I just pick up signals from sparks on an ordinary AM radio.
To make the sparks I use a low-current 1000-volt power supply,
though perhaps an induction coil would be better.
(The power supply is home-made, from a recipe in ZAP! by Morrison
et al. If anyone knows where to get the ZAP! manual, I'd be
interested in hearing. Left my copy behind when I changed
jobs.)