| 摘要 |
In the tuner for the UHF and VHF ranges, a self-oscillating mixer stage is provided for the high frequency range, whilst a separate, externally controlled mixer stage is used for the lower frequency range or ranges. To simplify the circuit and use of the necessary circuit components more efficiently, the self-oscillating mixer stage is switched over to operate as an oscillator for operation in the lower frequency range. For this purpose, an additional inductance 13, 14, 15 is switched into a resonant circuit 7 for the UHF range by means of a switch 23 and reduces the resonant frequency by the required amount. In addition, additional feedback is obtained for the lower frequency range or ranges by at least one additional feedback loop 26, 30 and a switch 27, 31 provided in the loop, enabling the oscillator to oscillate reliably. <IMAGE> |
