FM RECEIVER FOR RECEPTION OF SPECIAL ANNOUNCEMENTS AND GENERAL PROGRAMS

摘要

The VHF receiver has a detector for a 57KHZ AM subcarrier and an AM modulator for the same subcarrier. The subcarrier's AM modulation controls switches in the LF stage. A first device measures the degree of AM modulation by an area ident. signal. The first device produces a control signal for the switches when the percentage modulation by the area ident. signal drops significanty from a given value. The control signal drops significantly from a given value. The control signal persists for the duration of the drop. The drop is 50 percent of the given value. Other drops and limits are possible. The detector is followed by an AGC amplifier and filter.