If you want to have a single continuous dish, then yes, you need a large space. There's no real need for it, though, when you can have a whole bunch of small reflectors focusing the beam onto a single point. Sort of like this: https://www.youtube.com/watch?v=tebn2rs8QHk
A system like that would work fine on top of buildings - it would take a lot of maintenance, especially during the storm season, but you could just have the mirrors rigged up with sensors and let a computer handle the focusing.
If you want to have a single continuous dish, then yes, you need a large space. There's no real need for it, though, when you can have a whole bunch of small reflectors focusing the beam onto a single point. Sort of like this: https://www.youtube.com/watch?v=tebn2rs8QHk
A system like that would work fine on top of buildings - it would take a lot of maintenance, especially during the storm season, but you could just have the mirrors rigged up with sensors and let a computer handle the focusing.