Radio reference photographs retain their original source attribution.
fx4cr.jpg: BG2FX / F5BUD, FX-4CR User Manual V1.6, cover photograph; https://bg2fx.com/manuals
fx4l.jpg and fx4c.jpg: BG2FX official product page; https://bg2fx.com/transceivers-1
See docs/FIRMWARE.md for exact source URLs and limitations. Photographs cannot distinguish R/VR/V hardware.
