Parallel transmission (PTx) research platforms are challenging to implement and to integrate with commercial MRI systems. A prototype PTx research platform was demonstrated that leverages off-the-shelf software-defined radio (SDR) for flexibility and scalability, with easy integration and moderate cost. The SDR system was evaluated on the bench and connected to a commercial 3-T MRI system for an initial RF shimming demonstration. Substantial latency was found, likely due to the preliminary software implementation, but overall measurements and images were promising. Scaling to 32 transmit channels and applications other than RF shimming are expected to be practical.