Antique radio


An antique radio is a radio receiving set that is collectible because of its age and rarity.

Types of antique radio

Morse receivers

The first radio receivers used a coherer and sounding board, and were only able to receive continuous wave transmissions, encoded with Morse code. Later transmission and reception of speech became possible, although Morse code transmission continued in use until the 1990s.
All the following sections concern speech-capable radio, or wireless telephony.

Early home-made sets

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. Radio sets from before 1920 are rarities, and are probably military artifacts. Sets made prior to approximately 1924 were usually made on wooden breadboards, in small cupboard style cabinets, or sometimes on an open sheet metal chassis. Homemade sets remained a strong sector of radio production until the early 1930s. Until then there were more homemade sets in use than commercial sets.
Early sets used any of the following technologies:
These basic radios used no battery, had no amplification and could operate only high-impedance headphones. They would receive only very strong signals from a local station. They were popular among the less wealthy due to their low build cost and zero run cost. Crystal sets had minimal ability to separate stations, and where more than one high power station was present, inability to receive one without the other was a common problem.
Some crystal set users added a carbon amplifier or a mechanical turntable amplifier to give enough output to operate a speaker. Some even used a flame amplifier.

Tuned radio frequency sets

were the most popular class of early radio, primarily because the Radio Corporation of America had a monopoly on the superheterodyne circuit patents and it was more profitable for companies to jump into radio manufacturing TRF sets. These used several valves to provide RF amplification, detection, and audio amplification. 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. The sound quality produced from "moving-iron" speakers used on such sets is sometimes described as torturous, although by the late 1920s the Kellogg-Rice dynamic speaker had begun to find favor due to its superior sound-reproduction ability.
Speakers widely used on TRF sets included:
TRF sets used no regeneration, and were merely several stages of tuned RF amplifiers in series feeding a detector tube which extracted the audio intelligence from the RF signal. TRF sets, depending on the number of stages they employed, could have poor-to-superb sensitivity and corresponding selectivity. Audio reproduction quality of TRF sets was limited by the available loudspeakers. "High Fidelity" was not to become a radio marketing concept until the mid-1930s and was not realized until the advent of FM broadcasting.
Reaction sets, also known as regenerative receivers, rely on positive feedback to achieve adequate gain. 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 on nearby properties.
Early TRF sets had typically two or three tuning knobs and tube filament voltage-control rheostats, all of which had to be set correctly to receive a station. Later TRF sets had ganged tuning, AC house current operation, and eliminated the filament voltage adjustments. All of these changes greatly simplified operation and made radio a household appliance that even a small child could operate, instead of the highly skilled hobbyists of the brief preceding generation. Reaction sets also had the filament adjustment rheostats for each valve, and again settings had to be right to achieve reception.

Superheterodyne receivers

In the era of early radio, only RCA and a select number of competing "prestige" radio manufacturers could afford to build a superheterodyne receiver. RCA had exclusive rights to the superheterodyne circuit patents and extracted high licensing fees from other companies who sought to build superhet sets. RCA also vigorously prosecuted patent infringers. This situation helped propel RCA to the forefront of radio manufacturers in the 1920s due to the higher efficiency of the superhet circuit- a situation which lasted until the patents expired in the early 1930s, at which time a flood of low-cost superheterodyne receivers hit the market.
Early superhets were often used with the relatively expensive moving coil speakers, which offer a quality of sound unavailable from moving iron speakers.
Most post-1932 commercial radios were superhets, and this technology is still in widespread use in radio receivers today, implemented with transistors or integrated circuits.
The advantages of superhets are:
  • Excellent sensitivity and selectivity
  • Ease of designing the set for multiple-band operation, enabling reception of foreign broadcasts
  • High stability
  • Well controlled bandwidth
  • Well shaped RF passband avoids the uncontrolled tone variations of TRF sets, and gives good selectivity
The disadvantages before about 1932 were:
  • High patent-licensing costs.
  • Need for specialized test equipment to perform conversion-stage filter alignments.
In general the technical and manufacturing advantages of the superhet ensured that the TRF set became quickly obsolete once the patent restrictions on superhets were eliminated.

Farm radios

Prior to the Rural Electrification Act of 1936, the vast majority of rural farms in America did not have electricity. Many rural areas of the Midwest and South did not receive commercial power until the 1960s. Until that point, special radios were made to run on DC power. The earliest so-called "farm radios" used the "A", "B", and "C" batteries typical of 1920s radio sets; these farm radios were identical to those used in cities. Somewhat later, farm radios were made to be run on 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, from a bank of lead-acid storage batteries charged from a gas powered generator or a wind-charger. The 32-volt system could also power other specially made appliances as well as electric lights around the farm. Other farm radios, especially from the late 1930s to the 1950s, reverted to using a large "A-B" dry cell that provided both for the tube plates and for the tube filaments, as did most tube-based portable radios of that era.

Foxhole radios

World War 2 created widespread urgent need for radio communication, and foxhole sets were built by people without access to traditional radio parts. A foxhole radio is a simple crystal sets
radio receiver cobbled together from whatever parts one could make or scrounged from junked equipment. Such a set typically used salvaged domestic wiring for an antenna, a double-edged safety-razor blade and pencil lead for a detector, and a tin can, magnet and some wire for an earpiece. Razor blades of the era were chemically coated and this coating could function as a diode, in the same way that a galena cat's whisker detector operates.

Wooden consoles

The console radio was the center piece of household entertainment in the era of radio. They were big and expensive, costing hundreds of dollars in the late 1930s and were often coupled with a phonograph. Tending to be a major acquisition for a middle-class family, these large radios were usually placed in living rooms. 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, Sears, Westinghouse, Motorola, Zenith and others. Brands such as Zenith made a few high priced models mainly produced moderately priced radios
Some premium makers such as E. H. Scott and Silver-Marshall started around $500–$800 range in the 1930s and 1940s.

Table-top wood-cased radios

Table top radios came in many forms:
  • "Cathedral style", an upright rectangular box with a rounded top
  • "Tombstone style" are rectangular boxes that are tall and narrow like a tombstone
  • "Table top" are rectangular, with width being the larger dimension. Table top radios are usually placed in the kitchen, living room, or bedroom, and sometimes used out on the porch.

    Bakelite

The availability of the first mass-produced plastic Bakelite allowed designers much more creativity in cabinet styling, and significantly reduced costs. However, Bakelite is a very brittle plastic, and dropping a radio could easily crack or break the case. Bakelite is a brown-black mouldable thermosetting plastic, and is still used in some products today.
In the 1930s some radios were manufactured using Catalin, which is the phenolic resin component of bakelite, with no organic filler added, but nearly all historic bakelite radios are the standard black-brown bakelite color. 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.