Selective signal tuning device

Claim 2

In a radio receiver having an input circuit of adjustable reactance and providing an output in the form of a subcarrier characterized by an off-channel direct current component; a selective signal tuning device, comprising, mechanical means for adjusting the reactance of the input circuit of the receiver, a magnetic clutch having an output element and an input element, said output element being connected to said reactance adjusting means, a tuning control connected to said input element for adjusting said input reactance when said clutch is energized, a first filter receiving said receiver output including said direct current component and adapted to reject the band of frequencies therefrom constituting the subcarrier signal, a second filter receiving said receiver output and adapted to pass the band of frequencies constituting the subcarrier thereof and rejecting the direct current component, means for determining the average output of said first filter, means for comparing the magnitude of the average output of said first filter including said direct current component with the output of said second filter, and means controllable by said comparing means for deenergizing said clutch to arrest adjustment of the reactance of said input circuit whenever the output of said second filter exceeds the average output of said first filter, whereby said receiver is tuned to provide an output constituted by the frequencies passed by said second filter.

Claim 3

In a tunable frequency modulation radio receiver having an input circuit of adjustable reactance and providing an output in the from a subcarrier characterized by an off-channel direct current component; a selective signal tuning device, comprising, mechanical means for adjusting the reactance of the input circuit of the receiver, a magnetic clutch having an output element and an input element, said output element being connected to said reactance adjusting means, a tuning control connected to said input element for adjusting said input reactance when a magnetizing current is applied to said clutch, a first filter receiving said receiver output and adapted to pass outputs having frequencies extending from direct current to a relatively high frequency except the band of frequencies constituting the subcarrier which are rejected, a second filter receiving said receiver output and adapted to reject all outputs except those within the band of frequencies constituting the subcarrier, a first amplifier including rectifying means for amplifying and rectifying the output of said first filter, a second amplifier including rectifying means for amplifying and rectifying the output of said second filter, a difference network receiving the outputs of said first and second amplifier and providing a signal having a first polarity whenever the output of said first amplifier exceeds the output of said second amplifier and providing an opposite polarity whenever the output of said second amplifier exceeds the output of said first amplifier, and a multivibrator adapted to apply magnetizing current to said clutch in accordance with the polarity and the output of said difference network, said multivibrator being adapted to magnetize said clutch whenever the output of said first amplifier exceeds the output of said second amplifier, whereby the receiver is tuned to provide an output constituted by the frequencies passed by said second filter.

Claim 4

In a tunable frequency modulation radio receiver having an input circuit of adjustable reactance and providing an output in the from a subcarrier characterized by an off-channel direct current component; a selective signal tuning device, comprising, mechanical means for adjusting the reactance of the input circuit of the receiver, a magnetic clutch having an output element and an input element, said output element being connected to said reactance adjusting means, a tuning control connected to said input element for adjusting said input reactance when a magnetizing current is applied to said clutch, a first filter receiving said receiver output and adapted to pass outputs having frequencies extending from direct current to a relatively high frequency except the band of frequencies constituting the subcarrier which are rejected, a second filter receiving said receiver output and adapted to reject all outputs except those within the band of frequencies constituting the subcarrier, a first amplifier including rectifying means for amplifying and rectifying the output of said first filter, a second amplifier including rectifying means for amplifying and rectifying the output of said second filter, a difference network receiving the outputs of said first and second amplifier and providing a signal having a first polarity whenever the output of said first amplifier exceeds the output of said second amplifier and providing an opposite polarity whenever the output of said second amplifier exceeds the output of said first amplifier, and a multivibrator adapted to apply magnetizing current to said clutch in accordance with the polarity and the output of said difference network, said multivibrator being adapted to magnetize said clutch whenever the output of said first amplifier exceeds the output of said second amplifier, whereby the receiver is tuned to provide an output constituted by the frequencies passed by said second filter.