MF-HF Equip. and Comms:
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 3500 miles. Toward late afternoon and evening what effect would be noticed?
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Correct AnswerCommunications should gradually deteriorate and become impossible on this frequency at night.
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Communications should be maintained with slight improvement in the signal received from the shore station.
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The gray line effect will prevent communications after dark.
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Communications should improve and peak at night.
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A ship at anchor has been communicating with a shore station approximately 200 miles distant on a frequency in the 4 MHz band through mid-morning. Toward the late afternoon and evening, what effect should be noticed?
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Communications should be maintained with slight improvement in the signal received from the shore station.
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Correct AnswerCommunications should gradually improve and peak at night and early morning.
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Communications should slowly deteriorate but may be continued throughout the night.
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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 SITOR (NBDP) with a shore station some 1800 miles distant?
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VHF-FM
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Lower HF bands
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Correct AnswerHigher HF bands
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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?
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VHF-FM
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Higher UHF bands
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Communications are impossible at this distance.
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Correct AnswerHF 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?
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Correct AnswerMF
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VHF-FM
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22 MHz band
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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?
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By consulting propagation tables.
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Correct AnswerListen to shore station "free signals" and choose the band with the strongest signal.
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If static interference is present, try lower bands first.
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During nighttime, choose higher frequencies. Choose lower frequencies in the daytime.
Tags: none
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