Presumably the concentration of the beam diverges as the square of the distance - and possibly the accuracy of the aiming during the pulse, which could also degrade at least linearly with range.It is impressive to be able to react to something as brief as the flight of a mortar round; we have been playing cat-and-mouse with some mortar crews in Iraq lately. Certainly would be a warm-fuzzy feeling to have this unit next door to your barracks!