|Fig 318A - Exploded view of an early automobile
radio receiver, model PS-CL, made in Brazil by PenaSimon, circa
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.
|Fig. 318 - Early type of automobile radio
with separate tuning unit.
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
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.
|Fig 318B - The radio frequency stage of automobile
radio model PS-LC.
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
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.
|Fig. 319 - The electrical and mechanical assembling
of the pushbutton tuner.
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.