Circuit Mini FM transmitter – video assembly instructions

Circuit Mini FM transmitter – video assembly instructions


Instructions, how to build a mini station from cheapest simplest components. Either frequency, modulation, FM (frequency modulation), sends the component values ​​at around 100 MHz Mini Transmitter Instruction Building a super spy bug transmitter.

The 20k resistors together with the resistance of the condenser microphone sets a voltage divider composed of the (dc) operating point of the transistor. Since the resistance of the microphone capsule to the beat changes of the sound waves, does this change and the operating point of the transistor, or in other words, the transistor amplifies the low-frequency voltage to the (electret) microphone comes in a common emitter circuit, the low-frequency signal is at the base and is amplified by the transistor.

Simultaneously, the transistor amplifies the RF signal but also in basic circuit. A small portion of the vibration of the oscillator circuit from the collector (amplifier output) on the 5.6 pF capacitor to the emitter (high-frequency amplifier input of the base) is fed back, the drive current Fliest from the emitter to the base and then 3.3 on the nF capacitor to ground. The capacitor on the basis of mass must be small enough that it does not hinder the low-frequency audio signal, but also large enough that the high-frequency, virtually unhindered tiles to ground. The 470 ohm resistor at the emitter stabilizes the operating point and sets the input resistance of the base circuit.

The whole thing is rather something like an emitter circuit audio amplifier circuit combined with a basic high-frequency amplifier with only one transistor.

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