3.4 KiB
3.4 KiB
G9B – Basic dipole and monopole antennas
- G9B01 (B)
What is a characteristic of a random-wire HF antenna connected directly to the transmitter?
- A. It must be longer than 1 wavelength
- B. Station equipment may carry significant RF current
- C. It produces only vertically polarized radiation
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D. It is more effective on the lower HF bands than on the higher bands
- G9B02 (B)
Which of the following is a common way to adjust the feed point impedance of an elevated quarter-wave ground-plane vertical antenna to be approximately 50 ohms?
- A. Slope the radials upward
- B. Slope the radials downward
- C. Lengthen the radials beyond one wavelength
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D. Coil the radials
- G9B03 (D)
Which of the following best describes the radiation pattern of a quarter-wave ground-plane vertical antenna?
- A. Bi-directional in azimuth
- B. Isotropic
- C. Hemispherical
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D. Omnidirectional in azimuth
- G9B04 (A)
What is the radiation pattern of a dipole antenna in free space in a plane containing the conductor?
- A. It is a figure-eight at right angles to the antenna
- B. It is a figure-eight off both ends of the antenna
- C. It is a circle (equal radiation in all directions)
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D. It has a pair of lobes on one side of the antenna and a single lobe on the other side
- G9B05 (C)
How does antenna height affect the azimuthal radiation pattern of a horizontal dipole HF antenna at elevation angles higher than about 45 degrees?
- A. If the antenna is too high, the pattern becomes unpredictable
- B. Antenna height has no effect on the pattern
- C. If the antenna is less than 1/2 wavelength high, the azimuthal pattern is almost omnidirectional
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D. If the antenna is less than 1/2 wavelength high, radiation off the ends of the wire is eliminated
- G9B06 (C)
Where should the radial wires of a ground-mounted vertical antenna system be placed?
- A. As high as possible above the ground
- B. Parallel to the antenna element
- C. On the surface or buried a few inches below the ground
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D. At the center of the antenna
- G9B07 (B)
How does the feed point impedance of a horizontal 1/2 wave dipole antenna change as the antenna height is reduced to 1/10 wavelength above ground?
- A. It steadily increases
- B. It steadily decreases
- C. It peaks at about 1/8 wavelength above ground
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D. It is unaffected by the height above ground
- G9B08 (A)
How does the feed point impedance of a 1/2 wave dipole change as the feed point is moved from the center toward the ends?
- A. It steadily increases
- B. It steadily decreases
- C. It peaks at about 1/8 wavelength from the end
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D. It is unaffected by the location of the feed point
- G9B09 (A)
Which of the following is an advantage of using a horizontally polarized as compared to a vertically polarized HF antenna?
- A. Lower ground losses
- B. Lower feed point impedance
- C. Shorter radials
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D. Lower radiation resistance
- G9B10 (D)
What is the approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz?
- A. 8 feet
- B. 16 feet
- C. 24 feet
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D. 33 feet
- G9B11 (C)
What is the approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz?
- A. 42 feet
- B. 84 feet
- C. 132 feet
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D. 263 feet
- G9B12 (A)
What is the approximate length for a 1/4 wave monopole antenna cut for 28.5 MHz?
- A. 8 feet
- B. 11 feet
- C. 16 feet
- D. 21 feet