File:Regenerative receiver circuit on table 1922.jpg

English: A homemade vacuum tube regenerative radio receiver from 1922, with its parts screwed to a table top, showing the antique components used. The regenerative receiver, invented in 1913 by Edwin Armstrong was one of the most popular types of radio, and hundreds of thousands were sold and homemade during the "radio craze" of the early 1920s to receive the first radio broadcasts, which were just beginning at that time. This example uses three triode vacuum tubes (center), the lefthand one is the regenerative detector and the other two are audio amplifiers. It uses the common Armstrong or "tickler" feedback circuit, in which energy from the plate circuit of the detector tube is fed back into the input using magnetically coupled coils, increasing the gain and selectivity . This is accomplished by the three-coil honeycomb (or duo-lateral) variocoupler (hoops, at left). The center coil is connected to the grid circuit of the detector tube. The lefthand coil is the input tuned circuit, connected to a wire antenna. The righthand coil is the "tickler" coil, connected to the detector plate circuit, which provides feedback. The coils can be pivoted on hinges to increase or decrease the coupling, to vary the feedback and thus the gain. The two cylindrical components with knobs (foreground right) are variable tuning capacitors which make up the input and output tuned circuits. Smaller knobbed objects in front of the tubes are rheostats (potentiometers) used to set the biasing of the tubes. The four grey rectangular objects in the background are "B" batteries which provide the DC plate voltage for the tubes. They are specialized batteries designed for radios, with taps on each cell so the plate voltage can be adjusted by cutting in more or fewer cells. Regenerative sets like this were largely replaced by superheterodyne receivers in the 1930s
Alterations to image: Cropped out table legs and earphones on side of table.