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Marine Radio revision module 2 of 10
Core fixed and handheld marine VHF Radio controls, listening watch, PTT, power, squelch, and range limits.
9 guided lessons · 19 practice questions · 19 flashcards
Lesson 1 of 9
What you will learn
Use the listen–think–press–speak–release cycle so a routine call does not mask existing or higher-priority traffic.
Marine VHF is a shared, one-speaker-at-a-time system. Listen before transmitting, prepare the short message, hold push-to-talk only while speaking, then release it promptly to hear the reply.
The MCA advises operators to listen before transmitting, keep transmissions brief and avoid unnecessary conversation. A clear-looking display does not prove the channel is free: turn the volume up, use a workable squelch setting and listen long enough to recognise an exchange already in progress.
Voice marine VHF is effectively one speaker at a time. If two stations transmit together, neither message may be understood. Push-to-talk, or PTT, switches the set from receiving to transmitting; while PTT is held, that radio cannot receive the reply.
Distress, urgency and safety traffic take priority over routine traffic. If you hear higher-priority traffic, stop routine calling and keep the channel available. VHF is a communication aid: an agreement made by radio does not replace the collision-avoidance duties in the COLREGs or the need to navigate the vessel safely.
You want to call a marina on its published working channel. When you listen, you hear the marina answering another yacht.
1. Listen
Keep the volume audible and wait for the existing exchange to finish; do not press PTT merely to reserve a turn.
2. Prepare
Have the called station, your vessel identity and the reason for the call ready before transmitting.
3. Transmit and release
Make the brief call, release PTT immediately and listen for the reply.
Sense check: If your radio remains silent because PTT is still pressed, you are transmitting—not listening.
Optional quick check
Section 1 of 9
Lesson 2 of 9
What you will learn
Distinguish transmit power, receive volume and squelch, then set each control for the real task without assuming one control can fix another.
Transmit power affects the strength sent from the radio; volume affects how loudly received audio is heard; squelch sets the threshold below which receiver noise and weak signals are muted.
Volume changes received loudness, not transmit range. Set it so a call can be heard above the cockpit, engine or cabin noise. Turning the volume down after a call can silently end the listening watch even though the set still appears to be on.
Squelch is a receiver noise gate. On a manual control, open it until noise is heard, then close it only far enough for the noise to disappear; on an automatic or preset control, follow that radio's instructions and verify that weak traffic remains audible. Too little squelch causes constant hiss, while too much can hide a weak call.
Use low transmit power first for nearby routine communication; it limits unnecessary interference. The MCA's small-craft guidance makes distress the exception to that low-power-first habit. Power cannot repair a muted receiver, a wrong channel, a damaged antenna or a station that is out of coverage.
| Control | What it changes | Misconception to reject |
|---|---|---|
| Volume | Loudness of received audio | It does not increase transmitted range |
| Squelch | Receiver mute threshold | Maximum squelch does not improve reception |
| Low / high power | Transmitter output setting | High power cannot fix every no-reply problem |
| PTT | Receive or transmit state | Holding it does not reserve the channel |
The display is lit and the channel is correct, but you hear no traffic and receive no reply from a nearby marina.
1. Check reception
Raise volume and verify the squelch control is not suppressing every weak signal.
2. Check transmission
Confirm the intended low/high power setting and that PTT is actually switching the set to transmit.
3. Check the chain
If silence continues, check channel purpose, antenna, position, range and whether the station is listening.
Sense check: If opening squelch produces receiver noise, the audio path is alive; that does not prove the antenna or transmitted call is effective.
Optional quick check
Section 2 of 9
Lesson 3 of 9
What you will learn
Explain why VHF coverage is mainly line of sight and judge antenna height, condition and surroundings before treating transmit power as the solution.
Marine VHF coverage depends heavily on the radio horizon between both antennas. A sound masthead installation normally reaches farther than a low handheld, but no fixed mileage is guaranteed.
VHF signals travel mainly by line of sight. Raising either antenna usually extends the radio horizon, so a masthead antenna on a yacht often gives better coverage than a handheld at cockpit or sea level. The height of the receiving coast or ship station matters too.
Cliffs, harbour walls, buildings, vessel structure and terrain can screen a signal. Coaxial cable loss, corrosion, loose connectors, water ingress or a damaged antenna can also weaken the path. A high-power set connected to a poor antenna system may perform worse than expected.
Published sea-area coverage is not a personal range guarantee. The MCA notes that a vessel with an antenna below four metres or a portable set may have a smaller coverage area. Treat a handheld as valuable backup with lower antenna height, limited battery endurance and device-specific waterproofing—not as an automatic substitute for a sound fixed installation.
A yacht can hear a coast station outside the harbour but loses contact after moving behind a high breakwater.
1. Consider geometry
Ask whether terrain or structure now blocks the line between the two antennas.
2. Inspect the installation
Check the selected antenna, visible cable run, connectors and signs of damage before assuming the radio itself has failed.
3. Choose a safe response
If the call is routine, reposition or use the appropriate procedure; if safety is affected, escalate according to the real priority and available equipment.
Sense check: A strong transmission heard in open water and lost behind solid terrain points to propagation or screening, not necessarily the volume setting.
Optional quick check
Section 3 of 9
Lesson 4 of 9
What you will learn
Locate and operate the essential controls on the vessel's actual fixed and handheld radios before stress makes a menu search unsafe.
SRC knowledge must transfer to the set in front of you. Know how to power it, select a channel, set volume and squelch, choose transmit power, operate PTT and return to the required watch channel.
The CEPT SRC syllabus explicitly includes channel selection, dual-watch or scanning facilities, power connection, on/off, PTT, high/low output, volume, squelch and dimmer controls. Layouts differ: a function that has a labelled knob on one set may sit behind a soft key or menu on another.
Familiarisation should be deliberate and non-transmitting. Use the manual, simulator, training mode or a powered-off walk-through; do not press the distress control or make an unnecessary live transmission to discover what a button does.
A helm briefing should identify the channel being monitored, the way back to Channel 16, the vessel call sign and MMSI card, the location of the handheld, and the person controlling routine radio use. Familiarity reduces delay, but it does not replace correct priority or procedure.
A relief skipper joins a charter yacht whose VHF menu is different from the set they normally use.
1. Locate
Point out power, channel selection, volume, squelch, low/high power, PTT, Channel 16 return and display dimmer.
2. Confirm state
Read the displayed channel, power level, watch facility and position status rather than assuming the last crew left them correctly.
3. Rehearse safely
Talk through a routine call and a return to the watch channel without creating live traffic.
Sense check: If a crew member cannot return the radio to receive mode after a practice explanation, PTT operation is not yet secure.
Optional quick check
Section 4 of 9
Lesson 5 of 9
What you will learn
Maintain an audible listening watch and use dual watch or scanning as aids without losing track of the channel that actually received the call.
A radio only contributes to safety when someone can hear and interpret it. Volume, squelch and watch facilities must support attention rather than create a false sense of coverage.
The MCA's small-craft guidance says to maintain a listening watch on Channel 16 whenever practicable. Vessel requirements and local instructions can add other watch obligations, so use the current passage plan, notices and equipment guidance for the operating context.
Dual watch commonly monitors Channel 16 alongside a selected working channel. Scan checks a programmed list. These are receiving aids: device behaviour varies, a strong signal may stop the scan, and neither function proves that a call was heard or understood.
When a watch facility stops on a signal, identify the displayed channel before replying. Keep the volume usable and the squelch no tighter than necessary. Radio use must not distract the watchkeeper from navigation, visual lookout or collision avoidance.
The radio stops scanning and you hear the final words of a call, but you did not see which channel caused the stop.
1. Do not guess
Look at the display and identify the received channel before pressing PTT.
2. Recover context
Listen for identity and purpose; if uncertain, request a repeat using correct procedure.
3. Restore the watch
After the exchange, return the radio to the required listening arrangement.
Sense check: Dual watch listens on two relevant channels; it does not transmit on both or turn Channel 70 into a voice channel.
Optional quick check
Section 5 of 9
Lesson 6 of 9
What you will learn
Choose between the fixed set and handheld, and between low and high transmit power, by considering priority, range, antenna and battery—not one control in isolation.
A fixed masthead installation usually provides the stronger normal communication path; a handheld adds resilient backup. Low power is the routine starting point nearby, while distress is the explicit exception.
A fixed VHF commonly combines higher available transmitter output with a higher antenna and the vessel's main electrical supply. A handheld can continue if the fixed installation or main supply is lost, but its low antenna, battery endurance and device-specific waterproofing limit what should be expected from it.
Start nearby routine calls on low power. This reduces unnecessary interference and may be all that is needed. For distress, use the effective available means and do not let a routine low-power habit delay the alert; follow the complete distress procedure taught in the dedicated module.
High power can strengthen the transmitted signal, but it cannot restore a damaged aerial, bad connector, discharged battery, incorrect channel or screened radio path. Diagnose the whole chain and preserve the handheld's charge for the circumstances in which it may be the only working set.
The fixed radio goes dark after an electrical fault, while a charged handheld remains available in the cockpit.
1. Preserve communication
Use the working handheld and move its antenna to the best safe height and position available.
2. Manage energy
Keep transmissions brief, monitor battery state and use the manufacturer's approved spare or charging arrangement.
3. Address the failed link
Check the protected supply and fixed installation only when safe; do not assume the handheld has equal coverage.
Sense check: A handheld that works within a marina proves local communication, not that it can match a masthead fixed set offshore.
Optional quick check
Section 6 of 9
Lesson 7 of 9
What you will learn
Complete a short channel, set, message and priority check before a routine call, then troubleshoot no reply without making a longer, less controlled transmission.
A five-second pre-call check prevents many confused calls: confirm the intended station and channel, the radio state, the message priority and the essential words you need to send.
Before pressing PTT, identify whom you are calling, verify the published channel and listen. Confirm usable volume and squelch, the intended transmit power and the vessel identity. Put the request, position or other critical information in a short order that can be spoken clearly.
After transmitting, release PTT and listen. If there is no reply, do not fill the channel with a continuous or increasingly long call. Recheck the channel and radio state, wait for a reasonable interval, repeat briefly, or use the appropriate alternative procedure for the priority and risk.
A no-reply result is evidence, not a diagnosis. The other station may be busy or not listening; the channel may be wrong; your receiver, antenna or power may be mis-set; terrain may block the path. If the situation becomes urgent or distressing, change to the correct priority procedure rather than repeatedly treating it as routine.
| No-reply check | Question | Unsafe shortcut |
|---|---|---|
| Channel and watch | Is this the current channel, and is either station listening? | Calling continuously |
| Receive controls | Can weak traffic pass the volume and squelch settings? | Adding transmit power |
| Antenna and range | Is the path screened or the installation damaged? | Assuming a fixed mileage |
| Priority | Is this still routine, or have conditions genuinely changed? | Inventing urgency |
You are approaching a harbour and need a berth instruction while also monitoring traffic and steering.
1. Set
Confirm the harbour's current published channel, radio controls and low-power routine setting.
2. Script
Prepare the called station, your vessel identity and one clear request before transmitting.
3. Receive
Release PTT, listen and write down or read back critical instructions when needed.
Sense check: If you cannot state the station, your vessel and the request in one short outline, you are not ready to press PTT.
Optional quick check
Section 7 of 9
Lesson 8 of 9
What you will learn
Set up the actual radio in a repeatable order and verify the displayed channel, watch facility, power and receiver controls before transmitting.
A safe set-up is an observed sequence, not a remembered default. Power the set, read the display, establish audible reception, confirm the channel and watch mode, select suitable transmit power and preserve a readable display.
Start with the vessel's operating instructions. Confirm the radio has the correct supply, power it on, read the displayed channel and look for warning or position-status indications. Raise volume to a usable level, then set manual or automatic squelch according to the radio's instructions.
Select the intended channel and verify any dual-watch or scan facility. Do not assume the channel that stopped a scan is the one you intended to use. Confirm low/high output before the call and know the control that returns directly to Channel 16.
Use the display dimmer to protect night vision without making the channel, power, position or alert information unreadable. Press PTT only when ready to transmit and release it immediately afterward. The final check is behavioural: can you hear, identify and respond while still navigating safely?
You join a night watch and the previous operator has left the display dim, scan active and the power setting unclear.
1. Read before changing
Identify the current channel, scan or watch state, power level and any warning indication.
2. Make reception usable
Set a readable dimmer level, audible volume and device-appropriate squelch.
3. Confirm the call state
Select the required channel and power, listen, transmit only when ready, release PTT and restore the watch.
Sense check: A display that is comfortable in darkness is still too dim if the channel or alert state cannot be read without delay.
Optional quick check
Section 8 of 9
Lesson 9 of 9
What you will learn
Verify antenna condition, DSC position input and protected power together so an apparent working display is not mistaken for a reliable distress-capable installation.
A VHF/DSC set depends on three external links: a sound antenna path, current position information and dependable power. Failure of any one can weaken or misdescribe an alert.
Inspect the antenna, mounting, coaxial cable and connectors for looseness, corrosion, damage and water ingress. Do not make a live transmission into a disconnected or known-damaged antenna system. A powered display proves only that some supply has reached the set—not that radio-frequency energy reaches the antenna.
The MCA recommends an automatic position source for equipment that includes position in a distress alert. Confirm the radio is receiving a current position from its internal or external navigation source. If the installation requires manual position and time, update them using the radio's procedure and recognise that stale data can misdirect assistance.
The CEPT syllabus includes power connections, charging and battery maintenance. MCA guidance recommends considering an emergency source able to power both the radio and the electronic position-fixing source. Use correct voltage, protection and manufacturer-approved battery arrangements; record and rectify a failed link before relying on the system.
Worked example
A crew is preparing a yacht after winter storage. The fixed radio receives a weather transmission, the position field is dated and the handheld battery indicator falls quickly.
Sense check: The system is ready only when voice, antenna, current position and dependable power have each been verified; one successful reception cannot stand in for all four.
The fixed VHF powers on, but its position field is blank and the mast cable was disturbed during rig work.
1. Antenna path
Inspect the aerial, mounting and accessible cable/connectors; arrange competent testing if integrity is uncertain.
2. Position path
Check whether the radio is receiving current automatic position data, or update position and time by the approved manual route.
3. Power path
Confirm the normal and planned emergency supplies, protection, battery condition and power to the position source.
Sense check: A blank or obviously stale position alongside a lit display means the safety chain is incomplete even though voice reception may still work.
Optional quick check
Section 9 of 9