I have been working on a large coil for the crystal radio initiative. This is a few pics of it
Frequency : 800khz
Number of turns: 18
Wire length : 247'
Wire diameter : 0.5"
I made a hemisphere from copper pipe, with a 16 point aluminum star as my top load. All that is left is to bury my 4 a/c radiators as my ground, wrap a 12" by 2 turn secondary coil on the bottom and build my resonant capacitor. Hopefully I can tune it up to receive some usable energy. U can follow me https://youtu.be/HyRhUStqzt4