NDB Flashcards
What is the frequency for NDB
190 KHZ - 1750 KHZ
“Hundred and a bit to thousand and a bit”
What signal does a NDB transmit
Omnidirectional
How to identify a NDB
By morse code
2 letters = locator (short range)
3 letters = NDB (long range)
What is the morse code for a NDB usually transmitted on
AM (NON A2A)
How is a NON A1A beacon identified
Requires a BFO (beat frequency oscillator)
What does a ADF (automatic direction finding) require on the aircraft
Loop antenna
Sense antenna
Sensor
Receiver
Is a sense antenna omnidirectional or directional
Omnidirectional
Is a loop antenna directional or omnidirectional
Kinda directional depending on how aligned with signal = all of nothing
What happens if you use a loop and a sense antenna
No ambiguity in direction
What is the accuracy of a loop antenna
Has 2 null positions = ambiguity = could be 180° off
What is a BFO
Beat frequency oscillator / tone
Used to identify NON A1A
Introduces a signal that mix with NDB signal to create tone = mix 2 frequencies to create a 3rd in the audible range
What is ANT
When the loop antenna is disconnected = increased clarity of identification
But no bearing is available
Some indicators might park needle at 90° or 270°
What is the danger of ADF
Don’t know if it works or not
But if beacon doesn’t work then NDB doesn’t work
What is a RBI
Relative bearing indicator
= relative to nose of airplane
Bearing = relative bearing + heading
What is a RMI
Radio magnetic indicator
= RBI + compass
= rotates like compass = QDM (head) QDR(tail)
What happens is compass card is stuck in a RMI
Turns into a RBI with random heading at top (what it froze on)
Where is variation measured for NDB
Aircraft
What does BFO do
Creates time for NON A1A
What is the NDB cone of confusion
Area above NDB where signal is disturbed
40° either side of vertical
What is the difference between fixed and moving card ADF
Moving card has heading bug
What is NDB homing
Needle starts to move opposite direction to drift
If you make corrective turns to keep needle at 12 o’clock
= Cheever approach to NDB
What is accuracy if NDB
+/- 5°
What happens to NDB distance at night
Distance signal travels increases
Usable distance decreases
How much do u need to increase power by to double and triple the range of a NDB
Double = 4x power Triple = 9 x power
What is static interference on a NDB
Most likely caused by active CB
can make ADF completely unreliable
What is night / twilight effect on a NDB
Occurs between sunset / sunrise
Causes ‘hunting needles’
Due to
Sky waves + surface waves mixing which can lead to fading
What is coastal refraction NDB
The signal refracting due to a change in speed over the coastline
When is there no coastal refraction error in the NDB
If the NDB is on the coast exactly
If the A/c is on a angle of 90°
How does distance inland affect coastal refraction NDB
Further inland = worse error
What is multi path propagation (mountain effect) NDB
Radio waves bounce (reflect) off the terrain and follow several paths between the NDB and A/C
What is bank angle error (Dip) NDB
Needle points into turn
What is quadrantal error NDB
Aircraft structure bends incoming wave
Least error on cardinals (not 0)
Worst midway between
