| 摘要 |
PURPOSE:To prevent a cross modulation under a strong electric field and a malfunction caused by suppressing the sensitivity, by controlling the attenuation quantity of an attenuator which is provided on a radio control use receiver, by a sub-circuit of other system. CONSTITUTION:Under a strong electric field in which across modulation is generated, an amplification by an FET Q3 and a transistor TR Q4 is executed in order to control an object signal. A detecting output is supplied to an attenuator 6 from a collector of a PNP TR Q5, and a forward voltage is generated by diodes D1, D2 for constituting the attenuator 6 through a resistance R. When the forward voltage exceeds a value corresponding to a forward on-voltage of about 0.5V, the diodes D1, D2 become a conducting state, and a high frequency current flows to an earth or a power source side through both the diodes D1, D2 and is attenuated. Capacitors C1, C2 have a small capacity of 2-5pf, therefore, a bad influence caused by coupling of each of a tuning circuit T1 and a matching transformer T2 is prevented, and also an attenuation effect can be increased. |
