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G.E. B-52
Majestic 66
Arvin 25
Motorola 34
Audiola 346
Studebaker-Philco
RCA Victor M-105
Postal T
Crosley 103
Zenith 462
New Auto Sets and Features
Radio-Craft, July 1934


A special airplane-type tuning control is installed, with receiver, at the factory of the Hudson Motor Car Company. It harmonizes with all other instruments.

Auto-radio receivers have improved considerably in design and appearance in the past few months. Practically all models are now constructed in single unit fashion, containing dynamic speaker and "B" power supply unit. Tuning controls are improved in appearance and mechanical construction. The circuit improvements and tubes used are such as to produce an equivalent to that of an excellent home receiver.


Packard radio tuning control in arm rest.

The installation procedure for auto sets has also been refined considerably. A radio receiver in a car now is a thing of beauty, in addition to being a necessary convenience. As suggested in the photographed illustrations below, the tuning controls may be so located in any one of various places in a car, that it will contribute to the tuning ease and interior appearance. Many new cars include radios as standard equipment.

The auto radio of a few years ago was a crude affair, in comparison with present models. Whereas the old model consisted of numerous boxes to hold the receiver chassis, speaker and "B" batteries, and the tubes were such that very little amplification of the meager signal (generally obtained from most auto antennas) fed to them was derived; the new sets are practically just the opposite in that every imperfection has been eliminated. The latest in auto-radio receivers is a single unit with just one or two bolts, at the most, necessary to anchor it to the car. Today "B" batteries have been done away with, a "B" supply unit that obtains its power from the car battery being employed to furnish the necessary plate voltages. This unit may be either of the motor-generator type, or a vibrator which chops the 6 V. D.C. (from the storage battery) into pulsating D.C., stepped up by a transformer to approximately 225 V., A.C. and then rectified and filtered by a special rectifying tube and filter arrangement. Some receivers employ a mechanical rectifier, operated "in step" with the vibrator "chopper," to eliminate the necessity for an extra tube.


Packard, tuning control on instrument panel.

Essentially, what has been, to a great extent, responsible for the tremendous improvement in efficiency of present-day car sets is the development of new and improved tubes. Such tubes as the 6A7, 6B7, 78 and the 41 permit greater amplification, larger power outputs at initially lower plate voltages, besides a circuit arrangement that enables the tube to perform double functions, such as composite first-detector and oscillator, or second-detector and A.V.C. or I.F. stage. This, when summed up, means simply that a tremendous saving in tubes is accomplished without impairing the efficiency of the receiver. In addition, the versatility from one, by means of multiple functions (outlined) and reflexing. As a matter of fact, most of the 5 and 6 tube receivers that are manufactured are the equivalent of 7 and 8 tube sets of a few years ago.


Standard type of installation (Packard), tuning control mounted on steering column. Set mounted behind instrument panel.

Insofar as reproduction is concerned, the new auto sets reproduce with a quality comparable to most home receivers. Some of these sets employ class A amplification in the final audio output stage, so that a relatively large power output is delivered to the speaker, resulting in ample volume without "forcing" the volume control until that strained quality or tone is obtained. Of course, all of the present manufactured models include the dynamic type of loudspeaker.

 

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