Seventy years ago this month, the July 1948 issue of Popular Science carried the plans for this ambitious project, a five-tube set which could be used either as a portable with an internal 6-volt storage battery, or mounted under the dash, as a car radio. On the go, it would be powered by the car battery and hooked to an external antenna. But at the flip of a switch, it could be unplugged and operated on its internal battery. In either configuration, it had a vibrator power supply inside.

The internal battery could be charged from the car, or directly off AC power. The AC charger consisted of only a selenium rectifier and a hefty “260 ohm 100 watt” resistor to drop the voltage.

The set featured one stage of RF amplification in front of the converter for added sensitivity. Both the battery and vibrator were military surplus for high quality at a low cost.