Decoding Inmarsat AERO 1545 MHz with a Backfire Helix and JAERO
Thank you to Nagy István for writing in and sharing with us his video showing how he uses a home-made backfire helix antenna and the JAERO software to receive and decode Inmarsat Aero at 1545 MHz. AERO messages are a form of satellite ACARS, typically containing short messages from aircraft, and some channels also support digital voice communications.
The backfire helix is an antenna design that consists of a helically wound wire, typically wound around a 3D-printed frame, attached to a large backplane. Recently, a similar design called a 'heliocone' has become popular for use with 1.7 GHz polar orbiting satellites.
In the video, Nagy shows two designs, one of his own and the other by Digitalelektro, and the good SNR that he's achieved with them in JAERO.
Later, I tried various other antenna designs. One aluminum reflector is made from an old cookie tin, and the other from screwed-on covers from an old multiswitch.
One boom is a cardboard tube, the other a wooden slat. The signals with the 1m dish and 3 inline amplifiers are excellent!
All materials (except the NOOelec SDR and the SAW filter) come from scrap metal!!!
Gruß Micha
Nice setup, I’m planning to buy a C-band LNB, and I would like to capture C-band Aero signals with same 180cm dish.
I’ve now conducted tests in the C-band for the second time. With my very old (20-year-old) C-band LNB and my 1m dish, I’m not receiving any signals from Inmarsat.
At least not the signals required for JAERO.
I have no idea which satellite the signals in the photos are coming from. However, I strongly recommend scanning the spectrum for bursts before powering up the LNB. Some peaks aren’t signals. The IF frequencies, of course, have to be converted to 4 GHz frequencies. A PDF frequency list is available on the JAERO website:
AERO-Cband-burst-March-2016-Europe
Good Luck
Micha
Maybe you need larger dish. I don’t know why. Derek Sgc success received it, but he has larger dish.
https://www.youtube.com/watch?v=uq4BwsPcQrE&t
Gruß Micha
Try a larger dish. My 180cm dish is enough for strongest transponders. I can decode aircraft routes. LNB works fine. Local oscillator is 5150Mhz, so in my case the transponders are near on 1527 MHz.
It only worked with the second option.
An old 65cm dish, some wire, wood, screws, aluminum foil, and an F-connector.(+ 3x Inline Amplifier)
The signals are now significantly stronger. Then the AERO voice channels in the JAERO also work.
Inmarsat experiments are always interesting. Even with the smallest antennas, it is possible to receive relatively strong signals and decode data channels. I conducted my first experiments with the antenna from a GPS navigation system.
I simply mounted the ceramic antenna on a board covered with aluminum foil and connected it to the RTL-SDR (NOOElec) via an F-connector and three inline amplifiers. It should be clear that the aluminum foil does not touch the F-connector, the inline amplifiers have their own independent power supply, and the RTL-SDR is protected by a DC block.
The Inmarsat voice channels cannot be received with these antennas!