gnss-sdr VS RTLSDR-Airband

You realise you can write software yourself to interpret the signals from GPS satellites? Here's an open-source implementation.

Something I always enjoy pointing out is that GPS signals can be decoded by anybody, the source code is available here. Needless to say, there are references and calculations based on satellites all over it.

If you're interested in running some code, there's [1] which is fairly active, but as I recall is Linux only. There is also [2] which is a Matlab (or Octave) GNSS receiver implementation; quite well documented and informative. It's meant to be a companion to the author's book [3], which itself I found quite concise and approachable.

[1] https://github.com/gnss-sdr/gnss-sdr

They like to pretend it is using towers or balloons or something else, none of them have ever coherently answered it with a viable way this could result in the GPS we can use from the device in our pocket. It also casually expands the circle of people involved in this conspiracy by thousands, to include all developers at Apple and other phone manufacturers that write/maintain the GPS components of their OS as well as contributors to open source projects like GNSS-SDR, an open-source software-defined GNSS receiver.

People also have to write the software to compute your location from these broadcasts, this means basically every company that has produced GPS receivers would have to be in on it. But there's an open source one, surprisingly nobody has raised an issue as to why it contains all this weird code that doesn't make sense if it's not coming from a satellite.

GNSS-SDR

You're all correct, except there are not that many $30 SDRs out there. Also, most SDRs have clearly superior capabilities to the RTL-SDR, though those capabilities often are not required.

BTW, for simple AM/FM demodulation I cannot recommend enough the handy https://github.com/charlie-foxtrot/RTLSDR-Airband. For example most of LiveATC.net feeds run on it.

rtlsdr_airband, but again requires knowing the frequencies of interest ahead of time.

You may want to give RTLSDR-Airband a look. Its designed for analog AM/NFM voice traffic and can be configured to operate on any frequency your rtlsdr dongle can handle. It can also be configured to output to an mp3 file, in addition to other things like IceCast.

There’s an example service config file in the repo: https://github.com/charlie-foxtrot/RTLSDR-Airband/blob/main/init.d/rtl_airband.service

I have been streaming the output from RTLSDR-Airband (https://github.com/charlie-foxtrot/RTLSDR-Airband) with icecast2 for several (5?) Years now, and I have some time and inclination to look at reducing latency (currently best is 10s, but often much more.)

https://github.com/szpajder/RTLSDR-Airband Might be what you are looking for, although I don't know the performance requirements. It has a scan mode detailed here: https://github.com/szpajder/RTLSDR-Airband/wiki/Configuring-channels-for-scan-mode