AN/APG-5 is a "Radar set, Gun laying, Automatic range finder, 2.5 GHz, Pulse, range 150-3000 yards, used on B-17 and B-24."
Ok I got the CP-8 range unit, now what. Sort of like having a doorknob and needing a house to go with it.
Looked at the links posted by qaa.
From what I see, all you really need is one of those rotatable machine guns. If you set the gun up on your roof, you'll be all set for any incoming UFOs. Or, OTOH if Noah happens by with his Ark.
Fred