Android smartphone converted into wideband SDR via modem firmware and Bluetooth oscillator

Researcher Logan Zarov has demonstrated a method to transform a standard LG D325 Android smartphone into a wideband receiver without requiring external SDR hardware. The project utilizes a rooted device running LineageOS to gain the necessary system permissions for low-level hardware manipulation.

By applying a specific modem firmware update and performing minor physical modifications to the antenna, the device can access baseband data streams. This approach allows the smartphone to function as a receiver across a broad frequency range, including shortwave bands, by repurposing existing wireless chipsets.

Technical implementation of the smartphone SDR

• Baseband Access: The method relies on persuading existing radio chips in common wireless interfaces to expose their raw baseband data streams.
• Local Oscillator Hack: The system achieves wideband reception, including MHz-range shortwave, by utilizing the onboard Bluetooth radio to act as a local oscillator.
• Software Requirements: The process requires a rooted environment running LineageOS and a custom modem firmware update to enable SDR functionality.
• Hardware Modification: The conversion involves minor physical modifications to the antenna wiring to facilitate the expanded frequency range.

Why it matters

This development demonstrates how existing consumer hardware and open-source mobile operating systems like LineageOS can be repurposed for specialized radio engineering. It highlights the potential for low-cost, wideband signal analysis using ubiquitous mobile hardware rather than expensive dedicated SDR peripherals.