The unmanned aircraft system (UAS) market is expected to grow to more than $60 billion by 2025, and with each passing year the potential for threats due to these often hard-to-detect craft is only going to increase. Successful military-focused counter-UAS (c-UAS) solutions may neutralize these threats today, but these threats continue to evolve. Software-defined radio (SDR) will continue to play a key role in c-UAS solutions for the foreseeable future.