Time was when most radio sets had no software at all, and those that had any didn’t do much with it. But Joseph Mitola III, an engineer working for a company called Eâ¿¿Systems (now part of Raytheon), envisioned something very different—a mostly digital radio that could be reconfigured in fundamental ways just by changing the code running on it. In a remarkably prescient article he wrote in 1992 for the IEEE National Telesystems Conference, he dubbed it software-defined radio (SDR).

A few short years later, Mitola’s vision became reality. The mid-1990s saw the advent of military radio systems in which software controlled most of the signal processing digitally, enabling one set of electronics to work on many different frequencies and communications protocols. The first example was the U.S. military’s Speakeasy radio, which allowed units from different branches of the armed forces to communicate effectively for the first time. But the technology was costly and rather unwieldy—the first design took up racks that only a large vehicle could carry around.

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