72 lines
3.4 KiB
Markdown
72 lines
3.4 KiB
Markdown
G9C – Directional antennas
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- [[G9C01]] (A)
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Which of the following would increase the bandwidth of a Yagi antenna? #card
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- A. Larger-diameter elements
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- B. Closer element spacing
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- C. Loading coils in series with the element
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- D. Tapered-diameter elements
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- [[G9C02]] (B)
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What is the approximate length of the driven element of a Yagi antenna? #card
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- A. 1/4 wavelength
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- B. 1/2 wavelength
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- C. 3/4 wavelength
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- D. 1 wavelength
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- [[G9C03]] (A)
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How do the lengths of a three-element Yagi reflector and director compare to that of the driven element? #card
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- A. The reflector is longer, and the director is shorter
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- B. The reflector is shorter, and the director is longer
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- C. They are all the same length
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- D. Relative length depends on the frequency of operation
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- [[G9C04]] (B)
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How does antenna gain in dBi compare to gain stated in dBd for the same antenna? #card
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- A. Gain in dBi is 2.15 dB lower
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- B. Gain in dBi is 2.15 dB higher
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- C. Gain in dBd is 1.25 dBd lower
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- D. Gain in dBd is 1.25 dBd higher
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- [[G9C05]] (A)
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What is the primary effect of increasing boom length and adding directors to a Yagi antenna? #card
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- A. Gain increases
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- B. Beamwidth increases
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- C. Front-to-back ratio decreases
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- D. Resonant frequency is lower
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- [[G9C06]] Question Removed (section not renumbered)
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- [[G9C07]] (C)
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What does “front-to-back ratio” mean in reference to a Yagi antenna? #card
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- A. The number of directors versus the number of reflectors
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- B. The relative position of the driven element with respect to the reflectors and directors
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- C. The power radiated in the major lobe compared to that in the opposite direction
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- D. The ratio of forward gain to dipole gain
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- [[G9C08]] (D)
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What is meant by the “main lobe” of a directive antenna? #card
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- A. The magnitude of the maximum vertical angle of radiation
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- B. The point of maximum current in a radiating antenna element
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- C. The maximum voltage standing wave point on a radiating element
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- D. The direction of maximum radiated field strength from the antenna
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- [[G9C09]] (B)
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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? #card
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- A. Approximately 1.5 dB higher
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- B. Approximately 3 dB higher
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- C. Approximately 6 dB higher
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- D. Approximately 9 dB higher
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- [[G9C10]] (D)
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Which of the following can be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth of a Yagi antenna? #card
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- A. The physical length of the boom
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- B. The number of elements on the boom
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- C. The spacing of each element along the boom
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- D. All these choices are correct
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- [[G9C11]] (A)
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What is a beta or hairpin match? #card
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- A. A shorted transmission line stub placed at the feed point of a Yagi antenna to provide impedance matching
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- B. A 1/4 wavelength section of 75-ohm coax in series with the feed point of a Yagi to provide impedance matching
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- C. A series capacitor selected to cancel the inductive reactance of a folded dipole antenna
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- D. A section of 300-ohm twin-lead transmission line used to match a folded dipole antenna
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- [[G9C12]] (A)
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Which of the following is a characteristic of using a gamma match with a Yagi antenna? #card
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- A. It does not require the driven element to be insulated from the boom
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- B. It does not require any inductors or capacitors
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- C. It is useful for matching multiband antennas
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- D. All these choices are correct
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