Norvitra VHF Simulator

A realistic training environment for VHF maritime radio communication. This guide covers everything you need to operate the simulator — from making your first radio check to completing distress call scenarios.

📋 Regulatory basis Procedures in this simulator follow ITU Radio Regulations Chapter VII (Articles 30–34, GMDSS), ITU-R M.541 (DSC operational procedures) and ITU-R M.1171-1 (radiotelephony procedures for routine calls in the maritime mobile service).

What the simulator does

The Norvitra VHF Simulator puts you on the bridge of a vessel and connects you to a live AI-powered coast radio station. You operate a realistic VHF radio — changing channels, sending DSC calls, and communicating by voice or text — while the coast radio responds in real time with the correct procedures and appropriate accent for the region.

Scenarios range from routine radio checks to distress calls (MAYDAY), urgency calls (PAN PAN), safety broadcasts (SÉCURITÉ), and more. Each exercise is evaluated and scored against the ITU standard.

⚓ Full version Sections marked Full in the sidebar are available in the full course version. The free demo gives you Free Roam plus one graded exercise — a radio check with Shetland Coastguard — with three vessels and three coast radio stations to choose from.

System Requirements

Requirement	Details
Browser	Google Chrome or Microsoft Edge (recommended). Firefox supported. Safari supported with limitations.
Screen	Minimum 1025px width. Tablet in landscape mode or desktop. Not supported on phones.
Microphone	Required for voice input (PTT). Text input is always available as fallback.
Speakers / headset	Required to hear coast radio voice responses.
Internet	Required. The AI and voice systems require a live connection.

💡 Best experience Use Google Chrome or Microsoft Edge on a desktop or laptop for the most reliable voice recognition and audio playback.

Interface Overview

The simulator is divided into five main areas:

Norvitra VHF Simulator interface showing an active Radio Check exercise with Shetland Coastguard — The simulator during a Radio Check exercise. Left column: mission briefing and vessel data. Right column: VHF radio and message log.

① VHF RADIO

The Radio

Change channels, use PTT, send DSC calls. The display shows your current channel and GPS position.

② MESSAGE LOG

Communication Log

All transmitted and received messages appear here. Type your message and press Enter, or use the PTT button.

③ MISSION

Current Exercise

Shows the exercise briefing, your objective, and the Restart button. In Free Roam, shows "Select mission".

④ ACTIVE VESSEL

Your Vessel

Your vessel name, callsign, MMSI, type, position and home port. In full version, you can switch vessels.

⑤ ACTIVE COAST RADIO

Coast Radio Station

The coast radio you are communicating with. Each station has its own voice, accent, and working channels.

The three information cards

The left column contains three cards that give you all the context you need for the current exercise.

Mission card showing Radio Check – Tallinn Radio scenario briefing — **Mission card** — scenario briefing, mode badge, Restart and End Exercise buttons.

Active vessel card showing Odin motorboat details — **Vessel card** — your vessel name, callsign, type, POB and current position.

Active coast radio card showing Reykjavik Radio and MMSI — **Coast radio card** — active station name and MMSI for DSC calls.

Channels

Channel 16 is the international calling and distress channel. All maritime vessels maintain a listening watch on CH16. This is where you make your initial call — the coast radio will then direct you to a working channel for the actual exchange.

VHF radio showing Channel 16 on display — The VHF radio. LCD display shows current channel and GPS position. Function buttons: 16/C, DSC, DW, MENU. Right knobs: VOL, SQ, CH.

💡 Rule of thumb Always start on Channel 16. Switch to a working channel when instructed. Return to Channel 16 when done.

Changing channels on the radio

1

Rotate the CH knob

Click and drag the rightmost knob on the radio to scroll through channels, or click the CH button.

2

Press 16/C to return

The 16/C button on the radio face returns you instantly to Channel 16.

3

Confirm on the display

The LCD display shows CH 16 — confirm the correct channel before transmitting.

Common working channels

Channel	Use
CH 16	International calling and distress. Always monitored.
CH 20	Common working channel for Norwegian Coastal Radio South.
CH 67	Working channel used by some coast radio stations.
CH 70	DSC digital calling only — never used for voice.

Push to Talk (PTT)

The PTT button activates your microphone and sends your speech to the AI coast radio. Hold it for at least 3 seconds to activate, then speak your message clearly and release.

How to use PTT

1

Click and hold the PTT button

The button is on the left side of the radio handset. The mic indicator will turn orange (listening).

2

Speak your message

Speak clearly at a normal pace. Maritime radio language is formal — use "over" to indicate you are done speaking.

3

Release the button

The simulator transcribes your speech and sends it to the coast radio AI. The response appears in the message log and is spoken aloud.

No microphone? Type your message in the text field at the bottom of the screen and press Enter. This works exactly like speaking into the radio.

DSC – Digital Selective Calling

DSC is the digital signalling layer of GMDSS. Before making a voice call, you can send a DSC call to the coast radio — the radio then acknowledges, assigns a working channel, and you establish voice contact on that channel.

Sending a DSC routine call

1

Press the DSC button

Opens the DSC menu on the radio display.

DSC menu showing ROUTINE option selected — DSC menu — use [↑][↓] to navigate, [ENT] to confirm.

2

Select Routine

Navigate to Routine call using the arrow buttons.

3

Enter the coast radio MMSI

Type the 9-digit MMSI of the coast radio (e.g. 002570000 for Norwegian Coastal Radio South).

4

Press ENT twice to send

The DSC call is transmitted. Wait for the acknowledgement (DSC Ack).

5

Switch to the assigned channel and call

Your radio switches automatically. Pick up the handset and initiate voice contact — it is your responsibility to call first after DSC.

💡 DSC distress In a distress situation, the DSC Distress button sends an automatic distress alert with your position and MMSI before you make a MAYDAY voice call.

⚠ Call first — don't wait After a DSC acknowledgement, you must initiate voice contact. If you do not call within a short time, the coast radio will call you — as shown below. They will attempt this twice before closing the session.

Coast radio calling the vessel after DSC acknowledgement — If you do not call after the DSC acknowledgement, Shetland Coastguard calls twice — then closes with: *"MAYDAY Nordic Star. Nothing heard. Shetland Coastguard commencing rescue operation based on DSC data. Out."*

DSC Distress sequence

The following sequence shows what happens when a DSC distress alert is sent:

Radio display showing DSC distress alert sent, awaiting acknowledgement — 1. DSC distress alert sent — awaiting acknowledgement.

Radio display showing DSC distress sent and message log — 2. System confirms DSC distress sent in message log.

Radio display showing RCVD DISTRESS ACK from coast radio — 3. DSC acknowledgement received from Shetland Coastguard (MMSI 002320014). Press [ENT] to acknowledge — then switch to voice on CH 16.

Making Contact

All radio calls follow the same structure: identify the station you are calling, identify yourself, and state your purpose. Repeat the station name three times on first contact.

Standard call format (CH 16)

You transmit: [Station name], [Station name], [Station name].
This is [vessel name], [vessel name], [vessel name].
Callsign [phonetic callsign].
[Purpose of call], over.

Coast radio replies: [Vessel name], [callsign], this is [Station name].
Switch to channel twenty – channel two zero, over.

After switching channels, re-establish contact with full identification and state your purpose again.

ITU-R M.1171-1 When communication is established, your callsign or identification may thereafter be transmitted once only (§ 8.4).

Message Log

The message log displays the complete communication history for your current session. Your messages appear on the right; coast radio messages appear on the left.

Use the Pause button to pause the coast radio's spoken response. Use Skip message to advance to the next response immediately.

Radio Check

A radio check confirms that your radio is transmitting and receiving correctly. It is standard procedure before departure. There are three methods:

Method 1 — Call on Channel 16

You on CH 16: [Coast Radio], [Coast Radio], [Coast Radio].
This is [vessel], [vessel], [vessel].
Callsign [phonetic]. Radio check, over.

Coast radio replies: [Vessel], [callsign], this is [Coast Radio].
Switch to channel twenty – channel two zero, over.

Switch to channel 20, re-establish contact, and complete the radio check on the working channel.

Method 2 — Call directly on a working channel

You on working channel: [Coast Radio], [Coast Radio].
This is [vessel]. Callsign [phonetic].
Radio check on channel twenty – channel two zero, over.

Coast radio replies: [Vessel], [callsign], this is [Coast Radio].
You are loud and clear, over.

Method 3 — DSC Routine call

Send a DSC Routine call to the coast radio MMSI. After acknowledgement, switch to the assigned channel and initiate voice contact for the radio check.

💡 Good practice Always confirm the signal report back to the coast radio: "Loud and clear also. Thank you, out."

Being Understood — Best Practice

The simulator uses speech recognition and language processing to interpret what you say. Like a real coast radio operator, it reads your words as they come — with no prior knowledge of who is calling. The clearer your identification, the more reliably it will respond correctly.

The ambiguity problem

Consider this transmission: "This is Sea Hawk". Is Sea Hawk the vessel name, or is Hawk the callsign? A coast radio operator — human or AI — cannot know without more context. This is exactly why ITU-R M.1171-1 requires callsigns to be stated explicitly and separately from vessel names.

How to make yourself clear

1

State vessel name and callsign separately

Use a natural pause or the word "callsign" to separate them. Never run them together.

2

Use the word "callsign" explicitly

This is the most reliable method — the simulator will always parse correctly when you say the word "callsign".

3

Use phonetics for your callsign

Spell your callsign using the NATO phonetic alphabet. This is correct procedure and also the most reliable for speech recognition.

4

Use a slash to separate name and callsign

When typing your message, a slash ( / ) is a clear separator that the simulator always recognises.

Examples — from ambiguous to clear

❌ Ambiguous — avoid Humber Coastguard, this is Sea Hawk. Radio check, over.

Problem: is "Hawk" a callsign or part of the vessel name?

✓ Acceptable — single-word vessel name Humber Coastguard, this is Odin. Radio check, over.

No ambiguity — but the simulator will still ask for your callsign.

✓✓ Best — explicit callsign keyword Humber Coastguard, this is Sea Hawk, callsign Mike Romeo Yankee Zulu. Radio check, over.

✓✓ Best — slash separator (text input) Humber Coastguard, this is Sea Hawk / MRYZ. Radio check, over.

Real-world note This is not just a simulator limitation — it reflects real maritime radio procedure. ITU-R M.1171-1 §8 requires that callsigns be stated clearly and separately from vessel names. A coast radio operator receiving an unclear identification will always ask for clarification, just as the simulator does.

Microphone & Voice

The simulator uses your microphone to capture your radio transmissions. Speak clearly at a normal pace when the PTT button is active — the simulator transcribes your speech and sends it to the coast radio AI.

If voice recognition is unavailable or not working, the text input field at the bottom of the screen is always available as an alternative. Type your message and press Enter — it works identically to speaking.

Microphone Calibration Full version

The simulator does not just record you — it transcribes what you say and grades it. If it mishears your callsign or your position, the exercise fails for the wrong reason. Calibration is how you find out, before it costs you a mark, whether the simulator can hear you clearly.

It runs the first time in the course lesson Before we begin → Set up your microphone. You can start it again at any time from the microphone icon (🎙️) in the simulator's top bar.

What happens

You read four short lines. For each one you press START RECORDING, wait for the countdown, read the line aloud, and press STOP RECORDING. The simulator then shows you two things: exactly what it heard, and a diagnosis of your audio level. A summary at the end tells you how many of the four came through.

Test	What it checks
1 · Emergency situation	Ordinary speech at radio pace. Sets the baseline level.
2 · MMSI	Nine digits in a row — the hardest thing for speech recognition to get right.
3 · Position	Degrees and minutes, read digit by digit.
4 · Identity and callsign	The phonetic alphabet, and letters mixed with digits.

Reading the level bar

The bar moves while you are recording. The two marks on it are not decoration — they are the working range.

Below 15 the speech recognition has to guess. Above 85 the sound clips: the loudest parts are cut flat, and whole words disappear. Steady peaks in the middle band are what you want.

Distance to the microphone

Distance matters more than any setting. Too far away and the room is louder than you are; too close and your breath and plosives overload the input.

Aim the microphone past the corner of your mouth rather than straight at it. That keeps the p- and b-sounds from hitting the capsule directly, without losing any level.

Mic Boost

Mic Boost is the slider next to the level bar. It turns your microphone up or down inside the simulator, after the microphone and before anything listens — so it changes both the bar and what the speech recognition receives. Your browser's own automatic level control is switched off deliberately, which makes this the only volume control in the chain.

The simulator says	What to do
Weak signal	Move closer first. Raise Boost a little only if you are already at a sensible distance.
Audio clipping	Lower Boost, or move back. Both work; distance is the more reliable of the two.
Noise	Boost is amplifying the room. Move closer and lower Boost — that improves your voice relative to the noise, which raising Boost never does.
Clarity	The level is fine; the words were not. See the next section.

Order matters Find the distance first, then fine-tune with Boost. Boost amplifies the room exactly as much as it amplifies you, so it cannot rescue a microphone that is too far away — it only makes a distant, noisy signal into a loud, distant, noisy signal.

Speaking clearly

Radio speech is not ordinary speech. The simulator is tuned for the real thing, and so is the examiner.

Rule	Why
Even pace, no rushing	The transcription needs the gaps between words to find the word boundaries.
Do not shout	Shouting distorts and compresses. It reads as clipping, not as clarity.
Digits one at a time	“Two — five — seven”, never “two hundred and fifty-seven”. This is correct radio procedure, and it is the form the simulator is built to read.
Positions digit by digit too	“Five nine degrees, two two decimal five minutes north” — not “fifty-nine” and “twenty-two”.
Callsigns in phonetics	LG6756 is “Lima Golf Six Seven Five Six”. Letters on their own are too easily confused.

If a test does not come through Look at what the simulator registered before changing anything. Wrong words at a good level is a speech problem — slow down, or spell the digits. Nothing registered at all is a signal problem — check distance, Boost, and browser permission, in that order.

⚠ Browser permission The first time you record, your browser asks for microphone access. Click Allow. If you accidentally clicked Deny, or nothing at all happens when you record, go to your browser's site settings and enable microphone access for this site. Check there too that the right microphone is selected — a laptop with a headset plugged in often defaults to the wrong one.

Language Settings Full version

The simulator supports three language modes:

Setting	Effect
UI Language	The interface language — labels, buttons and menus. Choose Norwegian, English, or German.
Radio Language	The language of radio procedures. English is the international standard (ITU-R). Norwegian available for Norwegian waters.
TTS Voice	The coast radio voice. Automatically matched to the selected coast radio and region — British English for UK stations, Danish for Lyngby Radio, etc.

Course exercises When completing a course exercise (locked mode), the radio language is set by the scenario and cannot be changed. This ensures the exercise matches the international standard.

Your Vessel Full version

In the full version, you can select from multiple vessels. Each vessel has a unique name, callsign, MMSI, type, and home port. The vessel information is used in all radio procedures — make sure you know your vessel's callsign in phonetics before starting an exercise.

Vessel data

Field	Description
Name	Your vessel name. Used in all radio calls.
Callsign	4-letter radio callsign. Always spoken in phonetics (e.g. OZAN → Oscar Zulu Alpha November).
MMSI	9-digit Maritime Mobile Service Identity. Used for DSC calls.
Type / Length / Tonnage	Vessel specification. Required in some distress calls.
POB	Persons on board. Required in distress and urgency calls.

Coast Radio Station Full version

The full version includes 10 coast radio stations across Europe, Asia-Pacific and the Atlantic. Each station has its own MMSI, working channels, TTS voice, and regional accent.

Station	MMSI	Area	Accent
Norwegian Coastal Radio South	002570000	Norwegian coast	Norwegian
Shetland Coastguard	002320014	North Sea (Shetland)	British English
Humber Coastguard	002320007	North Sea (Yorkshire)	British English
Falmouth MRCC	002320011	English Channel	British English
Lyngby Radio	002191000	Skagerrak / Kattegat	Danish
Elbe Weser Radio	002181000	German Bight	German
Reykjavik Radio	002510100	North Atlantic	Icelandic
Palma Radio	002241022	Mediterranean	Spanish
Tallinn Radio	002760001	Gulf of Finland	Estonian
Manila Radio	005450099	South China Sea	Philippine English
Sydney Radio	005030230	Tasman Sea	Australian English

When you switch coast radio, your vessel's position automatically moves to within the station's service area, and the TTS voice switches to the correct regional accent.

Scenarios Full version

Scenarios are structured exercises with a specific situation, objective, and evaluation. Each scenario locks the coast radio, vessel, position, and radio language to ensure a realistic and consistent training environment.

Scenario types

Type	Signal	Description
Routine	🟢	Radio check, link call, DSC test
Distress	🔴	MAYDAY — immediate danger to life or vessel
Urgency	🟠	PAN PAN — serious situation, not immediately life-threatening
Safety	🟡	SÉCURITÉ — navigational or meteorological warning
Cancel	🟢	Cancelling a false distress alert
Relay	🟠	Relaying a MAYDAY on behalf of another vessel
SAR	🔴	Search and rescue coordination

Starting a scenario

1

Click "Select mission"

Opens the exercise selection menu.

2

Choose a scenario

Select from the list. The briefing panel shows your vessel, position, and objective.

3

Click "Start exercise"

The simulator locks the coast radio and vessel, positions your vessel, and you are ready to communicate.

Free Roam Full version

Free Roam lets you explore the radio freely without a structured exercise. There is no evaluation and no set objective — use it to practice specific phrases, experiment with channels, or get familiar with the interface before attempting a scored scenario.

⚠ Emergency calls in Free Roam MAYDAY, PAN PAN and SÉCURITÉ calls are blocked in Free Roam. These procedures are only available in structured scenarios to ensure correct evaluation.

Evaluation & Scorecard

When you complete a scenario, the simulator presents a scorecard with an evaluation of your performance. The scorecard shows:

Item	Description
Result	Pass / Perfect / Needs improvement
Successes	Procedures executed correctly
Errors	Missing or incorrect elements
Warnings	Minor deviations from standard procedure
Violations	Serious procedural breaches

Evaluation Report showing Critical Error with deviations listed — Example scorecard after a distress exercise. Left column shows what was done correctly. Right column shows deviations from correct procedure.

Use Try again to repeat the scenario immediately. Use Close to review log to study the full message history before retrying. Your result is sent to the course platform when the exercise is completed in a lesson.

Action Card

The Action Card is a scenario-specific reference panel that opens as a floating window inside the simulator. It shows the full procedure for the current exercise — including example radio phrases, step-by-step instructions, and vessel data.

Click the Action Card button in the header, next to the clock, to open it. You can drag and resize the panel. It does not affect the exercise or your score.

💡 Training vs. exam In training mode, use the Action Card freely — it is there to guide you. In exam conditions, the Action Card may be hidden by your instructor.

Fullscreen

The fullscreen button sits in the header beside the Action Card button. When the simulator is embedded in a lesson page it runs in a fairly small frame; fullscreen gives you the whole screen, which makes the channel display and the DSC menu much easier to read.

Press Esc or click the button again to leave fullscreen. The header stays visible either way, so the button is always within reach.

💡 On iPhone and iPad Safari does not allow true fullscreen for web pages. Instead you will be offered Add to Home Screen — open the simulator from that icon and it runs without the browser bars.

Phonetic Alphabet

All callsigns and letters are spoken using the NATO phonetic alphabet. Memorise this before your first radio exercise.

Letter	Word	Letter	Word
A	Alpha	N	November
B	Bravo	O	Oscar
C	Charlie	P	Papa
D	Delta	Q	Quebec
E	Echo	R	Romeo
F	Foxtrot	S	Sierra
G	Golf	T	Tango
H	Hotel	U	Uniform
I	India	V	Victor
J	Juliet	W	Whiskey
K	Kilo	X	X-ray
L	Lima	Y	Yankee
M	Mike	Z	Zulu

Numbers

Number	Spoken as	Number	Spoken as
0	Zero / Nought	5	Five / Fife
1	One / Wun	6	Six
2	Two	7	Seven
3	Three / Tree	8	Eight / Ait
4	Four / Fower	9	Nine / Niner

Troubleshooting

The coast radio does not respond

Make sure you are on the correct channel. The coast radio only responds on its working channels and on Channel 16. If the scenario has started, check the exercise briefing for which channel to use.

Voice recognition is not working

Check that your browser has microphone permission for this site. In Chrome: click the lock icon in the address bar → Microphone → Allow. If recognition still fails, the simulator will automatically fall back to text input.

The coast radio voice is not playing

Click anywhere on the page to unlock audio — browsers require a user gesture before audio can play. If the problem persists, check your system volume and make sure the browser tab is not muted.

The scenario did not start automatically

In course lessons, the scenario should start automatically within a few seconds of the page loading. If it does not, click the Restart button in the exercise panel.

The simulator is too small on my screen

The simulator requires a minimum screen width of 1025 pixels. Use a desktop or laptop computer, or a tablet in landscape mode. The simulator is not supported on phones.

Still having issues? Contact support at support@gmdsstraining.com and include your browser name and version, and a description of what happened.