We have recently proposed a novel 2 × 2 multiple-input multiple-output (MIMO) system that utilizes a single leaky coaxial cable (LCX) as two antennas. In this paper, we further propose a 4 × 4 MIMO system by combining two LCXs that have different radiation characteristics into one composite cable and evaluate characteristics of the channel with different spacing between the LCXs. Since the different radiation characteristics create different propagation paths, the proposed system with small spacing between LCXs can realize an efficient channel condition for 4 × 4 MIMO transmission. As a result of measurement at 2.4 GHz band, the smaller spacing as to 1 cm between LCXs makes better 4 × 4 MIMO channel condition for transmission. This result indicates that the proposed system can reduce the space requirement for system deployment.