Limekiln Engineering is organized around the development of software defined radio (SDR) solutions to modernize large scale RF communication and control systems. The firm also can perform customized cyber vulnerability analysis in the RF domain. A properly designed SDR system can enable the User incrementally add functionality to deploy systems without being locked into a proprietary solution with a particular hardware vendor allowing for a flexible system that minimizes maintenance costs and extends the longevity of the deployed system. Legacy RF systems based on ASICs and FPGAs, while often performant, do not lend themselves to long term maintenance. The combination of long procurement processes with traditional "waterfall" development practices can lead to a system being deployed with technology that is already out of date, and long FPGA development cycles further exacerbate this problem. In our experience, many legacy RF systems can be readily replaced with a flexible SDR architecture. For high performance and demanding requirements, signal processing algorithms can be accelerated with General Purpose Graphics Processor Units (GPGPUs) which often outperform their dedicated hardware counterparts as well as offer transparent performance upgradability by drop-in hardware replacement with no software changes necessary.