Triode amplification factors

The theoretical formulae for the amplification factor of a triode given by Ollendorf [Abstr. 1935B00675], Herne [Abstr. 1944B00986], Vogdes and Elder [Abstr. 1924A00929] are checked experimentally for the special cases of thick grid wires and of small grid-anode distance. The comparison is carried out in an experimental valve with variable electrode distances in the first case and by means of the rubber sheet method in the second case. Ollendorf's formulae give the greatest accuracy. Tables for the practical use of these formulae are given.