I have been looking around SatNOGS and can’t seem to find an exact answer on how we obtain any data (if there was any) from an observation. I only can find wav files which don’t exactly make sense because no SDR utilities can make sense of them.
Hey @KD9KCK !
From the audio recordings you can decode much data (for now manually). Check our Observations category for many of them. Direwolf and gr-satellites are just two examples of programs you can use to extract data from recordings.
We are also really close on releasing the automated decoding functionality integrated in gr-satnogs and network.satnogs.org with automatic submission to db.satnogs.org. In the meantime people that decode telemetry data submit it through the SiDS protocol in db.satnogs.org (check the stats page!)
In addition to direwolf and gr-satellites, in Windows you can pipe the audio into hs-soundmodem and from there to any number of DK3WN’s decoders found at http://www.dk3wn.info/software.shtml much the same way PE0SAT has it documented here, only without the SDR source: http://www.pe0sat.vgnet.nl/decoding/block-diagram/
So the recordings are already demodulated?
Also only one of those would work for me. (Direwolf) as gr-satelites appears to be linux only. (Not windows)
Was hoping the recording was in a standard format the normal tools could use.
I have GNURadio installed on my windows. But the addons that were listed before are not built for windows. (And I really don’t want to be building stuff from source)
So SatNOGS is not exactly what it seemed to be when I first saw it. (Was thinking the data was in a directly usable form. Example a I/Q data .wav file that GNURadio and SDR# can understand. Not a odd .ogg file)
I may look into how hard it would be to recover the raw I/Q data by re-modulating the FM with the proper carrier. But one of the mentioned problems with ogg will cause me problems…
Let me draft up a post tonight from home where I can walk you through a windows workflow for decode that does not need gnuradio. You don’t need to go back to raw I/Q to do it.
The ideal is a completely automated process from reception to decode. We have RX and demod solved for (for FM modes), and automated decode is currently being worked on. As long as a satellite is using a published standard we should be able to decode automatically without a human intervening.
I/Q data definitely helps when human intervention is needed to fix demodulating or to work against multiple simultaneous streams. The issue here is in the bigger picture of a global network, the size of I/Q data is not feasible to work with. My station has peaked around ~35 observations in a day and at over a gig of data each, the backend network won’t scale (without some large source of funding for big data storage), nor would it work for low bandwidth or data capped connections around the world.
There is another discussion going on right now about saving an I/Q stream locally (as a tee from the demodulated stream) which then the ground station operator could use it, but that limits the usefulness quite a bit and again, with the size and frequency of observations may be problematic for Raspberry Pi SD cards.
Only reason I am looking for I/Q data is so I can use common software on it. (Most have no idea how to use audio in a .ogg file.)
And using GNURadio is no problem… The problem is getting the information into GNURadio on windows. Also as a side note. Maybe adding the signal strength into the information about the observation might be useful for some people.
But yeah I/Q data is huge. (Unless you stream it into a compressor) Also the Raspberry Pi (Modle B version 1 at least) supports SD cards up to 64 GB (Have not bought a bigger one so I don’t know if it works for larger ones.)
A 9 minuete I/Q data file at .9 Mhz bandwidth is 300 MB.
Sorry this took a while, got half way through it and lost power last night in a storm. I started a new thread for this howto:
Sort of seems very long. But i guess that is what I have to live with. (Unless I re-modulate and pull the I/Q and just feed it into the decoders built into GNURadio.)
So question why are the GNURadio addon (gr-satellites) made for linux only? (Unless I can manage to build it)
This is why the project exists to fully automate the process…
This is a suite of gr modules written by someone outside of this project. I don’t believe there is a reason they would not build for windows, but I don’t know of anyone who has done it either.
So the project exists to automate yet it made it more complicated till you can get that working… Just saying that that is a bit odd…
The reason they are not built for windows is because the fact that no one cares about windows when it comes to SDR. (I only say this because if you look up SDR stuff windows gets the short end of the stick…)
I don’t think I follow you - the need to automate is there because it is so complicated otherwise.
I disagree with that a bit - you are totally right for many aspects of gnuradio and gnuradio based apps. Otherwise, there are a whole lot of other SDR apps in Windows that you don’t have elsewhere (like sdr-radio.com and sdrsharp). In addition, SDR transceivers for ham radio operators come with mostly windows apps.
but none of those help for our use case here, so…
Well with out this project you would just have to wait for the satellite to be over head and receive the data (I/Q) and pass it thru the decoder of your liking. (GNURadio’s builtin stuff in my case)
Here currently you have this long way of having to use a .ogg (Free to use… But lossy…) to then pipe into something meant for use with a sound card and a normal radio.
Oh, I see what you mean. There are multiple ways of doing it today, that admittedly convoluted way is how it is done in Windows…
using gr-satellites in linux it is a simple one-liner, including the wav conversion through sox.
Even on linux its easier to deal with I/Q data that most demodulates expect. (It saves the trouble of having to rewrite them like this project has been)
Also on linux you still have to take the time to install everything that makes gr-satelites work. (Over 8 other OOT addons plus the compiler and dependancies for them all)…
I guess have to fire up my Debain VM if I want to even try messing with this stuff. (As I am not filling my windows with software that has the webpages in a different language then I read… I just don’t trust it)