Fig 318A - Exploded view of an early automobile radio receiver, model PS-CL, made in Brazil by PenaSimon, circa 1954.
Fig. 318 - Early type of automobile radio with separate tuning unit.
Due to constructive conception of the earlier automobile radios, basically it was possible to find models comprising, the tuning section or dial incorporated or even separated from the main chassis, as a remote unit. In the former model, the radio receiver was mounted underneath the car’s panel. Certainly, the operation of this kind of radio by the end user was not an easy task. Thus, the model with separate dial was the most practical one, as the tuning unit could be mounted easily in the car’s steering wheel arbor.
The remote unit or dial was connected to the main chassis by mean of flexible shaft, provided with a worm gearing system to decrease the backlash and so improving the mechanical movement during the tuning. Fig 318
Fig 318B - The radio frequency stage of automobile radio model PS-LC.
So far, even considering this type of electro-mechanical arrangement the broadcasting radio stations tuning was quite trick mainly due to the drift in the radio frequency stage. This handicap was soon overcome by the development of the automatic frequency control circuit responsible for the birth of the push-button tuning.
Essentially the push-button tuner consited of a set of fixed capacitors, with tight tolerances either in capacitance as well as in the coefficent of temperature, working with permeability-tuned coils in both oscillator and intermediary frequency circuits allowing stable preset tuning with a low drifting level.
Fig 318C - An early automobile radio’s 6 Volt power supply using vibrator.

Furthermore the push-button tuning still had another advantages as: the possibility to preset from 4 to six radio stations, shifiting from automatic to manual tuning, operation with the mostly often popular circuits frequenly available in those days as, the tuned radio frequency and superheterodyne topologies, as well as decreasing the receiver’s manufacturing cost due to the reduction of the chassis size for the automatic frequency control circuit assembling. Fig 319
Fig. 319 - The electrical and mechanical assembling of the pushbutton tuner.
Due to the continuous technological evolution in its eletrical and mechanical concepts around 1940 the automobile radio had good selectivity and sensitivy as with a small antenna it was possible to tune feeble radio stations signals.
In the early forties was the booming days of radio broadcasting with news, sports events, special annoucements, soap operas and greatest unexpected reaction as occurred in the Hallowe’en eve in 1938, when H.G.Wells’ realistic drama “War of the World” panicked thousand of people in New York city, believing the earth was invaded by creatures from the planet Mars.
Thus due to the enormous technological possibilities, soon radio was used in others types of communications fields as by radioing photographs and texts gave birth of the fac-simile transmissions.