
Power levels are low, but the people involved believe there is enough energy to power monitoring systems and alert people of forest fires using energy derived from trees.
Simple QRP projects, 10m, 8m, 6m, 4m, FT8, 160m, WSPR, LF/MF, sub-9kHz, nanowaves and other random stuff, some not related to amateur radio.
Regen receivers are simple, but effective. I have designed and built several. See my website . One of the classics was by Charles Kitchen N...