That's my point. A dish antenna is highly directional, so an tx/rx antenna pointed towards the sky can be detected/jammed effectively only by standing in between the antenna and the target it's pointed to, ie the satellite. It's not a thin line, but it's still a limited area, and the minor lobes of its radiation pattern produce a very faint signal which can become negligible by burying or covering most of the dish in all directions except the one it's aimed to.