G9 Questions
42 questions in this subelement. Click any question ID for more details.
Answer: B
What is the relationship between high standing wave ratio (SWR) and transmission line loss?
AThere is no relationship between transmission line loss and SWR
BHigh SWR increases loss in a lossy transmission line
CHigh SWR makes it difficult to measure transmission line loss
DHigh SWR reduces the relative effect of transmission line loss
Answer: D
What is the nominal characteristic impedance of “window line” transmission line?
A50 ohms
B75 ohms
C100 ohms
D450 ohms
Answer: C
What causes reflected power at an antenna’s feed point?
AOperating an antenna at its resonant frequency
BUsing more transmitter power than the antenna can handle
CA difference between feed line impedance and antenna feed point impedance
DFeeding the antenna with unbalanced feed line
Answer: B
How does the attenuation of coaxial cable change with increasing frequency?
AAttenuation is independent of frequency
BAttenuation increases
CAttenuation decreases
DAttenuation follows Marconi’s Law of Attenuation
Answer: D
In what units is RF feed line loss usually expressed?
AOhms per 1,000 feet
BDecibels per 1,000 feet
COhms per 100 feet
DDecibels per 100 feet
Answer: D
What must be done to prevent standing waves on a feed line connected to an antenna?
AThe antenna feed point must be at DC ground potential
BThe feed line must be an odd number of electrical quarter wavelengths long
CThe feed line must be an even number of physical half wavelengths long
DThe antenna feed point impedance must be matched to the characteristic impedance of the feed line
Answer: B
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?
A1:1
B5:1
CBetween 1:1 and 5:1 depending on the characteristic impedance of the line
DBetween 1:1 and 5:1 depending on the reflected power at the transmitter
Answer: A
What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?
A4:1
B1:4
C2:1
D1:2
Answer: D
What standing wave ratio results from connecting a 50-ohm feed line to a 10-ohm resistive load?
A2:1
B1:2
C1:5
D5:1
Answer: A
What is the effect of transmission line loss on SWR measured at the input to the line?
AHigher loss reduces SWR measured at the input to the line
BHigher loss increases SWR measured at the input to the line
CHigher loss increases the accuracy of SWR measured at the input to the line
DTransmission line loss does not affect the SWR measurement
Answer: 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?
ASlope the radials upward
BSlope the radials downward
CLengthen the radials beyond one wavelength
DCoil the radials
Answer: D
Which of the following best describes the radiation pattern of a quarter-wave ground-plane vertical antenna?
ABi-directional in azimuth
BIsotropic
CHemispherical
DOmnidirectional in azimuth
Answer: A
What is the radiation pattern of a dipole antenna in free space in a plane containing the conductor?
AIt is a figure-eight at right angles to the antenna
BIt is a figure-eight off both ends of the antenna
CIt is a circle (equal radiation in all directions)
DIt has a pair of lobes on one side of the antenna and a single lobe on the other side
Answer: C
How does antenna height affect the azimuthal radiation pattern of a horizontal dipole HF antenna at elevation angles higher than about 45 degrees?
AIf the antenna is too high, the pattern becomes unpredictable
BAntenna height has no effect on the pattern
CIf the antenna is less than 1/2 wavelength high, the azimuthal pattern is almost omnidirectional
DIf the antenna is less than 1/2 wavelength high, radiation off the ends of the wire is eliminated
Answer: C
Where should the radial wires of a ground-mounted vertical antenna system be placed?
AAs high as possible above the ground
BParallel to the antenna element
COn the surface or buried a few inches below the ground
DAt the center of the antenna
Answer: 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?
AIt steadily increases
BIt steadily decreases
CIt peaks at about 1/8 wavelength above ground
DIt is unaffected by the height above ground
Answer: 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?
AIt steadily increases
BIt steadily decreases
CIt peaks at about 1/8 wavelength from the end
DIt is unaffected by the location of the feed point
Answer: A
Which of the following is an advantage of using a horizontally polarized as compared to a vertically polarized HF antenna?
ALower ground losses
BLower feed point impedance
CShorter radials
DLower radiation resistance
Answer: D
What is the approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz?
A8 feet
B16 feet
C24 feet
D33 feet
Answer: C
What is the approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz?
A42 feet
B84 feet
C132 feet
D263 feet
Answer: A
What is the approximate length for a 1/4 wave monopole antenna cut for 28.5 MHz?
A8 feet
B11 feet
C16 feet
D21 feet
Answer: B
What is the approximate length of the driven element of a Yagi antenna?
A1/4 wavelength
B1/2 wavelength
C3/4 wavelength
D1 wavelength
Answer: A
How do the lengths of a three-element Yagi reflector and director compare to that of the driven element?
AThe reflector is longer, and the director is shorter
BThe reflector is shorter, and the director is longer
CThey are all the same length
DRelative length depends on the frequency of operation
Answer: B
How does antenna gain in dBi compare to gain stated in dBd for the same antenna?
AGain in dBi is 2.15 dB lower
BGain in dBi is 2.15 dB higher
CGain in dBd is 1.25 dBd lower
DGain in dBd is 1.25 dBd higher
Answer: A
What is the primary effect of increasing boom length and adding directors to a Yagi antenna?
AGain increases
BBeamwidth increases
CFront-to-back ratio decreases
DResonant frequency is lower
Answer: C
What does “front-to-back ratio” mean in reference to a Yagi antenna?
AThe number of directors versus the number of reflectors
BThe relative position of the driven element with respect to the reflectors and directors
CThe power radiated in the major lobe compared to that in the opposite direction
DThe ratio of forward gain to dipole gain
Answer: D
What is meant by the “main lobe” of a directive antenna?
AThe magnitude of the maximum vertical angle of radiation
BThe point of maximum current in a radiating antenna element
CThe maximum voltage standing wave point on a radiating element
DThe direction of maximum radiated field strength from the antenna
Answer: B
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?
AApproximately 1.5 dB higher
BApproximately 3 dB higher
CApproximately 6 dB higher
DApproximately 9 dB higher
Answer: D
Which of the following can be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth of a Yagi antenna?
AThe physical length of the boom
BThe number of elements on the boom
CThe spacing of each element along the boom
DAll these choices are correct
Answer: A
What is a beta or hairpin match?
AA shorted transmission line stub placed at the feed point of a Yagi antenna to provide impedance matching
BA 1/4 wavelength section of 75-ohm coax in series with the feed point of a Yagi to provide impedance matching
CA series capacitor selected to cancel the inductive reactance of a folded dipole antenna
DA section of 300-ohm twin-lead transmission line used to match a folded dipole antenna
Answer: A
Which of the following is a characteristic of using a gamma match with a Yagi antenna?
AIt does not require the driven element to be insulated from the boom
BIt does not require any inductors or capacitors
CIt is useful for matching multiband antennas
DAll these choices are correct
Answer: D
What is the feed point impedance of an end-fed half-wave antenna?
AVery low
BApproximately 50 ohms
CApproximately 300 ohms
DVery high
Answer: C
In which direction is the maximum radiation from a VHF/UHF “halo” antenna?
ABroadside to the plane of the halo
BOpposite the feed point
COmnidirectional in the plane of the halo
DOn the same side as the feed point
Answer: A
What is the primary function of antenna traps?
ATo enable multiband operation
BTo notch spurious frequencies
CTo provide balanced feed point impedance
DTo prevent out-of-band operation
Answer: D
What is an advantage of vertically stacking horizontally polarized Yagi antennas?
AIt allows quick selection of vertical or horizontal polarization
BIt allows simultaneous vertical and horizontal polarization
CIt narrows the main lobe in azimuth
DIt narrows the main lobe in elevation
Answer: A
Which of the following is an advantage of a log-periodic antenna?
AWide bandwidth
BHigher gain per element than a Yagi antenna
CHarmonic suppression
DPolarization diversity
Answer: A
Which of the following describes a log-periodic antenna?
AElement length and spacing vary logarithmically along the boom
BImpedance varies periodically as a function of frequency
CGain varies logarithmically as a function of frequency
DSWR varies periodically as a function of boom length
Answer: B
How does a “screwdriver” mobile antenna adjust its feed point impedance?
ABy varying its body capacitance
BBy varying the base loading inductance
CBy extending and retracting the whip
DBy deploying a capacitance hat
Answer: A
What is the primary use of a Beverage antenna?
ADirectional receiving for MF and low HF bands
BDirectional transmitting for low HF bands
CPortable direction finding at higher HF frequencies
DPortable direction finding at lower HF frequencies
Answer: B
In which direction or directions does an electrically small loop (less than 1/10 wavelength in circumference) have nulls in its radiation pattern?
AIn the plane of the loop
BBroadside to the loop
CBroadside and in the plane of the loop
DElectrically small loops are omnidirectional
Answer: D
Which of the following is a disadvantage of multiband antennas?
AThey present low impedance on all design frequencies
BThey must be used with an antenna tuner
CThey must be fed with open wire line
DThey have poor harmonic rejection
Answer: A
What is the common name of a dipole with a single central support?
AInverted V
BInverted L
CSloper
DLazy H