Transadmittance and Input Conductance of a Lighthouse Triode at 3000 Megacycles

Measurement of the transadmittance and input conductance of a lighthouse triode at 3000 Mc. as a function of the cathode-to-grid transit angle θ1are described, and results are given. These measurements indicate that, for small values of θ1(that is, for close spacings and high current densities), transadmittances of 50 to 70 per cent of the low-frequency values can be obtained even with relatively coarse grids. On such tubes, however, the input conductance is about two to three times as high as might be expected. When θ1, becomes of the order of 10 radians, the transadmittance falls to about 20 per cent of its low-frequency value. The input conductance falls off considerably for large θ1, but there is no indication of negative input conductance. A discussion is given of the conspicuous discrepancy between the experimental results and the results predicted for an "ideal" tube.