Posts Tagged ‘NAVTEX’
NAVTEX is a one-way bulletin service for maritime vessels that allows them to print out up-to-date weather and navigational warnings. NAVTEX is broadcast in the SITOR / FSK mode (using a 170Hz frequency shift) on 518KHz and 490KHz.
Stations throughout the world, usually located near the coast or large inland waterways such as the Great Lakes, transmit scheduled broadcasts once every four hours. They have a ten-minute 'slot' which is often not fully used. Conversely, some stations consistently run over their allotted time slot with longer then normal bulletins.
Most NAVTEX stations run a minimum of 400W, with most of them in the 1000W or higher range, making for some interesting DX targets around the world. Under good conditions, it is not unusual to log NAVTEX stations from the Far East here on the west coast or from Europe, on the eastern side of North America.
Simple software can be downloaded and used to decode NAVTEX broadcasts but you'll need to feed audio from your receiver into your computer's sound card. Most amateurs already have some method of doing this, usually via the 'mic' or 'line' input on the computer.
Today's CLE 'heads-up' is to give participants extra time to flesh-out their system, especially if you have not tried decoding these transmissions before ... But the learning-curve is not a difficult one.
From CLE organizer, Brian Keyte (G3SIA), comes the follow by way of the Yahoo NDBlist Group:
Our seventh Navtex Co-ordinated Listening Event will soon be here.
The sixth Navtex Event (CLE168) was in March 2013.
Many NDB List members have 'discovered' the NAVTEX mode from our
earlier CLEs and found it fascinating. Any NavtexDX members who
haven't taken part in a CLE before can discover the value of comparing
their results with the rest of us - in a constructive, non-competitive way!
Days: Friday 27 March - Tuesday 31 March
Times: Start and end at midday, your local time
QRG: 490kHz and 518 kHz (no other frequencies please)
We are adding the extra 24 hours at the end, to help us to cover
the two frequencies adequately.
Newcomers to Navtex are very welcome to join in - my simple Introduction
to get you started is below. For the much better FULL DETAILS AND ADVICE
go to our info page ( http://www.ndblist.info/ ) and select the box to visit
the Datamodes Section or direct to http://www.ndblist.info/datamodes.htmhttp://www.ndblist.info/datamodes.htm
All the Navtex information is in the lower part there:
Details are given of several good decoders which are freely available
including Dirk's excellent YaND and the SeaTTY decoder which can
be used without charge for a 30-day trial period. Members' Navtex
reports are included in REU/RNA/RWW, also reached via
This advice is a bit early to give extra time to prepare for decoding.
Please look out for the Final Details about three days before the CLE
starts. It will include important advice about log making, etc.
## This Listening Event is for the NDB List AND the NavtexDX List.
The advice is going to both Lists, and so will my 'Final Details' and the
Combined Results after the event, etc.
If you are a Member of NavtexDX, please continue to post to that list.
If you are ONLY a Member of NDB List please post any NAVTEX CLE logs
to NDB List (including any trial sessions before the CLE).
Whichever List(s) you belong to, do give the event a try.
From: Brian Keyte G3SIA ndbcle'at'gmail.com
Location: Surrey, SE England (CLE Co-ordinator)
NAVTEX - A SIMPLE INTRODUCTION
The worldwide NAVTEX system transmits navigational and meteorological
warnings and forecasts and urgent marine safety information to ships.
It provides a fascinating variation on our hobby, needing all the usual
skills with receivers and aerials and knowledge of different propagation
conditions, but adding some good DX reception, interesting navigational
messages and the ability to leave your receiver and PC 'listening all night'
while you are fast asleep! These short notes are just intended to GET YOU
STARTED, taking some of the initial mystery out of Navtex and Decoding,
explaining as simply as possible how to receive your first stations, how to
identify them and how to report your loggings.
1. TUNING TO A NAVTEX SIGNAL Set your receiver to show 516.30 kHz
on the dial for 518 kHz (or 488.3 for 490 kHz) with USB setting and
a wide filter, such as 2 kHz (Or, with CW setting, set your receiver to
the actual Navtex frequency and the BFO to +1.7 kHz).
You should occasionally hear the background noise replaced by the
warbling sounds of a Navtex signal.
2. GETTING SIGNALS TO YOUR PC Make an audio connection from the
receiver to the PC sound card input. It's best to use the more professional
advice about how to do that, but I just take a length of co-ax from the two
terminals of one side of some primitive headphones direct to the PC's line
input socket. You should be able to hear the signal in the speakers by
adjusting the PC volume control settings (playback and/or recording). If
necessary you could use the microphone input socket, but it is important
to AVOID OVERLOAD which could damage the sound card.
3. INSTALLING A DECODER PROGRAM A decoder program (see the Navtexsection in the Website) is easily installed in your PC - just follow the
advice. When you have succeeded with your first decodes we recommend
using YaND, which has many features designed specially for our needs.
As a very simple 'starter' though, I recommend the free Frisnit decoder.
Go to http://www.frisnit.com/navtex/ and in Downloads select NAVTEX
decoder (PC). Just save the 'navtex.exe' file, then double click on it.
With a 1700 Hz setting on the display, in no time you will see the incoming
Then move on to Dirk's YaND, which identifies the received Stations for you,
helps you to set up your log in the right format for REU/RNA, etc. and has
many extra features.
Alternatively, SeaTTY is also a very good decoder with some extra features.
It is quite easy to install and use and its 30-day trial is free of charge.
4. RECOGNISING THE STATIONS You will find that most Navtex messages
start with 'ZCZC' and end with NNNN. The ZCZC is followed by two letters
and two numbers - e.g. OA12. The first letter gives you a good idea which
Station you have received and it tells you the times of day, 4 hours apart,
when that station is likely to transmit. Most of the 'O' stations transmit
starting at 02:20, then 06:20, 10:20, etc. The World is split into Navtex
areas and there is often only one Navtex station using each letter in each
area. In North West Europe (Area 01) an 'O' station heard on 518 kHz is
likely to be Portpatrick in Scotland, but it might be from Malta (Area 03)
or even St Johns, Newfoundland (in Area 04). The actual messages should
remove any doubt about which of the possible stations it is - the messages
may include the Station Name (e.g. 'MALTA RADIO'), or the Navtex Area
Number or geographical references, latitude/longitude, etc.
The second letter (A) shows what kind of message it is and the rest
provides a message number.
5. STATION IDENTS We use our own way of identifying each station in our
logs and station lists. It always starts with a '$' which means 'this is a
Navtex Station' and it allows us to include these stations in lists with the
other kinds of beacons in the Rxx database, etc. Immediately after the $
comes the two-digit Area Number (most of the eastern part of N.America is
area 04). Last comes the Station Letter - an important part which provides
the main 'key' to the station sending the message. So the 'O' station above
would be $01O if Portpatrick, $03O if Malta and $04O if St Johns. You can
find lists of the Navtex stations and the times they transmit in Rxx and
from Alan's World Database in the Navtex Section of the Website.
YaND automatically works out for you everything in 4. and 5. above!
### IMPORTANT: However, WHICHEVER decoder you use it is important to
CHECK ALL YOUR LOG ENTRIES. Make sure that each decoded message
shows the as-transmitted Station letter and that each message
contains text confirming the identity of the Station you are showing.
6. OVER TO YOU! You can sit and watch the messages arriving or just leave
your receiver and decoder program running overnight, then look through the
messages afterwards to see what you have caught.