TRF sets, depending on the number of stages they employed, could have poor-to-superb sensitivity (ability of the set to pick up faint signals) and corresponding selectivity (ability to parse adjacent stations from one another). TRF sets used no regeneration, and were merely several stages (typically three) of tuned RF amplifiers in series feeding a detector tube which extracted the audio intelligence from the RF signal. Speakers widely used on TRF sets included: 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 (moving-coil) speaker had begun to find favor due to its superior sound-reproduction ability. 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. These used several valves (tubes) to provide RF amplification, detection, and audio amplification. Tuned radio frequency sets (TRF sets) were the most popular class of early radio, primarily because the Radio Corporation of America (RCA) had a monopoly on the superheterodyne circuit patents and it was more profitable for companies to jump into radio manufacturing TRF sets. Some crystal set users added a carbon amplifier or a mechanical turntable amplifier to give enough output to operate a speaker. 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. They were popular among the less wealthy due to their low build cost and zero run cost. They would receive only very strong signals from a local station. These basic radios used no battery, had no amplification and could operate only high-impedance headphones. Crystal set with carbon or mechanical amplifier.Until then there were more homemade sets in use than commercial sets.Įarly sets used any of the following technologies: Homemade sets remained a strong sector of radio production until the early 1930s. 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. Radio sets from before 1920 are rarities, and are probably military artifacts. More stations opened in cities across North America in the following years and radio ownership steadily gained in popularity. 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. 1930s style homemade one-tube regenerative radio
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