Ham radio.

On the surface, it just sounds like listening to a bunch of old farts babbling on about their enlarged prostates, and tbf, there is a bit of that if you never go any deeper than 2M/70cm voice modes.

But there’s just SOOOO much you can do.

Want to see how far you can bounce a signal off a mirror laying on the surface of the moon? Yup. You can do that.

Want to launch and communicate with your own satellite? Yup. It’s a thing.

Want to remotely control devices from hundreds of miles away without using the internet? Yup.

Want to gps track your car at all times, even when there’s no cell phone service? That’s called APRS.

Want to have a conversation with astronauts on the ISS as it flies overhead? They’ve got ham equipment on board.

You can even play with broadcasting and/or receiving “secret” tv and radio stations - that is, they’re on alternate frequencies that regular TVs and radios don’t pick up.

It just goes so deep.