wave transmission had drawbacks, and the focus shifted to undamped waves or continuous wave (CW) transmission. The arc converter could produce high power CW transmissions. The typical damped wave receiver was ineffective for receiving CW because CW had, ideally, no modulation of the radio frequency during the period of the dot or dash. Several methods were employed to generate an audible tone at the receiver: (1) a chopper, (2) a variable condensor with rotating plates (slope demodulation), (3) a tikker, (4) a separate heterodyne, and (5) the autodyne. Fessenden researched the heterodyne detector. Application The autodyne was widely used in both commercially produced and amateur receiver designs from shortly after the time of its invention until the middle 1930s. It became popular at the beginning of the Depression (ca early 1930s) for first detector applications in superheterodyne receivers. More recently, autodyne converters are employed in radio receivers for the AM and FM broadcast band. A single transistor combines the functions of amplifier, mixer and local oscillator of an otherwise conventional superheterodyne receiver. Such a stage accepts as input the antenna signal, and provides an output to the intermediate frequency amplifier. In this application, the transistor is made to self-oscillate at the local oscillator frequency. The autodyne detector has appeared in specialized fields in the 1960s through the 1990s. See also Direct-conversion receiver (also called "homodyne" or "zero-IF" receiver) Frequency mixer Heterodyne has comments on Fessenden and theory References Revised to 24 May 1921. Google Books. Damped and undamped wave transmission. page 503 describes autodyne 0.015 pW sensitivity. p 505, heterodyne not so good for damped waves; mushy sounds. External links . History of radio in 1925. https://web.archive.org/web/20120207233031/http://ieee.cincinnati.fuse.net/reiman/01_2003.html reprint of portion of . About John V. L. Hogan DOI.org Museum of Broadcasting, 2012, Mystery Radio, https://web.archive.org/web/20150504041938/http://www.museumofbroadcasting.org/pearson.html early radio design goal was reducing the number of tubes . Autodyne detector after RF amplifier and limiter ; single tube in VT fuze used as oscillator, transmitter, and autodyne detector. Electronic engineering