Why Marine Radio Matters on the Exam
5-8
Radio questions on OUPV exam
Approximately 5 to 8 questions from the Deck General Safety module cover radio communications.
406 MHz
EPIRB distress frequency
406 MHz EPIRBs link to COSPAS-SARSAT satellites. Must be registered with NOAA before use.
9 digits
MMSI number length
U.S. vessel MMSIs begin with 338 (documented) or 367 (state registered). Must be registered to be useful.
Marine radio communications questions on the USCG OUPV and Master exams focus on channel assignments, distress procedures, Digital Selective Calling, FCC licensing, and emergency devices. Most candidates miss questions in this section because they know the basics but get tripped up on details — which channel is DSC-only, what the Restricted Radiotelephone Operator Permit requires, or the exact sequence of a MAYDAY call. This guide covers every detail tested.
VHF Channel Assignments — Complete Reference
U.S. VHF marine channels. The exam focuses heavily on Ch 16, 22A, 13, and 70.
| Ch | Frequency | Primary Use | Type |
|---|---|---|---|
| 16 | 156.800 MHz | International distress, safety, and calling — mandatory watch | Distress |
| 6 | 156.300 MHz | Inter-ship safety communications | Safety |
| 9 | 156.450 MHz | Boater calling channel — recreational alternative to Ch 16 | Calling |
| 13 | 156.650 MHz | Bridge-to-bridge navigation at 1 watt — mandatory on commercial vessels | Navigation |
| 22A | 157.100 MHz | U.S. Coast Guard primary working channel and safety broadcasts | USCG |
| 67 | 156.375 MHz | U.S. inland waters bridge-to-bridge (alternate to Ch 13) | Navigation |
| 70 | 156.525 MHz | DSC digital distress alerting only — NO voice transmissions | DSC |
| 12 | 156.600 MHz | Port operations and vessel traffic services | Port Ops |
| 14 | 156.700 MHz | Port operations and vessel traffic services | Port Ops |
| WX1 | 162.550 MHz | NOAA weather broadcast — receive only | Weather |
| WX2 | 162.400 MHz | NOAA weather broadcast — receive only | Weather |
| WX3 | 162.475 MHz | NOAA weather broadcast — receive only | Weather |
Channel 16 — The Prime Rule
Monitor Channel 16 at all times while underway. Leave 16 only to communicate on a working channel, then return immediately. This is the single most tested rule in the radio section of the USCG exam.
Channel 70 — No Voice Ever
Channel 70 is reserved exclusively for Digital Selective Calling digital signals. Voice transmissions on Channel 70 are illegal and interfere with automated distress alerting. Exam questions often ask what channel DSC uses — the answer is always Channel 70.
Radio Watch Requirements
Under FCC regulations and international GMDSS rules, vessels carrying radio equipment must maintain specified watches. The USCG exam tests which watch is required on which channel and for which vessel type.
All VHF-Equipped Vessels Underway
- ▸Maintain continuous watch on Channel 16 whenever the radio is on
- ▸Only leave Ch 16 while actively communicating on a working channel
- ▸Return to Ch 16 immediately after the working channel conversation ends
- ▸This applies to recreational and commercial vessels alike
DSC-Equipped Vessels
- ▸Must maintain a watch on Channel 70 (DSC) in addition to Channel 16
- ▸Modern Class D VHF radios with DSC maintain Ch 70 watch automatically
- ▸DSC watch allows automatic reception of digital distress alerts from other vessels
Compulsory Ships — GMDSS
- ▸Vessels over 300 gross tons on international voyages must comply with full GMDSS
- ▸Required to watch VHF Ch 16, VHF Ch 70 DSC, and MF 2187.5 kHz DSC
- ▸Must carry Navtex receiver for automated safety broadcasts
- ▸GMDSS requirements are heavily tested in Master exam radio sections
MAYDAY Distress Call — Full Procedure
Use MAYDAY only for grave and imminent danger to life or the vessel. Transmit on Channel 16 at maximum power (25 watts).
Complete MAYDAY Script
MAYDAY MAYDAY MAYDAY
Spoken three times, clearly and distinctly
THIS IS [vessel name] [vessel name] [vessel name]
Your vessel name spoken three times
MAYDAY [vessel name]
MAYDAY spoken once, then your vessel name once
MY POSITION IS [latitude and longitude, OR bearing and distance from a landmark]
Give the most precise position possible. If GPS is available, read coordinates directly.
I AM [nature of distress]
Sinking, on fire, medical emergency, taking on water, dismasted, etc.
I HAVE [number] PERSONS ON BOARD
Exact count helps search and rescue confirm all persons are accounted for
[Any other useful information]
Vessel description, color, hull type, whether EPIRB is activated, if you are abandoning ship
OVER
End transmission and listen for 15 seconds. If no response, repeat the entire call.
After the Distress Call
- Wait 15 seconds. If no response, repeat the call on Channel 16.
- After two attempts on Channel 16 with no response, try MF SSB on 2182 kHz.
- If your radio has DSC, send a DSC distress alert on Channel 70 before or alongside the voice call.
- Activate your EPIRB if the situation requires it — EPIRB transmits independently to satellites.
- Keep the radio on and monitor Channel 16 for the Coast Guard response.
MAYDAY Relay
If you hear a MAYDAY call but the distressed vessel receives no response, you may transmit a MAYDAY Relay on their behalf. Say: MAYDAY RELAY MAYDAY RELAY MAYDAY RELAY, ALL STATIONS, THIS IS [your vessel name]. Then relay the distress information as received. This is appropriate if the distressed vessel is out of range of the Coast Guard but within range of you.
Urgency and Safety Signals
PAN-PAN
Pronounced pahn-pahn. Derived from the French word panne meaning breakdown. Used when a vessel or person is in a serious situation that may develop into a distress if help is not provided, but is not yet life-threatening.
PAN-PAN PAN-PAN PAN-PAN
ALL STATIONS
THIS IS [vessel name x3]
[position, nature of urgency, assistance needed, OVER]
Common uses:
- ▸ Person overboard (if not immediately life-threatening)
- ▸ Medical situation requiring evacuation
- ▸ Engine failure in busy shipping lane
- ▸ Loss of steering near hazards
SECURITE
Pronounced say-cure-ee-tay. A navigational or meteorological safety announcement. Broadcast by the Coast Guard, port authorities, and vessels encountering hazards. Not a distress — a warning.
SECURITE SECURITE SECURITE
ALL STATIONS
THIS IS [USCG SECTOR / vessel name]
[navigational hazard, special warning, OUT]
Common uses:
- ▸ Drifting buoy or debris in shipping lane
- ▸ Severe weather warning broadcast
- ▸ Aids to navigation off station
- ▸ Large vessel transiting a narrow channel
Priority Order — Exam Tip
MAYDAY
Grave and imminent danger to life or vessel
PAN-PAN
Urgency — serious but not immediately life-threatening
SECURITE
Safety — navigational or weather hazard
Digital Selective Calling (DSC) and MMSI
DSC is the digital distress and calling system integrated into modern VHF radios. It allows a vessel in distress to send an automated digital alert that includes the vessel identity, position, and nature of distress — without requiring the operator to speak. DSC operates exclusively on Channel 70.
How DSC Works
- Connect your DSC VHF radio to a GPS source (internal or external)
- Program your vessel's registered MMSI number into the radio
- In a distress: lift the red guard cover and press the DSC distress button
- Hold for 5 seconds — the radio transmits a digital alert on Ch 70
- The alert broadcasts your MMSI, position, nature of distress, and time
- Switch to Channel 16 and transmit your voice MAYDAY call
MMSI Registration
An MMSI is a 9-digit unique vessel identifier — like a phone number for your DSC radio. You must register it before use.
U.S. MMSI Format:
- 338XXXXXX — USCG-documented vessels (via FCC)
- 367XXXXXX — State-registered recreational vessels
- 003669999 — Example format (9 digits total)
Recreational boaters register free through BoatUS (boatus.org/mmsi) or Sea Tow. Commercial vessels must use the FCC. An unregistered MMSI triggers a false alarm protocol and delays rescue.
DSC Exam Key Facts
FCC Licensing Requirements
Operating marine radio equipment is regulated by the FCC. As a USCG-licensed captain, you will need to understand two separate FCC authorizations: one for the vessel and one for yourself.
FCC Ship Station License
The Ship Station License authorizes the vessel to operate its radio equipment. It must be kept on board and presented to FCC inspectors on demand.
Required when:
- ▸Operating a commercial vessel (carrying passengers for hire)
- ▸Traveling to any foreign port
- ▸Using SSB MF or HF radio
- ▸Operating in foreign waters
Valid for 10 years. Filed online at fcc.gov/licensing. Not required for recreational vessels operating only in U.S. waters with VHF only.
Restricted Radiotelephone Operator Permit
Any person who operates a ship station radio — including the captain — must hold a Restricted Radiotelephone Operator Permit (RR Permit) issued by the FCC.
Key facts:
- ▸No written exam required — just application and fee
- ▸Issued for the life of the holder (does not expire)
- ▸Filed using FCC Form 605
- ▸Authorizes operation of VHF, SSB, and satellite radios
- ▸Must be in the operator's possession when on duty
Higher-level permits (Marine Radio Operator Permit, GMDSS Radio Operator License) are required for operating GMDSS equipment on compulsory ships.
Exam Trap: Recreational Exemption
U.S. recreational vessels operating only in U.S. waters are exempt from the Ship Station License requirement for VHF radio. However, once you accept payment to carry passengers, the vessel is no longer recreational — it requires a Ship Station License. The RR Permit for the captain is always required regardless of vessel type.
EPIRB — Emergency Position Indicating Radio Beacon
An EPIRB is a satellite-linked distress beacon that transmits a distress signal when activated. Modern 406 MHz EPIRBs are detected by the COSPAS-SARSAT satellite network and relay the beacon's identity and position to Mission Control Centers, which alert the appropriate rescue coordination center.
406 MHz
Primary distress frequency — detected by COSPAS-SARSAT satellites. Position accuracy within 2-5 km, or better with GPS-linked EPIRB (within 100 meters).
121.5 MHz
Secondary homing frequency — allows SAR aircraft and vessels to home in on the EPIRB location once the search area is narrowed.
Registration
Must be registered with NOAA (beaconregistration.noaa.gov) before use. Registration is free and links the beacon to vessel and owner emergency contacts.
Activation
Manual activation (pull antenna and switch) or automatic (float-free and water-activated hydrostatic release). Category I EPIRBs are automatic; Category II are manual only.
EPIRB Categories — Exam Distinction
Category I
Automatic float-free. Mounted in a bracket with a hydrostatic release. If the vessel sinks, water pressure releases the bracket and the EPIRB floats to the surface and activates automatically. Can also be activated manually. Required for offshore commercial vessels.
Category II
Manual activation only. Must be grabbed and taken into the liferaft. More common on smaller recreational vessels. Less reliable in rapid sinking scenarios because it depends on crew action.
EPIRB Exam Points
- ▸Unregistered EPIRB causes delays — SAR must treat as potential false alarm
- ▸Test EPIRB only during the first 5 minutes of any UTC hour, for a maximum of 3 sweeps
- ▸Battery must be replaced by the expiration date marked on the unit
- ▸If accidentally activated, turn off and immediately notify USCG on Ch 16
- ▸GPS-integrated EPIRBs provide location within 100 meters vs 2-5 km for standard
SART — Search and Rescue Transponder
A SART is a radar transponder used by survivors in a liferaft or survival craft to help rescuers locate them. It responds to 9 GHz X-band radar pulses from searching vessels or aircraft by transmitting 12 reply pulses.
SART vs EPIRB — Critical Distinction
The EPIRB alerts the rescue coordination system via satellite and is used to initiate a SAR response. It covers hundreds of miles but cannot guide rescuers to an exact location once they are nearby.
The SART is used in the final homing phase — once searching vessels or aircraft are in the area, they use their radar to detect the SART and home in to the exact position of the survivors.
Both devices are required equipment on GMDSS vessels. For recreational and small commercial vessels, an EPIRB plus a SART or PLB provides comprehensive emergency signaling capability.
Exam Note on SART
Exam questions ask what pattern appears on radar when a SART is activated nearby. The answer is a series of 12 blips or dots arranged in a line or arc on the radar display, with the SART at the end of the arc nearest the vessel's heading. As you approach the SART, the dots spread into circles.
AIS — Automatic Identification System
AIS is a VHF-based transponder system that automatically broadcasts a vessel's identity, position, course, speed, and other data to nearby vessels and shore stations. It operates on VHF channels 87B (161.975 MHz) and 88B (162.025 MHz).
Class A AIS
Required on SOLAS vessels (300+ GT on international voyages, 500+ GT domestically, and passenger vessels). Transmits every 2-10 seconds when moving. Full SOTDMA technology.
Class B AIS
Voluntary or required for some commercial vessels. Transmits every 30 seconds. Lower transmit power than Class A. Recommended for all offshore passages.
AIS Receiver Only
Displays AIS targets from other vessels but does not transmit. Useful for situational awareness but your vessel is invisible to others on AIS.
AIS Data Transmitted
AIS improves collision avoidance by providing CPA (Closest Point of Approach) and TCPA (Time to Closest Point of Approach) calculations on chart plotters. It does not replace radar or a visual watch. AIS can be spoofed or switched off — do not rely on it exclusively for traffic separation.
SSB HF Radio — Long-Range Communications
Single Sideband High Frequency (SSB HF) radio operates between 2 and 30 MHz and provides long-range communications far beyond the line-of-sight limitations of VHF. HF radio signals travel by sky wave propagation — bouncing off the ionosphere — allowing communication over hundreds to thousands of nautical miles.
2182 kHz
International MF distress and calling frequency. Monitored by the Coast Guard. Required listening period every hour from H+00 to H+03 and H+30 to H+33 (3 minutes of silence for distress).
4125 kHz
MF/HF SSB distress and safety working frequency used in conjunction with 2182 kHz for distress communications.
Propagation
Sky wave: HF signals reflect off the ionosphere, enabling long-range communication. Ground wave: lower HF and MF signals travel along the surface for shorter ranges (300-400 nm on MF).
Weather Fax
Offshore weather charts (RTTY/Wefax) are transmitted on SSB HF. Vessels offshore receive high-resolution weather charts directly on SSB-equipped laptops or receivers.
VHF vs SSB Comparison
| Feature | VHF | SSB HF |
|---|---|---|
| Range | 20-25 nm (line of sight) | Hundreds to thousands of nm |
| Propagation | Line of sight only | Sky wave and ground wave |
| FCC License | Ship Station (commercial) | Ship Station required |
| Operator Permit | RR Permit required | RR Permit or higher |
| Distress Freq | Ch 16 (156.800 MHz) | 2182 kHz (MF) |
| Weather | WX1-WX7 receive only | SSB weather fax, Navtex |
| Coast to Coast | No | Yes, with conditions |
Radio Propagation on the Exam
VHF propagation is line-of-sight only — antenna height limits range. Higher antennas extend range (approximately 1.22 times the square root of antenna height in feet, in nautical miles). The exam may ask why two vessels with VHF cannot communicate at long distances — the answer is the curvature of the earth blocking the line-of-sight path.
NOAA Weather Channels
NOAA Weather Radio All Hazards broadcasts continuous weather information from a network of transmitters covering U.S. waters. These are receive-only channels — you cannot transmit on them. All VHF marine radios sold in the U.S. include WX channel capability.
| Channel | Frequency | Coverage (Primary) |
|---|---|---|
| WX1 | 162.550 MHz | Most widely used — primary NOAA weather channel in most regions |
| WX2 | 162.400 MHz | Alternate coverage where WX1 signal is weak |
| WX3 | 162.475 MHz | Alternate coverage — different transmitter networks |
| WX4 | 162.425 MHz | Supplemental NOAA weather coverage |
| WX5 | 162.450 MHz | Supplemental NOAA weather coverage |
| WX6 | 162.500 MHz | Supplemental NOAA weather coverage |
| WX7 | 162.525 MHz | Supplemental NOAA weather coverage |
What NOAA Broadcasts
- ▸Marine forecasts for coastal and offshore zones
- ▸Coastal waters forecasts (out to 25 nm)
- ▸Offshore forecasts (25-250 nm)
- ▸High seas forecasts (beyond 250 nm)
- ▸Storm warnings and watches
- ▸Tsunami and other hazard alerts
Special Marine Warnings
When the USCG issues an Urgent Marine Information Broadcast (UMIB) or the NWS issues a Special Marine Warning (thunderstorms, waterspouts, or winds exceeding 34 knots not covered in the regular forecast), a preliminary announcement is made on Channel 16, and the information is broadcast on Channel 22A (USCG) or on the local NOAA WX channel. Monitoring WX channels and Ch 16 underway is essential for weather awareness.
Radio Prowords and Procedure Words
Standard prowords ensure clear, unambiguous communications. The exam tests these definitions — particularly the distinction between OVER and OUT, and why you should never say REPEAT on a vessel.
| Proword | Meaning and Use |
|---|---|
| MAYDAY | Grave and imminent danger — requires immediate assistance |
| PAN-PAN | Urgency — serious but not immediately life-threatening |
| SECURITE | Safety/navigational hazard announcement |
| OVER | Transmission complete — reply expected |
| OUT | Transmission complete — no reply expected |
| ROGER | Message received and understood |
| WILCO | Will comply with instructions received |
| AFFIRMATIVE | Yes (do not say yes or yeah) |
| NEGATIVE | No |
| SAY AGAIN | Please repeat — never say repeat on a vessel |
| STAND BY | Wait — I will contact you shortly |
| BREAK | Pause between sections of a long message |
| SEELONCE MAYDAY | Radio silence — issued by rescue authority during distress |
| SEELONCE FEENEE | End of radio silence — distress situation resolved |
Never Say REPEAT on a Vessel
In military and maritime communications, REPEAT is a fire direction command meaning fire again with the same data. On a vessel, always say SAY AGAIN to request that a message be transmitted again. This distinction is tested on the exam.
NATO Phonetic Alphabet
Used to spell vessel names, call signs, and other critical information clearly over radio. Every letter must be memorized for the exam — and for real-world use.
A
Alpha
B
Bravo
C
Charlie
D
Delta
E
Echo
F
Foxtrot
G
Golf
H
Hotel
I
India
J
Juliet
K
Kilo
L
Lima
M
Mike
N
November
O
Oscar
P
Papa
Q
Quebec
R
Romeo
S
Sierra
T
Tango
U
Uniform
V
Victor
W
Whiskey
X
X-ray
Y
Yankee
Z
Zulu
Phonetic Numbers
0
ZE-RO
1
WUN
2
TOO
3
TREE
4
FOW-er
5
FIFE
6
SIX
7
SEV-en
8
AIT
9
NIN-er
Radio Log Requirements
FCC regulations require commercial vessels to maintain a radio communications log (also called a station log). The log serves as the official record of the vessel's radio operations and must be kept on board and available for inspection.
Required Log Entries
- ▸Date, time, and duration of radio watches
- ▸Vessel name and call sign (MMSI)
- ▸All distress, urgency, and safety traffic transmitted or received
- ▸Position of the vessel at least once per watch
- ▸All malfunctions of radio equipment
- ▸Maintenance and repair actions
- ▸Radio equipment tests conducted
- ▸EPIRB tests and battery check dates
Retention Requirements
Radio logs involving distress or safety communications must be retained for a minimum of 3 years from the date of the entry. Routine operational logs must be retained for periods specified by FCC regulations based on vessel category. All logs must be available for FCC inspection.
Exam Context
Radio log questions on the USCG exam most often appear in the context of distress communications. Key point: all distress calls, whether transmitted or received, must be logged immediately with exact time and content. The log entry for a MAYDAY must include the position given, the nature of distress, and the response taken.
Calling Procedure — Standard Practice
Call on Ch 16: [Vessel name x3], THIS IS [your vessel name x3], OVER
If no response in 2 min, try again. After 3 attempts, wait 15 min.
When contact is established, agree to switch: Switch to channel XX, OVER
Both vessels switch to the agreed working channel
Conduct business briefly on working channel, end with OVER or OUT
Return to Ch 16 watch immediately after completing communication
Frequently Asked Questions
What is the primary purpose of VHF Channel 16?
Channel 16 (156.800 MHz) is the international distress, safety, and calling channel. All vessels equipped with VHF radio must monitor Channel 16 continuously while underway, except when communicating on a working channel. It is used to initiate contact with other vessels or the Coast Guard, and to transmit distress calls. Never use Channel 16 for routine conversation.
What is Channel 22A used for?
Channel 22A (157.100 MHz) is the primary working channel for communications with the U.S. Coast Guard. After establishing contact with the USCG on Channel 16, you switch to Channel 22A to conduct business. It is also used for USCG safety broadcasts and Urgent Marine Information Broadcasts (UMIB). The 'A' suffix designates the U.S. simplex version of the channel.
What is the complete MAYDAY distress call script?
Transmit on Channel 16: (1) MAYDAY MAYDAY MAYDAY. (2) THIS IS [vessel name three times]. (3) MAYDAY [vessel name]. (4) My position is [latitude/longitude or bearing and distance from a landmark]. (5) I am [nature of distress: sinking, fire, medical emergency, etc.]. (6) I have [number] persons on board. (7) [Any other useful information: vessel description, color, hull type, EPIRB activated, etc.]. (8) OVER. Wait 15 seconds for a response. If none, repeat the call on Channel 16. If still no response, try 2182 kHz on SSB MF radio.
What is Digital Selective Calling (DSC) and how does it work?
DSC is a digital distress and calling system built into Class D (and higher) VHF radios. It operates on Channel 70, which is reserved exclusively for digital DSC signals — no voice transmissions are permitted on Channel 70. When a distress alert is sent, the radio broadcasts your MMSI number, position (if GPS is connected), type of distress, and time. The Coast Guard and nearby DSC-equipped vessels receive the alert automatically. After sending a DSC distress alert, the operator must switch to Channel 16 and transmit a voice MAYDAY call.
What is an MMSI number and how do you get one?
An MMSI (Maritime Mobile Service Identity) is a unique 9-digit identification number programmed into a DSC-equipped VHF radio. It functions like a phone number for your vessel and is transmitted automatically with every DSC call. U.S. recreational boaters can register for a free MMSI through BoatUS or Sea Tow. Commercial vessels must register through the FCC. You must register your MMSI before using it — an unregistered MMSI delays search and rescue response because rescuers cannot identify the vessel.
What FCC licenses does a USCG-licensed captain need?
A captain operating a commercial vessel needs two FCC authorizations: (1) A Ship Station License for the vessel itself, required for any commercial vessel, any vessel traveling to foreign ports, and any vessel using SSB or HF radio. The license is valid for 10 years and is filed online with the FCC. (2) A Restricted Radiotelephone Operator Permit (RR Permit) for the captain personally. This permit is required to operate any ship station radio and costs a one-time fee. No examination is required. It is filed using FCC Form 605 and does not expire.
What is the difference between MAYDAY, PAN-PAN, and SECURITE?
These are the three levels of maritime urgency signals, in descending order of severity. MAYDAY (from the French m'aidez, help me) signals grave and imminent danger to life or vessel requiring immediate assistance. PAN-PAN (from the French panne, breakdown) signals urgency — a serious situation that may develop into a distress but is not yet life-threatening. SECURITE (French, safety) is a navigation safety announcement broadcast by the Coast Guard or other authorities to warn mariners of hazards such as debris, buoys off station, or severe weather. All three are preceded by the signal word spoken three times.
What radio watch requirements apply to commercial vessels?
Under FCC regulations, vessels required to have a radio must maintain a continuous watch on Channel 16 while underway. Compulsory ships (generally vessels over 300 gross tons on international voyages, and passenger vessels) must also maintain a watch on 2182 kHz MF. Under GMDSS rules, vessels are required to maintain a DSC watch on Channel 70. Commercial vessels on international voyages are subject to full GMDSS requirements. For OUPV exam purposes, the key rule is: monitor Channel 16 at all times when the radio is in use.
What is an EPIRB and how must it be registered?
An EPIRB (Emergency Position Indicating Radio Beacon) is a distress beacon that transmits on 406 MHz to the COSPAS-SARSAT satellite network and on 121.5 MHz for homing. When activated — manually or automatically upon immersion — it transmits a distress signal with the vessel's identification. Every 406 MHz EPIRB must be registered with NOAA (free, online at beaconregistration.noaa.gov) before use. Registration links the beacon to the vessel and owner contact information, which dramatically speeds up rescue response. Unregistered EPIRBs result in delayed rescue and potential civil penalties.
What is a SART and when is it used?
A SART (Search and Rescue Transponder) is a radar transponder used by survivors in a liferaft or survival craft to help rescuers locate them. When triggered by an interrogating radar signal from a searching vessel or aircraft, it responds with a series of 12 blips on the radar screen forming an arc or line pointing toward the SART location. SARTs operate on the 9 GHz (X-band) marine radar frequency. An AIS-SART is a newer type that transmits position via AIS rather than radar and may appear on an AIS display as a distress target.
What is SSB HF radio and when is it required?
SSB (Single Sideband) HF (High Frequency) radio operates in the 2-30 MHz range and provides long-range communications — hundreds to thousands of miles — unlike VHF which is line-of-sight (approximately 20-25 nautical miles). SSB is used for offshore passage-making and is required on vessels subject to full GMDSS requirements. The international distress frequency on MF SSB is 2182 kHz. Weather fax and offshore weather broadcasts are also received on SSB. An FCC Ship Station License is required to operate SSB radio.
What are the NOAA weather channels on VHF radio?
NOAA broadcasts continuous weather information on WX1 (162.550 MHz), WX2 (162.400 MHz), and WX3 (162.475 MHz), plus additional channels WX4 through WX7 covering different geographic regions. These are receive-only channels — you cannot transmit on them. Broadcasts include marine forecasts, coastal warnings, and special marine warnings. The USCG issues Urgent Marine Information Broadcasts (UMIB) on Channel 16 followed by Channel 22A, and NOAA issues special marine warnings on WX channels. All VHF radios sold in the U.S. include WX channel capability.
What radio log requirements apply to commercial vessels?
Commercial vessels required to carry a radio must maintain a radio log (also called a radio communications log or station log). Required entries include: the date and time the watch begins and ends, distress calls received or transmitted, tests of radio equipment, and maintenance actions. The log must record the vessel name and call sign, and be kept for a minimum period specified by FCC regulations. While specific OUPV exam questions on log format are less common, candidates should know that commercial vessels must keep a log and that distress communications must always be recorded.
Exam Quick Reference — Radio Section
Channel 16 is Always Primary
Monitor Ch 16 at all times underway. Only leave for a working channel and return immediately. This is the most tested radio rule on the OUPV and Master exam.
Channel 70 — DSC Only, No Voice
DSC digital distress alerting operates exclusively on Channel 70. Voice transmission on Ch 70 is prohibited. Exam questions often include this as a distractor.
MAYDAY Then Voice
DSC distress alert on Ch 70 must be followed by a voice MAYDAY on Ch 16. The digital alert alone is not sufficient — voice communication is required.
Three Urgency Levels in Order
MAYDAY (grave, imminent danger to life or vessel), PAN-PAN (urgency, not yet life-threatening), SECURITE (navigational or safety hazard). Priority determines which traffic is cleared from the channel.
RR Permit for Every Captain
The Restricted Radiotelephone Operator Permit is required for any person who operates a ship station radio. No exam, one-time fee, does not expire. File FCC Form 605.
EPIRB Must Be Registered
A 406 MHz EPIRB must be registered with NOAA before it provides useful SAR information. Registration is free. Unregistered beacon means delayed rescue.
SART Shows 12 Dots on Radar
When a SART is interrogated by a 9 GHz X-band radar, it returns 12 pulses that appear as a line of 12 dots on the radar display. The SART is at the end of the line.
MMSI Is 9 Digits
Maritime Mobile Service Identity numbers are always 9 digits. U.S. documented vessels start with 338; state-registered recreational vessels start with 367. Must be registered before use.
Related Study Guides
EPIRB Complete Guide
Category I vs II, hydrostatic release, COSPAS-SARSAT, false alarm procedures.
Deck General Safety
Fire classes, PFDs, flares, stability, MARPOL, and all emergency equipment.
Marine Weather Guide
Barometer trends, fronts, Beaufort scale, storm warnings, and VHF weather channels.
VHF Radio Quick Reference
Channel assignments, calling procedure, prowords, and phonetic alphabet at a glance.
Emergency Procedures
Man overboard, flooding, fire at sea, abandoning ship, and SAR coordination.
Marine Electronics
GPS, radar, depth sounder, AIS, chartplotter, and electronic navigation.
Practice Marine Radio Questions on NailTheTest
Test your knowledge with real OUPV and Master-style radio questions — Channel 16 rules, MAYDAY procedures, DSC and MMSI, FCC licensing, EPIRB, and phonetic alphabet. Instant feedback and AI-powered explanations on every question.
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