NDBs Flashcards
NDBs use what frequency bands
Low and medium frequency bands - 190KHz/1750KHz
Space waves/sky waves and surface waves
Locator Beacon range/use
10-25nm
NDB for final approach
Low powered/LF/MF/Two letter ident
En route NDB range/use
50nm or more
Approach procedures and en route
Frequency range of NDB
190KHz to 1750 KHz
N0N A1A
Unmodulated no modulation no information - N0N
A1A continuous wave - 50nm range - BFO used to ident - breaks it up into chunks
Signal cut therefore no tracking when identifying
N0N A2A
Modulated continuous wave - no BFO required - amplitude modulated
Cone of confusion
Area where ADF needle becomes inaccurate
40 degrees above antenna
Height (nm) x tan (40) x 2 (both sides)
How do you double the range of NDB
Power x4
Calculating range overland
2 square root of power in watts
Calculating range oversea
3 square root of power in watts
Limitations of ADF
No indication of failure
Static interference
Mountain effect
Static from CB clouds
Dusk/dawn effect
Night Effect
Sky waves slow/bend/return signals causing interference from other NDB stations on same frequency
Range increases but accuracy decreases
Coastal refraction
NDB inland to coast become inaccurate when density changes and speeds up over ocean causing bending
Bearing inaccurate NDBs closer to coast less affected as less change in density
Greatest when NDB is inland and at acute angle - Neville when perpendicular
Dip Error
Banking moves antenna therefore needle flops towards direction of turn
ICAO Accuracy requirements
+- 6 degrees
+- 5 degrees in UK
Fading
Most common in MF frequency occurs between twilight and night
Weak sky waves return at night due to reduced density in ionosphere and less attenuation
How do you find true bearing of the NDB from the aircraft when given relative bearing of NDB to aircraft and compass heading
Compass heading + relative bearing
If greater than 360 take away 360 degrees
CDMVT to calculate true bearing to the NDB - use the above as the compass and apply deviation from the ac and variation from the ac to get true heading
Wavelength names
1-10m = metric
10-100m = decametric
100-1000m = hectometres (NDBs/ADFs)
1000-10,000m = kilometric (NDBs/ADFs)
Homing
Point at the NDB with relative bearing 0 degrees
Keep the needle on the nose
Wind will blow off track but repoint ac at needle
Used to get TO a NDB
Tracking to NDB
Choose inbound or outbound course to beacon
Maintained by applying wind correction angle
Used to guide ac to and from NDBs
Mountain Effect on NDBs
LF/MF radio waves - ground waves - diffraction of waves - scattered
Coastal refraction counter measures
Use NDBs closer to the coast
Fly at 90 degrees to signal along coast
Fly higher
How is a en route NDB identified vs a locator
Morse code - 3 letter identifier for en route NDB
Morse code - 2 letter identifier for locators
Coastal effect gets worse when
Angle of incidence decreases
Maximum from 0 to 30 degrees from the shoreline
Why is bearing indicator erratic on N0N/A1A when ident
Due to BFO being on to receive on a normal receiver
NDB ident (locator vs en route)
Morse code signal repeated every 10 seconds
En route = 3 letter identifier
Locator = 2 or 1 letter identifier
What is a locator
NDB - LF/MF - 190 to 1750KHz
Quadrantal Error
Wave front from NDB can be distorted by ac structure which approached the aerial
Fading is associated
Night effect of NDBs
ADF needle in a turn will
Point slightly in direction of down going wing as becomes out of balance
Which frequency band is fading most likely to occur
Medium frequency
