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Lernkarten
Which is a suitable length of a simple dipole antenna utilised for 113 MHz?
113 cm
Which of the characteristics below is an advantage of slotted radar antenna as opposed to parabolic antenna?
Less side lobes
Which of teh following antennas is non-directional (nicht ausgerichtet)
Vertical dipole antenna in the horizontal plane
radio waves: Refraction
radio waves to change direction when entering a different medium => speed depend son the material it passes
radio waves: Reflection
when a surface interrupt a radio waves's propagation path => some of the energy pf the radio wave diffuse and part of it is sent back to the transmitter
radio waves: Diffraction
radio wave to be bend around obstacles => New waves from along the wave front
radio waves: Interference
radio waves of the same frequency superimpose => constructive= result increases the amplitude destructive= result decreases the amplitude
radio waves: Absorption / attenuation
weaken radio waves => caused by the transformation of electromagnetic energy into other forms of energy , mainly heat
radio waves: Doppler effect
the radio wave to change frequency => If transmitter and receiver are approached (Convergence) the frequency increases proportional to approach speed ==> if a car approaches to a person, the pitch (audio frequency) becomes higher
Ionosphere
the numerous layer of electrically charged gas atoms
Ionisation:
when the sun's high energy ultraviolet light waves enter the ionosphere layer of the atmosphere, strike a gas atom and literally knock an electron away from its parent atom
=> When a negative electron is nocked away from the atom, the atom itself becomes positively charged
recombination
when free electron and positive ions collide => the positive irons return to their original neutral atom state ==> Afternoon and evening
Ionosphere layers
60-400 km
D: 60-100:km => ability to absorb low frequency signals
E: 100-180 km ==> actually it si almost gone by midnight
F: 180-400 KM => F1 und F2 = daylight ==> Night only F ==> suitable for HF, long distace transmission
space waves
radio waves for VHF band transmission and higher ===> worldwide ==> travels directs from antenna to antenna = qui-optical
Ground waves
surface waves => for MF and lower => along the curvature of the Warth
Sky waves
Lf and HF ==> sky waves is expected to return to the surface => ski distance
Skip distance:
skip zone:
Skip distance: between the trasnmitting antenna and teh first return of teh sky waves ==> affects LF wave = NDB
skip zone: dead space => between the end of teh ground waves and teh first return of teh sky waves
Which factor determine teh range of a radio wave within the LF/MF band during daytime
transmitted power and Earth surface condition (ground waves )
Which is the propagation (Vortpflanzung) path followed by radio waves within the VLF (Very low frequency) frequency band
ground waves during day and night
Vertcal antenna is non-directional. it means?
send in all directions
Weiter der Driecket Waves => space waves ausrechnen
1.22 * Wurzel Höhe
VDF => ANtenne? Bereich?
VDF: 118 - 136.975 MHz
direction sensitive antenna systen = dipole antenna or adcock ==> (LF/MF) ==> HEUTE NUR NOCH VHF
Line of sight ==> Distanz
Ob es eine Verbindung geben kann ==> Theoretische Reiweiweite des Signals
LoS(NM)= 1.23 \(({ \sqrt{H Transmitter}+\sqrt{H receiver} })\)
QDR
Magnetic Bearing FROM the station ==> MN
QTE
True Bearing from the station ==> TN
QDM
Magnetic Bearing to station ==> Homing ==> MN
QUJ
True Bearing to station ==> TN
QTF
Position ==> information about the position => two or more DF stations are involved and communicate their bearing
quality of bearing (VDF)
A: +/- 2 Grad
B: +/- 5 Grad
C: +/- 10 Grad
D: accurancy below class C
Which factor may improve VDF operation?
Increasing in altitude
Synchronous transmission to a VDF station by 2 different aircraft can cause
deflection of measured bearing
VDF Signals are usually no worse than :
Class B - 5 deg
Abnormal long ranges may be experienced on VDF channels, caused by...
Super refraction of signals in the atmosphere
The VDF antenna can detect aircraft direction and is called
Adcock
In which one of the following circumstances is ground direction finding (VDF) likely to be used to fix an aircraft's position?
The indicator of the ground VDF equipment responds to...
The principle used in VOR bearing measurement is...
phase comparison
An RMI indicates aircraft heading. To convert the RMI bearings of NDBs and VORs to true bearings the correct combination for the application of magnetic variation is...
NDB: aircraft position VOR: beacon position
An aircraft is flying on a heading of 270° (M). The VOR OBS is also set to 270° with the full left deflection and FROM flag displayed. In which sector is the aircraft from the VOR ground station
NW
If an aircraft flies along a VOR radial it will follow a...
great circle track
