This repository contains custom open-source firmware for Quansheng UV-K1/K5 V3 handheld ham radios, built around the PY32F071 MCU. It is a fork in the lineage DualTachyon → Egzumer → F4HWN → this project, adding features gated by compile-time flags (ENABLE_FEAT_F4HWN_*, ENABLE_NOAA, ENABLE_DTMF_CALLING, etc.). The firmware is bare-metal C (no RTOS in the application code despite CMSIS-RTOS2 RTX5 being vendored), with a main-loop architecture and an overlay app system using an app_api_t struct of function pointers. The build system uses CMake presets, per-app build.sh scripts, and a Docker wrapper (compile-firmware.sh) producing .elf/.bin/.hex artifacts. A pack_app.py script packs raw binaries into .app blobs. The repository vendors a large CMSIS_5 tree (~20k+ files), most of which is unused DSP/RTOS/validation code, bloating the repo. The README explicitly warns that flashing can brick radios, and overlay apps run with full privileges (no MPU). Notable engineering patterns include the overlay app API (function-pointer-based, placed in .text.entry section), an LL I2C driver mirroring STM32 LL conventions, and extensive conditional compilation. However, the codebase shows drift: deprecated compile-with-docker.sh retained as a forwarding shim, repetitive per-app build scripts, vendored CMSIS that may be outdated, and a license placeholder in the CMSIS bundle. Maintenance is active with recent commits, but the fork lineage and vendored dependencies create ongoing merge/upstream complexity. This is purely an embedded application repository - no datasets, ML models, or research artifacts are present.