Sensitivity Controls-Manual and Automatic

Control of sensitivity is a problem that must go hand in hand with improvement in sensitivity. A highly sensitive receiver requires a total attenuation of as much as 160 db. Of this 80 db may be called "sensitivity control" which is that portion of control that permits a one-volt carrier to be received without demodulator overload. The remaining 80 db may be called "level control" with which the loud speaker response is attenuated to the proper level. The various basic manual control methods are discussed. Generally, manual control is accomplished in one or both of two ways; viz., 1. Attenuate r-f input. 2. Alter vacuum tubes' characteristics. The requirements for an ideal automatic sensitivity control are set down and the various basic systems discussed. High carrier level demodulator distortion as it affects certain systems is pointed out.