In order to increase the rf signal to be detected, we bought two kinds of rf cables. The first one is to connect the combiner and the converter, the signal frequency is 6.55 GHz and the length is 2 m. The second one is to connect the converter and the phase detector placed outside of the tunnel, the signal frequency is 0.72 GHz and the length is 30 m. We measured the loss factor of these cables. They were found to be 1.37 dB/2m and 2.6 db/30m, respectively.