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Subelement B
MF-HF-DSC-SITOR (NBDP) Equip. & Ops:
Section 15
Receiver Faults-2:
The MF/HF receiver fails to suppress the AF output in the absence of a sufficiently strong input signal. What is the most likely cause?
  • The AGC circuit has failed.
  • The BFO circuit has failed.
  • Correct Answer
    The squelch circuit has failed.
  • The AF amplifier circuit has failed.
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The MF/HF receiver fails to produce any AF output. An ohmmeter reading is near zero between speaker leads. What is the most likely cause?
  • The 3 - 30 MHz amplifier stage has failed.
  • The speaker is shorted out.
  • Excess negative feedback is reducing AF gain.
  • Correct Answer
    The audio amplifier stage has failed.
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The MF/HF transceiver produces strong AF output but no signals are heard on any frequency. What is the most likely cause?
  • Correct Answer
    The transceiver is connected to a "Dummy Load."
  • A high Standing Wave Ratio (SWR) in the antenna system.
  • A "crowbar" circuit in the power supply is activated.
  • The squelch circuit has failed.
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The MF/HF transceiver produces strong AF output but no signals are heard on any frequency. What is the most likely cause?
  • The squelch sensitivity control is set too high.
  • Correct Answer
    There is an open circuit in the transmission line to the antenna.
  • The final stage of the AF amplifier circuit has failed.
  • The power amplifier stage in the receiver has failed.
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The MF/HF transceiver fails to produce AF output but the radio is powered on and "TX" is illuminated. What is the most likely cause?
  • The speaker is shorted out.
  • Correct Answer
    A shorted Push-To-Talk circuit in the microphone.
  • A "crowbar" circuit in the power supply has engaged.
  • The final stage of the AF amplifier circuit has failed.
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A received signal on a MF/HF transceiver breaks up rapidly and repeatedly. The signal alternates between mid scale and zero on the "Signal" meter. What is the most likely cause?
  • Intermittent gain in the AF amplifier circuit.
  • The squelch sensitivity control is set too high.
  • Correct Answer
    An intermittent connection between the antenna and coupler.
  • The AGC circuit has malfunctioned.
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