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


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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...

This site seems to suggest the use of the 555 timer in astable mode to generate frequency modulation from a source. The typical transmitter uses a tank circuit with an inductor and trimmer capacito...

This is the second article that gives assembly instructions for FM transmitter kit. ... This contributes to the FM transmission frequency. ... On the image below, you can see how I have connected t...

FM transmitters can be complicated to build, that's why I'm teaching you how to make a foolproof FM transmitter. There's no need ... Someone posted that same circuit more than 9 years ago on a foru...

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 is a simple wireless FM transmitter circuit which uses RF communication to transmit the medium or low power FM signal. Its maximum range is 2 km.