returns to the medium from which it originated.
Important for VHF radio transmission and radar.
Refraction The change of speed and/or direction of radio wave as it moves from one medium to another (different
density of the mediums), due to change of environment:
• Coastal refraction: change in signal due to coastline effect,
• Atmospheric refraction: (especially in low altitude) change in temperature, pressure or humidity,
• Ionospheric: caused by passing through ionized layers
Multipath: The signal arrives at the receiver via more than one path (the signal being reflected from surfaces near
the receiver).
Bandwidth “The difference between the upper and lower frequencies in a transmission”
Smaller frequencies:
• Long-distance communication,
• Travel unaffected over large distances → Less attenuation.
Larger frequencies: have greater energy and can carry more information.
Polar diagram It is simply a line joining all points of equal signal strength
Doppler Shift The difference between the frequency you perceive the waves striking you and the actual frequency of
or Doppler the waves.
Frequency
Fading “The interference of sky wave with the ground wave”
When a receiver picks up two signals with the same frequency, and the signals will interfere with each
other causing changes in the resultant signal strength and polarisation. (EASA)
Scalloping “Imperfection or deviation in the received VOR signal”
• It causes the signal to 'bend' as a result of reflections from buildings or terrain.
• Course Deviation Indicator: slowly or rapidly shift from side to side.
ROD
𝒇𝒕 100
𝑹𝑶𝑫 ( ) = 𝐺𝑆 ∗ ∗ 𝐺𝑙𝑖𝑑𝑒 𝑝𝑎𝑡ℎ 𝑎𝑛𝑔𝑙𝑒
𝒎𝒊𝒏 60
100
∗ 𝐺𝑙𝑖𝑑𝑒 𝑝𝑎𝑡ℎ 𝑎𝑛𝑔𝑙𝑒 = 𝑔𝑙𝑖𝑑𝑒 𝑝𝑎𝑡ℎ % (𝟑° = 𝟓%)
60
• Every 10 kts increase of GS, an increase of 50 ft/min of ROD
• Every 10 kts decrease of GS, a decrease of 50 ft/min of ROD
Height
𝑅𝑎𝑛𝑔𝑒 ∗ 𝑔𝑙𝑖𝑑𝑒 𝑝𝑎𝑡ℎ 𝑎𝑛𝑔𝑙𝑒
𝑯𝒆𝒊𝒈𝒉𝒕 (𝒇𝒕) = ∗ 6076𝑓𝑡
60
𝑅𝑎𝑛𝑔𝑒 ∗ 𝑔𝑙𝑖𝑑𝑒 𝑝𝑎𝑡ℎ 𝑎𝑛𝑔𝑙𝑒
𝑯𝒆𝒊𝒈𝒉𝒕 (𝑵𝑴) =
60
,Frequency Bands
Frequency Band Frequencies Wavelengths Civil Aeronautical Usage Propagation Path
Very Low Frequency At least affected by
3 – 30 kHz 100 – 10 km Nil
(VLF) reception
Surface Wave
Low Frequency (LF) 30 – 300 kHz 10 – 1 km NDB/ADF
(Sky Wave)
NDB/ADF, long range Surface Wave
Medium Frequency (MF) 300 – 3000 kHz 1000 – 100 m
communications (Sky Wave)
SKY WAVE
High Frequency (HF) 3 – 30 MHz 100 – 10 m Long range communications
(Surface Wave)
Short range communication,
Very High Frequency VDF,
30 – 300 MHz 10 – 1 m Space Wave
(VHF) VOR, ILS localizer, marker
beacons
ILS glide path, DME, SSR,
Ultra-High Frequency
300 – 3000 MHz 100 – 10 cm Satellite communications, Space Wave
(UHF)
GNSS, long range radars
Super High Frequency RADALT, AWR, MLS, short
3 – 30 GHz 10 – 1 cm Space Wave
(SHF) range radars
Extremely High
30 – 300 GHz 10 – 1 mm Nil Space Wave
Frequency (EHF)
• VLF is the frequency at which sky waves should at least affect reception, because VLF is not usually used as sky
wave.
, Non-Ionospheric Propagation
Surface Wave The electromagnetic waves travel along the surface Earth (EASA):
• From about 20 kHz to about 50 MHz (Upper end of VLF to the lower end of VHF).
• The portion of the wave in contact with the surface of the earth is retarded causing the wave
to bend round the surface of the earth; a process known as diffraction.
• Comprises LF, MF, HF
Space Wave The electromagnetic wave travel through the air direct from the transmitter to the receiver (EASA):
• The space wave is made up of two paths, a direct wave and a reflected wave.
• Comprises VHF, UHF, SHF, EHF:
o Limited in range as they are NOT REFLECTED BY IONOSPHERE,
o DO NOT HAVE a SURFACE WAVE.
• At frequencies of VHF and above radio waves start to behave more like visible light creating
a radio horizon with the radio frequencies.
• The only atmospheric propagation at these frequencies is LINE OF SIGHT:
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