This video shows a breadboard software defined radio receiving signals from far away using the FT8 protocol via the wsjtx application. The radio is based on the Tayloe mixer/detector from my previous video which explains the Tayloe detector and is found here: https://youtu.be/UKtBHGlY9Kg?si=WNXedpNNS-6W3CfR
The raspberry Pi Pico program is trivial. It uses the PIO module to generate the needed quadrature square waves. The source is on github: https://github.com/grughuhler/grug_lo_gen
An si5351 module is probably a better way to generate the square waves. See NA5Y's channel and the Dr Volt video. Modules are cheap on Amazon.
Also see the video Dr Volt made on receivers of this type. I was inspired by his video, and he gives more instructions on how to build this circuit and use Quisk.: https://youtu.be/HCDi5qV1cmU?si=DQ8V_Wa4z4sjusms
NA5Y's channel has information of making better SDR radios: https://www.youtube.com/@na5y/videos.
Quisk: https://james.ahlstrom.name/quisk/
See also https://github.com/grughuhler/grug_misc_projects