Development and initial observations of a Long-period VHF Broadband Digital Interferometer

The VHF Broadband Digital Interferometer (BDITF) has three antennas on one site to receive the VHF impulsive EM waves and locates lightning channels including recoil leaders traveling at high speed in theory. The conventional VHF BDITF records impulsive EM waves by incoming triggering signals, and the amount of recorded EM waves is limited by its memory capacity. Therefore, it is hard for the conventional VHF BDITF to display the total process of lightning development. In this paper, we design and operate a Long-period VHF BDITF that records VHF signals continuously for a maximum of 40 minutes, and present its observation results during the summer of 2013 in Osaka, JAPAN.