A business card size homebrew 40 meter XCVR project from Ray Ring:
I tweaked my previous XCVR design to use push button tuning and made the board layout extremely compact. I improved the side tone injection to be absolutely perfect – not too loud, full break in and no clicks. I went ahead and integrated my switch cap 8 pole CW filter. The schematic is fairly simple with 65 parts or so.. and the whole design fits into a 3D printed enclosure the size of an business card.
Project info at Circuit Salad homepage.
Check out the video after the break.