How far apart do Base Cores have to be. I 've built a nice little cave base and I'm trying to build a second base next to it. However I'm over 70 meters away from the core on the first base and the Ghost core for the second base still comes up red. What's strange is that if I move to the other side of the base the Ghost core will turn green in less than 20 meters. So, is there some rule about core distance?