Adaptation of radio receiver sensitivity to the antenna noise value

If an electronically-controlled wide-band linear attenuator is connected between the input circuits and the anntenna, changes in its transmission coefficient will alter the sensitivity of the receiver and the level of useful signal and noise. Methods of automatic production of a control signal by the attenuator are considered. If the control signal depends only on the useful signal, the result is an automatic volume control system. If the control signal depends on the noise produced by detection of the input, the result is an automatic sensitivity control system, which depends on the quantity of incoming noise. The automatic control system is useful with small signal-to-noise ratios.