| 摘要 |
PURPOSE:To attain small sized and low cost tuner by providing two local oscillating circuits changed over and driven selectively in response to the reception system to use circuits in common other than a local oscillating circuit. CONSTITUTION:The local oscillating circuit 3 is used for the reception of the 1st system, the local oscillating circuit 3' is used for the reception of the 2nd system different from the 1st system, and any one of both the circuits 3, 3' is driven in response to the reception system for the case. Center conductors L10, L10' for tuning of each circuit are arranged closely around a conductor L8 for coupling a mixer circuit 2 symmetrically and either conductor is driven with proper changeover in response to the reception system. Thus, it is possible for other circuits such as RF amplifier circuit and mixer circuit in common use for both the systems and it is not required to prepare tuners for the number of the reception systems, thereby attaining small size and low cost. |
