In electronics, the dynatron oscillator, invented in 1918 by Albert Hull at General Electric, is an obsolete vacuum tube electronic oscillator circuit which uses a negative resistance characteristic in early tetrode vacuum tubes, caused by a process called secondary emission. It was the first negative resistance vacuum tube oscillator. The dynatron oscillator circuit was used to a limited extent as beat frequency oscillators (BFOs), and local oscillators in vacuum tube radio receivers as well as in scientific and test equipment from the 1920s to the 1940s but became obsolete around World War 2 due to the variability of secondary emission in tubes.
Dynatron vacuum tube signal generator, 1931. It covered the range 1.8 to 15 MHz. The circuit was used in signal generators due to its frequency stability, which was compared to crystal oscillators
The dynatron oscillator circuit was also used as the local oscillator in early vacuum tube superheterodyne radio receivers, such as this 1931 Crosley model 122 seven tube radio.
Albert Wallace Hull was an American physicist and electrical engineer who made contributions to the development of vacuum tubes, and invented the magnetron. He was a member of the National Academy of Sciences.
Albert W. Hull
