The HBR-MK2 QRP transceiver is an impressive homemade transceiver designed by Alex R2AUK to operate across 8 HF bands, 80, 40, 30, 20, 17, 15, 12, and 10 meter in both Continuous Wave (CW) and Single Sideband (SSB) modes. This project represent a significant improvement over its predecessor, the HBR, addressing several limitations on bands coverage.
HBR-MK2 Design
One of the most notable aspects of the HBR-MK2 is its thoughtful design. The transceiver features independent receiving and transmitting paths, which share only a reference oscillator and quartz filters. This kind of separation enhances the overall performance and minimizes interference, that is a typical issue in many multi-mode transceivers.
The project incorporates a voltage-controlled amplifier (VCA) for automatic gain control (AGC), ensuring optimal signal clarity.
The built-in microphone amplifier with compression allows operators to maintain a consistent audio level, making it easier to communicate without needing to adjust their speaking volume constantly. The heart of the HBR/MK2 is the STM32F103 microcontroller, which manages signal processing efficiently. The use of printed circuit boards (PCBs) instead of traditional point-to-point wiring significantly reduces digital noise and improves electromagnetic compatibility, resulting in a more reliable and compact device.
HBR-MK2 Features
In terms of performance, the HBR MK2 delivers an output power of 5 to 10 watts in SSB mode and 5 to 8 watts in CW mode. The receiver boasts impressive sensitivity and selectivity, allowing for clear reception even in challenging conditions. The transceiver effectively handles interference from AM broadcast stations, which is a common problem for HF operators, especially during nighttime operations. One of the standout features of the HBR-MK2 is its essential but user-friendly interface. It includes quick frequency selection for five favorite frequencies, making it easy to switch between commonly used bands. The mode selection switch and intuitive controls enhance the overall user experience, allowing operators to focus on communication rather than troubleshooting.
Features:
- Covers 80, 40, 30, 20, 17, 15, 12 and 10 meters
- Classical single IF superheterodyne design
- Effective IF derived AGC
- Voice compression
- Supports RIT and XIT
- 10-30 WPM Elekey-B type keyer + straight key mode
- Keyer supports record and playback, programmable with paddles
- Five favorite frequencies per band (press NEXT/PREV in FAST mode)
- Class AB amplifier provides 5-10W in both CW and SSB
- Has a S-meter and a SWR meter
- Open-source firmware, schematic and 3D-printable enclosure
The modular design of the HBR/MK2 opens the door for future enhancements. Users can easily integrate additional features such as a built-in battery, automatic tuner, or even a sound card for digital modes. The flexibility in design ensures that the transceiver can evolve with the needs of its operator.
Contributing to the project
For those interested in replicating or modifying the project, all source materials and design files are available on GitHub, making it accessible to the amateur radio community.