OnAirSatellite & navigation · Experimental
Decode Inmarsat-C with an SDR
OnAir receives Inmarsat-C. Inmarsat-C satellite messages (EGC safety and news broadcasts) near 1537.7 MHz.
What Inmarsat-C is
Inmarsat-C is a maritime satellite messaging system. Its broadcasts carry safety information (SafetyNET) and system messages.
Frequencies and where it is used
Maritime satellite broadcasts.
In OnAir the tuning shortcut is EGC, L-band; you can enter any frequency your radio reaches.
What OnAir shows for Inmarsat-C
Safety messages (SafetyNET) and system information.
This receiver is built from the published specification and checked end to end on simulated signals. It has had little or no testing on real transmissions yet, so reports and recordings on Discord are welcome.
Which radio you need
This mode sits at a high frequency, so check that your radio tunes it: a HackRF covers 1 MHz to 6 GHz, and RTL-SDR stops near 1.7 GHz. Some modes at these frequencies also need a fast radio (10 to 20 Msps) or a dish and an LNB.
Questions about Inmarsat-C
Can I decode Inmarsat-C with an RTL-SDR?
Probably not: an RTL-SDR tunes up to about 1.7 GHz. A HackRF (1 MHz to 6 GHz) or another wideband radio is the usual choice for this frequency range.
Is it legal to receive Inmarsat-C?
Receiving satellite downlinks is generally legal. Encrypted or spread content is not decoded, and voice codecs that are patented are not shipped with OnAir.
Can I try Inmarsat-C in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.
Try it without a radio
OnAir includes built-in synthetic test signals for most modes, so you can open this screen, see the layout and try the controls before you own a radio. The Tour button walks you through the app.