86 lines
3.5 KiB
Markdown
86 lines
3.5 KiB
Markdown
T9A – Antennas: vertical and horizontal polarization, concept of antenna gain, definition and types of beam antennas, antenna loading, common portable and mobile antennas, relationships between resonant length and frequency, dipole pattern
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- [[T9A01]] (C)
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What is a beam antenna? #card
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- A. An antenna built from aluminum I-beams
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- B. An omnidirectional antenna invented by Clarence Beam
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- C. An antenna that concentrates signals in one direction
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- D. An antenna that reverses the phase of received signals
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- [[T9A02]] (A)
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Which of the following describes a type of antenna loading? #card
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- A. Electrically lengthening by inserting inductors in radiating elements
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- B. Inserting a resistor in the radiating portion of the antenna to make it resonant
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- C. Installing a spring in the base of a mobile vertical antenna to make it more flexible
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- D. Strengthening the radiating elements of a beam antenna to better resist wind damage
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- [[T9A03]] (B)
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Which of the following describes a simple dipole oriented parallel to Earth's surface? #card
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- A. A ground-wave antenna
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- B. A horizontally polarized antenna
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- C. A travelling-wave antenna
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- D. A vertically polarized antenna
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- [[T9A04]] (A)
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What is a disadvantage of the short, flexible antenna supplied with most handheld radio transceivers, compared to a full-sized quarter-wave antenna? #card
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- A. It has low efficiency
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- B. It transmits only circularly polarized signals
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- C. It is mechanically fragile
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- D. All these choices are correct
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- [[T9A05]] (C)
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Which of the following increases the resonant frequency of a dipole antenna? #card
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- A. Lengthening it
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- B. Inserting coils in series with radiating wires
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- C. Shortening it
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- D. Adding capacitive loading to the ends of the radiating wires
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- [[T9A06]] (D)
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Which of the following types of antenna offers the greatest gain? #card
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- A. 5/8 wave vertical
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- B. Isotropic
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- C. J pole
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- D. Yagi
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- [[T9A07]] (A)
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What is a disadvantage of using a handheld VHF transceiver with a flexible antenna inside a vehicle? #card
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- A. Signal strength is reduced due to the shielding effect of the vehicle
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- B. The bandwidth of the antenna will decrease, increasing SWR
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- C. The SWR might decrease, decreasing the signal strength
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- D. All these choices are correct
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- [[T9A08]] (C)
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What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? #card
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- A. 112
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- B. 50
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- C. 19
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- D. 12
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- [[T9A09]] (C)
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What is the approximate length, in inches, of a half-wavelength 6 meter dipole antenna? #card
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- A. 6
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- B. 50
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- C. 112
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- D. 236
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- [[T9A10]] (D)
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In which direction does a half-wave dipole antenna radiate the strongest signal? #card
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- A. Equally in all directions
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- B. Off the ends of the antenna
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- C. In the direction of the feed line
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- D. Broadside to the antenna
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- [[T9A11]] (C)
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What is antenna gain? #card
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- A. The additional power that is added to the transmitter power
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- B. The additional power that is required in the antenna when transmitting on a higher frequency
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- C. The increase in signal strength in a specified direction compared to a reference antenna
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- D. The increase in impedance on receive or transmit compared to a reference antenna
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- [[T9A12]] (A)
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What is an advantage of a 5/8 wavelength whip antenna for VHF or UHF mobile service? #card
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- A. It has more gain than a 1/4-wavelength antenna
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- B. It radiates at a very high angle
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- C. It eliminates distortion caused by reflected signals
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- D. It has 10 times the power gain of a 1/4 wavelength whip
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