A yagi antenna is VERY directional and at these frequencies line-of-sight only. You are aiming into the air. I'd say it would be practically impossible to accid

A yagi antenna is VERY directional and at these frequencies line-of-sight only. You are aiming into the air. I'd say it would be practically impossible to accidentally interfere with cell-phone communication. This is a realistic counter-attack (and theoretically easy).