NDB Flashcards
Type of modulation - NDB
Amplitude modulated
Freq of NDB
190KHz to 1750KHz
Equipment in the a/c used for NDB
Loop antenna
Sense antenna
ADF receiver
An indicator
Different ways to present NDB
Fixed card ADF (radio compass) Moving card ADF Radio magnetic indicator (RMI) Symbols on an electronic navigation display (EFIS ND) Radio magnetic indicator (RMI)
Relative bearing, fixed card
The cardinal points do not move only the needle moves
Relative bearing, moving card
Rotate heading after each turn
Gives you the bearing of the NDB in relation to your current heading
QDM/ magnetic steer equation
Relative bearing + magnetic HDG = QDM
Have to convert the units into relative bearing or magnetic heading o QDM for it to work
Tracking accuracy NDB
Class B - so it must be within +- 5 degrees of the desired track
Coverage and range of the NDB
Limited by power and line of sight
D=1.23(square root Rx + square root Tx)
New power/old = (New range/old) squared
So if you double the range, power has to go up by 4x
NDB transmission consists of
Sky waves and surface waves
NDB range at night
NDB range will increase due to ionosphere becoming smaller and higher
However, the useable range will decrease due to mixing
NDB system limitations
Biggest drawback is the lack of failure flags
Different errors that effect NDB accuracy
Static interference Night effect Coastal refraction Multi path propagation Quadrantal error Bank angle error
Static interference error NDB
Most significant
Can make the ADF completely unreliable
Makes the needle point at anything noisy,
Night/ twilight effect
Due to the raised ionosphere
Sky and surface waves get closer together and they mix which causes fading
Reduces the operational range of the NDB
Coastal refraction
As there is less friction over the sea than over the land
The signal gets bent due to the speed change
If the beacon on the coast has limited angular distance, there will be no bending
The further inland the beacon is, the stronger the bending is
Multi path propagation
Could be known as mountain effect
Applies to every radio aid
Radio waves bounce off terrain/objects and pick up the reflected signal instead of the actual
Bank angle error
Caused by the change in voltages through the loop antenna
Makes the needle point into the turn
Quadrantal errors
Caused by the a/c structure bending the wave as it reaches the a/c
Has a insignificant effect on the cardinal points
The most significant if the ave is coming from midway between each cardinal point
