Tekmanoid STD-C Decoder Updated: New Paid LES Decoder + EGC Visualization

The Tekmanoid EGC STD-C decoder was recently updated and a new commercial paid version was released. The paid version now supports the decoding of LES STD-C messages. Previously the only other decoder that we knew of which was able to decode LES messages was the www.inmarsatdecoder.com software. The inmarsatdecoder.com software costs €100, and while the price for the Tekamanoid decoder is not advertised, it is less than €100, and a bit more affordable for the average person.

Tekmanoid STD-C Decoder Receiving LES Message.
Tekmanoid STD-C Decoder Receiving LES Message.

The free versions of both decoders only decode the EGC broadcast messages which contain SafetyNET messages. These include messages like weather reports, shipping lane activity and hazards such as submarine cables and oil rig movements, pirate activity, refugee ship reports, missing ship reports, and military exercise warnings. 

The paid version can decode the other non-broadcast private LES STD-C channels. LES STD-C channels typically contain email like messages sent to and from ships. Mostly it’s company messages about the ship route plans, cargo discussions, repair/fault discussions, ship performance information and weather reports etc. Sometimes small files are also downloaded. Each Inmarsat satellite contains about 7 LES channels each run by a different telecommunications company, so one may be of interest to you.

The paid version of the Tekmanoid decoder also has a nice feature for visualizing the SafetyNET EGC messages. Every now and then an alert containing coordinates and an area is sent out. Usually it is something like a distress alert from an EPIRB or the search area for a missing vessel. The decoder generates an HTML file that displays these areas on a map, alongside the text message.

STD-C EGC Distress Alert on map
STD-C EGC Distress Alert on map

The author of the Tekamnoid software allowed us to test his new paid version for free. We ran the software using signal from an Outernet patch antenna and LNA. An RTL-SDR V3 + SDR# was used as the receiver, and the audio was piped to the Tekmanoid decoder with VB-Cable. Decoding was almost flawless on both LES and EGC STD-C channels. In a previous recent update the Tekmanoid decoder was updated for improved decoding performance, and now in our opinion it is almost or just as good as the inmarsatdecoder.com software.  

If you are interested in learning more about decoding Inmarsat STD-C we have a tutorial available here. LES channels for the Inmarsat satellite in operation over your geographic location can be found on UHF-Satcom’s website.

LES STD-C Inmarsat Channels
LES STD-C Inmarsat Channels

Remember that LES STD-C messages are not publicly broadcast, so in some countries it may not be legal to receive them. Most countries will have a law that says you can receive and decode the data, but you may not act upon or use to your advantage any information from the messages.

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william Galoosis jr

 alex How do I go about getting a copy of Tekmanoid?


&0x7F of course


 alex, is the LES (Land earth station) basically a ground station sending data? My Google-fu is failing me on a more detailed description besides that. Interested to know more before buying the LES version. I’m landlocked here and there’s a 1000+ miles between me and saltwater in any direction, so if my understanding holds I’d be hard pressed to RX any earth based transmissions…? Wondering whether it would do me any good to buy other than supporting the development? (which isn’t a bad thing) Thanks for some great software. I’ve used an older version on and off for a few years.

 admin: I would have sworn I posted to this thread yesterday and now it’s gone. What’s up?


 alex, maybe I read wrong. Looks like data downlinks strictly for land based stations.


Unless you live in the north or the south pole, you should have coverage. They originate from landbased earth (duh?) stations (LES) and you get the downlink to the ships. Marine related mostly. Software released to satisfy curiosity.


OK, Thanks. Too early in the morning I guess. After I posted that I found a PDF that explained it to my coffee deprived mind.

pic related


“many more blocks left to be decoded…”
a challenge for tekmanoid !


many more signals on the inmarsats…
sorry, its not ironic.
thank you.


No problem, thank you too!


First sdr software in a long time tt isn’t made from “illegally decompiled” software


Tekmanoid…the original 🙂
Thanks for the love!


they didn’t take the blurring too serious, huh