As C4 begins to charge the amount of current flowing through C4 reduces which results in less current flowing through R2. This increase in voltage on the emitter therefore results in a smaller value of Vbe and this reduction in Vbe reduces the conduction of Q1. Current flowing through R2 will result in a voltage drop across R2 and since R2 is connected to the emitter of Q1, the same voltage will be present on the emitter of Q1. This rush of current will also pass through C4 via capacitive coupling which will result in current flowing through R2. When power is applied to the circuit, a rush of current flows through the inductor. The oscillator consists of C2, L1, C4 and R2 with the frequency of oscillation being determined by C2 and L1 only. The next stage is the modulation/oscillation stage which provides a carrier signal which is then modulated by the input signal. R1 provides biasing for the transistor by feeding a small amount of current into the base (which prevents the transistor from turning off). C3 is used to couple the input signal so that no DC component is fed into the transmitter. Input signals into the FM transmitter must not contain a DC component as it would adversely affect the modulation/oscillation stage (by saturating the transistor) and therefore no FM signal would be generated. The input stage consists of capacitors C3 and C1, and resistor R1. The circuit has three main stages, the input stage, the modulation stage, and the output.
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