Historical Electronics Museum, Inc. - History of the Nation's Defense Electronics
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What do acorns, doorknobs, lighthouses, mushrooms, rockets, peanuts, and pencils have in common?

They are all descriptive names of vacuum tubes. Tubes are usually named for their electrode arrangement, such as diode, triode, pentode. Some are named for their function, such as kinescope. A few are even named after their inventor, like the Geiger counter or Zahl tube. But some tubes were given names based on their shape, having nothing to do with their electrical function.

The RCA UV-199 is one of several types dubbed a "peanut" tube because of its relatively small size. It is a receiving detector-amplifier triode, with a short-pin 4 contact base. It was about half the size of its 1922 contemporaries, but was still much larger than the subminiature tubes developed in the 1930s for hearing aids.

Many of these odd names were used for tubes designed for very high frequency operation. Their construction made possible very short leads to connect to the internal electrodes, reducing the lead inductance.

Acorn tubes were developed in 1933 by RCA. Their baseless short lead construction allowed them to be used at frequencies above 100 MHz. This 954, introduced in 1935, is an RF pentode used in VHF receivers.

Western Electric introduced the baseless "doorknob" style in the mid 1930s. The WE 316A triode could produce 6.5 watts at 500 MHz. It was used in several WW II radars.


Western Electric introduced this WE-713A pentode in 1943. It was called a "mushroom" tube, for obvious reasons. Although it has a standard octal base, the electrodes are mounted horizontally inside the small envelope, to allow short connecting leads for high frequency operation. It is a predecessor of the miniature type 6AK5, which was used extensively in radar receiver IF amplifiers from WW II onward.

General Electric introduced the "lighthouse" tube in the 1940s, they were also called "disk seal" tubes,. The top cap is the anode connection, and the disk is the grid connection. The planar arrangement allowed very close spacing of the cathode and grid electrodes, reducing the electron transit time. This GE 2C40 could operate at well over 3 GHz. These tubes could also be installed directly inside coaxial resonators. A variety of receiver and transmitter types were produced.


RCA introduced this 5675 "pencil tube" in 1949, another disk seal type. The base has been eliminated altogether. It could produce 0.5 watt up to 1700 MHz.

Sylvania introduced yet another style of grid seal tube they called "rocket" tubes. The two rings are the anode and grid connections, and the filament is a coaxial connection. The 5767, also introduced in 1949, was usable up to 3300 MHz.

Steven N. Stitzer
November 2005


The National Electronics Museum is organized into thirteen related exhibit galleries:
1. Fundamentals Gallery
2. Communications Gallery
3. Early Radar Gallery
4. Cold War Radar Gallery
5. Modern Radar Gallery
6. Countermeasures Gallery
7. Under Seas Gallery
8. Electro-optical Gallery
9. Space Sensor Gallery
10. Past Gallery
11. Web Gallery
12. WWII Radar Kiosk
13. Cold War Radar Kiosk

Click here for an Adobe pdf showing the gallery layout

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