Craig Smith of Firefly Workshop (South Milwaukee, WI)
With my crystal radio projects, I recently made a dual coil variometer tuner. Connected to a diode, crystal earphone, antenna & ground wires (no batteries) I tuned in 1540 KXCL Waterloo Iowa from 270 miles away here in Milwaukee. The coils were wound on a segment of thinwall 3” PVC, and a segment of 2” PVC coupler. My antenna is a 35’ wire running out my window and atop my fence. I am amazed of the performance of simple scrap materials put together just right. http://www.crystalradio.net is the best resource for beginners and experts.