PP6EOJ
Newbie
Hello friends. What services besides STD-C and AERO can I decode on these satellites? Where are the voice transmissions (8400Hz) that I could decode with Jaero in L band? Thanks.
INMARSAT (98W AND 54W) L BAND AND C BAND
- Thread starter PP6EOJ
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There is no software for other modes. I used to decode INMARSAT-D/IsatM2M using my own means but that service terminated.
In the case of INMARSAT 8400 voice, 98W uses a global beam with channels between 1542.9 and 1543 MHz. You can watch the data channels (1545 and 1546 MHz) using aero and look at the C-channel folder to see direction to the voice channels but aero rounds the frequencies. 54 W uses spot (local) beams and it appears Brazil is 1547.4-1547.5 Mhz.
In the case of INMARSAT 8400 voice, 98W uses a global beam with channels between 1542.9 and 1543 MHz. You can watch the data channels (1545 and 1546 MHz) using aero and look at the C-channel folder to see direction to the voice channels but aero rounds the frequencies. 54 W uses spot (local) beams and it appears Brazil is 1547.4-1547.5 Mhz.
Freemor
Member
There is also Iridium sats on L-band that you can decode if you are using an SDR. (lots of videos out there on how so I wont waste space here.) Some voice stuff on there to. @dlwtrunked's suggestion about watching the C-Channel tab on Jaero is a good one. I've just gotten into all this myself as I got an L-band patch antenna recently. There are a bunch of other signals on L-band. Watching the ACARS data or the STD-C data you can pich out the downlink frequency ranges. I haven't taken a stab at decoding those as it is early days for me yet. some of the wideband signals are probably BGAN (Broadband Global Area Network). Those would be fun to decode but I havn't see any one working on that yet. Plus it might the mostly or totally encrypted.
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I have yet to see *good* friendly software for Iridium. Note that Skyterra-1 and MexSat-2 use the same frequency area as INMARSAT but I have not seen anyone decoding them.
Freemor
Member
There is a nice listing of the L-Band frequencies at https://uhf-satcom.com/satellite-reception/l-band
I can see that this might be the thing that get me into picking apart and figuring out how to decode not previously decoded signals
@dlwtrunked yeah, the Iridium stuff isn't very point and click but worth mentioning. I've already managed to pull out a couple of voice calls on it. Nothing interesting but a fun couple of hours of radio hacking.
I can see that this might be the thing that get me into picking apart and figuring out how to decode not previously decoded signals
@dlwtrunked yeah, the Iridium stuff isn't very point and click but worth mentioning. I've already managed to pull out a couple of voice calls on it. Nothing interesting but a fun couple of hours of radio hacking.
RFI-EMI-GUY
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Decoding Iridium Voice would indeed be interesting. I wonder how fleeting the calls are since you would need to be close to the footprint of any activity I would suppose.
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Those (uhf-satcom) are far out of date as seemingly never updated despite changes. I have posted a list here in the past but I am working with someone else who is trying to coordinate a current list with new info on INMARSAT, Skyterra-1, and Mexsat-2 (though nothing has been decoded on the last two, some frequencies have been found). I posted a list in a more appropriate RR forum (see below), but *a lot much more* is known now through coordination via the other person in the last couple months. That list is still in rigorous preparation.
INMARSAT-C and Aero update to my frequency list
The attached is an update to my INMARSAT-C and Aero list of frequencies seen in Eastern U.S. last updated in August. There are 3 additions in it.
Also, another place to watch for related information is
main@acars-vdl2.groups.io | Messages
acars-vdl2.groups.io
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Freemor
Member
@dlwtrunked, Sounds like you are quite into this. Can you recommend good reading that would head me down the path to being able ti pick apart and decode unidentified signals? I know there are tools out there like sigDigger and fldigi but as yet I've only played with those a little. I really need to devote some time to learning GNU-radio too I guess.
thebaldgeek
thebaldgeek
As @dlwtrunked said, they are way out of date on that site.
I have a new page on my site (due to go live again 'soon') that I believe will help your main question of voice frequencies.
Also my site: Decoding ADSC, ADSB, ACARS, VDL2, Iridium, HF-DL and other aircraft type messages. on the L-Band page - down the bottom section - has all the current data frequencies and data rates. These are very accurate and up to date. Soon will add the voice call frequencies from the new page.
Also, the latest Jaero (as of Nov 22nd 2023) fixes the rounding errors. My site feeds are all updated. I'm hope those feeding airframesio will update soon.
@Freemor DragonOS is very easy to get up and running on Iridium. I 99.8% dont recommend voice since its so fragmented and you cant select between aircraft and lost / lonely explorer calls.
Also @Freemor Im working on the BGAN. Cant say too much just yet.
I have a new page on my site (due to go live again 'soon') that I believe will help your main question of voice frequencies.
Also my site: Decoding ADSC, ADSB, ACARS, VDL2, Iridium, HF-DL and other aircraft type messages. on the L-Band page - down the bottom section - has all the current data frequencies and data rates. These are very accurate and up to date. Soon will add the voice call frequencies from the new page.
Also, the latest Jaero (as of Nov 22nd 2023) fixes the rounding errors. My site feeds are all updated. I'm hope those feeding airframesio will update soon.
@Freemor DragonOS is very easy to get up and running on Iridium. I 99.8% dont recommend voice since its so fragmented and you cant select between aircraft and lost / lonely explorer calls.
Also @Freemor Im working on the BGAN. Cant say too much just yet.
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JAERO, STD-C, and MultiPSK are the only ones I know for INMARSAT.
Freemor
Member
@thebaldgeek Yes I use DragonOS when I want to do something quickly that I haven't got set up on my main radio computer yet. Its what I've been using for the current sat stuff as I dont have jaero/SDRReceiver/iridium-tools built on my main radio computers yet. Now that I've seen how all the bits work I'll build them for my 2 radio computers. Both are Arch linux machines so I'll have to build a lot straight from the Git repos as there aren't PKGBUILDS for those yet.
I suspect I was not clear enough in my pervious message. I wasn't asking about tools to decode. I was trying to ask about tools, books, info on how one goes about reverse engineering a signal. I'm skilled enough to look at a signal and be able to sus out AM FM SSB and can discern quite quickly digital vs analogue. What I want to learn to do is to dig into a digital signal that I find. How does one determine if its FSK, PKS, ASK, or some sort of Quatrature signal and them how does one figure out which of the many of each type of those it is. And once one has the right signal modulation how does one go about analyzing the structure of the digital stream.
Basically I'm looking for resources that will let me move into tackling a signal from a very low level. Most discussions of such I come across are basically using something like FLDigi and throwing best guess settings at the signal until something works. which to me seems like trying to use a high level tool to solve a low level problem. Not a good fit. There must be tools out there better suited for the job.
I suspect I was not clear enough in my pervious message. I wasn't asking about tools to decode. I was trying to ask about tools, books, info on how one goes about reverse engineering a signal. I'm skilled enough to look at a signal and be able to sus out AM FM SSB and can discern quite quickly digital vs analogue. What I want to learn to do is to dig into a digital signal that I find. How does one determine if its FSK, PKS, ASK, or some sort of Quatrature signal and them how does one figure out which of the many of each type of those it is. And once one has the right signal modulation how does one go about analyzing the structure of the digital stream.
Basically I'm looking for resources that will let me move into tackling a signal from a very low level. Most discussions of such I come across are basically using something like FLDigi and throwing best guess settings at the signal until something works. which to me seems like trying to use a high level tool to solve a low level problem. Not a good fit. There must be tools out there better suited for the job.
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What you are wishing to undertake is non-trivial and some can require hardware costing at least several thousand. And then it is still difficult. I suggest you start with JAERO and a program like MultiPSK to become familiar with various modes. You will need an SDR and some experience before going further. Keep in mind, I do not know your skills and training in writing this. I have reverse engineered several signals and it took as short as several weeks to over a year of spare time with one. (Despite a Ph.D. in mathematics and electronics experience,it was still difficult. I wish it was easier.)
Freemor
Member
Thanks for the reply. I understood when asking that it'd be non-trivial. And that there would be easier bits and much much harder ones.
I've had an SDR for several years now and have chased signal from 10Hz -> 1.7GHz (I don't yet have an LNA block to go higher). I've decoded most of the easier modes DMR, P25, AIS, ADS-B, ACARS, FT4/8, POCSAG/FLEX, NRSC5, Etc. I'm skilled enough to spot a lot of the clues in the pan/scan/waterfall, Can spot FSK/MFSK by eye on lower density signal. I can of course Identify Several of the above by their sounds because I'm an oldtime and still listen a lot...
Just realized that explaining in more detail is gonna feel like hijacking this thread. So Perhaps better to continue this some other place on the forums.
PP6EOJ
Newbie
Hello friend. Just asking a question: are these frequencies the ones I should tune into on my SDR on the 54W satellite? Thank´s.
Attachments
thebaldgeek
thebaldgeek
For voice. Yes. For data no, for those use the list on my Github for the data frequencies and rates: Decoding ADSC, ADSB, ACARS, VDL2, Iridium, HF-DL and other aircraft type messages. You will find the 4 Inmarsats and the ACARS data on the 'L-Band' page.
PP6EOJ
Newbie
Thank you Very much, my friend.
Hi thebaldgeek,
I was a good follower of your website, but I think you took a break. We can naturally see the RX frequencies in the picture because we entered them ourselves. But we cannot see the TX frequencies in Jaero. The TX frequencies are also visible in the table on your website. Can we do this with Jaero? Thank you in advance for your help.
