Seventy-five years ago this month, the February 1947 issue of Popular Science showed this simple one-tube radio kit, the Laco Kitcraft Model 200.  The kit sold for $6, and featured a single 1L4 (or 1T4 or 1U4) tube, and required 1-1/2 volts for the filament, and anywhere from 22-1/2 to 90 volts for the B+.

According to the magazine, it was perfect for the youngster who wanted his or her own radio.