NAVTEX broadcasts are sent:

In categories of messages indicated by a single letter or identifier.

NAVTEX has a table of letters and what type of message the letter represents.

For example, A is Navigational Warning, while B is Meteorological Warning.

A message that includes at close to start of FE stands for Pilot Service Message, Meteorological Forecast.

For more information on Navigational Telex message machine see:

[Wikipedia on NAVTEX]1

NAVTEX from Marine Insights

US Coast Guard NAVTEX MARITIME SAFETY BROADCASTS

Federal Register on NAVTEX move to satellites proposal

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MSI can be obtained by one (or more) of the following:

All of the above.

Marine Safety Information is available from all three sources:

• Navigation Telex (NAVTEX)
  
• SafetyNET
  
• Radio Telex (HF NBDP)

For US Coast Guard MSI info see:

US Coast Guard NAVTEX MARITIME SAFETY BROADCASTS

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Which of the following is the primary frequency that is used exclusively for NAVTEX broadcasts internationally?

518 kHz.

The NAVTEX sends messages on 518 kHz and also on 490 kHZ. The English-only International frequency is the 518 kHZ.

Regional or local broadcasts in any language are made on 490 kHz.

For more information see:

US Coast Guard NAVTEX MARITIME SAFETY BROADCASTS

Also, see Marine Insights article on NAVTEX On Ships: Working, Types Of Messages And Advantages

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What means are used to prevent the reception of unwanted broadcasts by vessels utilizing the NAVTEX system?

Programming the receiver to reject unwanted broadcasts.

US Coast Guard provides programming instructions to avoid unwanted signals:

Point 7: Program to accept only messages with B1 character of NAVTEX station for current area to avoid not relevant information.

Point 8: Program with B2 character with the special message characters (A-Z) you want to receive. The messages under A, B, and D must be received.

Point 9: Don't confuse characters in B1 (station identifiers) with type of messages for B2. Always verify that programming was done correctly.

US Coast Guard NAVTEX MARITIME SAFETY BROADCASTS

Also, see Marine Insights article on NAVTEX On Ships: Working, Types Of Messages And Advantages

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When do NAVTEX broadcasts typically achieve maximum transmitting range?

Middle of the night.

During the day, there are D, E, F1, and F2 atmospheric radio layers. But at night, with no sun exciting electrons in the air, there are only two layers, E and F.

Without the radio wave absorption layers, low to medium frequency waves (medium frequency 518 kHz) propagate further. NAVTEX broadcasts at 518 kHz.

Also, low watt broadcast stations can be heard much further.

US Coast Guard NAVTEX MARITIME SAFETY BROADCASTS

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What is the transmitting range of most NAVTEX stations?

Typically 200-400 nautical miles (360-720 km).

NAVTEX broadcasts occur on 518 and 490 KHz. These MF signals have a 200-400 mile range with the higher range being after dark.

See National Weather Service site for the section on NAVTEX. It also has sections on GMDSS, INMARSAT-C SafetyNET, and Iridium SafetyCast.

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