| 摘要 |
PURPOSE:To prevent the drawing effect and erroneous tuning by operating the servo lock system only within a certain frequency ragne at the center of an accurate tuning point. CONSTITUTION:Electronic switch 17 is provided between DC amplifier 5 and local oscillator 6; and when the output of oscillation frequency f1 of crystal oscillator 12 whose integral multiple is equal to the transmission frequency of each broadcast station is applied to frequency converter 10 through high-frequency generation circuit 11, the beat frequency of the output frequency of local oscillator 6 and the higher harmonic of oscillation frequency f1 is obtained. These beat component have only components within a specific frequency band detected by BPF 13. When electronic switch 17 is closed by this detection signal, the servol lock system is operated to obtain automatically a correct tuning. |
