I'm building (or rather, debugging) a lightning detector that detects the electromagnetic charge emitted by a lightning bolt. I need a good way to generate a little lightning as a test signal and I'm currently using a the piezo electric part of an electric lighter which generates a small spark. The piezo electric element generates about 20 to 25 kV and produces a spark that is about 3 mm long. If I hold it two meters from my antenna, at what distance does an average lightning bolt need to be to produce the same amount of energy in my antenna? Of course a lot of estimations and averages will need to be used, but roughly?