NAV6c
User Guide

NAVTEX is a worldwide system for the broadcast and automatic reception of maritime safety information (MSI) in English by means of narrow-band direct-printing telegraphy. It provides shipping with navigational and meteorological warnings and urgent information, free of charge.

NAVTEX is a component of the IMO/IHO Worldwide Navigational Warning Service and is included within the Global Maritime Distress and Safety System (GMDSS).

NAVTEX transmissions are sent from coastal stations situated worldwide. Each station is allocated a time slot every four hours so that many stations can share the same frequency without interference. Stations typically have a transmission range of 250–300 nautical miles.

The NAV6c eNAVTEX System receives messages on three frequencies simultaneously:

The system automatically receives and categorises maritime safety messages:

• New Messages — recently received MSI, highlighted on arrival
• Nav Warnings — hazards and changes affecting safe navigation
• SAR Alerts — search and rescue operations
• Met Warnings — urgent meteorological hazard warnings
• Weather Forecasts — scheduled sea-area weather forecasts

View your vessel's heading on the Conning page, monitor position and course on the Navigation page, and track your route on the Chart.

Tap the gear icon or visit the Control Center to access system settings. Key settings include:

• General Settings — display and language options
• NAVTEX Settings — station and message type selection
• WiFi Settings — network connectivity

Swipe down from the left side of the title bar

Swipe down from the left side of the title bar to open the notifications panel. This panel slides down from the top and shows received alerts and system notifications.

• ⇧
  Close — swipe up on the panel or tap outside it
• 🔒
  Use the Clear button to dismiss all notification indicators
• 👍
  Tap a notification to navigate to the relevant page (e.g. a SAR alert)

Swipe down from the right side of the title bar

Swipe down from the right side of the title bar to open the quick settings panel for fast access to common controls:

• Brightness slider — adjust screen brightness
• Mode toggle — switch between light and dark mode
• Volume slider and mute button
• WiFi toggle — enable or disable wireless
• Control Center button — open full settings
• Help button — view help for the current page

Swipe up on the panel or tap outside it to close.

The dot navigation bar along the bottom of the screen

The row of dots along the bottom of the screen represents your currently open pages. Each dot corresponds to one page.

• •
  The active dot is highlighted and slightly larger to show which page you are on
• 👌
  Tap any dot to jump directly to that page
• ⌂
  Tap the background area of the navigation bar to open or return to the Home page
• ⇆
  Swipe left or right on the bar to move between open pages

The page list showing all open pages as icons

Swipe up from the dot navigation bar to open the page list, which shows all open pages as icons.

• Tap an icon to switch to that page
• Drag an icon to reorder pages
• Long press an icon to enter close mode for that page

NAVTEX messages contain maritime safety information broadcast by coastal stations worldwide. The system automatically receives, stores, and categorises these messages covering navigational warnings, weather forecasts, search and rescue alerts, and other safety information.

Each message is shown with a summary header bar

Each message in the list is shown with a header bar. Tap a message to expand it and view the full text. The header contains:

• Subject Icon — icon on the left representing the message category
• Message Identifier — B1B2 station and subject letters plus two-digit serial number (e.g. UE93 = station U, subject E, message 93)
• Time Received — shown as HH:mm MMM d (e.g. 14:30 Jan 5)
• Station Name — name of the transmitting station
• Frequency Icon — which NAVTEX frequency the message was received on
• Signal Strength — receive quality of the best intercept
• Read/Unread — envelope icon; closed = unread, open = read. Tap to toggle.

Every NAVTEX message begins with a standard four-character header that uniquely identifies each message and determines how it is categorised and displayed.

B1 — Station Identifier

A single letter identifying the transmitting station. For example, A is Niton (UK) and G is Cullercoats (UK) on 518 kHz. Each NAVAREA has its own set of station assignments.

B2 — Subject Indicator

A single letter describing the type of information in the message:

B3B4 — Serial Number

A two-digit number from 01 to 99 identifying the individual message. Serial numbers are assigned sequentially and recycled when they reach 99.

All received NAVTEX messages are stored in memory regardless of whether they are currently selected for display. The system has sufficient storage for many weeks of messages even in areas with high NAVTEX activity. When the store is full, new messages overwrite the oldest messages.

If the same message is received more than once (stations repeat messages at regular intervals), only the best quality version is kept. The system compares repeated transmissions to repair errors caused by noisy or weak signal conditions.

Each message is marked as new when first received. Once you have reviewed a message, it can be marked as read. This makes it easy to identify which messages have arrived since you last checked, particularly after being away from the display for a period.

Alert messages are those which the system has identified as requiring priority attention. A message may be flagged as an alert based on its category (such as SAR messages, which are always treated as alerts) or because it has a serial number of 00, which in the NAVTEX system indicates an urgent broadcast that must not be suppressed by receiver filtering.

Navigational warnings alert mariners to hazards and changes that affect safe navigation. These include:

• New or uncharted obstructions, wrecks, and shoals
• Changes to aids to navigation (lights, buoys, beacons)
• Cable and pipe-laying operations
• Military exercises and firing practice areas
• Offshore construction and exploration activities
• Drifting hazards such as containers, mines, or large debris
• Changes to established shipping routes or traffic separation schemes

Navigational warnings use subject indicator A in the NAVTEX message header. Subject indicator L is used for additional navigational warnings when the volume of warnings exceeds what can be covered under letter A.

SAR alerts contain information about vessels or persons in distress and ongoing rescue operations. These messages may include:

• Distress positions and descriptions of vessels in difficulty
• Requests for vessels in the area to keep a lookout or assist
• Details of ongoing rescue coordination including search areas
• Piracy warnings and armed robbery alerts

SAR messages are of the highest priority in the NAVTEX system. A serial number of 00 in a SAR message indicates an urgent broadcast that cannot be filtered or rejected by the receiver.

Meteorological warnings are urgent notices of hazardous weather conditions that may affect the safety of vessels at sea. These include:

• Gale warnings — winds of Beaufort force 8 (34–40 knots) or above expected
• Storm warnings — winds of Beaufort force 10 (48–55 knots) or above expected
• Hurricane/typhoon warnings — winds of Beaufort force 12 (64+ knots) expected
• Warnings of severe icing, restricted visibility, or other hazardous conditions

Weather warnings differ from weather forecasts (message type E) in that they indicate conditions that pose an immediate or imminent danger. Warnings are issued as conditions develop and are updated or cancelled as the situation changes.

Meteorological forecasts provide detailed weather predictions for defined sea areas. These typically include wind direction and strength, sea state, swell, visibility, and general weather conditions such as rain, fog, or thunderstorms.

Forecasts are broadcast at scheduled times, usually several times per day. Check the NAVTEX Timetable page for broadcast schedules in your area.

The 518 kHz frequency is the primary international NAVTEX channel. All broadcasts on this frequency are in English, making it the universal channel for maritime safety information worldwide. Since 1993, NAVTEX receiving capability on 518 kHz has been mandatory for certain vessels under SOLAS.

The world's oceans are divided into NAVAREAs (numbered I to XXI), each managed by a national hydrographic authority. Each NAVAREA has its own set of station assignments, with each station identified by a single letter (A to X).

Stations share the 518 kHz frequency using a time-division system where each station is allocated a ten-minute transmission slot every four hours. The power of each transmission is regulated to avoid interference between stations sharing the same letter in adjacent NAVAREAs.

The 490 kHz frequency is designated for national NAVTEX broadcasts. Unlike the international 518 kHz service which is always in English, national broadcasts may be in the local language of the broadcasting country, allowing coastal authorities to provide more detailed regional information.

National NAVTEX supplements the international service with additional information that may include more localised navigational warnings, detailed coastal weather forecasts, port information, and regional notices.

NAVTEX stations share each frequency using a time-division system. The 24-hour day is divided into four-hour cycles, and within each cycle every station is allocated a fixed ten-minute transmission slot. This means each station transmits up to six times per day at regular four-hour intervals.

Stations are assigned a letter from A to X, and their transmission slot is determined by this letter. Station A transmits first in each cycle, station B next, and so on. Because each slot is only ten minutes long, up to 24 stations can share the same frequency without overlapping.

The transmission power of each station is regulated so that its signal covers approximately 250–300 nautical miles. This controlled range means that stations with the same letter designation in different NAVAREAs will not interfere with each other.

The Conning page analogue display

The Conning page is a unique analogue display showing overlapping vectors for Heading (course through the water), Course Over the Ground (COG), Set (a combination of leeway and tide), and wind. All vectors are displayed relative to the current heading, which is shown in digital form at the top of the screen.

Vector Symbols

• Single-headed arrow — Heading
• Double-headed arrow — Course Over the Ground (COG)
• Triple-headed arrow — Set
• Variable tail feathers — Wind (meteorological convention: 5 kts per half feather, 10 kts per full feather, 50 kts per triangle)

Computed Set and Drift and other related parameters are shown in digital form at the bottom of the screen. Heading data is sourced from connected NMEA compass or GPS instruments and updates in real time.

The Navigation page displays your vessel's current position, heading, speed over ground, and depth information at a glance. Data is sourced from connected NMEA instruments and GPS receivers.

Use this page to monitor your vessel's real-time navigation parameters. The display updates automatically as new data is received from your instruments.

The Chart page displays your vessel's position on an OpenStreetMap-based nautical chart. AIS vessel traffic is overlaid on the chart when available.

• Pan — drag the chart with one finger
• Zoom — use pinch gestures to zoom in and out
• AIS targets — tap on AIS targets to view vessel details
• Auto-centre — the chart automatically centres on your vessel position when GPS data is available

The Waypoint View shows waypoint navigation information and a graphical "rolling road" display of the boat position and course relative to the course line. The rolling road display can be used to steer the boat along the course line whilst keeping the cross track error within chosen limits.

The Waypoint View shows:

• Waypoint name and position
• Time to Go (TTG — hours, minutes and seconds)
• Range and bearing to waypoint
• Closing speed to waypoint
• Cross Track Error (XTE)
• COG and SOG

The Navigation Log page records your vessel's track over time, showing position, speed, and heading at regular intervals. Log entries are recorded automatically at configurable intervals. You can view the log as a list or plot the track on a chart.

The AIS Targets page shows vessels detected by the Automatic Identification System. Each target displays vessel name, MMSI, position, course, and speed. Tap a target to view detailed vessel information including:

• Closest Point of Approach (CPA)
• Time to CPA (TCPA)

AIS data is received from connected AIS receivers.

The Satellite page shows GPS satellite status including the number of satellites in view, their signal strength, and position in the sky. The sky plot shows satellite positions relative to your vessel.

The Odometer page tracks your vessel's distance travelled calculated from GPS position data. It shows both:

• Trip distance — resettable at any time
• Total distance — cumulative distance record

The Barometer page shows air pressure information in a plotted format. The current air pressure, barometric tendency, and Beaufort Scale forecast are also displayed.

Monitoring pressure trends is essential for weather forecasting at sea. A falling barometer indicates approaching low pressure and potentially deteriorating weather. A rising barometer generally indicates improving conditions.

The tendency describes the rate of pressure change over the last hour:

• Steady — less than 0.03 hPa change
• Rising or falling slowly — 0.03 to 0.5 hPa
• Rising or falling — 0.5 to 1.2 hPa
• Rising or falling quickly — 1.2 to 2.0 hPa
• Rising or falling rapidly — greater than 2.0 hPa

The wind forecast is derived from the rate of pressure change. More rapid changes in pressure generally indicate stronger winds:

• Less than 1.0 hPa/h: Beaufort 0–5 at sea, 0–4 on land
• 1.0 hPa/h or more: Beaufort 6 at sea, 5 on land
• 2.0 hPa/h or more: Beaufort 7–8 at sea, 6–7 on land
• 3.0 hPa/h or more: Beaufort 9–12 at sea, 8–12 on land

The Sources page shows all connected data sources and their current status. This includes NMEA instruments, GPS receivers, AIS receivers, and NAVTEX receivers.

Use this page to verify that all your instruments are connected and providing data. Each source shows its connection status and data update rate.

The NAVTEX Monitor page shows raw NAVTEX data as it is received from the NAVTEX antenna. This is useful for diagnostics and verifying receiver operation.

The monitor displays the raw character stream including message headers and error characters. None of the message filtering from your NAVTEX settings is applied here — all incoming data is shown regardless of station selection or error rate.

The display includes the low-level phasing characters contained within transmissions and marks transmission errors with special characters.

The NMEA Monitor page shows raw NMEA 0183 sentences as they are received from connected instruments. Each sentence is displayed with its timestamp and source.

Use this to troubleshoot instrument connections and verify data quality.

The Control Center provides access to all system configuration pages. Tap an icon to open the corresponding settings page. From here you can configure:

The General Settings page allows you to configure the display language, date and time format, units of measurement, and other system-wide preferences.

All received NAVTEX messages are stored in memory regardless of your current filter settings. The messages you see on screen are selected from this store by applying filters. This means you can change your mind later about which messages to display and still view messages that were received previously but were not selected for display at the time.

You can control which stations' messages are displayed. Unless you filter out stations that are not relevant to your current location, the display can become cluttered with data from distant stations.

When connected to a GPS, stations can be selected automatically based on your position:

• Show messages from only the nearest station
• Show messages from all stations within range of your current position
• Manually enable or disable individual stations

You can further refine displayed messages by filtering on message type. Each NAVTEX message category (navigational warnings, meteorological warnings, weather forecasts, SAR alerts, etc.) can be independently enabled or disabled.

NAVTEX messages become less relevant over time. The system can automatically hide messages older than a configurable age limit. The default is three days, which is the period that NAVTEX messages officially remain valid. Older messages are still stored and can be viewed by increasing the age limit.

You can configure alert preferences for different message types to control audible and visual notifications when new messages arrive.

The WiFi Settings page allows you to connect to wireless networks for software updates and cloud services. You can scan for available networks, enter passwords, and manage saved connections.

The Vessel Settings page allows you to enter your vessel's details including name, call sign, MMSI number, and vessel dimensions. This information is used for AIS identification.

The Navigation Settings page allows you to configure navigation display parameters including units of distance, speed, and depth. You can also set navigation log recording intervals.

The Barometer Settings page allows you to configure pressure units, display range, and alarm thresholds for the barometric pressure display.

• Add a source by tapping the green + button and entering an IP address and port
• Remove a source by tapping the red X button beside it

Demo Mode

Enable Demo Mode to simulate NMEA data when no live instruments are connected. Use the Reset button to restore default source settings.

The Storage Settings page shows the available storage space and allows you to manage stored data including navigation logs, NAVTEX messages, and chart tiles.

You can clear cached data to free storage space. Chart tiles are downloaded and cached automatically as you browse the chart.

The database contains details of NAVTEX transmitting stations from around the world. Each entry includes the station identifier letter (A to X), its NAVAREA, station name, latitude, longitude, transmission range, and operational status.

The station database is used to:

• Display station names in message headers
• Determine which stations are nearest to your position or within range
• Populate the broadcast timetable

The Software Updates page allows you to check for and install software updates. A WiFi connection is required to check for updates.

The Power Settings page provides options to restart or shut down the device. Use restart when troubleshooting issues or after configuration changes that require a restart.

The Diagnostics page provides system health information including CPU temperature, memory usage, and network status. Use this page to troubleshoot system issues.

Diagnostic information can be useful when contacting technical support. You can also export diagnostic logs from this page.

The About page shows product information including the software version, serial number, and company details. It also displays the OpenStreetMap licence information.