Year

Inventor

Invention - Discovery - Development

1883

T. A. Edison

Accidental discovery of emission and rectifier effects (vacuum tube)

1898

P. Lennard

Usage of an electrostatically operating auxiliary electrode with cathode-ray experiments

1901

O. W. Richardson

Electron emission theory explains Edison effect

1902

C. Hewitt

Relay effect by magnetic arc control (controlling an ionic discharge)

1903

P. Lennard

Usage of wire-mesh grids to electrostatically control electron velocity

1903

A. Wehnelt

Discovery of the excellent emission qualities of alkaline earths (oxide cathode)

1904

J. A. Flemming

Using the electron tube as a high-frequency detector

1906

R. v. Lieben

Vacuum amplifier tube with magnetically controlled electron flow

1906

L. de Forest

Detector tube with plate control

1907

L. de Forest

Audion patent (single-grid tube)

1908

J. A. Flemming

Tungsten filament for electron tubes

1910

R. v. Lieben

Control grid (amplifier with mercury vapor filled tube)

1910

J. Langmuir

Improving emission by thoriated-tungsten filament

1911

O. v. Bronk

Radio-frequency amplifier

1912

AEG

Mass production of Lieben tubes

1912

L. de Forest

Regeneration - positive feedback

1912

G. Leithäuser

Supressor-grid arrangement for cathode-ray experiments

1913

J. Langmuir

Space-charge grid circuit

1913

A. Meißner

Oscillator by positive feedback

1913

J. Langmuir

Significance of high vacuum for the space charge

1915

W. Schottky

Increasing transconductance by dual control

1915

Schenkel

Indirect heated cathode

1916

W. Schottky

Protective grid

1919

A. W. Hull

Screen grid

1926

Jobst/Telegen

Suppressor grid (pentode)

1932

K. Steimel

Hexode

1933

K. Steimel

Triode-hexode

B.2

The Radio Receiving Tube in Germany - Development 1923-1949

Year

Application goals

Solutions

Tube types

1923 - 1926

Audio-frequency amplifiers and radio-frequency detectors

Usage of the already available tungsten-filament tubes

RE11

Reducing the heater power consumption

Econo-tubes (dark heaters) with thoriated-tungsten filaments and oxide-coated filaments

Thoriated: VALVO Oekonom, RE064, RE144;
Oxide: RE063, RE152

1927

Standardization of basing

The "Europe" base

all subsequently manufactured pin-socket tubes

Reproduction by loudspeaker

Special output tubes

RE134, L413

1928

AC power line heating

Indirect heated tubes

REN1004, W4110

AC power line rectifying

Rectifier tubes

RGN1503, G1503

More powerful output stage

5-watt and 10-watt power triodes

RE304, RE604, LK460

1929

Improved gain and stability on RF stages

Screen-grid tubes

H406D, RES044, RES094

Increased plate resistance and improved grid-to-plate capacitance

RF pentodes (screen-grid tubes with suppressor grid)

RENS1820, H2018D

1930

DC power line operation

Tubes with heaters for series connection

180-mA heater current series

Improving efficiency and gain of output tubes

Power pentode

RES174d, RES164, L416D

1931

Simplified generation of an automatic gain control voltage

Diodes and twin diodes (combined multi-unit tubes)

REN924, AN4092

Automatic gain control for fading compensation

Screen-grid tubes with remote-cutoff characteristic

RENS1214, H4125D

1932

Improving RF amplification

Common usage of the pentode concept for RF amplifier tubes

RENS1264, H4111D

Larger audio power output

9-watt power pentodes

RES964, L496D

1933

Perfecting the superheterodyne converter stage

Hexode multiplicative mixer

RENS1224, X4122

More efficient gain control

Fading hexodes with dual control

RENS1234, X4123

1934

Gain control within the converter stage

Mixer tubes with remote-cutoff characteristic (triode-hexode or octode)

ACH1, AK1, BCH1

1935

Standardization of tube types

Introducing the "letter" series

A-, C-, E-series

Constructional improvements

New design methods - grid cap

AC2, AF7 etc.

Decreasing the heater warm-up time

Fast heating cathode

-

AC/DC operation

Special AC/DC tubes

C-series

Reduced heater power for simple AC/DC radios (VE301GW)

Econo-tubes with 50-mA heater current

V-series

Unified basing system

Aussenkontakt socket

A-, C-, V-series

Automobile radios for 6-volt and 12-volt starter battery operation

Special automobile tubes

E-series

More economical battery operation

Battery tubes with 2-volt filaments

K-series

Class-B push-pull amplifier with grid current driving

KDD1

1936

Sonic improvements

High-performance power tubes

AD1, AL4

1937

Tuning indication by shadow-angle control

Electron-ray tubes (Magic Eye)

AM2

Larger audio output for high-end radios

18-watt power pentode

AL5

1938

Uniform heater for AC, DC, and battery operation (automobile)

Tubes with 6.3-volt heater and 200-mA current consumption

E-section of Miniwatt series (red tubes)

Standardization to general-purpose usage and removal of unwanted side-effects

Tubes of the "harmonic" series with steel enclosures (metal types) and standard bases. Electrical improvements (gliding screen-grid voltage, forward automatic gain control, lower capacitances, input and noise characteristics etc.)

E-series with metal tubes

1939

Simplification of the medium-range superheterodyne receiver

Combined triode/power tetrode

ECL11

Improved tuning indication

Dual-range indicator tube

EM11

Reducing the heater power consumption of AC/DC radios

Special tubes of the "harmonic" series with 100-mA heater current

U-series with metal tubes

1940

Improving the short-wave performance by shorter electrode connections

Tubes with integrated glass bases

E- and U-series of the Miniwatt Loctal tubes

More economically battery-operated radios, circuit simplification and miniaturization

Metal tubes - using 1.2-volt filament batteries - based on the "harmonic" principles

D-series with metal tubes

Reducing the heater power consumption of AC/DC high-end radios

Completion of the U-series

UL12, UM11, UF11, UFM11

1945

Improving low-end radios at most economical power consumption

Completion of the V-series

VEL11

1946

Improving the selectivity of low-end radios by re-introduction of the small superheterodyne receiver

Completion of the V-series

VCH11

1947

Reducing the physical size, improving the VHF (FM) performance

Miniature tubes

E- and U-section of the Rimlock series

1949

Improving the small superheterodyne receiver (110/220 volts change-over switch and dial illumination)

Completion of the Miniwatt tubes by U-series types with 100-mA heater

UCH5, UF5, UF6, UBL3, UL2, UY4

Completing the U-section of the "harmonic" series

UEL11 und UY2