Detecting Characteristics of Electron Tubes

It is pointed out that owing to the progress of the radio art the opinions heretofore held as to the importance of the part played by detector efficiency in a receiving set are in need of revision. Taking the well-known analysis of the operation of a detector tube with condenser and grid leak, curves are derived from the static characteristics of a typical general purpose tube showing the performance of the tube as a detector under certain conditions of operation. A method is described of measuring the output of a detector tube with a standard incoming signal, and experimental results obtained with the tube used for deriving the curves are compared with those obtained from theoretical considerations, showing that the method can be used to give a true picture of the effect on detector efficiency of variations in operating conditions. Sample curves are given, showing the wide variations obtained in the efficiency of certain types of standard tubes by relatively slight changes from the customary operating conditions, and also the variations in efficiency of a number of similar tubes under normal operating conditions.