Notes on Grid-Circuit Detection

A dynamic method of finding ∂²ig/∂eg²or ∂kg/∂eg, the main term in grid-circuit rectification, is given. This method is based upon formulas given by Chaffee and Browning and consists in calculating ∂kg/∂egfrom the change of d.c. when a known a.c. input voltage is applied to the grid. The values of ∂kg/∂egfound by the dynamic method are compared with the values found by the usual method. The effect of frequency, internal grid resistance, and external resistance on the detection voltage introduced in the plate circuit are also considered. An experimentally determined curve is given showing the detector frequency distortion of a commercial set for a 2-megohm grid leak and for a ½-megohm grid leak.