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Amateur Radio 2024 - General > G9 – ANTENNAS AND FEED LINES [4 Exam Questions – 4 Groups] 46 Questions > Flashcards

G9 – ANTENNAS AND FEED LINES [4 Exam Questions – 4 Groups] 46 Questions Flashcards

1
Q

“Which of the following factors determine the characteristic impedance of a parallel conductor feed line?”

A. The distance between the centers of the conductors and the radius of the conductors
B. The distance between the centers of the conductors and the length of the line
C. The radius of the conductors and the frequency of the signal
D. The frequency of the signal and the length of the line

A

A. The distance between the centers of the conductors and the radius of the conductors

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2
Q

“What is the relationship between high standing wave ratio (SWR) and transmission line loss?”

A. There is no relationship between transmission line loss and SWR
B. High SWR increases loss in a lossy transmission line
C. High SWR makes it difficult to measure transmission line loss
D. High SWR reduces the relative effect of transmission line loss

A

B. High SWR increases loss in a lossy transmission line

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3
Q

“What is the nominal characteristic impedance of “window line” transmission line?”

A. 50 ohms
B. 75 ohms
C. 100 ohms
D. 450 ohms

A

D. 450 ohms

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4
Q

“What causes reflected power at an antenna’s feed point?”

A. Operating an antenna at its resonant frequency
B. Using more transmitter power than the antenna can handle
C. A difference between feed line impedance and antenna feed point impedance
D. Feeding the antenna with unbalanced feed line

A

C. A difference between feed line impedance and antenna feed point impedance

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5
Q

“How does the attenuation of coaxial cable change with increasing frequency?”

A. Attenuation is independent of frequency
B. Attenuation increases
C. Attenuation decreases
D. Attenuation follows Marconi’s Law of Attenuation

A

B. Attenuation increases

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6
Q

“In what units is RF feed line loss usually expressed?”

A. Ohms per 1,000 feet
B. Decibels per 1,000 feet
C. Ohms per 100 feet
D. Decibels per 100 feet

A

D. Decibels per 100 feet

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7
Q

“What must be done to prevent standing waves on a feed line connected to an antenna?”

A. The antenna feed point must be at DC ground potential
B. The feed line must be an odd number of electrical quarter wavelengths long
C. The feed line must be an even number of physical half wavelengths long
D. The antenna feed point impedance must be matched to the characteristic impedance of the feed line

A

D. The antenna feed point impedance must be matched to the characteristic impedance of the feed line

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8
Q

“If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is adjusted to present a 1:1 SWR to the transmitter, what is the resulting SWR on the feed line?”

A. 1:1
B. 5:1
C. Between 1:1 and 5:1 depending on the characteristic impedance of the line
D. Between 1:1 and 5:1 depending on the reflected power at the transmitter

A

B. 5:1

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9
Q

“What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?”

A. 4:1
B. 1:4
C. 2:1
D. 1:2

A

A. 4:1

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10
Q

“What standing wave ratio results from connecting a 50-ohm feed line to a 10-ohm resistive load?”

A. 2:1
B. 1:2
C. 1:5
D. 5:1

A

D. 5:1

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11
Q

“What is the effect of transmission line loss on SWR measured at the input to the line?”

A. Higher loss reduces SWR measured at the input to the line
B. Higher loss increases SWR measured at the input to the line
C. Higher loss increases the accuracy of SWR measured at the input to the line
D. Transmission line loss does not affect the SWR measurement

A

A. Higher loss reduces SWR measured at the input to the line

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12
Q

“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
D. It is more effective on the lower HF bands than on the higher bands

A

B. Station equipment may carry significant RF current

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13
Q

“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
D. Coil the radials

A

B. Slope the radials downward

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14
Q

“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
D. Omnidirectional in azimuth

A

D. Omnidirectional in azimuth

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15
Q

“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)
D. It has a pair of lobes on one side of the antenna and a single lobe on the other side

A

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

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16
Q

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

A

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

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17
Q

“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
D. At the center of the antenna

A

C. On the surface or buried a few inches below the ground

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18
Q

“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
D. It is unaffected by the height above ground

A

B. It steadily decreases

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19
Q

“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
D. It is unaffected by the location of the feed point

A

A. It steadily increases

20
Q

“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
D. Lower radiation resistance

A

A. Lower ground losses

21
Q

“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
D. 33 feet

A

D. 33 feet

22
Q

“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
D. 263 feet

A

C. 132 feet

23
Q

“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

A

A. 8 feet

24
Q

“Which of the following would increase the bandwidth of a Yagi antenna?”

A. Larger-diameter elements
B. Closer element spacing
C. Loading coils in series with the element
D. Tapered-diameter elements

A

A. Larger-diameter elements

25
Q

“What is the approximate length of the driven element of a Yagi antenna?”

A. 1/4 wavelength
B. 1/2 wavelength
C. 3/4 wavelength
D. 1 wavelength

A

B. 1/2 wavelength

26
Q

“How do the lengths of a three-element Yagi reflector and director compare to that of the driven element?”

A. The reflector is longer, and the director is shorter
B. The reflector is shorter, and the director is longer
C. They are all the same length
D. Relative length depends on the frequency of operation

A

A. The reflector is longer, and the director is shorter

27
Q

“How does antenna gain in dBi compare to gain stated in dBd for the same antenna?”

A. Gain in dBi is 2.15 dB lower
B. Gain in dBi is 2.15 dB higher
C. Gain in dBd is 1.25 dBd lower
D. Gain in dBd is 1.25 dBd higher

A

B. Gain in dBi is 2.15 dB higher

28
Q

“What is the primary effect of increasing boom length and adding directors to a Yagi antenna?”

A. Gain increases
B. Beamwidth increases
C. Front-to-back ratio decreases
D. Resonant frequency is lower

A

A. Gain increases

29
Q

“What is meant by the “main lobe” of a directive antenna?”

A. The magnitude of the maximum vertical angle of radiation
B. The point of maximum current in a radiating antenna element
C. The maximum voltage standing wave point on a radiating element
D. The direction of maximum radiated field strength from the antenna

A

D. The direction of maximum radiated field strength from the antenna

30
Q

“In free space, how does the gain of two three-element, horizontally polarized Yagi antennas spaced vertically 1/2 wavelength apart typically compare to the gain of a single three-element Yagi?”

A. Approximately 1.5 dB higher
B. Approximately 3 dB higher
C. Approximately 6 dB higher
D. Approximately 9 dB higher

A

B. Approximately 3 dB higher

31
Q

“Which of the following can be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth of a Yagi antenna?”

A. The physical length of the boom
B. The number of elements on the boom
C. The spacing of each element along the boom
D. All these choices are correct

A

D. All these choices are correct

32
Q

“What is a beta or hairpin match?”

A. A shorted transmission line stub placed at the feed point of a Yagi antenna to provide impedance matching
B. A 1/4 wavelength section of 75-ohm coax in series with the feed point of a Yagi to provide impedance matching
C. A series capacitor selected to cancel the inductive reactance of a folded dipole antenna
D. A section of 300-ohm twin-lead transmission line used to match a folded dipole antenna

A

A. A shorted transmission line stub placed at the feed point of a Yagi antenna to provide impedance matching

33
Q

“Which of the following is a characteristic of using a gamma match with a Yagi antenna?”

A. It does not require the driven element to be insulated from the boom
B. It does not require any inductors or capacitors
C. It is useful for matching multiband antennas
D. All these choices are correct

A

A. It does not require the driven element to be insulated from the boom

34
Q

“Which of the following antenna types will be most effective as a near vertical incidence skywave (NVIS) antenna for short-skip communications on 40 meters during the day?”

A. A horizontal dipole placed between 1/10 and 1/4 wavelength above the ground
B. A vertical antenna placed between 1/4 and 1/2 wavelength above the ground
C. A horizontal dipole placed at approximately 1/2 wavelength above the ground
D. A vertical dipole placed at approximately 1/2 wavelength above the ground

A

A. A horizontal dipole placed between 1/10 and 1/4 wavelength above the ground

35
Q

“What is the feed point impedance of an end-fed half-wave antenna?”

A. Very low
B. Approximately 50 ohms
C. Approximately 300 ohms
D. Very high

A

D. Very high

36
Q

“In which direction is the maximum radiation from a VHF/UHF “halo” antenna?”

A. Broadside to the plane of the halo
B. Opposite the feed point
C. Omnidirectional in the plane of the halo
D. On the same side as the feed point

A

C. Omnidirectional in the plane of the halo

37
Q

“What is the primary function of antenna traps?”

A. To enable multiband operation
B. To notch spurious frequencies
C. To provide balanced feed point impedance
D. To prevent out-of-band operation

A

A. To enable multiband operation

38
Q

“What is an advantage of vertically stacking horizontally polarized Yagi antennas?”

A. It allows quick selection of vertical or horizontal polarization
B. It allows simultaneous vertical and horizontal polarization
C. It narrows the main lobe in azimuth
D. It narrows the main lobe in elevation

A

D. It narrows the main lobe in elevation

39
Q

“Which of the following is an advantage of a log-periodic antenna?”

A. Wide bandwidth
B. Higher gain per element than a Yagi antenna
C. Harmonic suppression
D. Polarization diversity

A

A. Wide bandwidth

40
Q

“Which of the following describes a log-periodic antenna?”

A. Element length and spacing vary logarithmically along the boom
B. Impedance varies periodically as a function of frequency
C. Gain varies logarithmically as a function of frequency
D. SWR varies periodically as a function of boom length

A

A. Element length and spacing vary logarithmically along the boom

41
Q

“How does a “screwdriver” mobile antenna adjust its feed point impedance?”

A. By varying its body capacitance
B. By varying the base loading inductance
C. By extending and retracting the whip
D. By deploying a capacitance hat

A

B. By varying the base loading inductance

42
Q

“What is the primary use of a Beverage antenna?”

A. Directional receiving for MF and low HF bands
B. Directional transmitting for low HF bands
C. Portable direction finding at higher HF frequencies
D. Portable direction finding at lower HF frequencies

A

A. Directional receiving for MF and low HF bands

43
Q

“In which direction or directions does an electrically small loop (less than 1/10 wavelength in circumference) have nulls in its radiation pattern?”

A. In the plane of the loop
B. Broadside to the loop
C. Broadside and in the plane of the loop
D. Electrically small loops are omnidirectional

A

B. Broadside to the loop

44
Q

“Which of the following is a disadvantage of multiband antennas?”

A. They present low impedance on all design frequencies
B. They must be used with an antenna tuner
C. They must be fed with open wire line
D. They have poor harmonic rejection

A

D. They have poor harmonic rejection

45
Q

“What is the common name of a dipole with a single central support?”

A. Inverted V
B. Inverted L
C. Sloper
D. Lazy H

A

A. Inverted V

Amateur Radio 2024 - General (10 decks)

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