ADF/NDB Flashcards
What is the normal mode position for automatic direction finding on the ADF?
ADF/COMP (compass on older systems)
State the range of frequencies usually employed by NDB’s.
Between 200-400KHz but up to 1750KHz in some instances
List at least three factors effecting NDB accuracy
Night Effect
Coastal Refraction
Mountain Effect
Precipitation Static
Thunderstorms
NDB coverage and range is reduced at night due to night effect when ____nm to ____nm from the station
when 70nm to 80nm from the station
NDB ground stations transmit a vertically polarised signal on a single frequency in (one direction, all directions, 360 different radials)
What is the correct answer?
all directions
The main purpose of the ADF sense aerial is to…
resolves the ambiguity of the two null positions, it creates only one null position
When passing overhead an NDB station the ident volume in the headset will (increase,decrease) until overhead where it will significantly reduce or mute for a brief period
What is the correct answer?
increase
NDB signals can suffer from coastal refraction. When the signals cross a coastline at a (oblique, right) angle they are not suscepted to bending
What is the correct answer?
right angle
NDB coastal refraction causes signals to bend toward (land mass, water,)
What is the correct answer?
toward land mass
List the basic components of an aircraft ADF
ADF Receiver
Loop Antenna Aerial
Sense Aerial
Control Panel
Instrument (RBI or RMI)
The fixed-loop ADF uses two loop antenna’s, it (does, does not) require a sense antenna
What is the correct answer?
**Does **require a sense antenna
Prior to using an NDB beacon for navigation, each time an NDB is tuned you must check: (list all three)
Correct frequency
Identify NDB by listening to the identification code
Bearing needle is indicating the expected bearing
Max voltage will be induced in the ADF Loop antenna when the loop antenna is (face on to the wave, 45° angle to the wave, 90° parallel to the wave)
What is the correct answer?
90° parallel to the wave
With regard to NDB coastal refraction, the ____ the angle the greater the refraction
the shallower the angle the greater the refraction
If you are experiencing needle fluctuation at night it maybe due to night effect, if available you could..
Do what to remedy the situation? list two options
**Use another beacon within the 70-80nm skip distance
Use another beacon of significantly lower frequency**
List the advantages of the fixed-loop ADF
Fewer moving parts
More aerodynamic installation possible
Is more trouble free
When an NDB signal is directly straight ahead of the aircraft nose, the ADF needle points (9 o’clock, 12 o’clock, 6 o’clock) relative
What is the correct answer?
12 o’clock relative
NDB night effect is caused by the aircraft ADF receiving both surface waves and **(direct waves, sky waves, VHF waves) **
What is the correct answer?
surface waves and sky waves
When passing overhead an NDB you should expect the instrument needle to…
show large swings from side to side or rotate 180° relative and then settle down
When the ANT/REC/VOICE function on the ADF control panel is selected it (only uses the sense aerial, only uses the loop aerial, uses both aerials)
What is the correct answer?
Uses only the sense aerial
Factors effecting operational range of an NDB are: (list at least three)
Transmit Power
NDB Frequency
Time of Day
Type or Surface
Receiver Efficiency
When using the LOOP function of the ADF which aerial is disabled?
The Sense aerial is disabled
List the common options available to reduce or remedy fluctuating NDB signals caused by mountain effect
**Increase in altitude
Use a higher frequency NDB**
NDB range will normally be greater over (land,water) than over (land,water)
Which combination gives the correct answer?
NDB range will normally be greater over water than over land
When in the vicinity of an active thunderstorm the ADF will (not be effected, show minor deviation, become totally unreliable)
What is the correct answer?
**become totally unreliable
(as it points to the source of sparatic radio energy generated by the thunderstorm)**
Describe the BFO/CW Mode of the ADF
(Beat Frequency Oscillator or Continuous Wave) Used to identify un modulated, interupted transmissions to identify the NDB station. It is not used in NZ and not used for navigation
What is the purpose of the ADF VOICE function? (also called ANT or REC)
It is used to provide clearer audio of the identification station, no directional information from ADF needle is given
When a null is detected by the ADF Loop antenna (max voltage, no voltage) will be induced because the waves hit the antenna at the same time and phase
What is the correct answer?
No Voltage
Describe the use of the ADF LOOP function
Used to manually control the loop through a crank handle or switch and maybe used in difficult reception conditions such as static or extreme range, it is rotated manually to the null position.
The lower the NDB frequency the (shorter, longer) the range
What is the correct answer?
longer the range
