79 lines
2.9 KiB
Markdown
79 lines
2.9 KiB
Markdown
T7C – Antenna and transmission line measurements and troubleshooting: measuring SWR, effects of high SWR, causes of feed line failures; Basic coaxial cable characteristics; Use of dummy loads when testing
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- [[T7C01]] (A)
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What is the primary purpose of a dummy load? #card
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- A. To prevent transmitting signals over the air when making tests
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- B. To prevent over-modulation of a transmitter
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- C. To improve the efficiency of an antenna
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- D. To improve the signal-to-noise ratio of a receiver
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- [[T7C02]] (B)
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Which of the following is used to determine if an antenna is resonant at the desired operating frequency? #card
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- A. A VTVM
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- B. An antenna analyzer
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- C. A Q meter
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- D. A frequency counter
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- [[T7C03]] (B)
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What does a dummy load consist of? #card
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- A. A high-gain amplifier and a TR switch
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- B. A non-inductive resistor mounted on a heat sink
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- C. A low-voltage power supply and a DC relay
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- D. A 50-ohm reactance used to terminate a transmission line
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- [[T7C04]] (C)
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What reading on an SWR meter indicates a perfect impedance match between the antenna and the feed line? #card
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- A. 50:50
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- B. Zero
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- C. 1:1
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- D. Full Scale
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- [[T7C05]] (A)
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Why do most solid-state transmitters reduce output power as SWR increases beyond a certain level? #card
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- A. To protect the output amplifier transistors
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- B. To comply with FCC rules on spectral purity
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- C. Because power supplies cannot supply enough current at high SWR
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- D. To lower the SWR on the transmission line
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- [[T7C06]] (D)
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What does an SWR reading of 4:1 indicate? #card
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- A. Loss of -4 dB
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- B. Good impedance match
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- C. Gain of +4 dB
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- D. Impedance mismatch
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- [[T7C07]] (C)
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What happens to power lost in a feed line? #card
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- A. It increases the SWR
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- B. It is radiated as harmonics
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- C. It is converted into heat
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- D. It distorts the signal
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- [[T7C08]] (D)
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Which instrument can be used to determine SWR?
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- A. Voltmeter
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- B. Ohmmeter
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- C. Iambic pentameter
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- D. Directional wattmeter
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- [[T7C09]] (A)
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Which of the following causes failure of coaxial cables? #card
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- A. Moisture contamination
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- B. Solder flux contamination
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- C. Rapid fluctuation in transmitter output power
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- D. Operation at 100% duty cycle for an extended period
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- [[T7C10]] (D)
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Why should the outer jacket of coaxial cable be resistant to ultraviolet light? #card
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- A. Ultraviolet resistant jackets prevent harmonic radiation
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- B. Ultraviolet light can increase losses in the cable’s jacket
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- C. Ultraviolet and RF signals can mix, causing interference
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- D. Ultraviolet light can damage the jacket and allow water to enter the cable
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- [[T7C11]] (C)
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What is a disadvantage of air core coaxial cable when compared to foam or solid dielectric types? #card
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- A. It has more loss per foot
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- B. It cannot be used for VHF or UHF antennas
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- C. It requires special techniques to prevent moisture in the cable
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- D. It cannot be used at below freezing temperatures
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