1.PRINCIPLE OF NAVTEX SYSTEM

1.1How NAVTEX Works

NAVTEX is an acronym meaning Navigational Telex, and as its name shows, it is a kind of narrow band radio teletype system for sending (by frequency shift keying) text messages expressed in a 7-unit code. The difference is that a NAVTEX transmitter transmits nine control characters (header code) ahead of the main message, so that the receiver can identify the station, message type and serial number automatically.

1.2NAVTEX System Operation

For navigation purposes, the world is divided into 16 areas as shown in the figure below. Each Navtex station has an identification code, from “A” to “Z”. The frequency assigned to Navtex are 518 kHz and another (490 or 4209.5 kHz), and many stations exist in the same service coverage.

If the stations were to transmit without any rule, the system would collapse due to mutual interference. To avoid this problem, the following rules apply.

•The transmission schedule is determined so that two or more stations having a common service area may not overlap in time.

•Each station transmits with minimum required power to cover its service area (200 to 400 nautical miles nominal).

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Furuno NX-700A manual Principle of Navtex System, How Navtex Works, Navtex System Operation
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NX-700A specifications

The Furuno NX-700A is an advanced navigation system designed specifically for professional mariners and commercial vessels. Known for its robust performance and precision, it integrates state-of-the-art technology to enhance safety and efficiency at sea. One of the most notable features of the NX-700A is its dual-channel frequency system, which allows for improved target detection and tracking capabilities. This dual-channel operation ensures that the system can differentiate between multiple targets, reducing the risk of collisions and enhancing situational awareness.

Another significant aspect of the NX-700A is its high-resolution display. The system is equipped with a large LCD screen that provides clear and detailed graphical representations of surrounding waters, including navigational aids and potential hazards. The intuitive interface allows for easy operation even in challenging conditions, ensuring that crews can concentrate on their primary task: safe navigation.

Further enhancing the usability of the NX-700A is its advanced GPS functionality. The system employs multi-GNSS (Global Navigation Satellite System) technology, enabling it to obtain accurate position fixes from various satellite constellations, including GPS, GLONASS, and BeiDou. This capability ensures that mariners receive reliable positioning data regardless of their location, which is crucial during navigation in remote areas.

The NX-700A also features robust connectivity options, including NMEA 2000 and NMEA 0183 support. This allows the system to interface seamlessly with other onboard equipment, such as autopilots, engine monitoring systems, and electronic chart plotters. Such integration enhances operational efficiency and aids in maintaining a central command point for navigation.

Marine safety is further bolstered with the NX-700A's built-in man-overboard function, which provides rapid and precise positioning information in emergency situations. The system can also store critical navigational data, which can be accessed quickly during emergencies, contributing to enhanced safety protocols on board.

In summary, the Furuno NX-700A is a sophisticated navigation solution that combines high-resolution displays, advanced GPS technology, dual-channel frequency systems, and robust connectivity. Whether used in fishing vessels, cargo ships, or pleasure yachts, the NX-700A stands out as a reliable tool for enhancing maritime safety and navigation efficiency. With its user-friendly interface and essential features, it embodies the modern requirements of marine navigation technology.
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