School of Electrical Engineering.

The possibility of making the antenna of an MST radar too large is pointed out. It is not that the signal ceases to become stronger beyond some critical antenna size; the received scattered signal actually becomes weaker as the antenna size is increased whenever the target is in the near field, Fresnel region of the antenna. The Arecibo antenna is a case in point. It is supposed that MST work would benefit to use a feed which illuminated only a portion of the dish.