DXRDXR ASOC EXAM PRACTICE PORTAL · VU3DXR.IN
OPEN LEARNING LIBRARY

ASOC Question Bank

Browse MCQs, correct answers and explanations free of charge. No registration is required.

31 matching questions

Question #14Antennas and Radio Wave Propagation

Among the following which is not a directional antenna

  1. Whip antenna ✓ Correct answer
  2. Yagi-Uda antenna
  3. Loop antenna
  4. Dish antenna
Explanation: A whip antenna is generally omnidirectional in the horizontal plane.

Open this question separately

Question #28Antennas and Radio Wave Propagation

Sky wave propagation utilizes

  1. Troposphere
  2. Stratosphere
  3. Ionosphere ✓ Correct answer
  4. Exosphere
Explanation: Sky-wave propagation relies on refraction/return of radio waves by the ionosphere.

Open this question separately

Question #29Antennas and Radio Wave Propagation

Ionosphere does not have _______ layer.

  1. C ✓ Correct answer
  2. D
  3. E
  4. F
Explanation: The recognised ionospheric regions are D, E, F1 and F2; there is no C layer.

Open this question separately

Question #30Antennas and Radio Wave Propagation

Which layer of ionosphere disappears during night time?

  1. C
  2. D ✓ Correct answer
  3. E
  4. F
Explanation: The D layer largely disappears at night because solar ionisation falls.

Open this question separately

Question #31Antennas and Radio Wave Propagation

In dealing with sky/ground wave propagation, the area of silence where no signals are received is the

  1. dead zone
  2. skip distance
  3. skip zone ✓ Correct answer
  4. propagation distance.
Explanation: The skip zone is the region between the end of ground-wave coverage and the first returned sky wave.

Open this question separately

Question #32Antennas and Radio Wave Propagation

Frequencies lesser than the critical frequency are

  1. passed into space
  2. the most desirable
  3. returned to earth ✓ Correct answer
  4. refracted by the F2 layer
Explanation: Below the critical frequency, a wave can be refracted back toward Earth under suitable ionospheric conditions.

Open this question separately

Question #37Antennas and Radio Wave Propagation

Which antenna is used for direction finding purpose?

  1. Loop antenna ✓ Correct answer
  2. Active Whip antenna
  3. Whip antenna
  4. Dipole antenna
Explanation: A loop antenna has a directional null and is commonly used for radio direction finding.

Open this question separately

Question #135Antennas and Radio Wave Propagation

Line of sight propagation is the mode of communication in

  1. LF
  2. HF
  3. MF
  4. VHF ✓ Correct answer
Explanation: VHF propagation is predominantly line-of-sight; UHF is also line-of-sight, but the available option D is VHF.

Open this question separately

Question #170Antennas and Radio Wave Propagation

How does the wavelength of a radio wave relate to its frequency?

  1. The wavelength gets longer as the frequency increases
  2. The wavelength gets shorter as the frequency increases ✓ Correct answer
  3. There is no relationship between wavelength and frequency
  4. The wavelength depends on the bandwidth of the signal

Open this question separately

Question #171Antennas and Radio Wave Propagation

What is the formula for converting frequency to wavelength in meters?

  1. Wavelength in meters equals frequency in Hertz multiplied by 300
  2. Wavelength in meters equals frequency in Hertz divided by 300
  3. Wavelength in meters equals frequency in megahertz divided by 300
  4. Wavelength in meters equals 300 divided by frequency in megahertz ✓ Correct answer

Open this question separately

Question #260Antennas and Radio Wave Propagation

The wavelength of a broadcast station at 1000 KHz is

  1. 30 Meters
  2. 300 Meters ✓ Correct answer
  3. 0.3 Meteors
  4. none of these

Open this question separately

Question #321Antennas and Radio Wave Propagation

Which is used as a multi-band HF receiving antenna

  1. Conical horn
  2. Long-periodic ✓ Correct answer
  3. Square—loop
  4. Folded-dipole

Open this question separately

Question #322Antennas and Radio Wave Propagation

The designed output impedance of the antenna socket of most modern transmitters is nominally:

  1. 25 ohm
  2. 50 ohm ✓ Correct answer
  3. 75 ohm
  4. 100 ohm

Open this question separately

Question #324Antennas and Radio Wave Propagation

If the antenna is vertical with respect to earth, then waves are

  1. Constant
  2. Polarized vertical ✓ Correct answer
  3. Polarized horizontal
  4. None of these

Open this question separately

Question #386Antennas and Radio Wave Propagation

The wavelength for a frequency of 25 MHz is:

  1. 15 m
  2. 32 m
  3. 4 m
  4. 12 m ✓ Correct answer
Explanation: The wavelength is λ = c/f ≈ 300/25 = 12 metres. The option text was cleaned of OCR spillover.

Open this question separately

Question #404Antennas and Radio Wave Propagation

The most suitable antenna for receiving VHF range is

  1. Dipole
  2. Log periodic
  3. Yagi ✓ Correct answer
  4. None of the above 208.Which of the following instruments can be used to determine if an antenna is resonant at the designed frequency?

Open this question separately

Question #517Antennas and Radio Wave Propagation

How does the wavelength related to frequency?

  1. The wavelength gets longer as the frequency increases
  2. The wavelength gets shorter as the frequency increases ✓ Correct answer
  3. There is no relationship between wavelength and frequency
  4. The wavelength depends on the bandwidth of the signal

Open this question separately

Question #518Antennas and Radio Wave Propagation

What is the formula for converting frequency to wavelength

  1. Wavelength in meters equals frequency in hertz multiplied by 300
  2. Wavelength in meters equals frequency in hertz divided by 300
  3. Wavelength in meters equals frequency in megahertz divided by 300
  4. Wavelength in meters equals 300 divided by frequency in megahertz ✓ Correct answer

Open this question separately

Question #528Antennas and Radio Wave Propagation

A coaxial feed-line is constructed from

  1. a single conductor
  2. two parallel conductors separated by spacers
  3. braid and insulation around a central conductor ✓ Correct answer
  4. braid and insulation twisted together

Open this question separately

Question #564Antennas and Radio Wave Propagation

Which part of the atmosphere enables the propagation of radio signals around the world?

  1. The stratosphere
  2. The troposphere
  3. The ionosphere ✓ Correct answer
  4. The mesosphere

Open this question separately