4 layers35.1 × 76.3 mm

Tiny4FSK
New-England-Weather-Balloon-Society/Tiny4FSK
Horus Binary v2 HAB Tracker
90 parts96CERN-OHL-W-2.0
Boards in 2 GitHub repositories, designed in KiCad, that use the BK-53 by MPD (- Button And Strip Battery Connector ROHS). See how each wires it, with its parts, size, README and files; the BK-53’s symbol, footprint and pinout are on its own page.