Yeah noticed, but I was suprised it wasn't actually completely black but with just quick flash of an image once in a while.
Yeah. The coverage area of the transmitter must be massive.
It's likely an omnidirectional antenna on the satellite and a (very directional) tens-of-meters ground station (or series of them) following the satellite's position.
Or the antenna is always mostly in the direction of earth, and the spin (from the point of view of the earth) just has the antenna describe a circle.