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Subel. B
6 questions
Subelement B

MF-HF-DSC-SITOR (NBDP) Equip. & Ops:

Section 18

Transmitter Faults-2:

Which of the following conditions indicate the proper operation of a 150 Watt MF/HF transmitter in the F1B ARQ mode?

  • The RF power meter indicates constant output at a level between 125 watts and 150 watts during transmission.
  • The RF power meter indicates power output only when characters are typed on the NBDP keyboard.
  • The RF "S" meter indicates a signal level between 125 watts and 150 watts during NBDP reception.
  • Correct Answer
    The RF power meter indicates an output that fluctuates between 0 and 150 watts during transmission.
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Which of the following conditions indicate the proper operation of a 250 Watt MF/HF transmitter in the F1B FEC mode?

  • Correct Answer
    The RF power meter indicates constant output at a level between 225 watts and 250 watts during transmission.
  • The RF power meter indicates power output only when characters are typed on the NBDP keyboard.
  • The RF "S" meter indicates a signal level between 225 watts and 250 watts during NBDP reception.
  • The RF power meter indicates an output that fluctuates between 0 and 250 watts during transmission.
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Which of the following conditions could cause very low RF output in a MF/HF transmitter operating in the F1B FEC mode?

  • Failure of a voltage controlled oscillator in the IF amplifier stage.
  • Correct Answer
    A high Standing Wave Ratio (SWR) in the antenna system.
  • The connection of a transceiver is connected to a "Dummy Load" antenna.
  • Failure of a SSB bandpass filter in the stage preceding the RF amplifier.
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which of the following troubleshooting methods is not valid for finding the fault in a MF/HF transmitter operating in the F1B FEC mode?

  • Visual inspection of the transmitter (control settings, signs of physical damage or overheating, etc.)
  • Power supply testing with a DVM to ensure all prescribed operating voltages are within acceptable limits.
  • Correct Answer
    Modulation testing with a RF spectrum analyzer to measure frequency deviation in the transmit mode.
  • Input/Output checks with a 10:1 oscilloscope probe to identify any points of severe signal degradation.
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Which of the following conditions could cause zero RF output in a MF/HF transmitter operating in the F1B FEC mode?

  • The connection of a transceiver is connected to a "Dummy Load" antenna.
  • The failure of the voice bandpass filter in the stage preceding the RF amplifier.
  • Correct Answer
    The activation of a "crowbar" circuit in the power supply to prevent an unregulated voltage increase.
  • The generation of a positive VCO feedback signal to a Phase Locked Loop circuit in the transmitter.
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Which of the following conditions indicate improper operation of a 150 Watt MF/HF transmitter in the F1B FEC mode?

  • The RF power meter indicates constant output at a level between 125 watts and 150 watts during transmission.
  • The SWR meter indicates 125 watts forward RF power and 5 watts reflected RF power during transmission.
  • The RF "S" meter fluctuates depending on the strength of the received signal during NBDP reception.
  • Correct Answer
    The RF power meter indicates an output that fluctuates between 0 and 150 watts during transmission.

Improper fluctuates!!

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