Results
Q1. Which of the following is considered a primary advantage of Single Sideband (SSB) emissions over standard AM?
Reduced power requirements
Q2. A Doppler shift will occur?
All of the options are correct
Q3. The phase of the reference wave is 240Degree as the phase of the variable wave is 045Degree. Find the phase difference between reference and variable wave ?
195
Q4. An apparent decrease in the transmitted frequency, which is proportional to the transmitter velocity, will occur when?
The transmitter moves away from the receiver
Q5. The Low Altitude Radio Altimeter (RADALT) uses the following wavelengths? (You must know – RADALT frewuency: 4200 MHz to 4400 MHz )
Centimetric Band Name Wavelength (m) Millimetric 0.001 – 0.009 m Centimetric 0.01 – 0.09 m Decimetric 0.1 – 0.9 m Metric 1 – 9 m Decametric 10 – 99 m Hectometric 100 – 999 m Kilometric 1,000 – 9999 m
Q6. Considering a primary radar system, what kind of aerials are used?
One directional antenna both for transmitting and for receiving. The primary radar operates on the echo-principle: ground radar facility transmits pulses of radio waves that are reflected from the aircraft back to the radar facility. The pulses must have sufficient energy to “travel” to the aircraft and back. There is no equipment required on board the aircraft as the radio waves get reflected from the aircraft structure itself. … Both the primary and secondary radars operating on the pulse principle use a directional antenna that is used both for the transmitting and receiving of the signals. …
Q7. Comparing a parabolic reflector with a flat plate antenna of the same size
the flat plate antenna generates less side lobes than the parabolic reflector. (and) the flat plate antenna has a considerably smaller beam width. Parabolic reflectors create more side lobe activity, which results in a waste of energy and a smaller range of the main beam. Newer technologies use flat plate (slotted) antennas with a less side lobe activity and a greater range (more energy in the beam). Another advantage is a smaller size of the antenna and less weight for creating the same performance.
Q8. If an aircraft’s Doppler system detects No an apparent change in the transmitted frequency, what does this indicate about the relative motion between the transmitter and the receiver?
They are moving at the same speed in the same direction
Q9. The ideal length of a half-wave dipole for a frequency of 112 MHz is:
1.3383 m
Q10. Into what range does ILS localizer wavelength fall? (You should know – ILS localizer frequency band: 108 MHz to 112 MHz)
Metric
Q11. Pulse modulation is used in______
SSR
Q12. A radio wave with a horizontal magnetic component would be best received by a……..aerial?
Vertical
Q13. An electromagnetic wave consists of an oscillating electric field (E) and an oscillating magnetic field (H). Which statement is correct?
when signal passes through the antenna, the “E” field is parallel to the wire and the “H” field is perpendicular to the wire.
Q14. An apparent increase in the transmitted frequency which is proportional to the transmitter velocity will occur when?
The transmitter moves towards the receiver
Q15. An electromagnetic wave is found to have a wavelength of 29.1 cm. In which frequency band is this wave located?
Q16. ** Which of the following is not an advantage of a slotted antenna (phased array)?
Directivity Slotted antennas or phased array antennas offer several advantages such as: Reduced side lobes (less unwanted radiation) Improved resolution (due to better beam shaping) Reduced power requirement (efficient beam steering) However, directivity is not considered an advantage specific to slotted antennas-because high directivity is a general feature of many directional antennas, not unique to slotted or phased arrays.
Q17. Wavelength is the distance from?
Wave crest to wave crest Wave crest to wave crest is correct answer Wavelength is distance from Crest to crest; trough to trough. Or distance travelled by wave in one cycle.
Q18. ** Helical antennas are used by GPS satellites for the following reasons:
because the signal has a circular polarization. Ref Ch 1: Explanation A helical antenna is an antenna consisting of a conducting wire wound in the form of a helix. … Helical antennas can operate in one of two principal modes: … • axial mode (VHF up to SHF), commonly used in satellite communication systems, which use circularly polarised radio waves…
Q19. Regarding the ionosphere, which of the following statements is true regarding the E-layer?
Its average height is 125 km and provides a max sky wave range of 1350 NM
Q20. The Automatic Direction Finder (ADF) uses the following wavelength? (You should know – ADF frequency band: 190 kHz to 1750 kHz)
Hectometric or Kilometric
Q21. Using a medium frequency band when is fading likely to occur?
Night with sky and ground waves generally during night, sky wave and ground reflected waves MAY meet in anti-phase and fading of signal occurs.
Q22. What describes polarization?
Orientation of the plane of oscillation of the electrical component (E) of the electromagnetic wave.
Q23. The bandwidth produced when a radio frequency (RF) of 3000 kHz is amplitude modulated with an audio frequency (AF) of 3 kHz is:
6 kHz
Q24. **Diffraction of an RF signal is a displacement of its propagation path due to:
Passing over obstacle with dimensions close to the wavelength
Q25. MF fading is most common?
At night due to the reception of both skywave and ground waves
Q26. Amplitude modulation is used in______
VOR and NDB
Q27. Which of the following will give the greatest surface wave range?
500 kHz low frequency greater ground range.
Q28. Why do most primary surveillance radars use circular polarization instead of simple linear (horizontal/vertical) polarization?
Reduce weather clutter: Symmetrical raindrops reverse the sense of circular polarization, allowing the radar to filter them out while keeping the asymmetrical aircraft return.
Q29. Which of the following is an advantage of single sideband (SSB) emissions?
All of the above
Q30. A radio signal has a frequency of 3 GHz, what is its wavelength?
10 centimeters
Q31. Which combination of factors will result in the greatest possible range for a surface wave?
Low frequency and high conductivity (sea water
Q32. The gain of an aerial is its ability to?
Compensate for attenuation Antenna gain helps compensate for attenuation by focusing energy more efficiently, thereby maintaining signal strength over longer distances.
Q33. A half wave dipole aerial suitable for transmitting an RF signal at 18 MHz should have an effective length of?
8.33 meters
Q34. *** Complete the following statement: ………… radio signals have a…………..range by………wave over………….than over………….
MF, greater, ground, sea, land
Q35. ** The ideal length for a Marconi aerial for a frequency of 2400 MHz is:
3.125 cm
Q36. The polarization of an electromagnetic wave describes:
the orientation of the plane of oscillation of the electrical component of the wave with regard to its direction of propagation.
Q37. Skip distance is longest by….and with a…. frequency.
Night, high
Q38. A loop antenna is commonly used in:
ADF receivers.
Q39. %% What is the minimum height for an aircraft at a range of 200 NM to be detected by radar at 1700 ft AMSL?
15 000 ft
Q40. An apparent increase in the transmitted frequency which is proportional to the transmitter velocity will occur when?
The transmitter moves towards the receiver
Q41. ** A radio wave with a horizontal magnetic component would be best received by a…….. dipole antenna.
vertical In the case of this question, we have a horizontal magnetic component of the signal, therefore the electrical component of the signal will be vertical => we have a vertical polarization. Therefore, for the best possible reception, the receiver antenna must also be vertical to receive the electrical component of the signal.
Q42. ** What causes the so called “night effect”?
A change in the direction of the plane of polarization due to reflections in the ionosphere poorly framed question: here is a more accurate phrasing : What is the primary cause of the “night effect” observed in radio navigation signals, particularly from NDBs? Explanation: When sky waves reflect off the ionosphere at night, their plane of polarization can rotate due to varying ionospheric conditions. Since NDB signals are linearly polarized, any change in polarization angle reduces the effective signal received by the aircraft’s antenna, leading to signal fading, distortion, or bearing errors – this is what we refer to as the night effect. Summary: NDBs use linear polarization Ionospheric reflection at night rotates the polarization plane Aircraft receivers may not align with the changed polarization -> signal loss or distortion
Q43. To establish and maintain effective HF communication, frequency at a given range:
Should be decreased at night In HF (High Frequency) communication, short-range sky wave propagation requires a lower frequency, as these waves reflect from lower ionospheric layers (like the E-layer). Long-range communication needs higher frequencies that can penetrate deeper and reflect from higher layers (like the F2-layer). Other options are incorrect: Frequencies increase with latitude. Lower frequencies are needed at night due to ionospheric changes Frequency is affected by both time of day and season
Q44. What is the lowest frequency where freedom from static interference can be guaranteed?
30 MHz space wave – VHF or Higher frequency, for Less static interference. static interference is worst at low freqency. so for sky wave – HF Communication – range 3 to 30 MHz, at 03 MHz- too much static — (caused by thunderstorm/Rain and other activity).
Q45. Two signals of the same frequency are received. The Reference wave is at its maximum positive peak (090) while the Variable wave is at its maximum negative peak (270). What is the phase difference between them?
Q46. # As the frequency of a transmitter is increased, the range of the ground wave will.
Decrease effective range decrease.
Q47. The term Doppler shift refers to:
The change in frequency measured at the receiver
Q48. Fading happens?
At night when ground waves and sky waves interfere with each other generally during night, sky wave and ground reflected waves MAY meet in anti-phase and fading of signal occurs.
Q49. Hertz (Hz) is:
the number of oscillations per second
Q50. The phase of the reference wave is 140 degree as the phase of the variable wave is 315Degree. Find the phase difference between reference and variable wave ?
185
Q51. A horizontally polarized electromagnetic wave:
has the E field horizontal. plane of polarization is plane Of E
Q52. A radio frequency (RF) of 2000 kHz (200 W) is amplitude modulated with an audio frequency (AF) of 100 kHz (40 W). By removing one sideband you can save ________ power being utilised by that side band.
20 W
Q53. A vertically polarized electromagnetic wave:
Has the E field vertical
Q54. An observer is located at a distance where the ground wave has attenuated to zero, but the sky wave has not yet returned to Earth. This specific area is known as the:
Dead Space: It is the gap between the end of the ground wave and the start of the first sky wave “hop.”
Q55. When a radio frequency (RF) of 2600 kHz is amplitude modulated with an audio frequency (AF) of 10 kHz, the frequency band will be.
2610 kHz to 2590 KHz
Q56. In Frequency Modulation (FM), how is the carrier wave specifically modified?
The frequency is modified by the amplitude of the AF
Q57. An electromagnetic wave consists of an oscillating electric field (E) and an oscillating magnetic field (H). Their propagation speed is:
the speed of light.
Q58. The speed of radio waves is:
300 million metres per second Light traveling through a vacuum moves at exactly 299,792,458 meters (983,571,056 feet) per second. That’s about 186,282 miles per second a universal constant known in equations and in shorthand as “c,” or the speed of light.