On Measurement of Signal Strength

The "shunted telephone" method of measuring audibility of received signals is discussed, and it is shown that the audibility factor as usually calculated, may vary widely from the true strength ratio. This is true whether shunted resistance or shunted impedance is taken as the basis of calculation. The author then determines the radio quantity corresponding to any determined audibility factor or strength ratio. This is of importance in connection with quantitative measurements on long distance transmission. An alternative comparison method of measuring incoming signal strength is described, wherein the antenna may be excited from a local buzzer of adjustable pitch and having an independent contact for the antenna "impulsing circuit." This method is regarded as more accurate than the usual one. Sustained waves should be used for transmission experiments, and these may be received, heterodyned, rectified, amplified, and measured quantitatively by a vibration galvanometer.