| 摘要 |
PURPOSE:To enhance the degree of separation between the signal and noise and thus to cut off the noise completely by putting the transistor for ON-OFF use into the parallel resonance circuit in order to vary the resonance frequency within the receiver when the noise is mixed up. CONSTITUTION:Secondary side coil L2 of input side transformer (a) forms the resonance circuit along with tuning capacitor C2, and transistor Q2 is connected in series between L2 and C2. In the same way, primary side coil L3 of output side transformer (b) forms the resonance circuit with tuning capacitor C3, and transistor Q3 is connected between L3 and C3. The base bias of transistor Q2 and Q3 is controlled by the presence or absence of the noise mixture to the receiver to be turned off and on with presence and absece of the noise respectively. At the OFF time, the resonance frequency of the resonance circuit is increase up to an extremely high level by the capacity amount of the OFF region, and thus the signal is attenuated completely. |
