EGC / LES std-C decoder

LATEST NEWS: v1.5.4.0 with "Buoy" mapping!

Below: EGC "polygon area" and oil-rig mapping:

Screncapture of version v1.5.0 below:

*The tuner section now has a spectrum analyzer and a "tuner needle". Unlike previous decoder versions, the panel is now interactive, so you can click on the signal you see and tuning is done! To start decoding now simply click on the most "energy rich" part of the signal bringing in such way the green "tuner needle" indicator there. The signal bar will immediately rise and the quality bar will soon follow. I want to thank Thomas Gerlach for making the spectrum analyzer publicly available!

*The "Terminal" window has been replaced by a 3-tab, tabbed pane. These tabs are:


1) Terminal - The classic window that spits out data from NCS and LES channels (all messages are processed and displayed in their entirety)


2) EGC tab - NEW tab (as shown in video below) providing a tremendously more user friendly interaction. The map that used to be generated outside the program, still is, but is now also shown on this window as well. Depending on the EGC message, the map will be either hidden or shown. All messages are kept persistently in an SQLite database and the last batch is always available for review even after firing up the program for a new session. Non-read messages will be in bold to indicate they are new messages that haven't been read. 


3) LES tab - NEW tab window giving an overview of the received LES messages, columns indicate received date, coding format, originating MES ID or email and message length. Just like the first PRO version, received binary messages are analyzed, appended with the correct extension (PDF, PNG, ZIP etc) and put in a folder.

*The Help menu that used to be a dead link now actually brings up a nice help-style menu window. My intention is to fill it with as much information as possible needed to get a newbie started and also provide, tips and hints for the more experienced.

Features of "pro" LES+EGC std-C decoder

full GUI interface Yes
visual quality, volume, sync, locked center frequency Yes
visual signal strength indicator
(useful for peaking antenna)
basic channel parameters from bulletin board Yes
good / bad frames counter Yes
user selectable colors for fore and background Yes

Group message decoding Yes
All encoding processing
(ITA2, ASCII, binary)

NCS file extension assignment based on file header analysis (third party app TrID by Marco Pontello) Yes
possibility to save decoded data to output file Yes
Sound device card input selector Yes
queued messages indicator EGC / LES respectively Yes
list of active LES frequencies sent on NCS Yes
automatically log RAW data messages for post processing Yes
LES file extension assignment based on file header analysis (third party app TrID by Marco Pontello) Yes

FleetNet & SafetyNet graphical map representation

LES channel message decoding! ~7 channels per satellite to explore Yes
LES channel all encoding processing Yes
Night mode Yes
Save sound card input Yes
Message counter Yes
Smart autoscroll for Terminal window Yes
Indicator of Ocean region serviced by satellite Yes
Sound notification upon EGC message v.1.5.0
Interactive tuner / spectrum analyzer v.1.5.0
Message persistency (SQLiteDB) between sessions v.1.5.0
Information spit in 3 tabbed pane v.1.5.0
Help section v.1.5.0
non-standard EGC area mapping (polygons etc) v1.5.1
mapping of oil-rigs v1.5.1
mapping of buoys v1.5.4


The Enhanced Group Call (EGC) service is a message broadcast service with global coverage (except the poles) within the Inmarsat-C communications system. Two of the services provided are:
  • FleetNET
  • SafetyNET
FleetNET is used to send commercial messages to individuals or groups of subscribers (for example, individual companies communicating with their own Mobile Earth Stations (MES)). SafetyNET is used for broadcasting Maritime Safety Information (MSI) such as navigational warnings, meteorological warnings, meteorological forecasts and other safety related information (including Distress Alert Relays) from official sources.

Requirements if using communications radio:

  • Communications Receiver covering 1550 MHz in USB mode
  • Parabolic dish and preamplifier or patch antenna for 1550 MHz
  • Low noise amplifiier for 1550 MHz right after antenna.
  • Clear view to one of the satellites. For pointing a dish, a rough estimate is given by
  • Suitable audio cable between receiver and PC soundcard.
  • PC with soundcard
  • Java Runtime Engine: JRE v1.8 JDK

Requirements if using SDR

(may vary slightly depending on setup)
  • RTL-SDR USB stick or more advanced SDR radio covering 1550 Mhz
  • Parabolic dish and preamplifier or patch antenna for 1550 Mhz
  • Low noise amplifier for 1550 MHz right after antenna.
  • Clear view to one of the satellites. For pointing a dish, a rough estimate is given by
  • USB extension cord
  • SDR#
  • Virtual Audio Cable
  • Java Runtime Engine: JRE v1.8 JDK

inmarsat setup

Mapping of "standard EGC" messages (circles / rectangles)

Tune your receiver to the NCS channel for your ocean region. That is ONE channel per Inmarsat C satellite - or per ocean region. You will receive navigational messages classified in Safety/Priority/Urgency/Distress. Its common to receive SAR (Search And Rescue) alerts or other messages addressed to a particular geographical area. The standardized messages can address areas shaped as a rectangles or a circles.
click on image for full size

Mapping of "non standard EGC" messages (polygons)

 Besides "circular" and "rectangular" areas, the latest pro release version analyzes the message content and attempts to decode area coordinates. The images below have been automatically generated by this process. This is an experimental feature.

Mapping of oil rigs

Oil-rigs positions layed out as reported in EGC messages

Slightly different look and feel below on v1.5.4.0

Mapping of buoys

Buoy positions layed out as reported


The pro decoder enables you receive traffic from LES channels. You have so much more to explore! Select any active LES channel and start receiving messages. Some have more traffic than others, try them all out. 
Below: A table with a list of the currently available channels as sent by the satellite, (live example from AOR-E below).


Useful for getting a first rough estimate, where to point the satellite dish

SDR receiver manufacturer. Personally I use the RSP2.


For information on price / payment method contact me on:
admin @
LES+EGC version
Latest pay version: 10 September 2019

This update will be made available to you who already have the old pro version.
If you haven't received it, you can contact me.


October 2008 - project start date
March 2017 - first pay version released


"I have to say that this software is a triumph." "I ran a wave audio file on a continuous loop for over 8 hours and your program is running flawlessly!" "Excellent results, and software works great"
"Many thanks for your time, it is greatly appreciated!"
"Just wanted to tell you I'm having a great time with your program!" "Just a thumbs up. The program works really good, and with the spectrum analyzer, I think it'll be excellent."