After playing a bit with my HackRF, I managed to receive some stuff.

Every day or so, balloons called “radiosondes” are launched, and I can actually receive those.

The payload you see below contains position data, battery status, altitude, and a bunch of other stuff.

If you’re curious about receiving those, there is a website tracking those, their TX frequency and all the data.

Warterfall display on an SDR showing quick bursts of data every second or so.

Airband is used by planes to communicate with the ground. Given I live near the Helsinki airport, I’m in a prime location to receive those properly.

For instance, here is small compilation of recordings:

Do note listening to airband might be illegal in some countries, for instance, Germany or North Korea. Always check your local laws (though unenforceable).