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Subel. J
6 questions
Subelement J
MF-HF Equip. and Comms:
Section 97
MF-HF Propagation-2; Day-Night-Winter-Summer
A ship has been communicating effectively on 16 MHz during daylight hours with a shore station at a distance of 3200 miles. Toward late afternoon and evening what effect would be noticed?
  • Correct Answer
    Communications should gradually deteriorate and become impossible on this frequency at night.
  • Communications should be maintained with slight improvement in the signal received from the shore station.
  • The gray line effect will prevent communications after dark.
  • Communications should improve and peak at night.
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A ship at anchor has been communicating with a shore station approximately 350 miles distant on a frequency in the 4 MHz band through early afternoon. Toward the late afternoon and evening, what effect should be noticed?
  • Communications should be maintained with slight improvement in the signal received from the shore station.
  • Correct Answer
    Communications should gradually improve and peak at night and early morning.
  • Communications should slowly deteriorate but may be continued throughout the night.
  • Communications should gradually deteriorate and become impossible on this frequency by night.
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At mid-day in the summer, what would be the best choice in attempting to communicate, using J3E voice with a shore station some 1800 miles distant?
  • VHF-FM
  • Lower HF bands
  • Correct Answer
    Higher HF bands
  • MF
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At mid-night, what would be the best choice in attempting to communicate, using SITOR (NBDP) with a shore station some 800 miles distant?
  • VHF-FM
  • Higher UHF bands
  • Communications are impossible at this distance.
  • Correct Answer
    HF bands
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At mid-day, what would be the best choice in attempting to communicate with a shore station some 75 miles distant?
  • Correct Answer
    MF
  • VHF-FM
  • 22 MHz band
  • 16 MHz band
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How can a GMDSS operator determine the best frequency band to choose for a SITOR (NBDP) transmission to a shore station?
  • By consulting propagation tables.
  • Correct Answer
    Listen to shore station "free signals" and choose the band with the strongest signal.
  • If static interference is present, try lower bands first.
  • During nighttime, choose higher frequencies. Choose lower frequencies in the daytime.
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