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Subelement B
MF-HF-DSC-SITOR (NBDP) Equip. & Ops:
Section 13
Receiver Technology:
What is the purpose of the BFO?
  • Correct Answer
    Re-injects the carrier frequency in the receiver's detector to demodulate the SSB signal.
  • Replace the missing sideband and carrier frequency.
  • Remove the carrier from H3E transmissions.
  • Inverts the SSB signal to remove interference.
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If the BFO is turned off what kind of emissions can still be received?
  • J3E and J2B
  • Correct Answer
    A3E and H3E
  • H3E and F1B
  • A1A and J3E
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If you are listening to another vessel's HF transmission and it sounds garbled what should you do?
  • Change the receive frequency to either adjacent channel.
  • Advise the other vessel that his transmission is faulty.
  • Correct Answer
    Use the "R.I.T." or "Clarifier" control to adjust the frequency of the receiver.
  • Adjust the squelch control to clear up the sound quality.
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What characteristics are desirable in an AGC circuit for SSB voice reception?
  • Slow attack and decay.
  • Slow attack and fast decay.
  • Fast attack and decay.
  • Correct Answer
    Fast attack and slow decay.
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What is the primary purpose of both a high and a low I.F. system in a HF receiver?
  • Correct Answer
    Using a high first I.F. amplifier results in eliminating image signals.
  • Using a high first I.F. amplifier results in less intermodulation products.
  • Using a low first I.F. amplifier results in fewer third harmonic signals.
  • Using a low first I.F. amplifier results in greater signal amplification.
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How does a noise blanker circuit work in a HF receiver?
  • A limiter circuit clips the peaks of the noise pulses.
  • Correct Answer
    The noise pulses are used to develop a blanking pulse for the I.F. amplifier.
  • The noise pulses operate on the ratio detector to blank the audio output.
  • A Noise blanker briefly reduces the gain of the RF amplifier when the noise pulses occur.
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