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31 matching questions

Question #565Antennas and Radio Wave Propagation

What causes “tropospheric ducting"?

  1. Discharges of lightning during electrical storms
  2. Sunspots and solar flares
  3. Updrafts from hurricanes and tornadoes
  4. Temperature inversions in the atmosphere ✓ Correct answer

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Question #569Antennas and Radio Wave Propagation

What is meant by the gain of an antenna?

  1. The additional power that is added to the transmitter power
  2. The additional power that is lost in the antenna when transmitting on a higher frequency
  3. the increase in signal strength when compared to a reference antenna ✓ Correct answer
  4. The increase in impedance on receive or transmit compared to a reference antenna

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Question #572Antennas and Radio Wave Propagation

Which of the following instruments can be used to determine if an antenna is resonant at the designed frequency?

  1. A multimeter
  2. Antenna analyzer ✓ Correct answer
  3. A “Q” meter
  4. A frequency counter

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Question #579Antennas and Radio Wave Propagation

A dummy antenna

  1. attenuates a signal generator to a desirable level
  2. provides more selectivity when a transmitter is being tuned
  3. matches an AF generator to the receiver
  4. duplicates the characteristics of an antenna without radiating signals ✓ Correct answer

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Question #584Antennas and Radio Wave Propagation

Magnetic and electric fields about an antenna are

  1. parallel to each other
  2. determined by the type of antenna used
  3. perpendicular to each other ✓ Correct answer
  4. variable with the time of day

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Question #585Antennas and Radio Wave Propagation

A half-wave antenna is often called a

  1. bi-polar
  2. Yagi
  3. dipole ✓ Correct answer
  4. beam

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Question #667Antennas and Radio Wave Propagation

A Yagi antenna is a type of

  1. Directional antenna ✓ Correct answer
  2. Omnidirectional antenna
  3. Isotropic antenna
  4. Dummy load
Explanation: A Yagi-Uda antenna is directional.

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Question #668Antennas and Radio Wave Propagation

An isotropic antenna is an

  1. Ideal point-source radiator used as a reference ✓ Correct answer
  2. Practical mobile whip
  3. Type of dummy load
  4. FM only antenna
Explanation: Isotropic radiator is a theoretical reference antenna.

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Question #669Antennas and Radio Wave Propagation

Ground wave propagation is most useful at

  1. MF and lower HF ✓ Correct answer
  2. Microwave only
  3. Optical frequencies
  4. VLF only never HF
Explanation: Ground-wave coverage is important on MF and lower HF.

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Question #670Antennas and Radio Wave Propagation

Skip distance is related to

  1. Sky-wave propagation ✓ Correct answer
  2. Optical fibre
  3. Waveguide only
  4. DC circuits
Explanation: Skip distance is a sky-wave propagation concept.

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Question #671Antennas and Radio Wave Propagation

The ionospheric layer most responsible for long-distance HF at night is often the

  1. F layer ✓ Correct answer
  2. D layer
  3. C layer
  4. G layer
Explanation: The F region supports much nighttime long-distance HF.

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