FCC Element 7 Practice Questions: GMDSS Radio Operator License (2026)

What GMDSS is, and the bands it uses

The fundamental concept the exam wants stated cleanly is this: GMDSS uses automated systems and satellite technology to improve emergency communications for the world's shipping industry. It was created by the IMO to replace a human listening watch with automatic distress alerting, so that a distress alert reaches search-and-rescue authorities ashore quickly, and those authorities can then call on nearby shipping to assist. Everything else in the system serves that goal. Element 7 grounds you in the radio spectrum that carries these alerts. Medium Frequency is 300 to 3,000 kHz and includes the 2 MHz marine distress and DSC frequencies. High Frequency is 3 to 30 MHz, the sky-wave band used for long-range work. Very High Frequency is 30 to 300 MHz, the line-of-sight band that carries marine VHF channels including Channel 70 for Digital Selective Calling. Knowing which band a frequency falls in tells you immediately whether a link is short-range and reliable or long-range and propagation-dependent.

Distress alerting, DSC and identities

The distress procedure is the reason the licence exists. A GMDSS distress alert must identify the station in distress and give its position and the time that position was valid, and it may add the nature of the distress, the assistance required and the unit's course and speed. On an Inmarsat terminal the first step is usually to press a dedicated distress button or hot key, which sends the alert to a rescue coordination centre at the highest priority automatically. A useful safety feature is that if an operator initiates a DSC distress transmission without inserting a message, the controller still sends it with stored default information rather than failing. Identities matter throughout: a large United States flag ship carries a four-letter call sign such as KBZY, a coast station SITOR or NBDP SELCAL is a four-digit number, a ship station SELCAL is five digits, and a DSC identity is a nine-digit MMSI. Reading a number's length tells you what kind of station it belongs to.

• A distress alert must give the station's identity, position and the time the position was valid.
• An Inmarsat distress is normally started with a dedicated distress button or hot key.
• SITOR SELCALs are four digits for coast stations and five digits for ships; an MMSI is nine digits.

Survival craft, NAVTEX, Inmarsat and MF/HF working

The rest of Element 7 covers the equipment and routines that keep a distress response working. A Search and Rescue Transponder responds to a 3-CM, 9 GHz, X-band radar as SAR craft approach, and better units give survivors a visual or audible indication that a radar is interrogating them; to maximise its range the SART should be held or mounted as high as possible and vertically, since a 10-CM S-band radar will not trigger it at all. For Maritime Safety Information, NAVTEX stations share the single frequency 518 kHz and avoid mutual interference by time-sharing, limited transmitter power and geographically separated station codes, achieving maximum range in the middle of the night when MF sky-wave propagation is strongest. If a NAVTEX message arrives too garbled to use, the correct action is to do nothing, because vital messages are repeated on the next scheduled broadcast. On the satellite side, before powering down an Inmarsat-C terminal or leaving one satellite footprint for another, always log out with the current Network Coordination Station. And across MF and HF working the governing rule is to use the lowest power that still achieves the necessary range, limiting interference to other users of the shared spectrum. Compulsory GMDSS ship stations must also be inspected at least once every 12 months by the FCC or a GMDSS Maintainer licence holder, and two licensed GMDSS operators must be carried.