Receiver with Automatic Selectivity Control Responsive to Interference

The selectivity requirements of a broadcast receiver that must be met in order for it to perform satisfactorily under service conditions are discussed. A superheterodyne receiver is described that has its selectivity controlled automatically to meet these requirements. It has intermediate-frequency selectors in which vacuum tubes are used to adjust the coupling between tuned circuits to effect adjustment of the selectivity. The tubes are controlled by signal-derived potentials so that the band width increases in accordance with the strength of the desired signal and decreases in response to undesired signals on adjacent channels. As a result, the selectivity and the fidelity of the receiver are maintained at optimum under all conditions of signal strength and interference.