Detection Characteristics of Screen-Grid and Space-Charge-Grid Tubes

This paper reports the results of measurements made to determine the grid-leak grid-condenser detection properties of screen-grid and space-charge-grid tubes. It is found that the rectifying properties of the grid circuit for the four-element tube used in these ways is about the same in character and magnitude as in three-element tubes with the same type of filament. The rectifying action in the grid circuit is largely independent of the voltages of the filament, plate, and second grid when compared at the same grid resistance. The space-charge-grid leak-condenser detector is superior to the screen-grid and most three-element grid leak-condenser detectors in that the space-charge-grid tube retains its full rectifying powers at adjustments which give full reproduction of the high notes. Grid detection with four-element tubes is superior or inferior to grid detection with three-element tubes primarily to the extent that audio-frequency amplification is more or less satisfactory in the two cases.