page_title: Barkhausen–Kurz tube
hierarchical_section_title: Barkhausen–Kurz tube
caption_attribution_description: English: An experimental 3 GHz microwave AM transmitter and receiver using a triode vacuum tube in Barkhausen-Kurz mode for both transmitting and receiving. In Barkhausen-Kurz mode the plate is biased near zero voltage while the grid is biased at a high positive voltage. The electrons oscillate back and forth through the grid, attracted by the grid and repelled by the low voltages on both the cathode and plate. The Barkhausen-Kurz was the first tube that could oscillate in the UHF range, and by the mid 30s could generate microwave frequencies. It was the only source of microwaves until the klystron was invented. The output frequency is determined by the geometry of the tube and the 4 cm half-wave antenna soldered directly to the grid terminal. The tubes and antennas are mounted at the focus of parabolic reflectors which are pointed at each other. In the receiver the Barkhausen-Kurz tube is operated below oscillation as an amplifier . Alterations to image: Edited two images together and added label pointing out B-K tube
context_page_description: The Barkhausen–Kurz tube, also called the retarding-field tube, reflex triode, B–K oscillator, and Barkhausen oscillator was a high frequency vacuum tube electronic oscillator invented in 1920 by German physicists Heinrich Georg Barkhausen and Karl Kurz. It was the first oscillator that could produce radio power in the ultra-high frequency portion of the radio spectrum, above 300 MHz. It was also the first oscillator to exploit electron transit time effects. It was used as a source of high frequency radio waves in research laboratories, and in a few UHF radio transmitters through World War 2. Its output power was low which limited its applications. However it inspired research that led to other more successful transit time tubes such as the klystron, which made the low power Barkhausen-Kurz tube obsolete.
context_section_description: The Barkhausen–Kurz tube, also called the retarding-field tube, reflex triode, B–K oscillator, and Barkhausen oscillator   was a high frequency vacuum tube electronic oscillator invented in 1920 by German physicists Heinrich Georg Barkhausen and Karl Kurz.  It was the first oscillator that could produce radio power in the ultra-high frequency (UHF) portion of the radio spectrum, above 300 MHz.  It was also the first oscillator to exploit electron transit time effects.  It was used as a source of high frequency radio waves in research laboratories, and in a few UHF radio transmitters through World War 2.  Its output power was low which limited its applications.   However it inspired research that led to other more successful transit time tubes such as the klystron, which made the low power Barkhausen-Kurz tube obsolete.
caption: Experimental low power 3 GHz AM communication link from 1938 uses Barkhausen-Kurz tubes for both transmitting and receiving
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