General Characteristics

Implementation Requirements

Hardware Systems

GMDSS-approved NAVTEX receivers contain an internal printer and cost between $800-$1500.

Non-GMDSS NAVTEX receivers, with a lower price since they are aimed at the recreational boating market, cost between $300-500. They substitute LED screens and RS-232 outputs for the more expensive GMDSS printers. The RS-232 output from such devices can be printed, manipulated and displayed using a serial connection to a PC.

Strictly speaking, you do not need a unique NAVTEX receiver. There are also a number of software packages available allowing messages to be decoded by a PC with a suitable receiver connected to the computer's soundcard. Any general-purpose radio receiver capable of receiving 518 kHz SSB can be used, and its output connected to the sound card of a PC where it can use a commercial software package. 


Effective October 1, 2006, the U.S. Coast Guard began broadcasting weather via NAVTEX four times per day, rather than six. (pg 64)

It has been reported that some mariners are experiencing difficulties receiving weather forecasts via NAVTEX, which may be a transmission issue, equipment issue, or combination of both. Be certain your NAVTEX receiver has been properly programmed with proper NAVTEX station and subject identifiers. A minimum of 4 forecasts should be received daily. Both good and poor reception reports, stating your position, date/time(s), and make/model of your NAVTEX receiver to; would be greatly appreciated

Effective November 30, 1999 at 1800 UTC, the National Weather Service began to issue a new series of forecast products specifically tailored to fit the broadcast ranges of the U.S. Coast Guard NAVTEX transmitters on the CONUS and Puerto Rico. This action was taken as there was insufficient time available to broadcast all existing NWS offshore and coastal marine forecasts within the coverage range of each of these transmitters which resulted in an unacceptably increasing number of missed broadcasts. The new NAVTEX forecast products are a blend of the existing offshore marine forecasts and coastal marine forecasts, however, the inshore portion of these forecasts contain less detail than available in the coastal forecasts. Mariners can continue to obtain NWS coastal marine forecasts by other means including NOAA Weather Radio, USCG MF Voice, USCG VHF Voice, NOAA telephone recordings and the Internet. NWS and the U.S. Coast Guard are working actively to improve the broadcast of marine forecasts via NAVTEX through a combination of product enhancements and technology upgrades.

Software used with a General-Purpose Receiver and a PC

SeaTTY 1.73

SeaTTY overview

A program to receive weather reports, weather charts and navigational warnings

SeaTTY Details

DXsoftDeveloper :
1.73Version :
Windows 95/98/ME/NT/2000/XP Platform :
1.8 MbFile Size :
Free to try; $35 to buy License :
December 09, 2006 Date Added :
SeaTTY screenshotScreenshot :
Software AwardRating :
Keywords : rtty, navtex, hf-fax, wefax, weather, weatherfax, navigational warning

SeaTTY Review


A program to receive weather reports, navigational warnings and weather charts transmitted on longwave and shortwave bands in RTTY, NAVTEX and HF-FAX (WEFAX) modes. Software also can automatically save NOAA Weather Radio SAME voice messages (NWR SAME) and them digital headers. None additional hardware is required - your need only receiver and computer with a sound card.

Changes in version 1.73:
The "Setup / Clear Rx Window Once a Day" option was made in place of receiving buffer auto-cutting. Some minor bugs were fixed.
Buy Now ( $35 ) Download SeaTTY Free Trial

NAVTEX decoder lets you decode and view NAVTEX transmissions on your PC. All you need is a radio capable of receiving 518kHz SSB to begin decoding signals. The program can also automatically upload your messages to a website for viewing online. See the product homepage for details.

NAVTEX Operations

The Transmitter Identification Character B(1)

The transmitter identification character B(1) is a single unique letter which is allocated to each transmitter. It is used to identify the broadcasts which are to be accepted by the receiver and those which are to be rejected. In order to avoid erroneous reception of transmissions from two stations having the same B(1) character, it is necessary to ensure that such stations have a large geographical separation. NAVTEX transmissions have a designed range of about 400 nautical miles.

NAVTEX stations in the U.S. use the following B(1) characters:

B(1) Character Station Starting Time Call Sign
F Cape Cod MA 0045Z NMF
N Chesapeake VA 0130 NMN
E Savannah GA 0040 keyed by NMN
A Miami FL 0000* NMA
R San Juan PR 0200 NMR
G New Orleans LA 0300 NMG
C Pt. Reyes CA 0000 NMC
Q Cambria CA 0045 NMQ
W Astoria OR 0130 NMW
Kodiak AK** 0300
O Honolulu HI 0040 NMO
V Guam 0100 NRV

Programming the Subject Indicators

The subject indicator character is used by the receiver to identify different classes of messages below. The indicator is also used to reject messages concerning certain optional subjects which are not required by the ship (e.g. LORAN C messages might be rejected in a ship which is not fitted with a LORAN C receiver). Receivers also use the B(2) character to identify messages which, because of their importance, may not be rejected (designated by an asterisk).

In the US, NAVTEX broadcasts use following subject indicator characters:

     A = Navigational warnings *
C = Ice reports
D = Search & rescue information, and pirate warnings *
E = Meteorological forecasts
H = LORAN messages
J = SATNAV messages (i.e. GPS or GLONASS)
L = Navigational warnings - additional to letter A
(Should not be rejected by the receiver)
V = Notice to Fishermen (U.S. only - currently not used)
W = Environmental (U.S. only - currently not used)
Z = No message on hand

Note: The subject indicator characters B, F and G are normally not used in the U.S. Since the National Weather Service normally includes meteorological warnings in forecast messages, meteorological warnings are broadcast using the subject indicator character E. U.S. Coast Guard District Broadcast Notices to Mariners affecting ships outside the line of demarcation, and inside the line of demarcation in areas where deep draft vessels operate, use the subject indicator character A.