Just toying with some cave measuring ideas, I mainly cave in the Dales.
Anyway, I had a conversation with a guy who used to design phased arrays to go on satellites and he said to think of it as an aperture. So a linear array can be thought of as a slot where the propagated beam pattern is roughly a cylinder with its axis along the slot. A cross would be the sum of an X-axis cylinder and a Y-axis cylinder and so would have a strong central lobe. When I get my act together I will probably do some experiments.