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FM Transmitter Circuits

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In a frequency modulation (FM) transmitter, it is added by varying the radio signal's frequency slightly. Many other types of modulation are used.

In an FM (frequency modulation) transmitter the frequency of the carrier is varied by the audio signal. Angle modulation is the proper term for modulation by changing the instantaneous frequency or phase of the carrier signal. FM transmitters can be stereo as well and using a PLL tunning circuit you can achive a stable audio transmition on FM band.
 
True FM and phase modulation are the most commonly employed forms of analogue angle modulation. Direct FM (true Frequency modulation) is where the frequency of an oscillator is altered to impose the modulation upon the carrier wave. This can be done by using a voltage-controlled capacitor (Varicap diode) in a crystal-controlled oscillator or frequency synthesiser.
The frequency of the oscillator is then multiplied up using a frequency multiplier stage, or is translated upwards using a mixing stage, to the output frequency of the transmitter.
 
 In some indirect FM solid state circuits, an RF drive is applied to the base of a transistor. The tank circuit (LC), connected to the collector via a capacitor, contains a pair of varicap diodes. As the voltage applied to the varicaps is changed, the phase shift of the output will change.
 

Circuits




When I was 8, I came across Art Swan's FM transmitter circuit. At the time I had no idea of where I'm supposed to buy the parts, so I recycled mine out of junk. I guess the biggest struggle that yo...

The FM transmitter circuit itself is based off one of [Art Swan]'s builds, but instead of the solderless breadboard construction you would expect to find in a small demo circuit, [Angelo] went all ...

Frequency modulation FM transmitter circuit diagram using simple transistors FM modulator electronic design construction audio transmitter schematic circuit.

You can also place the transmitter circuit close to any loud speaker so that the microphone picks up the sound and transmits to the tuned FM radio. WATCH THE EXPERIMENT VIDEO ON YOUTUBE · FM transm...

This circuit is a simple two transistor (2N2222) FM transmitter. No license is required for this transmitter according to FCC regulations regarding wireless microphones. If powered by a 9 volt batt...

The circuit itself is a slight variation on Kogawa's simplest FM transmitter design, and the method of building it is sometimes referred to as Manhattan style. It uses a piece of copper-clad circui...


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