The Vivid Unit is a palm-sized touchscreen SBC based on the Rockchip RK3399 and serves as the host platform for UUGear’s VU GPSDR, a low-cost GPS-disciplined SDR expansion board. The VU GPSDR is built around the Rafael Micro R860 tuner and Realtek RTL2832U ADC, targeting stable and portable software-defined radio applications.
For frequency stability and accurate timing, the board uses a 24 MHz PPS signal from the onboard u-blox NEO-M8N GPS module to discipline the Si5351 local oscillator. When paired with the Vivid Unit and Vivid Unit Extender, it forms a complete handheld SDR system with a 5.5-inch touchscreen, RK3399 processor, 4GB RAM, and 32GB eMMC storage, along with Wi-Fi, Bluetooth, speaker, microphone, and multiple I/O interfaces.
VU GPSDR specifications:
From a hardware perspective, the expansion board integrates an STM8S003F MCU and supports a frequency range of 500 kHz to 1.766 GHz with up to 3.2 MHz bandwidth (2.4 MHz recommended for stability). An onboard 108 MHz up-converter enables reception below 30 MHz for amateur and shortwave bands. RF connectivity includes one SMA input for the SDR antenna (no Bias-Tee) and one SMA output providing a software-adjustable clock via the Si5351.
The Si5351 local oscillator is disciplined by the 24 MHz PPS output from the u-blox NEO-M8N GPS module to ensure long-term frequency accuracy. The board also provides an onboard GPS antenna via an IPEX 1st gen connector with 5V Bias-Tee support and an I2C header for the GPS module. Additional hardware features include dual rotary encoders, two push buttons, a GPS fix LED, and an SWD header for the STM8 MCU. The board measures 210 × 110 × 10 mm and weighs 0.065 kg.
VU GPSDR Interfaces
GPSDR++ is a fork of the open-source SDR++ (v1.2.0) project and supports the VU GPSDR. Because the RK3399 on the Vivid Unit must handle real-time waterfall rendering and demodulation, enabling Mali-T860 GPU acceleration is recommended to avoid lag. On the Debian-based OS, users can install the gpsdrpp binary and the Vue (Vivid Unit Extender) package easily via apt.
The VU GPSDR expansion board is priced at €65.00 (around $77.40 USD) on the UUGear E-Shop. However, it is not a standalone product; users must also purchase the Vivid Unit (€99.00) and the Vivid Unit Extender (€28.00). Excluding antennas, the complete handheld setup totals approximately €192 (about $205 USD). More details are available on the company’s news page.
Niladri Chowdhury