Free GMDSS Radio Operator Questions and Answers — Questions and Answers
Question 1: What radio circuit samples analog signals, records and processes them as numbers, and then converts them back to analog signals?
- The pre-emphasis audio stage.
- The squelch gate circuit.
- The digital signal processing circuit. (Correct answer)
- The voltage-controlled oscillator circuit.
Correct answer: The digital signal processing circuit.
Explanation: <br> The digital signal processing circuit in radio communication samples analog signals converts them into digital format for processing as numbers using algorithms, and then converts them back to analog signals. This process improves the efficiency and reliability of communication in the Global Maritime Distress and Safety System (GMDSS).
Question 2: Which of the following statements about SSB voice transmissions is correct?
- They use A3E emissions which are produced by modulating the final amplifier.
- They use F3E emission which is produced by phase shifting the carrier.
- They normally use J3E emissions, which consist of one sideband and a suppressed carrier. (Correct answer)
- They may use A1A emission to suppress the carrier.
Correct answer: They normally use J3E emissions, which consist of one sideband and a suppressed carrier.
Explanation: <br> Single Sideband (SSB) voice transmissions typically use J3E emissions, where only one sideband is transmitted along with a suppressed carrier. This method is efficient in terms of power usage and bandwidth while still providing clear voice communication in radio transmission.
Question 3: How does the COSPAS-SARSAT satellite system determine the position of a ship in distress?
- By measuring the Doppler shift of the 406 MHz signal taken at several different points in its orbit. (Correct answer)
- The EPIRB always transmits its position which is relayed by the satellite to the Local User Terminal.
- It takes two different satellites to establish an accurate position.
- None of the above.
Correct answer: By measuring the Doppler shift of the 406 MHz signal taken at several different points in its orbit.
Explanation: <br> The COSPAS-SARSAT satellite system determines the position of a ship in distress by measuring the Doppler shift of the 406 MHz distress signal transmitted by an Emergency Position Indicating Radio Beacon (EPIRB). This Doppler shift is measured by multiple satellites as they pass over the distress beacon. By analyzing the Doppler shifts from different satellites and comparing them, the system can triangulate the position of the distress beacon and determine the location of the ship in distress.
Question 4: Which of the following contains a multirange AF voltmeter calibrated in dB and a sharp, internal 1000 Hz bandstop filter, both used in conjunction with each other to perform quieting tests?
- SINAD meter (Correct answer)
- Reflectometer
- Dip meter
- Vector-impedance meter
Correct answer: SINAD meter
Explanation: <br> A SINAD (Signal-to-Noise and Distortion) meter is used to measure the quality of a received signal, particularly in radio communication systems. It contains a multirange AF (audio frequency) voltmeter calibrated in decibels (dB) and a sharp, internal 1000 Hz bandstop filter. These components are used together to perform quieting tests, which assess the level of unwanted noise and distortion in a received signal.
Question 5: When sending a DSC call:
- Vessel's position will automatically be sent.
- Vessel's position will automatically be sent if the vessel is sending a "Distress Hot Key" alert. (Correct answer)
- Vessel's MMSI will indicate its ocean region.
- None of the above
Correct answer: Vessel's position will automatically be sent if the vessel is sending a "Distress Hot Key" alert.
Explanation: <br> When sending a Digital Selective Calling (DSC) distress alert using the "Distress Hot Key" function, the vessel's position will be automatically included in the distress message. However, for routine DSC calls or other types of DSC alerts, the vessel's position is not automatically sent unless manually included in the message by the operator. Therefore, option B is the most accurate statement regarding the automatic transmission of a vessel's position during a DSC call.
Question 6: You send a VHF-DSC Distress alert. What channel do you use for the follow-on voice transmission?
- Ch-12
- Ch-70
- Ch-13
- Ch-16 (Correct answer)
Correct answer: Ch-16
Explanation: <br> After sending a VHF-DSC Distress alert, the follow-on voice transmission should be conducted on Channel 16. Channel 16 is the international distress and calling frequency designated for maritime communication. It is monitored continuously by maritime authorities and other vessels to coordinate distress, safety, and emergency communications.
Question 7: The U.S. Country Code for voice transmission is:
- 1 (Correct answer)
- 011
- 001 for Southbury, 201 Santa Paula
- 581 for AOR-E, 582 for POR and 584 for AOR-W
Correct answer: 1
Explanation: <br> The U.S. Country Code for voice transmission is 1. This country code is used for international voice communications, including maritime radio communication, to indicate that the communication is originating from or intended for the United States.
Question 8: Which of the following two-way communications can be made through Inmarsat without charge?
- A service message that advises a vessel of other ship traffic in its vicinity.
- SafetyNETTM
- Distress traffic (Correct answer)
- Vessel position information when the ship's GPS fails.
Correct answer: Distress traffic
Explanation: <br> Inmarsat provides distress communication services free of charge. Ships in distress can transmit distress messages via Inmarsat without incurring communication charges. This is a critical service provided to ensure rapid response to emergencies at sea. Other types of two-way communications through Inmarsat typically involve subscription or usage charges.
Question 9: Which of the following maintenance functions is not the responsibility of the GMDSS Radio Operator?
- Visual inspection of equipment, including the antenna and associated components.
- Perform on-the-air verification checks.
- Perform scheduled testing of the battery's charged condition.
- Aligning the power output stage for maximum power. (Correct answer)
Correct answer: Aligning the power output stage for maximum power.
Explanation: <br> Aligning the power output stage for maximum power typically falls under the responsibility of a technician or engineer specialized in radio equipment maintenance. GMDSS Radio Operators are primarily responsible for operating and performing basic maintenance checks on GMDSS equipment, including visual inspections, on-the-air verification checks, and scheduled testing of the battery's charged condition. However, tasks involving technical adjustments or alignments of equipment components are usually performed by qualified maintenance personnel.
Question 10: Which of the following message categories cannot be disabled by the GMDSS Radio Operator?
- Navigational warnings
- Meteorological warnings
- Search and Rescue information
- All of the above (Correct answer)
Correct answer: All of the above
Explanation: <br> GMDSS Radio Operators cannot disable any of the message categories listed (Navigational warnings, Meteorological warnings, Search and Rescue information). These message categories are essential for maritime safety and must be continuously available to vessels operating in the area covered by the GMDSS. Disabling any of these categories could jeopardize the safety of maritime navigation and response to emergencies at sea. Therefore, they are not subject to discretionary disabling by the Radio Operator.
Question 11: A DSC call is received from a station with a MMSI number of 003669991. Which of the following types of stations is it from?
- A vessel operating in Sea Area A3.
- A group ship station
- A U.S. coast station (Correct answer)
- An Intercoastal vessel
Correct answer: A U.S. coast station
Explanation: <br> In the Maritime Mobile Service Identity (MMSI) number "003669991," the first three digits "003" indicate the country code for the United States. Therefore, a station with this MMSI number is from the United States. In the context of the options provided, "A U.S. coast station" is the most appropriate category for such a station.
Free GMDSS Radio Operator Questions and Answers
What radio circuit samples analog signals, records and processes them as numbers, and then converts them back to analog signals?