Practice Test Geeks(GROL) General Radiotelephone Operator License Practice Test
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Marine Electronics and Radar Systems Flashcards

7 cards from real GROL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Marine Electronics and Radar Systems flashcards as text

  1. What is the primary purpose of an Automatic Identification System (AIS) on a vessel?

    Answer: To automatically exchange navigation and vessel data with other AIS-equipped ships and shore stations

    AIS automatically broadcasts and receives vessel identification, position, course, speed, and other data between ships and shore stations to enhance maritime situational awareness and collision avoidance.

  2. On which VHF channels does Class A AIS operate for ship-to-ship and ship-to-shore communication?

    Answer: Channels 87B (161.975 MHz) and 88B (162.025 MHz)

    AIS operates on two dedicated VHF channels: AIS 1 (Channel 87B, 161.975 MHz) and AIS 2 (Channel 88B, 162.025 MHz), using TDMA digital modulation.

  3. What is the term for the phenomenon where radar waves reflect off the sea surface and then off a target at a low elevation angle, causing an apparent doubling of target returns?

    Answer: Multipath propagation

    Multipath propagation occurs when radar signals reach a target by both direct path and a path reflected off the sea surface, causing interference patterns and false target images.

  4. When a radar target shows a 'shadow' zone behind it on the display, what is the most likely cause?

    Answer: The target is blocking the radar beam from illuminating objects behind it

    Large targets such as ships or landmasses intercept the radar beam, preventing it from reaching and returning echoes from objects behind them, creating a radar shadow zone.

  5. What is the function of a radar reflector carried on a small vessel?

    Answer: To increase the vessel's radar cross-section so it is more visible to other ships' radar

    A radar reflector (typically a corner reflector) increases a small vessel's radar cross-section, making it return a stronger echo to another ship's radar and improving its detectability.

  6. In marine electronics, what does 'GMDSS Sea Area A1' designate?

    Answer: An area within approximately 20–50 nautical miles of a VHF coast station

    GMDSS Sea Area A1 is defined as an area within radiotelephone coverage of at least one VHF coast station in which continuous DSC alerting is available, typically within 20–50 nm of the coast.

  7. Which electronic navigation system uses phase comparison of signals from multiple shore-based transmitters to determine a vessel's position?

    Answer: LORAN-C

    LORAN-C (Long Range Navigation-C) determined position by measuring the time difference in reception of pulses from multiple shore-based transmitters operating at 100 kHz, using hyperbolic lines of position.