Mixed Q Feedback Flashcards
Amplitude vs Frequency Modulation
Amplitude - peaks go higher or lower. Spacing / Frequency stays the same.
Frequency - peak stays constant, frequency/spacing differs. Like an accordion.
How does MLS minimise multipath errors?
Transmissions can be INTERRUPTED to AVOID reflection by stationary objects
MLS components
Seperate azimuth
Seperate elevation
DME-ρ Facility
What frequency & freq. band does an ILS Marker beacon transmit?
75 Mhz - VHF Band
DME Error
0.25NM + 1.25% Range
100NM -> 0.25 + 1.25 = 1.5 total error.
Relation between HDG, RB, QDM
QDM = HDG + RB RB = QDM - HDG
Range of an NDB over Land & Sea
LAND = 2 x square root Power (W)
SEA = 3 x square root Power (W)
What is the maximum range of primary radar determined by
Max Range - PRF
81000/PRF = Range
What is minimum range of primary radar determined by?
Pulse Length
Definition of Garbling
2 aircraft, same direction, less than 1.7NM slant range.
Mode S Transponder - Short & Long P4 Calls
Short P4 - exclusively Mode S All Call
Long P4 - Mode A, C, S All Call
What do L1 & L2 codes eliminiate?
IONOSPHERIC PROPOGATION DELAY
NAVSTAR Satellite - orbit angle, duration & height
55 degrees to Earth’s Equatorial Plane, orbits in 12H. 20000km above Earth.
GLONASS Satellite
64.8 degrees to Earth’s Equatorial Plane - orbits in 11h 15’ at 19000km. Lowest of all
GALILEO
56 degrees to Earth’s Equatorial Plane - orbits in 14H. 23000km
How is distance from NAVSTAR/GPS receiver to the ground receiver transmitted?
Time taken for signal to arrive x speed of light.
Types of interference
‘REFLECTION’ is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.
‘DIFFRACTION’ is the phenomenon, which may be described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings.
‘REFRACTION’ is a change in direction of a radio wave as it passes from one medium to another and is most prevalent in lower frequencies.
This is seen in NDB LF/MF signals at night as the weakening layers of the Ionosphere (which completely attentuate the Space Wave by day) ‘bend’ the signal back towards the denser medium, i.e. The lower levels of the atmosphere, as it passes into the less dense regions. This can result in a signal being sufficiently refracted to return it to earth in the form of Skywave.
It is also seen in coastal refraction as the signal passes from land to sea and the signal ‘bends’ back towards the land.
‘INTERFERENCE’ is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude.
Directional antennae
Loop
Parabolic
Slotted
Helical
Omnidirectional antennae
Sense, Dipole
In aviation electronic systems the so-called Doppler principle may be used in:
VOR, GPS and MTS and the turbulence mode of AWR
What does the VDF provide?
Homing
The ILS receiver of an aircraft on approach and flying on the Glide Path will receive:
The modulation from both lobes at equal depth.
Scalloping
Rapid indicator changes, side to side of the approach path - cannot be followed by the aircraft.
What selection on the transponder must be made to transmit Mode A, C, S?
“ALT” / “ALT RPTG”