They were designed with the Zenith movable "Wavemagnet" antenna for which E. McDonald, head of Zenith, was granted two patents.
The other was for the hinge mount that allowed the Wavemagnet to be partly rotated while stuck to the window. Most later generations of the Wavemagnet are not rotatable. The illustrations in the patent applications are unmistakable in their depiction of these radios. Zenith portables use primarily loctal tubes with an octal 117Z6 rectifier. The 5G500 is a 5 tube radio with a 1LA6 as converter, 1LN5 as IF amp, 1LH4 as audio preamp/ detector, and 1LB4 as audio output.