NDB Flashcards Preview

R Nav > NDB > Flashcards

Flashcards in NDB Deck (30):

What is an NDB?

A non directional beacon (NDB) is a simple ground based radio signal that transmits an omnidirectional radio wave using LF and MF bands.

NDB, as in the name, bears no directional information.


What freq range does an NDB use?

190 to 1750kHz

NDB is a Class B non precision approach.


How is an NDB identified?

Normally 2 or 3 letters transmitted in morse code.


What are the disadvantages of using an NDB?

The lack of failure flags, so when the NDB is faulty there is no indication of this.

Only aviation specific NDBs are monitored and when it's faulty/out of use it will be published in the NOTAM.


What equipment is required for NDB?

NDB on the ground

On the aircraft:
Automatic DF (ADF)
Loop antenna
Sense antenna
An indicator


Why is a loop and a sense antenna required?

Because a loop antenna is not good at informing you of direction, and so a sense antenna is added to null out a point (cancelling out the 'wrong' beacon) to give you a direction.


Where is the variation applied for an NDB?

Variation is applied at the A/C


Name the 2 types of NDBs and it's range.

1. Locator beacon (LCT) - 10 to 25 NM
Suitable for approach procedures

2. NDB - range of 50NM or more
Suitable for en-route navigation and approach procedures


The display needle for an ADF points at....

The pointer indicates QDM; to the beacon while
The tail indicates QDR; from the beacon


What does the BFO or TONE selection switch on an ADF receiver do?

By selecting BFO or TONE on the ADF receiver it will ident the NDB's interrupted (pulse) signals. That is, the receiver will pick up the ident morse code from the NDB.

Specifically the N0N A1A NDB


What does the ANT switch on the ADF receiver do?

By selecting the ANT switch, the loop antenna is disconnected and the receiver will only pick up on AM LF/MF radio waves.

As the loop antenna has been disconnected, no bearing info can be obtained and so the display ADF display needle/pointer is parked.

Only when ADF is enabled can bearing to the station can be obtained.


When an NDB signal cannot be properly and clearly ident, what must you do?

Not use it!


What is an NDB's cone of confusion (silence)

As NDB's are designed to send out signals horizontally, there is an area above the NDB (40˚ either side of the vertical) that has a weak or no signal at all. This is called the COC.


What is the COC formula for an NDB?

Diameter of COC =
Height above the NDB x tan 40˚ x 2 ÷ 6080 (ft/nm)

If only want radius then do NOT 'x2'


There are 2 types of NDB ident transmission. What are they?

A0A A1A : (CW) Continuous wave
NDBs using interrupted carrier (pulse) to ident
So BFO/TONE must be selected on the receiver to.

A0A A2A: (MCW) Modulated continuous wave
NDBs using AM to ident
So ADF must be disconnected on the receiver to ident


What are the 4 RBI?

Fixed card ADF (radio compass)
Moving card ADF
Remote magnetic indicator (RMI)
Symbols on an electronic nav display (EFIS ND)


Identify the 4 elements that make up the airborne part of the NDB system:

Loop antenna
Sense antenna


What is the formula for RB?

Relative bearing = magnetic bearing - magnetic heading OR


What is the difference between the fixed and moving card ADF compared to the RMI display?

The RMI auto aligns the A/C magnetic HDG using inputs received from a remote indicating ˚M.


You are homing and flying towards the beacon, you drift right, what will happen to the compass?

The compass will decrease.


You are homing and flying towards the beacon, you drift left, what will the compass do?

Compass will increase


What will happen to the compass when you are homing and flying away from the beacon drifting left, and then right?

Away from beacon, drift right, compass will increase.

Away from beacon, drift left, compass will decrease.


What is the biggest drawback with the ADF?

The lack of failure flags


What is static interference?

What electrical charges in the atmosphere interferes with a signal. This happens largely in CB


What is night (twilight) effect?

This is where at night the ionosphere extends upwards and D layer disappears while the E and F layers remains.

Due to the increase in ionosphere depth, the signals can travel further and so interfere with other signals.


What is costal refraction?

Where signal changes direction due to the angle at which it travels over different terrain. Apart from parallel or perpendicular, the signal will alter course.

The greatest refraction is where the beacon is far in land and/45˚ angle. The refraction makes you think you're closer inland than you really are.


What is multi path propagation?

Aka mountain effect. This is where radio waves reflects off the terrain and follow several different paths between the NDB and A/C.


What is quadrantal error?

A/C structure bends incoming waves as it receives it. Therefore the min quadrantal error occurs at the cardinal points, max error at 45˚.


What are the 6 major errors suffered by DME?

• lack of failure flags
• static interference (think CB and lightning strikes too!!!!)
• night/twilight effect
• quadrantal error
• coastal error
• multi path propagation - refraction of signals


How does an A/C locate an NDB? Once located how do you then use the NDB?

BFO button needs to be pressed to ident the NDB, but then you have to press button again to switch it off so you can navigate with it.