The 955 is typical of the acorn designs, named for the glass cap holding the terminals with the main part of the tube extending from it. An acorn tube, or acorn valve, refers to any member of a family of VHF/ UHF

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...

s starting just before

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. They were named after their resemblance to the acorn, specifically due to the glass cap at one end of the tube that looked similar to the cap on an acorn. The acorn tubes found widespread use in

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmi ...

s and

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

systems. High-frequency performance is limited by (1) parasitic lead inductance and capacitance and skin effect, and (2) electron transit time (the time required to travel from cathode to anode). Transit time effects are complicated, but one simple effect is the

phase margin Phase or phases may refer to: Science *State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter), a region of space throughout which all physical properties are essentially uniform * Phase space, a mathematic ...

; another one is input conductance, also known as grid loading. At extremely high frequencies, electrons arriving at the grid may become out of phase with those departing towards the anode. This imbalance of charge causes the grid to exhibit a reactance that is much less than its low-frequency "open circuit" characteristic. Acorn- as well as Lighthouse tubes and

Nuvistor The nuvistor is a type of vacuum tube announced by RCA in 1959. Nuvistors were made to compete with the then-new bipolar junction transistors, and were much smaller than conventional tubes of the day, almost approaching the compactness of ea ...

s attempt to minimize this effect by arranging cathode, grid(s) and anode as closely spaced together as possible. The original range included about half a dozen tubes, designed to work in the VHF range. The 955 is a

triode A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's ...

. The 954 and 956 types are sharp and remote cut-off pentodes, respectively, all with indirect 6.3 V, 150 mA heaters. Types 957, 958 and 959 are for portable equipment and have 1.25 V NiCd battery heaters. The 957 is a medium-μ signal triode, the 958 is a transmitting triode with dual, paralleled filaments for increased emission, and the 959 is a sharp cut-off pentode like the 954. The 957 and 959 draw 50 mA heater current, the 958 twice as much. In 1942, the 958A with tightened emission specifications was introduced after it turned out that 958s with excessively high emission kept working after the filament power was turned off, the filament still sufficiently heating on the anode current alone. After the introduction of the miniature 7-pin base, the 954, 955 and 956 were made available with this base as 9001, 9002 and 9003. Other acorn tubes include: * American: :*

EIA Eia or EIA may refer to: Medicine * Enzyme immunoassay * Equine infectious anemia * Exercise-induced anaphylaxis * Exercise-induced asthma * External iliac artery Transport * Edmonton International Airport, in Alberta, Canada * Erbil Internation ...

: 5731 :* RETMA: 6F4, 6L4 * European: :*British: A40, A41, AP4, AT4, HA1, ZA1, ZA2 :*Continental: 4671, 4672, 4674, 4675, 4676, 4695 :* Mullard-Philips: D1C, D2C, D1F, D2F, D3F, D11F, D12F, E1C, E1F, E2F *

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

: 6С1Ж, 6Ж1Ж, 6К1Ж * Japanese: UN954, UN955 Larger, higher-power types such as the 316A, 368A, 388A, and 703A triodes and the 713A and 717A pentodes were referred to as ''Doorknob'' tubes. The introduction of the

EF50 In the field of electronics, the EF50 is an early all-glass wideband remote cutoff pentode designed in 1938 by Philips. It was a landmark in the development of vacuum tube technology, departing from construction ideas of the time essentially uncha ...

was the first serious competition for the acorn design, and replaced the acorns in many roles, especially post-war when millions of surplus EF50s were dumped on the market.

References

{{Thermionic valves Vacuum tubes

See also

References