Explanation:
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.
Explanation:
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.
Explanation:
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.
Explanation:
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).
Explanation:
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.
Explanation:
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.
Explanation:
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.
Explanation:
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.
Explanation:
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.
Explanation:
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.
Explanation:
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.
