Direction Finding (VDF + ADF) Flashcards
What is DF and RDF?
The measurements of the direction from which a received signal was transmitted.
What is a true radio bearing?
A radio bearing for which the reference is true north.
What is a magnetic radio bearing?
A radio bearing for which the reference direction is magnetic north
How does the DF ground equipment display bearing information?
By LED Cathode Ray Tube (CRT) in the compass rose and bearing readout
The accuracy fir tolerance fir bearings for DF is categorised as?
Class A: +/- 2 degrees
Class B: +/- 5 degrees
Class C +/- 10 degrees
Class D: worse than C
Will each unit have a classification for their DF?
Yes
What can a DF be used for?
To assist a pilot who may be temporarily uncertain of their position
List the Q codes
QTE
QDR
QDM
What is QTE?
True bearing of an aircraft in relation to the direction finding station/specified point
What is QDR?
The magnetic bearing of an aircraft in relation to the direction finding station or other specified point
What is QDM?
The magnetic heading to steer (with no wind) to make the direction finding station/specific point
What is triangulation?
A way that pilots can establish their approximate positions by obtaining two or more bearing from separate DF stations and plotting the point at which the bearings intercept.
What is homing?
The procedure of using the DF equipment at your radio station with the radio bearing of the aircraft transmission whereby the aircraft proceeds continuously towards the station following bearings from your DF equipment.
What are the 3 Conditions when a DF station can refuse to give bearings/headings/positions?
1) Conditions unsatisfactory
2) when bearings do not fall within calibrated limits of the station
3) When to do so would monopolise the frequency
What is radio bearing?
The angle(s) between the apparent direction of a definite source of emission of radio waves and a reference direction as determined at DF station
What frequency band does the ADF operate in?
Medium Frequency- 300KHz to 3MHz
What is an ADF?
A tuneable receiver fitted inside the aircraft.
What does the ADF Display?
Displays a relative bearing in relation to the aircraft’s heading using a pointer on a relative bearing indicator (RBI).
What aerial receives signal from the ground based equipment?
Loop aerial
What is an NDB
An omni-directional Transmitter
What waveband does it operate in?
LF (not in the uk MF band (190 to 1750KHz)
A NDB continuously transmits an audio tone with a morse signal identifier.
True or False?
True.
What is the average radius of an NDB?
Between 10 and 500nm
What are high powered NDBs used for?
Long range navigation on or off airways
What are low powered NDBs used for?
Used as airfields approach aids, known as locator beacons.
Do low powered NDBs have a limited range?
True.
What is a Radio Magnetic Indicator (RMI)?
An arrow superimposed onto the compass rose.
A QDM can read straight from the pointer.
Can a RMI house more than one arrow simultaneously?
Yes; to display bearing information to more than one beacon.
What does the radio bearing indicator (RBI) continuously display?
The relative bearing in relation to the aircraft’s heading.
List the NDB Errors (all 7 of them)
1) Static Interference
2) Station Interference
3) Mountain Effect
4) Costal Refraction
5) Night Effect
6) Quadrantal Error
7) Lack of System Malfunction
What is static interference?
Thunderstorms or heavy rain cause static interference. ADF needle will point at the centre of an active Thunderstorm.
What is station interference?
Large bearing errors caused by interference from transmitter operating on similar frequency.
What is mountain Effect?
LF and MF are surface waves and are reflected by any high ground .
What is costal refraction?
Faster over the sea than land. Further inland the NDB beacon the greater the bearing error.
What is night Effect?
Severe bearing errors are most likely to occur at sunrise and sunset.
Changes in ionosphere at night cause interference from transmissions
Why is quadrantal error?
Airframe on an aircraft reflects/refracts and re-flexes radio waves. NDB strong with weaker signal distorted by fuselage.
Maximum error when signal arrives at aircraft’s quadrantal point.
What is lack of system malfunction?
Components/systems failure difficult to detect, no failure warning device. Constant monitoring of system required.
What are the advantages of NDB?
MF not limited to line of sight
Range dependent on power of NDB
What are he disadvantages of NDB?
Not as accurate at VOR
Subject to errors (costal; static; mountain)
