7-A-097: MF-HF: Propagation #2: Daytime, Nighttime, Winter & Summer
7-97J1:
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?
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.
7-97J2:
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?
Communications should gradually improve and peak at night and early morning.
Communications should be maintained with slight improvement in the signal received from the shore station.
Communications should slowly deteriorate but may be continued throughout the night.
Communications should gradually deteriorate and become impossible on this frequency by night.
7-97J3:
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?
Higher HF bands
VHF-FM
Lower HF bands
MF
7-97J4:
At mid-night, what would be the best choice in attempting to communicate, using SITOR (NBDP) with a shore station some 800 miles distant?
HF bands
VHF-FM
Higher UHF bands
Communications are impossible at this distance.
7-97J5:
At mid-day, what would be the best choice in attempting to communicate with a shore station some 75 miles distant?
MF
VHF-FM
22 MHz band
16 MHz band
7-97J6:
How can a GMDSS operator determine the best frequency band to choose for a SITOR (NBDP)transmission to a shore station?
Listen to shore station "free signals" and choose the band with the strongest signal.
By consulting propagation tables.
If static interference is present, try lower bands first.
During nighttime, choose higher frequencies. Choose lower frequencies in the daytime.
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