For elder teckies: what was the function of thermionic valves in early radio sets?

Answer 1

The are also called radio "tubes".

They functioned the same as transistors and integrated circuits do in todays radios. They amplify RF, IF, and audio signals, and they act as oscillators.

A triode valve is very similar, in electrical characteristics, to a field effect transistor (FET).

Even today there are audiophiles who think tube (valve) amplifiers are superior, in sound, to transistor amplifiers. Some of the best guitarists today still use tube (valve) amplifiers.

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Answer 2

Thermionic valves ranged from the simple thermionic diode used for rectification, detection of AM signals, etc., right through to multi grid devices which had many applications including power amplification. They all relied on a specially coated cathode which, when heated (directly or indirectly), produced electrons. These electrons were attracted towards another element called an anode. Except for the diode, the electron stream so produced could be influenced on its way to the anode by applying voltages/signals to further elements called grids. Valves were designated by the number of elements they had - e.g., the triode had three (cathode, control grid and anode). Thermionic valves were able to rectify, detect, amplify, act as oscillators, power 'drivers' in audio systems, etc.. The heart of a typical radar system was the magnetron, itself a special form of thermionic valve where the electron streams were influenced by a powerful external magnet system to increase the available energy. . So you can see that 'thermionics' was (still is!) quite a complex field of technology. Incidentally, the thermionic valve is still in use today in the form of the Cathode Ray Tube, in which a beam of electrons is deflected, focused and driven across a specially coated screen, in a specific way, to produce the picture. Despite the, by now, long history of transitorised and integrated circuit products, to many people the thermionic valve audio amplifier is a preferred choice because of its perceived purer reproduction. And the CRT still takes some beating when it comes watching a TV picture where there is a lot of fast movement. In case you are thinking of buying one, a thermionic valve pre and power amplifier set up can cost several thousand UKP/USD.

Answer 3

Early radio set would have used a simply diode valve to demodulate the am signal and a triode or two for amplification.
These tended to have an accumulator to run the heater circuits and a 100V battery for the anode voltage.

Valve based car radios, would have the heaters run from the car battery and the anode voltage derived from a vibrator/transformer arrangement.
These were usually positoned under the driver's seat - useful heating in the winter.

My father ran a radio shop and my mum still has many radio valves in the garage.

Answer 4

THe thermonic valve was made firstly as a rectifier valve. it consisted of a directly heated cathode a( filament in a light bulb) and an annode, it was found that when the cathode was heated electrons would cross the barrier to the annode, and since the annode was cooler the electrons were trapped on the annode, when the annode was given a positive charge this enhanced the flow, it was then dicovered that if a grid were placed in the path of this electron flow it could be used to control the magnitude of the electrons crossing this gap the valve had then started to become more sophisticated and many more layers were placed in the vicinity of the original electron flow with indirectly heated cathodes the falve was stating to become very complicated with ion trap magnets outside ect.

Answer 5

Different valves were usedfor different purposes. They detected and magnified radio signals and were used in both radio and television receivers. The original cathode ray tubes were a type of valve.They were replaced by transistors which in turn have been superceded by semi conductors.

Answer 6

To minimise the static effect of tasky pig spam product. I'm pretty sure that's the correct answer.

Answer 7

these were superceded by n.p.n transistors