>>12754980We can't pick up radio signals from china because the earth is in the way. If earth were a hollow sphere and we lived on the inside, you'd be able to pick up a signal from china on the opposite side, assuming the signal is strong enough.
The signal from mars rovers is first beamed from the rover up to some satellites that are orbiting around mars, and then those satellites beam it to earth. We have multiple receiving stations here on earth so we can use whichever one is facing mars at the time. In that same way, we can send signals from china up to earth satellites and then back down over USA.
There's also a lot of noise in the signal coming back from mars. Imagine a radio station that's far away so there's lots of static. For that, we have some fancy processing algorithms to deal with that noise and make sure data gets back here uncorrupted, but that's for people smarter than me to explain.
