20 terms

G9C Antennas and Feed Lines

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G9C01 -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)
G9C02 -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
(B)
G9C03 -Which statement about a three-element, single-band 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
(B)
G9C04 -Which statement about a three-element; single-band Yagi antenna is true? A. The reflector is normally the longest parasitic element B. The director is normally the longest parasitic element C. The reflector is normally the shortest parasitic element D. All of the elements must be the same length
(A)
G9C05 -How does increasing boom length and adding directors affect a Yagi antenna? A. Gain increases B. Beamwidth increases C. Weight decreases D. Wind load decreases
(A)
G9C06 -Which of the following is a reason why a Yagi antenna is 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 to the side or behind the antenna D. It provides the highest possible angle of radiation for the HF bands
(C)
G9C07 -What does "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 ratio of forward gain to dipole gain
(C)
G9C08 -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
(D)
G9C09 -What is the approximate maximum theoretical forward gain of a three element, single-band Yagi antenna? A. 9.7 dBi B. 9.7 dBd C. 5.4 times the gain of a dipole D. All of these choices are correct
(A)
G9C10 -Which of the following is a Yagi antenna design variable that could be adjusted to optimize forward gain, front-to-back ratio, or 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. All of these choices are correct
(D)
G9C11 -What is the purpose of a gamma match used with Yagi antennas? A. To match the relatively low feed-point impedance to 50 ohms B. To match the relatively high feed-point impedance to 50 ohms C. To increase the front to back ratio D. To increase the main lobe gain
(A)
G9C12 -Which of the following is an advantage of using a gamma match for impedance matching of a Yagi antenna to 50-ohm coax feed line? A. It does not require that the elements be insulated from the boom B. It does not require any inductors or capacitors C. It is useful for matching multiband antennas D. All of these choices are correct
(A)
G9C13 -Approximately how long is each side of a quad antenna driven element? A. 1/4 wavelength B. 1/2 wavelength C. 3/4 wavelength D. 1 wavelength
(A)
G9C14 -How does the forward gain of a two-element quad antenna compare to the forward gain of a three-element Yagi antenna? A. About 2/3 as much B. About the same C. About 1.5 times as much D. About twice as much
(B)
G9C15 -Approximately how long is each side of a quad antenna reflector element? A. Slightly less than 1/4 wavelength B. Slightly more than 1/4 wavelength C. Slightly less than 1/2 wavelength D. Slightly more than 1/2 wavelength
(B)
G9C16 -How does the gain of a two-element delta-loop beam compare to the gain of a two-element quad antenna? A. 3 dB higher B. 3 dB lower C. 2.54 dB higher D. About the same
(D)
G9C17 -Approximately how long is each leg of a symmetrical delta-loop antenna? A. 1/4 wavelength B. 1/3 wavelength C. 1/2 wavelength D. 2/3 wavelength
(B)
G9C18 -What happens when the feed point of a quad antenna is changed from the center of either horizontal wire to the center of either vertical wire? A. The polarization of the radiated signal changes from horizontal to vertical B. The polarization of the radiated signal changes from vertical to horizontal C. The direction of the main lobe is reversed D. The radiated signal changes to an omnidirectional pattern
(A)
G9C19 -What configuration of the loops of a two-element quad antenna must be used for the antenna to operate as a beam antenna, assuming one of the elements is used as a reflector? A. The driven element must be fed with a balun transformer B. The driven element must be open-circuited on the side opposite the feed point C. The reflector element must be approximately 5% shorter than the driven element D. The reflector element must be approximately 5% longer than the driven element
(D)
G9C20 -How does the gain of two 3-element horizontally polarized Yagi antennas spaced vertically 1/2 wavelength apart typically compare to the gain of a single 3-element Yagi? A. Approximately 1.5 dB higher B. Approximately 3 dB higher C. Approximately 6 dB higher D. Approximately 9 dB higher
(B)