Xiegu XPA125B
Overview
The Xiegu XPA125B is a 100-watt linear amplifier covering 1.8–54 MHz, intended as the matched output stage for the Xiegu X6100 and other QRP-class transceivers in the 5–10 W drive range. Stack the X6100 on top, run an RF jumper and an ALC/CAT control lead, and the combination behaves as a single integrated 100-watt HF station from one 13.8 V supply. It carries its own LDG-style internal autotuner, collapsing the "amp plus separate tuner" stack into one box. This deep dive covers the hardware and RF envelope, the mode-by-mode thermal/duty-cycle behaviour, the front-panel-menu + internal-DIP "programming" workflow (no codeplug), and field use including antenna pairing, power supply, feedline, and grounding. Migrated from the Scanners project as part of the Scanners/Radios restructure Stage 2 Phase 2 (2026-06-16).
Context
The XPA125B sits firmly in the 100-watt class — the legal HF maximum in most general-class privileges and the natural pairing for a QRP rig you don't want to leave at 5 watts. Its value is integration: sharing a vendor with the X6100 means the ALC line, band-data line, and CAT/PTT cable drop straight in. Where it falls down: it's not a Tier-1 amp — no remote-control protocol, no SO2R port, protection that leans on foldback and thermal trip rather than fast over-current limiting. For its target user (the X6100 owner who wants 100 W without spending five figures) it does the job; for a contest station with stacked Yagis, look elsewhere. The amp has no per-channel state — the only configuration worth documenting is the internal DIP switches, the menu-set ALC/fan/VOX preferences, and the inter-box cabling (ALC/CAT/PTT/power).
