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SUBELEMENT G9 -- ANTENNAS AND FEED-LINES
[4 Exam Questions -- 4 Groups]

G9A Yagi antennas - physical dimensions; impedance matching; radiation patterns; directivity and major lobes
G9A01 (A)
When designing a Yagi antenna, how can the SWR bandwidth be increased?
A. Use larger diameter elements
B. Use closer element spacing
C. Use traps on the elements
D. Use tapered-diameter elements

G9A02 (B)
Approximately how long is the driven element of a Yagi 
antenna for 14.0 MHz?
A.   17 feet
B.   33 feet
C.   35 feet
D.   66 feet

G9A03 (B)
Approximately how long is the director element of a Yagi 
antenna for 21.1 MHz?
A.   42 feet
B.   21 feet
C.   17 feet
D.   10.5 feet

G9A04 (C)
Approximately how long is the reflector element of a Yagi 
antenna for 28.1 MHz?
A.   8.75 feet
B.   16.6 feet
C.   17.5 feet
D.   35 feet

G9A05 (B)
Which statement about a three-element Yagi antenna is true?
A.   The reflector is normally the shortest parasitic 
element
B.   The director is normally the shortest parasitic 
element
C.   The driven element is the longest parasitic element
D.   Low feed-point impedance increases bandwidth

G9A06 (A)
What is one effect of increasing the boom length and adding 
directors to a Yagi antenna?
A.   Gain increases
B.   SWR increases
C.   Weight decreases
D.   Wind load decreases

G9A07 (C)
Why is a Yagi antenna often used for radio communications 
on the 20-meter band?
A.   It provides excellent omnidirectional coverage in the 
horizontal Plane
B.   It is smaller, less expensive and easier to erect than 
a dipole or vertical antenna
C.   It helps reduce interference from other stations off 
to the side or behind
D.   It provides the highest possible angle of radiation 
for the HF bands

G9A08 (C)
What does "antenna front-to-back ratio" mean in reference 
to a Yagi antenna?
A.   The number of directors versus the number of 
reflectors
B.   The relative position of the driven element with 
respect to the reflectors and directors
C.   The power radiated in the major radiation lobe 
compared to the power radiated in exactly the opposite 
direction
D.   The power radiated in the major radiation lobe 
compared to the power radiated 90 degrees away from that 
direction

G9A09 (D)
What is the "main lobe" of a Yagi antenna radiation 
pattern?
A.   The direction of least radiation from the antenna
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

G9A10 (A)
What is a good way to get maximum performance from a Yagi 
antenna?
A.   Optimize the lengths and spacing of the elements
B.   Use RG-58 feed-line
C.   Use a reactance bridge to measure the antenna 
performance from each direction around the antenna
D.   Avoid using towers higher than 30 feet above the 
ground

G9A11 (D)
Which of the following is NOT a Yagi antenna design 
variable that should be considered to optimize the forward 
gain, front-to-rear ratio and SWR bandwidth?
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.   The polarization of the antenna elements

G9B Loop antennas - physical dimensions; impedance matching; radiation patterns; directivity and major lobes

G9B01 (B) Approximately how long is each side of a cubical-quad antenna driven element for 21.4 MHz? A. 1.17 feet B. 11.7 feet C. 47 feet D. 469 feet G9B02 (A) Approximately how long is each side of a cubical-quad antenna driven element for 14.3 MHz? A. 17.6 feet B. 23.4 feet C. 70.3 feet D. 175 feet G9B03 (B) Approximately how long is each side of a cubical-quad antenna reflector element for 29.6 MHz? A. 8.23 feet B. 8.7 feet C. 9.7 feet D. 34.8 feet G9B04 (B) Approximately how long is each leg of a symmetrical delta- loop antenna driven element for 28.7 MHz? A. 8.75 feet B. 11.7 feet C. 23.4 feet D. 35 feet G9B05 (C) Approximately how long is each leg of a symmetrical delta- loop antenna driven element for 24.9 MHz? A. 10.99 feet B. 12.95 feet C. 13.45 feet D. 40.36 feet G9B06 (C) Approximately how long is each leg of a symmetrical delta- loop antenna reflector element for 14.1 MHz? A. 18.26 feet B. 23.76 feet C. 24.35 feet D. 73.05 feet G9B07 (A) Which statement about two-element quad antennas is true? A. They compare favorably with a three-element Yagi B. They perform poorly above HF C. They perform very well only at HF D. They are effective only when constructed using insulated wire G9B08 (D) Compared to a dipole antenna, what are the directional radiation characteristics of a cubical-quad antenna? A. The quad has more directivity in the horizontal plane but less directivity in the vertical plane B. The quad has less directivity in the horizontal plane but more directivity in the vertical plane C. The quad has less directivity in both horizontal and vertical planes D. The quad has more directivity in both horizontal and vertical planes G9B09 (D) Moving the feed point of a multielement quad antenna from a side parallel to the ground to a side perpendicular to the ground will have what effect? A. It will significantly increase the antenna feed-point impedance B. It will significantly decrease the antenna feed-point impedance C. It will change the antenna polarization from vertical to horizontal D. It will change the antenna polarization from horizontal to vertical G9B10 (D) What does the term "antenna front-to-back ratio" mean in reference to a cubical-quad antenna? A. The number of directors versus the number of reflectors B. The relative position of the driven element with respect to the reflectors and directors C. The power radiated in the major radiation lobe compared to the power radiated 90 degrees away from that direction D. The power radiated in the major radiation lobe compared to the power radiated in exactly the opposite direction G9B11 (C) What is the "main lobe" of a cubical-quad antenna radiation pattern? A. The direction of least radiation from an antenna B. The point of maximum current in a radiating antenna element C. The direction of maximum radiated field strength from the antenna D. The maximum voltage standing wave point on a radiating element

G9C Random wire antennas - physical dimensions; impedance matching; radiation patterns; directivity and major lobes; feed point impedance of 1/2-wavelength dipole and 1/4- wavelength vertical antennas
G9C01 (A) What type of multiband transmitting antenna does NOT require a feed-line? A. An end-fed random-wire antenna B. A triband Yagi antenna C. A delta-loop antenna D. A Beverage antenna G9C02 (D) What is one advantage of using a random-wire antenna? A. It is more efficient than any other kind of antenna B. It will keep RF energy out of your station C. It doesn't need an impedance matching network D. It is a multiband antenna G9C03 (B) What is one disadvantage of a random-wire antenna? A. It must be longer than 1 wavelength B. You may experience RF feedback in your station C. It usually produces vertically polarized radiation D. You must use an inverted-T matching network for multiband operation G9C04 (D) What is an advantage of downward sloping radials on a ground-plane antenna? A. It lowers the radiation angle B. It brings the feed-point impedance closer to 300 ohms C. It increases the radiation angle D. It brings the feed-point impedance closer to 50 ohms G9C05 (B) What happens to the feed-point impedance of a ground-plane antenna when its radials are changed from horizontal to downward-sloping? A. It decreases B. It increases C. It stays the same D. It approaches zero G9C06 (A) What is the low-angle radiation pattern of an ideal half- wavelength dipole HF antenna installed a half-wavelength high, parallel to the earth? 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 is two smaller lobes on one side of the antenna, and one larger lobe on the other side G9C07 (C) How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna? 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 one-half wavelength high, the azimuthal pattern is almost omnidirectional D. If the antenna is less than one-half wavelength high, radiation off the ends of the wire is eliminated G9C08 (D) If the horizontal radiation pattern of an antenna shows a major lobe at 0 degrees and a minor lobe at 180 degrees, how would you describe the radiation pattern of this antenna? A. Most of the signal would be radiated towards 180 degrees and a smaller amount would be radiated towards 0 degrees B. Almost no signal would be radiated towards 0 degrees and a small amount would be radiated towards 180 degrees C. Almost all the signal would be radiated equally towards 0 degrees and 180 degrees D. Most of the signal would be radiated towards 0 degrees and a smaller amount would be radiated towards 180 degrees G9C09 (D) If a slightly shorter parasitic element is placed 0.1 wavelength away and parallel to an HF dipole antenna mounted above ground, what effect will this have on the antenna's radiation pattern? A. The radiation pattern will not be affected B. A major lobe will develop in the horizontal plane, parallel to the two elements C. A major lobe will develop in the vertical plane, away from the ground D. A major lobe will develop in the horizontal plane, toward the parasitic element G9C10 (B) If a slightly longer parasitic element is placed 0.1 wavelength away and parallel to an HF dipole antenna mounted above ground, what effect will this have on the antenna's radiation pattern? A. The radiation pattern will not be affected B. A major lobe will develop in the horizontal plane, away from the parasitic element, toward the dipole C. A major lobe will develop in the vertical plane, away from the ground D. A major lobe will develop in the horizontal plane, parallel to the two elements G9C11 (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 D. At the top of the antenna
G9D Popular antenna feed-lines - characteristic impedance and impedance matching; SWR calculations
G9D01 (A) Which of the following factors help determine the characteristic impedance of a parallel-conductor antenna 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 G9D02 (B) What is the typical characteristic impedance of coaxial cables used for antenna feed-lines at amateur stations? A. 25 and 30 ohms B. 50 and 75 ohms C. 80 and 100 ohms D. 500 and 750 ohms G9D03 (D) What is the characteristic impedance of flat-ribbon TV-type twin-lead? A. 50 ohms B. 75 ohms C. 100 ohms D. 300 ohms G9D04 (C) What is the typical cause of power being reflected back down an antenna feed-line? 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 G9D05 (D) What must be done to prevent standing waves of voltage and current on an antenna feed-line? A. The antenna feed point must be at DC ground potential B. The feed line must be cut to an odd number of electrical quarter-wavelengths long C. The feed line must be cut to 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 G9D06 (C) Under what conditions would you use an inductively coupled matching network with a dipole antenna fed with parallel- conductor feed line? A. It would not normally be used with parallel-conductor feed lines B. It would be used to increase the SWR to an acceptable level C. It would be used to match the unbalanced transmitter output to the balanced parallel-conductor feed line D. It would be used at the antenna feed point to tune out the radiation resistance G9D07 (A) If a 160-meter signal and a 2-meter signal pass through the same coaxial cable, how will the attenuation of the two signals compare? A. It will be greater at 2 meters B. It will be less at 2 meters C. It will be the same at both frequencies D. It will depend on the emission type in use G9D08 (D) In what values are RF feed line losses usually expressed? A. Bels/1000 ft B. dB/1000 ft C. Bels/100 ft D. dB/100 ft G9D09 (A) What standing-wave-ratio will result from the connection of a 50-ohm feed line to a resonant antenna having a 200-ohm feed-point impedance? A. 4:1 B. 1:4 C. 2:1 D. 1:2 G9D10 (D) What standing-wave-ratio will result from the connection of a 50-ohm feed line to a resonant antenna having a 10-ohm feed-point impedance? A. 2:1 B. 50:1 C. 1:5 D. 5:1 G9D11 (B) What standing-wave-ratio will result from the connection of a 50-ohm feed line to a resonant antenna having a 50-ohm feed-point impedance? A. 2:1 B. 1:1 C. 50:50 D. 0:0 G9D12 (B) What physical aspects of an air-insulated parallel- conductor transmission line determine its characteristic impedance? A. The RF resistance of the conductors and the length of the conductors B. The diameter of the conductors and the distance between their centers C. The RF resistance of the conductors and the dielectric constant of the insulation D. The resistance of each wire to RF ground and the antenna's impedance G9D13 (A) What would be the SWR if you feed a vertical antenna that has a 25-ohm feed-point impedance with 50-ohm coaxial cable? A. 2:1 B. 2.5:1 C. 1.25:1 D. You cannot determine SWR from impedance values G9D14 (C) What would be the SWR if you feed a folded dipole antenna that has a 300-ohm feed-point impedance with 50-ohm coaxial cable? A. 1.5:1 B. 3:1 C. 6:1 D. You cannot determine SWR from impedance values

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