Show HN: We built the smallest dual-band aircraft tracker

ADSBee m1421 is a 23.4 × 14.5 × 2.7 mm dual-band receiver for Mode S and UAT. It supports TIS-B/FIS-B uplinks and outputs GDL90, MAVLink 1/2, JSON, CSBee, and raw packets. The device weighs <2 g, uses <60 mW, and costs $48 (or $75 NDAA-compliant). Open-source firmware and schematics are available. The LR2021 chip limits reception to ADS-B downlink format 17, excluding squawk codes and non-ADS-B packets.