Tagged: std-c

InmarScope: An Inmarsat AERO and STD-C Decoder with Multichannel Decoding and Automatic Call Following

Over on the SignalsEverywhere YouTube channel, Sarah Rose has released InmarScope, a multichannel L-band Inmarsat decoder that connects directly to an RTL-SDR, Airspy, or HackRF. The software can receive and decode both aeronautical (AERO) and maritime (STC-C / EGC) traffic at the same time. Decoders are dropped directly onto the aligned FFT and waterfall by holding CTRL and left-clicking, and the software lets you stack Aero MSK (600/1200 bps), high-rate OQPSK (10500 bps), AMBE voice (8400 bps), and Inmarsat-C BPSK decoders side by side.

One of the more interesting features is automatic voice-call following. By monitoring the 10500 baud forward-link channels, InmarScope can receive C channel voice assignments and automatically retune the SDR to the assigned frequency, lock the carrier, decode and record the AMBE call, and then hop back to where it was. There is also a two-SDR mode that dedicates a second radio to voice with a live split-view spectrum so one radio stays on the P control channel while the other tunes to voice calls. For assignments that never get broadcast, there is also a Call Hunter feature that uses a squelch threshold to automatically drop the decoder when a call appears. When a call is playing, the built in flight map also decodes the aircraft hex ICAO address and looks it up on airplanes.live, showing the plane's position and route in real time.

Recent updates have added a community-editable band plan, message search and filtering, an IQ recorder that also captures the seconds before you hit record, and a web dashboard for browsing decoded data from a phone.

The software is completely open source on GitHub, and the C++ code can be compiled from source, or a precompiled Windows build is available on sarasforge.dev for $15, with Sarah's Patreon patrons getting it free.

We note that Inmarsat signals such as AERO and STD-C/EGC can be received with our RTL-SDR Blog L-band Patch Antenna, which is available in our store.

Multi-Channel Voice Following Inmarsat Decoder for Windows!

Decoding Inmarsat in 2026

Tech Minds: Testing out Discovery Dish for Inmarsat and Hydrogen Line Radio Astronomy

Over on YouTube Matt from the Tech Minds YouTube channel has recently uploaded a new video where he tests out our Discovery Dish antenna. Discovery Dish is designed to be a low-cost, portable solution for receiving L-band and S-band weather satellites, Inmarsat satellites, conducting amateur hydrogen line radio astronomy, and more.

In the video, Matt unboxes the Discovery Dish and provides an overview of the build process before demonstrating its use in decoding AERO and STD-C messages on Inmarsat. He then shows the dish and Inmarsat feed being used to receive Iridium satellites, and how they can be decoded using iridium-extractor with a HackRF or Airspy R2.

Finally, Matt swaps out the Inmarsat feed for the Hydrogen Line feed. Using SDR#, the IF AVG plugin, and Stellarium, he was able to obtain a clear hydrogen line peak.

This Discovery Dish Is The ONLY Satellite Dish You Will Need!

Tech Minds: Testing an Inmarsat L-Band Helix for Offset Satellite Dishes

In his latest video, Matt from the TechMinds YouTube channel tests out an LHCP L-band helix feed designed for receiving Inmarsat satellites. Matt pairs the feed with an 85cm satellite dish, an L-band LNA, and an Airspy Mini.

The L-band helix feed comes from a small German engineering company called nolle.engineering. The feed is priced at 94.70 Euros (incl. VAT) (~$102 USD), plus shipping costs. It is a passive antenna so it needs to be combined with an LNA to be usable with a typical SDR.

In the video Matt shows that the reception with the LHCP helix + dish setup is better than expected. He also compares it to a previous test he did with a longer RHCP helix antenna also produced by nolle.engineering. The RHCP antenna is used to be used without a dish, however, as expected the SNR is less than the dish + small LHCP feed setup. Matt then shows some Inmarsat signals being decoded including STD-C and Aero voice.

This L Band Helix Antenna Gives Amazing Performance

Decoding Inmarsat STD-C with Command Line Decoder STDCDEC and SigDigger

Over on his YouTube channel Aaron has uploaded a video showing how to use SigDigger and a C based command line Inmarsat STD-C decoder called 'stdcdec' together on his DragonOS SDR based Linux OS image.

STD-C is a marine satellite service that broadcasts messages that typically contain text information such as search and rescue (SAR) and coast guard messages as well as news, weather and incident reports. With the right software, an RTL-SDR and an appropriate L-Band satellite antenna like our 'Active L-Band 1525 - 1660 Inmarsat to Iridium Patch Antenna Set' these signals can be received and decoded.

The stdcdec software provides a way for command line only systems to receive and view STD-C data. In his video Aaron shows an example setup that uses SigDigger to determine the audio frequency offset, and receive the audio which is then passed to the stdcdec software. We note that SigDigger is a GUI based program but could probably be replaced with another CLI based program, in order to run on a headless system (as long as the tuning and audio center freq is determined before hand). Aaron is hoping to explore solutions for this in the future.

DragonOS Focal Rx and Decode Inmarsat-C Messages w/ SigDigger + STDCDEC (RTLSDR)

Two reviews of our new L-Band Patch Antenna + Stock Update

Last month we released our new L-band active patch antenna for sale, and not too long after we had a review from Frugal Radio praising it. We now have two more YouTube reviews available to share.

The first is from Tech Minds who does a teardown and demonstrates it receiving and decoding the Inmarsat STD-C NCS channel, receiving and decoding GPS and receiving Iridium signals. The second is from Mike Ladd from SDRplay, who tests it with an SDRplay RSP1A software defined radio. He shows that the patch works perfectly with an RSP1A, and demonstrates it receiving and decoding STD-C while mounted on the dash of his vehicle.

L-Band Patch Stock Availability Note: We note that we are already close to selling out of the first batch of these units as they sold much faster than expected! New sales of this patch are currently backordered but we expect to have a few more units from this first batch available by the end of next week. Also the freighter with Amazon USA stock should be arriving any day now, but it could still take a few weeks to get through the port and reach the warehouse due to the current port delays.

The second production batch of this antenna might still be a while away due to the electronic component shortage crisis occurring now, so if you were thinking about picking one up, please order ASAP.

RTL-SDR BLOG L-BAND Patch Antenna Version 2 - Inmarsat - Iridium - GPS

SDRplay RSP1a - RTL SDR Blog L-Band Patch antenna

Preorder Sale: Active L-Band 1525-1660 Inmarsat and Iridium Patch Back In Stock for $44.95

We have just received stock of our new L-band active patch antenna design. The antenna is designed for receiving RHCP L-band satellites such as Inmarsat, Iridium, GPS and other satellites that transmit between 1525 - 1660 MHz (please note that you cannot use it for weak signals that require a dish like HRPT or GOES). The antenna comes as a set with a large suction cup, 3M RG174 extension cable and bendable tripod to help with mounting. Preorder pricing is US$44.95 including free worldwide shipping to most countries shipped from our warehouse in Shanghai. At the end of this week (extended for one more week!) pricing will rise to the standard cost of US$49.95. Amazon stock will require time, and won't be in for at least 6+ weeks.

Please see our store to order the unit

Like our previous patch design, this is an actively amplified antenna as it contains a built in low noise amplifier which takes power from a 3.3 - 5V bias tee. This power is available from from our RTL-SDR Blog V3 dongles, and other SDRs like the Airspy, HackRF and SDRplay. It also has a built in SAW filter after the LNA to help reduce terrestrial interference.

Compared to the previous design the new patch is larger (175 x 175 mm) with higher gain and wider radiation pattern. This allows for much easier pointing of the antenna and for much stronger signals. The upper frequency range has also been extended to 1660 MHz from 1625 MHz. The included suction cup is also much larger allowing for the patch to point at more angles without being restricted by the window. The patch is enclosed within a new weatherproof plastic enclosure. 

L-Band Patch with Accessories
L-Band Patch Mounting Examples

The screenshots below show the patch receiving various signals like AERO, STD-C and Iridium

Inmarsat Reception
Inmarsat Reception
Airspy Showing Patch Bandwidth
GPS "hump" visible

Usage Tips

  • The antenna should be used with one meter or more of coax cable. It may perform poorly if the RTL-SDR is placed right at the antenna due to interference. If you want to run very long cable, then low loss coax should be used. 
  • The patch can be used flat, or angled towards the satellite. Angling it towards the satellite will yield significantly higher gain.
  • If you have very strong cell phone interference in your area, try using the patch a bit lower to the ground, and use buildings to block the interfering signal.
  • If you want to mount this on a car roof, you can use a standard mag-mount camera adapter.
  • When using the suction cup, ensure you wipe down the cup and the window surface before sticking it on. Have a backup plan in case the suction fails.

What can you do with this antenna?

Testing out the SDR-Kits L-band Inmarsat Patch Antenna for AERO

The SDR-Kits L-band Patch antenna is a modified GPS antenna designed for receiving Inmarsat satellite stations such as AERO and STD-C. They have another version for receiving Iridium frequencies as well. The patch costs £12.90 inc VAT in UK, or approx US$14 for non-UK customers. 

Over on his channel Frugal Radio has uploaded a video where he tests this patch antenna with an RTL-SDR Blog V3. The built in bias tee on the V3 is used to power the antenna. In the video he shows how he's able to receive and decode AERO using the JAERO decoding software and how he uses a a metal backing to improve reception.

SDR-Kits frugal L-band Inmarsat patch antenna review decoding CPDLC ADS-C with RTL-SDR v3 dongle!

YouTube Series on Inmarsat Decoding with Scytale-C

Paul (microp11) is the programmer behind the Scytale-C Inmarsat decoder which has become very popular with RTL-SDR owners. With Scytale-C, and RTL-SDR and an appropriate L-band antenna and amplifier it is possible to receive STD-C NCS data from Inmarsat satellites. This is a public broadcast which contains information like search and rescue (SAR) and coast guard messages as well as news, weather, pirate activity and other incident reports. If you're interested, we have a tutorial available here which uses different software.

Paul has recently created a 6-part video series explaining Scytale-C and all it's features. As well as showing how to setup a Scytale-C decoder with the SDR# plugin in order to receive the STD-C text data via the UI, Paul's series goes into more depth showing how to review and inspect the raw data packets, how to monitor multiple Inmarsat channels at once using SDR# Spyservers and how to use the map feature for plotting coordinate and region data.