Compared with the situation immediately preceding the Second World War, the overall picture by 1945 was that of much greater diversification. Highly specialised, costly devices, capable of generating extremely high powers, existed at one end of the spectrum, and mass-produced low-cost miniature receiving valves at the other. It was in the latter area that semiconductor diodes had established themselves at the expense of the thermionic valve, as a detector of microwave frequencies. Later developments, involving the transistor, have since almost entirely replaced the vacuum tube as a low-power, low cost mass produced device. It has not however been possible to replace the specialised high-power high-frequency transmitting devices, such as the klystron, magnetron and travelling-wave tube by any solid-state equivalent.

Inspec keywords: thermionic tubes; travelling wave tubes; microwave frequency convertors; klystrons; semiconductor diodes; magnetrons; low-power electronics

Other keywords: thermionic valve; miniature receiving valves; low cost mass produced device; transistor; microwave frequency detector; low-power device; travelling-wave tube; klystron; semiconductor diodes; magnetron

Subjects: Vacuum tubes