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effective 7/01/2015 thru 6/30/2019

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2015-G9B: Basic antennas

2015-G9B01: What is one disadvantage of a directly fed random-wire HF antenna?

You may experience RF burns when touching metal objects in your station

It must be longer than 1 wavelength

It produces only vertically polarized radiation

It is more effective on the lower HF bands than on the higher bands



2015-G9B02: Which of the following is a common way to adjust the feed point impedance of a quarter wave ground plane vertical antenna to be approximately 50 ohms?

Slope the radials downward

Slope the radials upward

Lengthen the radials

Shorten the radials



2015-G9B03: What happens to the feed point impedance of a ground plane antenna when its radials are changed from horizontal to sloping downward?

It increases

It decreases

It stays the same

It reaches a maximum at an angle of 45 degrees



2015-G9B04: What is the radiation pattern of a dipole antenna in free space in the plane of the conductor?

It is a figure-eight at right angles to the antenna

It is a figure-eight off both ends of the antenna

It is a circle (equal radiation in all directions)

It has a pair of lobes on one side of the antenna and a single lobe on the other side



2015-G9B05: How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?

If the antenna is less than 1/2 wavelength high, the azimuthal pattern is almost omnidirectional

If the antenna is too high, the pattern becomes unpredictable

Antenna height has no effect on the pattern

If the antenna is less than 1/2 wavelength high, radiation off the ends of the wire is eliminated



2015-G9B06: Where should the radial wires of a ground-mounted vertical antenna system be placed?

On the surface of the Earth or buried a few inches below the ground

As high as possible above the ground

Parallel to the antenna element

At the center of the antenna



2015-G9B07: How does the feed point impedance of a 1/2 wave dipole antenna change as the antenna is lowered below 1/4 wave above ground?

It steadily decreases

It steadily increases

It peaks at about 1/8 wavelength above ground

It is unaffected by the height above ground



2015-G9B08: 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?

It steadily increases

It steadily decreases

It peaks at about 1/8 wavelength from the end

It is unaffected by the location of the feed point



2015-G9B09: Which of the following is an advantage of a horizontally polarized as compared to a vertically polarized HF antenna?

Lower ground reflection losses

Lower feed point impedance

Shorter Radials

Lower radiation resistance



2015-G9B10: What is the approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz?

32 feet

8 feet

16 feet

24 feet



2015-G9B11: What is the approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz?

131 feet

42 feet

84 feet

263 feet



2015-G9B12: What is the approximate length for a 1/4 wave vertical antenna cut for 28.5 MHz?

8 feet

11 feet

16 feet

21 feet





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2015-G9A: Antenna feed lines: characteristic impedance, and attenuation; SWR calculation, measurement and effects; matching networks
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2015-G9C: Directional antennas
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