| 摘要 |
PURPOSE:To eliminate a changeover switch for paths of AM/FM signals, by making use of the characteristics of a ceramic filter. CONSTITUTION:For the characteristics of ceramic filters CFA and CFB, the CFA for FM waves functions as a capacitor of about 20PFD to a 455kHz AM intermediate frequency. While the CFB for AM waves functions as a capacitor of about 200PFD to a 10.7Hz FM intermediate freqyency. Therefore a circuit shown in the figure (A) has constitution shown in the figure (B) when it receives FM waves and then constitution shown in the figure (C) during reception of AM waves, respectively. Then a resistance R1 is provided between the output terminal of the CFB and a terminal No.3 to eliminate a switch. |
