In the late 1930s, Al Gross, a teenage ham radio enthusiast in Cleveland, OH, built some handheld devices that allowed his friends and him to communicate on an unused portion of the radio frequency band; he named his creation the "walkie-talkie." Although Gross's innovation later played an important part in World War II, neither it nor his other major inventions became commercially successful until many years after his patents expired.

As an electrical engineering student at Cleveland's Case School of Applied Sciences, Gross discovered a way to cause miniature vacuum tubes to operate at about 300 megahertz, a relatively unexplored high frequency. By 1938, he had built battery-operated models that allowed him to communicate with radio operators more than 45 kilometers away.