CONTROLLING DEVICE FOR TRANSMITTED OUTPUT

PURPOSE:To stabilize a transmitted output by stopping the control operation until the reflected wave electric power reaches to a prescribed level. CONSTITUTION:Emitters of transistors (TRs) 9a, 9b constituting a differential amplifier are connected to an emitter resistance 10 in common. Since the base voltage Ea of TR9a rises accompanied with the increment of travelling wave electric power, the collector potential of the TR9a rises and a TR1 is controlled in the cutoff direction. Consequently, power voltage to be applied to a transmitter drops and transmission electric power is supressed. On the other hand, when reflected wave electric power increases and reaches the Zener voltage Ez of a Zener diode 13, the diode 13 is connected and a TR14 is also connected. Accompanied with the connection, the TR9b is cut off and the TR1 is interrupted. Thus, the transmitter can be protected from damage due to the reflected wave electric power.