NAVTEX for Emergency Communication

Posted by Fred C (W6BSD) on Jan 25 2021

Many ham radio operators are interested in EMERCOM1. It can be useful to have a reliable source of weather information during an emergency. Some radios come with the NOAA2 frequencies already programmed in the memory. Hams have also programmed the following channels in their radios:

NOAA weather channels:

WX1 WX2 WX3 WX4 WX5 WX6 WX7
162.550 MHz 162.400 MHz 162.475 MHz 162.425 MHz 162.450 MHz 162.500 MHz 162.525 MHz

In this blog post, I will focus on another source of weather information that can be useful "when nothing else works," especially if you live along the coast: NAVTEX2.

NAVTEX short for NAVigational TEleX is an international automated service for the delivery of navigational and meteorological warnings and forecasts to ships. This information can also be useful if you are in a coastal area. The service is free and the weather bulletins are transmitted from the National Weather Authority or Coast Guards (in the US). NAVTEX messages are sent at 100 baud using FSK modulation with a frequency shift of 170 Hz. The frequency for English messages is 518 kHz and 490 kHz for broadcasts in other languages.

Each station worldwide has a 10-minute time slot, starting with the station identifier A at 00:00 UTC. Every station transmits every 4 hours. You can refer to the NAVTEX Stations list for transmission times. Since I live in California, I use the following table. My station ID is C for San Francisco.

Navarea 12 – Eastern Pacific:

Area kHz ID Station Operator Position Transmission times (UTC)
12 518 C San Francisco USA 37°55′32.66″N 122°44′2.6″W 00:20, 04:20, 08:20, 12:20, 16:20, 20:20
12 518 D Prince Rupert CAN 54°17′54.67″N 130°25′3.61″W 00:30, 04:30, 08:30, 12:30, 16:30, 20:30
12 518 H Tofino CAN 48°55′31.72″N 125°32′25.1″W 01:10, 05:10, 09:10, 13:10, 17:10, 21:10
12 518 J Kodiak ALS 57°46′53.78″N 152°32′15.3″W 01:30, 05:30, 09:30, 13:30, 17:30, 21:30
12 518 L Ayora EQA 00°45′S 90°19′W 01:50, 05:50, 09:50, 13:50, 17:50, 21:50
12 518 M Guayaquil EQA 02°17′S 80°01′W 02:00, 06:00, 10:00, 14:00, 18:00, 22:00
12 518 O Honolulu HWA 21°26′13.27″N 158°08′35.66″W 02:20, 06:20, 10:20, 14:20, 18:20, 22:20
12 518 Q Cambria USA 35°31′27.47″N 121°03′42.92″W 02:40, 06:40, 10:40, 14:40, 18:40, 22:40
12 518 W Astoria USA 46°12′14.36″N 123°57′20.3″W 03:40, 07:40, 11:40, 15:40, 19:40, 23:40
12 518 X Kodiak ALS 57°46′53.78″N 152°32′15.3″W 03:50, 07:50, 11:50, 15:50, 19:50, 23:50

Software

To decode the NAVTEX messages, I use Fldigi4. Fldigi is a program that decodes more than 18 digital modes used by radio amateurs, including NAVTEX and WEFAX. If you are a member of an EMERCOM team, I am sure someone is already using fldigi and can help you connect your radio and configure the software to your needs.

Fldigi receiving NAVTEX (click to enhence)

Using fldigi is simple, especially if you have a radio equipped with an internal sound card like any modern Icom radio. I have connected my Mac directly to my Icom IC-7200. If your radio does not have an internal soundcard, consider buying a Digital Mode Interfaces. The most popular ones are Signalink or RIGblaster, but any card should work just fine.

A couple of minutes before the transmission, tune your radio to 517 kHz, set fldigi to the frequency 518 kHz, and as soon as the transmission starts, you should see the signal on the waterfall, and the software will start printing the message in the receive window.

Once the transmission is over, you can save the received message by right-clicking on the mouse. Then you can now inform your EMERCOM team of any incoming weather.

Message example

The following text is an example of a complete weather update received on NAVTEX the day before a storm in Northern California.

ZCZC CB42
POC/COMMAND DUTY OFFICER/-/FLEWEACEN NORFOLK VA/LOC:NORFOLK VA/

TEL: 757-444-7583/EMAIL:FWC-NORFOLK.CDO(AT)NAVY.MIL//
RMKS/FZPN23 KWNM 252223
OFFN08
NAVTEX MARINE FCST FOR NRN CA WATERS
NWS OCEAN PREDICTION CENTER WA DC
223 PM PST MON JAN 25 2021
CONDITIONS GIVEN REPRESENT THE HIGHEST WITHIN THAT PERIOD.
...PLEASE REFER TO COASTAL WATERS FORECASTS (CWF) AVAILABLE
THRU NOAA WX RADIO A OTHER MEANS FORR DETAILED COASTAL
WATERS FORECASTS...
.SYNOPSIS...STRONG HIGH PRES W OF THE AREA WILL WEAKEN AND
DRIFT SW OF THE REGION TONIGHT INTO TUE AHEAD OF A COLD FRONT.
THE STRONG COLD FRONT WILL MOVE INTO THE N WATERS TUE, REACHING
THE CENTRAL WATERS BY TUE NIGHT AND THEN MOVING INTO THE S WATERS
WED. THE FRONT WILL THEN CONT MOVING SE ACROSS THE S WATERS
WED NIGHT THRU THU NIGHT BEFORE PASSING S OF THE AREA FRI. A
LARGE AREA OF LOW PRES WILL MOVE SE INTO THE N WATERS WED,
THEN LINGER OVER THE N AND CENTRAL AREAS WHILE SLOWLY WEAKENING
INTO THU, BEFORE MOVING INLAND THU NIGHT. ANOTHER COLD FRONT
WILL MOVE INTO THE N AND CENTRAL WATERS FRI, THEN INTO THE CENTRAL
AND S WATERS FRI NIGHT. ON SAT AND SAT NIGHT ANOTHER COLD FRONT WILL

MOVE SE INTO THE N AND CENTRAL WATERS.
PT ST GEORGE TO PT ARENA
...GALE WARNING...
.TONIGHT...NW WINDS 20 TO 30 KT. SEAS 12 TO 19 FT. SCATTERED

SHOWERS WITH VSBY 1 NM OR LESS.
.TUE...S WINDS 35 TO 45 KT. SEAS 11 TO 16 FT. CHANCE OF RAIN

WITH VSBY 1 NM OR LESS.
.TUE NIGHT...W TO SW WINDS 30 TO 40 KT. SEAS 12 TO 17 FT. RAIN

WITH VSBY 1 NM OR LESS.
.WED...W TO SW WINDS 20 TO 30 KT. SEAS 16 TO 23 FT. RAIN.
.WED NIGHT...N WINDS 15 TO 25 KT. SEAS 13 TO 21 FT.
.THU...N TO NW WINDS 15 TO 25 KT. SEAS 10 TO 17 FT.
.THU NIGHT...NW WINDS 10 TO 20 KT. SEAS 7 TO 12 FT.
.FRI...S WINDS 15 TO 25 KT. SEAS 6 TO 9 FT.
.FRI NIGHT...NW WINDS 20 TO 30 KT. SEAS 9 TO 13 FT.
.SAT...SW WINDS 25 TO 35 KT. SEAS 9 TO 14 FT.
.SAT NIGHT...S WINDS 20 TO 30 KT. SEAS 11 TO 15 FT.
PT ARENA TO PT PIEDRAS BLANCAS
...GALE WARNING...
.TONIGHT...NW WINDS 25 TO 35 KT. SEAS 12 TO 20 FT. SCATTERED

SHOWERS.
.TUE...SW WINDS 25 TO 35 KT. SEAS 11 TO 16 FT.
.TUE NIGHT...S WINDS 35 TO 45 KT. SEAS 12 TO 18 FT. RAIN WITH

VSBY 1 NM OR LESS.
.WED...S TO SW WINDS 35 TO 45 KT. SEAS 15 TO 23 FT. SCATTERED

SHOWERS WITH VSBY 1 NM OR LESS.
.WED NIGHT...S WINDS 30 TO 40 KT. SEAS 14 TO 22 FT.
.THU...N WINDS 25 TO 35 KT. SEAS 11 TO 18 FT.
.THU NIGHT...N TO NW WINDS 15 TO 25 KT. SEAS 9 TO 14 FT.
.FRI...W TO SW WINDS 10 TO 20 KT. SEAS 7 TO 11 FT.
.FRI NIGHT...S TO SW WINDS 10 TO 20 KT. SEAS 6 TO 11 FT.
.SAT...S TO SW WINDS 10 TO 20 KT. SEAS 7 TO 12 FT.
.SAT NIGHT...S WINDS 10 TO 20 KT. SEAS 7 TO 13 FT.//

NNNN
BRKZCZC CA49
SECTOR SAN FRANCISCO BNM SF-0011-21
CA-SAN FRANCISCO TO PT ARENA
1. NOAA ENVIRONMENTAL BUOY (LLNR 390)IS OFF STA.

NNNN
BRKZCZC CA21
SECTOR SAN FRANCISCO BNM SF-0010-21
CA-BODEGA HBR
1. BODEGA HBR CHAN LT 2 (LLNR 7780) HAS BEEN REP TO BE
EXTING.

NNNN
BRKZZZZ

  1. Emergency communications. 

  2. National Oceanic and Atmospheric Administration 

  3. NAVTEX short for NAVigational TEleX 

  4. Fldigi short for Fast light digital 


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