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 θ
1
are described, and results are given. These measurements indicate that, for small values of θ
1
(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 θ
1
, 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 θ
1
, 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.