If I was a vendor in Shenzhen selling SDR modules to the public, and I saw this come across the propaganda wire, I would think hard about if it is still worth it to keep selling the modules to Chinese customers.

China knows that direct control is hard to achieve at scale. They know they can simply state their intentions and let the chilling effects take over. Banning Flightradar24 is a statement of intention that every one of their citizens can see.

Any Realtek TV tuner USB stick can be used. They are for sale everywhere in China.

There was a time before the Great Firewall too. These things can change. I bet China isn’t too happy about over the air video transmission that can cross borders either, and would prefer for citizens to use approved digital streaming methods.

My question is what does it accomplishes for China? Foreign armies and terrorists can still get plane positions, only average citizen can't. What's the point?

The state might want to move people or things secretly by air.

As I said, just disable ADS-B transmission when doing shady stuff.

That would imply they have something to hide.

Or, they want some parties to know what they’re doing, but not the citizenry.

Maybe this is overly paranoid but I don’t think we should underestimate the Chinese government.

> Unless I misunderstand, I don't see the point: you can get this data with a RaspberryPi and an antenna available everywhere (and probably built in China).

I'm not sure about the relevant Chinese radio interception laws, but I think the difference between DIY receivers and Flightradar24 is that the website combines data from a great many listening stations across the world. You'd need one hell of an antenna to receive location data from a Chinese plane from all the way over in the EU or US, but these websites still allow us to see flight patterns above China.

> Military aircraft that shouldn't be seen should just disable data transmission.

Permanently disabling ADS-B on military aircraft sounds like a recipe for disaster.

It's literally flipping a switch.

Most importantly, I'm pretty sure any other superpower (i.e. the ones who are both interested in the data and who China might actually want to keep the data away from) will just pick it up with satellites. Those things don't just take pictures.

Don't need to be a superpower: https://spire.com/aviation/.