This circuit originated in Brazil. Here it is on the DXexplorer site. I think it has been on this blog some time ago.
See https://www.qsl.net/py2ohh/trx/pititico/pititico.html .
Incidentally, PY2OHH's site has a wealth of data.
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.
This circuit originated in Brazil. Here it is on the DXexplorer site. I think it has been on this blog some time ago.
See https://www.qsl.net/py2ohh/trx/pititico/pititico.html .
Incidentally, PY2OHH's site has a wealth of data.
My gear has been on much of the morning. UPDATE 1645z: Spotted by 147 stations with the best D4L (4517 km) and 159 stations spotted here in...