Functional Features of Gas-Filled Tube Triodes of the 20s of the XX Century

In the early 20s of the 20th centuries, a need arose for a radio tube that would have high sensitivity without the use of regeneration. To this end, a number of scientists conducted experimental studies on the influence of gaseous media on the functioning of a tube triode as a detector. Tubes of this type are called \u201csoft tubes\u201d and are often used in the detector stages of radio receivers. The work shows that after a large number of experiments with different gases, it was found that the result can be achieved if vapors of easily evaporating metals are used in tubes instead of gases. In this case, it is necessary to provide a gaseous environment in the tube with an extremely low ionizing potential. This allows the tube to effectively function as a detector with a minimum anode voltage of 8 V to 10 V. An alloy of sodium and potassium turned out to be a suitable medium for such detectors.