The duo shown here are putting together the one-tube receiver described in the November 1941 issue of Popular Mechanics.

The set was billed as being for the beginner who wanted to graduate from the crystal set stage, or for the radio experimenter who enjoyed pulling in some DX, an ability this set possessed.  The single tube was a 117N7-GT, so it required no A battery.  Instead, the filament was powered by the AC line.  The set was so efficient that it would run on a 30 cent 4.5 volt battery supplying the B+ voltage.  The required parts, including the tube and battery, but not including the headphones, priced out at about $4.50, even accounting for recent price increases.