Antique radio
The idea of radio as entertainment took off in 1920, with the opening of the first stations established specifically for broadcast to the public such as KDKA in Pittsburgh and WWJ in Detroit.
More stations opened in cities across North America in the following years and radio ownership steadily gained in popularity.
Early sets used any of the following technologies: These basic radios used no battery, had no amplification and could operate only high-impedance headphones.
Early TRF sets only operated headphones, but by the mid-1920s it was more common to use additional amplification to power a loudspeaker, despite the expense.
This approach provided high performance with a minimum number of expensive vacuum tubes, but these receivers tended to radiate RF interference in their immediate vicinity.
Consequently, there was a significant amount of hostility by neighbors of "regen" set users over maladjusted radios transmitting squealing noises and blocking reception [d] on nearby properties.
RCA had exclusive rights to the superheterodyne circuit patents and extracted high licensing fees from other companies who sought to build superhet sets.
Somewhat later, farm radios were made to be run on 6 V from a car or tractor battery, using an electromechanical vibrator to create a pulsating DC current that could be stepped up through a transformer to create the high voltage needed for the plates of the tubes- exactly as contemporary car radios did.
Other farm radios were designed to run on 32 V DC, from a bank of lead-acid storage batteries charged from a gas powered generator or a wind-charger.
Most early console radios were tall and narrow, but as the years went on they got shorter and wider in accordance with the Art Deco design precepts which had become popular Consumer console radios were made by RCA, Philco, General Electric, Montgomery Ward (under the Airline brand name), Sears (under the Silvertone brand name), Westinghouse, Motorola, Zenith and others.
[citation needed] Table top radios came in many forms: The availability of the first mass-produced plastic Bakelite allowed designers much more creativity in cabinet styling, and significantly reduced costs.
Bakelite as used for radio cabinets was traditionally brown, and this color came from the ground walnut shell flour added to the thermosetting phenolic resin as an extender and strengthening agent.
The invention of the transistor made it possible to produce very small portable radios that did not need a warm-up time, and ran on much smaller batteries.
They were convenient, though the prices were initially high and the sound quality of early models was not nearly as good as tube radios.
Today's radios are usually uneconomical to repair because mass production and technological improvements in numerous areas have made them so inexpensive to buy, while the cost of human labor and workshop overheads have increased greatly in comparison.
Vibrators are relatively unreliable as electromechanical components of limited life, buzz audibly, and produce radio interference.
A few radios used a bulkier and more expensive motor-generator or motor-alternator set called a "dynamotor" that spun a high-voltage generator or alternator using a 6- or 12-volt DC motor.
Chrysler and Philco announced an all-transistor car radio in the April 28, 1955, edition of the Wall Street Journal.
[1] This Philco car radio model was the first tubeless auto set in history to be developed and produced.
In most cases, at least the power supply section of line-operated radios must be refurbished to prevent damage to other components, but it can be assumed that most of the vintage capacitors are electrically "leaky" and that the electrolytic capacitors in the power supply have either lost capacity (leading to excess "hum") or shorted (potentially causing a damaging or fire-inducing short-circuit).
Proper repair or refurbishment requires an isolation transformer to remove the live connection, and care should be taken to never touch any metal part of the radio (chassis mounting screws, bare control shafts, etc.)
Many radios with a hot chassis use interlocks on the back to ensure that the line is disconnected before the rear can be accessed for tube replacement.
The sound quality of such radios is generally unimportant, since almost any defect in the audio signal will be masked by the butchery visited upon it by the loudspeaker.
The Inductor Dynamic Speaker solved the worst problems of earlier moving iron types, and provided a relatively pleasant listening experience.
The main defect of ID speakers was poor treble response, giving them a characteristic dull drone.
