An apparatus includes a backplane having a ground plane. Conductor through holes extend through the backplane in rows and columns for conductors to project through the backplane in orthogonal arrays. Each row and column of the conductor through holes includes ground holes, each of which is sized to receive only a single ground conductor, with the single ground conductor in connection with the ground plane. Each row and column of the conductor through holes also includes signal holes, each of which is sized to receive only a single signal conductor, with the single signal conductor free of a connection with the ground plane. The backplane further has a plurality of nonconductor through holes at locations between and offset from the rows and columns of conductor through holes, with each of the plurality of nonconductor through holes having plating electrically connected to the ground plane.