History of Vacuum Tube / Thermionic Valve

The history of the vacuum tube or thermionic valve from the first observations of the Edison Effect through early developments such as Fleming's Oscillation Valve and de Forest's Audion.

History of the Valve / Tube Includes:
History overview     Early discoveries     Fleming's oscillation valve     de Forest's Audion     Development of the basic idea     R-type valve     6L6 valve    

The vacuum tube or thermionic valve brought the dawn of the age of electronics. Its invention enabled the wireless technology of the day to move forward.

The history of the vacuum tube or thermionic valve brings many individual discoveries together that enable the invention to be made.

The history of the thermionic valve also moves on to tell of the further developments that were made.

All these individual elements take their place in the overall history of the thermionic valve or vacuum tube.

Image of an early valve from around 1910 - 1920 - possibly an R-type valve / tube.
Early Valve - possibly from around 1910

Valve history summary

During its history the vacuum tube or thermionic valve has played a pivotal role in many historical events and its invention has changed the way of everyday life.

Although the valve was first invented in 1904, and it was not widely used until the 1910s, the valve has been pivotal in laying the foundations of what we call electronics technology today. Radio technology, telecommunications, and many other areas all embraced the new thermionic technology, laying the basic foundations of many areas of technology that are taken for granted today.

As the need to valves / tubes grew, so did the requirements for their performance. To meet these needs operation at higher frequencies was needed along with higher levels of stability, gain and predictability.

A greater understanding of the physics behind the way in which these thermionic valves / vacuum tubes worked enabled much greater levels of performance to be achieved. As a result of this understanding, the performance of the valves improved and this enabled them to provide far higher levels of performance which in turn lead to their more widespread use.

Initially valves were expensive and only used in very small quantities. As an indication of this growth figures from the RCA company show that they sold about 1.25 million receiving valves or tubes in 1922 but by 1924 this has risen to 11.35 million.

Some of the key issues with valves that prevented their adoption were not only the cost of buying them, but the cost of running them. Early valves used directly heated cathodes and as a result required batteries to runt hem. Once indirectly heated valves were developed, this opened up their use considerably and they were more widely used in radios. In addition to this the superheterodyne radio required more valves to be used than the equivalent tuned radio frequency receivers started to be used around the late 1920s and early 1930s because of their superior performance. As these receivers were sued for domestic radios, the requirement for valves rose even more.

The outbreak of World War 2 was a key point in thermionic valve history. These devices came into their own as they were needed for electronic equipment of all sorts from radio receivers to transmitters, radar sets, electronic warfare equipment, telecommunications repeaters and much more.

During this period, valves were produced in vast quantities on both sides.

After the war, new requirements were placed on valves and the valve history or vacuum tube history shows that there was a major move towards miniaturisation. Early valves and their equipment were large. Now smaller equipment was needed and as a result smaller valves were produced.

However with the invention of the transistor in 1949, and its ultimate commercial use, the transistor was smaller, more reliable and consumed less power. Although initially they were not cheaper than valves, the prices soon fell leaving valves only used in some areas where their performance was superior. However as transistor and FET performance improved, there were very few areas were thermionic valve technology was superior to that of transistors. Accordingly the valve history shows that their use fell away sharply in the 1960s and by the 1970s very few valves were used.

Valve technology

Thermionic valve or vacuum tube technology developed to enable considerable degrees of functionality to be introduced into radio receivers and then the wider field of electronics.

Note on Vacuum Tube Technology:

Vacuum tubes or thermionic valves are based around the concept of thermionic emission. Using two electrodes enables diodes to be made that can rectify signals - further electrodes can be added to enable amplifiers to be made and other applications fulfilled.

Read more about Vacuum Tube Technology

Valve history timeline

There are some key dates in the development of the thermionic valve or vacuum tube. These dates are tabulated in a valve history timeline below:

Valve history timeline
Date Event
1640 Otto von Guericke first produces an air pump that is able to create a partial vacuum. A vacuum was required for the operation of thermionic valves.
1858 Julius Plucker demonstrates that magnetic fields can bend rays of what are later called cathode rays
1860 Joseph Swann patents the carbon filament lamp
1871 Sir William Crookes deduces that cathode rays consist of negatively charged particles.
1879 Thomas Edison files a US patent for a high vacuum incandescent lamp using a carbon filament
1883 Thomas Edison observes thermionic emission in a vacuum.
1883 Professor John Ambrose Fleming of University College London, presents a paper to the Physical Society on the 'Molecular Shadow.'
1885 Sir William Preece replicates the Edison effect and makes measurements, presenting a paper to the Royal Society.
1897 Guglielmo Marconi sets up his Wireless telegraph and Signal Company to exploit radio or 'wireless' technology.
1900 Ambrose Fleming becomes a consultant to Marconi.
1901 Marconi makes the first transatlantic radio transmission, but difficulties were encountered with detecting he signals
1904 Ambrose Fleming rectifies wireless signals using what he terms his oscillation valve - this is the first time the Edison effect has been used. It was a simple diode valve and sometimes referred to as a Fleming Diode.
1904 On 16 November 1904 Ambrose Fleming applies for a patent for his oscillation valve.
1906 Having undertaken many experiments, Lee de Forest in the USA adds a third electrode to Fleming's diode to produce what he termed his Audion. This device was still only used for rectification.
1908 Ambrose Fleming replaces the carbon filament normally used in the diode valve with a tungsten filament.
1912 Lee de Forest makes the first valve amplifier.
1915 In France the first hard vacuum triode was made. It was called the Type TM and during the second World War over 100,000 of them were manufactured.
1916 British equivalent of Type TM valve started manufacture - it was known as the R-Type valve.
1920 Capt. S R Mullard forms the Mullard Radio Valve Co. Ltd. This was to become a major manufacturer of valves and then transistors.
1920 Thoriated tungsten filament for valves / vacuum tubes developed by Irving Langmuir
1927 The first valve with a screen grid starts manufacture - the S625.
1936 The International Octal, or just octal base was introduced by RCA.
1938 Mazda introduce Mazda Octal valve base as competition to the International Octal base
1939 The Loctal base (B8B) valve base or tube socket was introduced in USA
1939 Philips introduce an all glass valve / tube with the B9G base.
1939 The B7G valve base introduced in the USA for use with all-glass vacuum tubes.

Image a selection of vacuum tubes / thermionic valves including R-type, 6L6, ECC83, 6CL6, etc

The valve history of tube history shows many improvements and developments are made to the basic concept. Over the years the performance the this technology improved beyond all recognition. Many different people each played their part in the history of the valve.

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