A sferics receiver is simply receiving radio noise with natural origins, mainly lightning, but also clouds of ions interacting with the earth's magnetic field. Here you have a simple schematic as an introduction into the world of VLF. The project is a slightly modified version from the one in the video in order to filter out the AM broadcast band interferences. Hopefully you will not deal with those as I did, since I have a bit antenna tower close by. Please watch the full video before ordering / using it. More details coming soon in the blog article. The PCB design here is an updated version using a smaller potentiometer in order to be able to fit the board in this small enclosure. It also has an audio connector placed on the PCB board directly.