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