When I was Cub Scout we had a schematic for building one of those using an empty Oatmeal container. It had an address of a town along the Mississippi in Illinois, I think it was Galena, where you sent off to get your pre-cut hunk of pyrite. I was too lazy to wind that big coil,
plus I got a lecture on how the church steeple next door would draw lightning down that copper wire antenna, into the house, setting it on fire and killing us all.(Funny, the 50 ft. TV antenna mast and twin lead going into the house much closer to the church steeple was never an issue....) Not until about 7 years later when lightning turned our fairly new GE set into a smoldering hulk. We had a new TV and free cable within a week. The cable company had needed permission for a right of way across our property for years to get to about a half mile of houses. It took a bolt out of the blue to get it done. We had twelve channels and were living in the lap of luxury.