Vayudoot Aviation

1. Reflection from the ionospheric layers is used in the following radio frequencies?

HF.

VLF.

VHF.

UHF.

2. When a transmitter is moving towards a receiver, the correct description of Doppler effect is?

There is an increase in apparent wavelength, which is independent of transmitter velocity.

There is a decrease in apparent wavelength, which is dependent of transmitter velocity.

There is an increase in apparent wavelength , which is dependent of transmitter velocity transmitter velocity.

There is a decrease in apparent wavelength , which is independent of transmitter velocity.

3. What is the wavelength of the ILS Localiser signal?

Myriametric

Centimetric

Hectometric

Metric

4. The VHF frequency band has a wavelength limit of?

1 m to 100 cm.

10 m to 1 m.

100 m to 10 m.

100 cm to 10 cm.

5. The Low Altitude Radio Altimeter (RADALT) uses the following wavelengths?

Centimetric

Decimetric

Myriametric

Metric

6. The Secondary Surveillance Radar (SSR) uses the following wavelengths?

Hectometric

Decimetric

Centimetric

Myriametric

7. When an LF radio wave passes over the Earth's surface it?

Slows down and is attenuated.

Speeds up, picks up electrons and becomes stronger.

Speeds up and is attenuated.

Slows down, picks up electrons and becomes stronger.

8. A half wave dipole aerial suitable for transmitting an RF signal at 18 MHz should have an effective length of?

166.67 metres.

83.33 metres

16.67 metres.

8.33 metres

9. According to ICAO Annex 10, in which frequency band(s) does a locator transmit?

HF

HF/VHF

MF/HF

LF/MF

10. Complete the following statement. .....radio signals have a ..... range by ..... wave over ..... than over .....?

MF, shorter, sky, sea, land.

MF, greater, ground, sea, land.

VHF, shorter, sky, sea, land.

MF, greater, ground, land, sea.

11. The gain of an aerial is its ability to?

Focus power

Overcome transmitter line resistance

Transmit intelligence.

Compensate for attenuation

12.
In the diagram, the phase difference between the two signals is?

90 degrees

360 degrees

180 degrees

270 degrees.

13. Which of the following statements is true?

Bandwidth must be reduced in order to reduce noise.

A broad bandwidth gives a narrow beam width.

A transmission's bandwidth is affected by the design of the aerial.

A narrow bandwidth improves beam width.

14. Fading happens?

At night when the signal is received by ground waves only.

At night when ground waves and sky waves interfere with each other.

In daytime when ground waves and sky waves interfere with each other.

At daytime when the signal is received by sky waves only.

15. The VHF Direction Finder uses the following wavelengths?

Hectometric

Decimetric

Centimetric

Metric

16. The Marker beacons use the following wavelengths?

Myriametric

Hectometric

Centimetric

Metric

17. Electromagnetic waves travel at?

The speed of light

The speed of sound

162 000 miles per hour.

300 000 metres per second

18. Skip distance is the?

Wavelength distance of a certain frequency

Highest critical frequency distance

Thickness of the ionosphere.

Range from the transmitter to the first returning sky wave.

19. Comparing a parabolic reflector with a flat plate antenna of the same size?

The parabolic reflector generates less side lobes that the flat plate antenna.

The flat plate antenna generates less side lobes than the parabolic reflector

The flat plate has a considerably smaller beam width

The parabolic reflector has a considerably smaller beam width

20. What is the wavelength of a radio signal with a frequency of 375 kHz?

12.5 metres

800 metres

80 metres

1.25 metres

21.
At night due to the reception of both sky waves and ground waves.

Decrease by night only.

Decrease.

Increase.

Increase over the sea.

22. The VHF Omnirange (VOR) uses the following wavelengths?

Metric

Decimetric

Hectometric

Centimetric

23. The frequency band for the Automatic Direction Finder (ADF) is?

Decimetric

Centimetric

Hectometric

Metric

24. A horizontally polarised electromagnetic wave?

Has the Z field horizontal

Has the H field horizontal.

Has the E field vertical

Has the E field horizontal.

25. The Instrument Landing System (ILS) uses the following wavelengths?

Centimetric

Hectometric

Metric

Decimetric

26. Assuming a frequency of 20 MHz, the wavelength will be?

80 metres

12.5 metres

1.25 metres.

800 metres

27. The frequency at which sky waves should least affect reception?

MF.

VLF.

HF

LF.

28. A radio wave with a horizontal magnetic component would be best received by a ......... aerial?

Vertical

Horizontal

Parabolic

Magnetic

29.
In the diagram below what is the phase difference of the higher amplitude signal from the reference signal?

315 degrees

135 degrees.

225 degrees

045 degrees.

30. Decimetric waves correspond to a frequency of?

300 to 3000 MHz.

3000 to 30000 MHz.

300 to 3000 kHz.

3000 to 30000 kHz.

31. An apparent decrease in the transmitted frequency , which is proportional to the transmitter velocity, will occur when?

The transmitter moves away from the receiver .

The transmitter moves towards the receiver.

The transmitter and the receiver move towards each other.

Both transmitter and receiver move away from each other.

32. A radio signal has a frequency of 3 GHz, What is its wavelength?

1.0 centimetres.

10 centimetres.

100 centimetres.

1 metres

33. Diffraction is the process by which?

A space wave penetrates the ionosphere.

A direct wave is bend around the form of the Earth.

Radio waves travel over and around objects.

A ground wave is attenuated over rough ground.

34. What causes the so called "night effect"?

A change in the direction of the plane of polarisation due to reflections in the ionosphere.

The difference in velocity of the EM waves over land and over sea at night.

Interference between ground waves and space waves.

The absence of the surface wave at distances larger than the skip distance.

35. An HF transmitter is tuned to a frequency that refracts from the E layer in the ionosphere. The maximum distance of the first returning sky wave is?

1500 km.

599 km.

1500 nm.

599 nm.

36. The distance Measuring Equipment (DME) uses the following wavelengths?

Decimetric

Centimetric

Metric

Hectometric

37. The wavelength of a radio signal with a frequency of 121.95 MHz?

2.46 centimetres

26.60 metres.

2.46 metres.

24.60 centimetres

38. Using a medium frequency band when is fading likely to occur?

Day time when snowing.

night time when snowing.

Day with sky and ground waves.

Night with sky and ground waves.

39. A radio transmitter modulator?

Couples the RF signal to an aerial

Ensures receiver compatibility

Superimposes an audio frequency signal (AF) onto a radio frequency signal (RF).

Tunes the aerial only

40. In the propagation of MF waves, the phenomenon of FADING is particularly found?

By day and when raining.

By day due to the combination of sky waves and ground waves.

At night, due to the combination of sky waves and ground waves.

At night and when raining.

41. Which of the folllowing statements is correct in respect to a RF signal?

Both the electrical component and the magnetic component of the signal are parallel to the aerial.

The magnetic component of the signal is parallel to the aerial.

The plane of polarisation is dictated by the oscillator unit in the transmitter.

The electrical component of the signal is parallel to the aerial.

42. Attenuation of a radio wave is the?

Change of amplitude by use of sidebands.

Reduction of its power by absorption, scattering or spreading.

Increase of its power by the combination of multi-path signals.

Change of its frequency by use of sidebands.

43. The skip distance of HF transmissions will increase with?

Higher frequency and higher position of the reflecting layer.

Lower frequency and lower position of the reflecting layer.

Lower frequency and higher position of the reflecting layer.

Higher frequency and lower position of the reflecting layer.

44. The wavelength of a radio signal transmitted at a frequency of 118.7 MHz?

25.3 centimetres

2.53 metres.

25.3 metres

2.53 centimetres

45. To establish and maintain effective HF communication, frequency at a given range?

Should be decreased at night.

Should only be varied by season, decreased in summer and increased in winter.

Should be increased at night.

Should remain constant.

46. A frequency of 2400 kHz is equivalent to a wavelength of?

0.8 metres

125 metres

8 metres.

105 metres

47. The wavelength of a radio signal is 200 metres. What is its frequency?

1.5 GHz.

15 MHz.

1.5 kHz.

1.5 MHz.

48. What is the frequency corresponding to a wavelength of 12 centimetres is?

3600 MHz.

360 MHz.

2500 kHz

2500MHz.

49. An aircraft travelling at 300 metres per second transmits a radio signal at 10 GHz to a stationary receiver. If the aircraft is flying directly towards the receiver and they are approximately at the same height, the received signal frequency will be?

11 MHz.

9.999989 GHz.

10.000011 GHz.

11 GHz.

50. What is the wavelength corresponding to a frequency of 75 MHz?

7.5 metres.

40 metres.

4 metres.

75 metres.

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