ADX MI2

ADX MI2 – Digital QRP HF SDR Transceiver Platform

The ADX MI2 is a compact, modular digital HF QRP transceiver system designed for modern amateur radio operation. It is part of the ADX family of radios and represents an improved evolution of the original ADX design, optimized for digital modes, PC control, and flexible band operation.

Built around a minimalist SDR-style architecture, the ADX MI2 is designed for simplicity, efficiency, and performance. It is intended primarily for computer-assisted digital communication modes such as FT8, FT4, JS8Call, and WSPR, using standard PC sound card interfaces.

The MI2 system integrates a receiver front-end, transmit stage, and modular band-pass filtering, allowing operation across multiple HF bands by simply swapping filter modules. This makes the platform highly flexible while keeping hardware complexity low.

The design supports USB-based CAT control and audio interface, enabling seamless integration with popular amateur radio software such as WSJT-X. The system behaves like a software-defined radio front end, with most signal processing handled by the connected computer.

The ADX MI2 also includes improvements over earlier versions, including enhanced USB integration, improved filtering, and a more stable modular architecture, making it a reliable platform for experimentation and everyday QRP operation.

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Key Features

• Digital QRP HF transceiver design
• Optimized for FT8, FT4, JS8Call, WSPR operation
• Modular plug-in band-pass filter system
• PC-controlled operation via USB (CAT + audio)
• SDR-style architecture using external DSP processing
• Lightweight and low-power design
• Supports multiple HF amateur bands via filter swapping
• Compatible with WSJT-X and similar software
• Based on the ADX project lineage (MI2 evolution of MINI/MINI+ designs)

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Applications

• Amateur radio HF digital modes
• QRP experimental transceiver builds
• SDR-style PC-controlled radio operation
• Educational RF and communications projects
• Multi-band portable HF operation

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System Overview

The ADX MI2 uses a modular architecture where the core radio handles RF conversion while the PC performs modulation/demodulation. Band selection is handled using plug-in low-pass or band-pass filter modules, allowing simple multi-band operation without redesigning the RF core.

Audio input/output and CAT control are handled through a USB interface, allowing full integration with modern digital radio software.

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What’s Included

• ADX MI2 main PCB (bare or assembled depending on kit)
• Support for external band filter modules
• Build documentation / wiring instructions