Frequency Modulated Oscillator (for FM Transmitter)

An oscillator can be built using LC (inductor-capacitor) tank circuit. When we vary the capacity of the capacitor in LC tank circuit then the frequency of the oscillator will vary according to capacitance change.  The idea of this modulator is by employing a varactor (voltage-dependent variable capacitor) in the LC tank circuitry. As the capacitance is controlled by a voltage level, then it can be controlled using audio signal from microphone. A signal from direct microphone output will be too small, so we need a pre-amp before feeding the signal to this circuit. This circuit assume a standard line level voltage for the input, so you can feed it with audio mixer, pre-amp, equalizer, or other various audio equipment.  We can use this circuit for FM wireless audio, microphone, other applications where a stable frequency modulated oscillator is needed. Just remember that this circuit is not a transmitter, so you’ll need an RF power amplifier to amplify the output in order to transmit via antenna. We can vary the LT to cover 75 to 150 MHz, as needed.

FREQUENCY MODULATED OSCILLATOR circuit schematic diagram

This entry was posted in RF and Video and tagged , , . Bookmark the permalink.,
Possibly Related to "Frequency Modulated Oscillator (for FM Transmitter)" Circuits

  • Two Transistors FM Transmitter
    Basically, this circuit is a radio frequency (RF) oscillator that operates around 100 MHz. The audio which is picked up and amplified by the electret microphone is fed into the audio amplifier stage built around the first transistor. Output from … Continue reading →...
  • Voltage Controlled Oscillator for Commercial FM Band
    VCO (voltage controlled oscillator) is an electronic signal generator which produce a signal that has variable frequency depends on a voltage level at its control input. Many VCO circuits are based on ramp generator to produce a variable frequency output, … Continue reading →...
  • PLL Oscillator for Medium Wave Frequency
    What is a PLL oscillator? PLL stands for phase locked loop, and this means a control method by comparation of the controlled plant or system to a reference clock or oscillator, that the plant is controlled to synchronize the clock. … Continue reading →...
  • 10 Hz to 10 Khz Voltage Controlled Oscillator
    Voltage-controlled oscillator (VCO)  is an oscillator that its frequency is controlled using a voltage signal.  The VCO described here provide both triangular and square wave output. The control voltage can be varied between 5 mV to 5 V, to produce … Continue reading →...
  • 567 IC Oscillator With Double Frequency Out
    Sometimes, a precise two different frequencies are needed in synchronized circuit design, one  with certain frequency and another with exactly double frequency. Usually we build two clock signals with frequency with 1:2 frequencies by feeding an oscillator into a binary … Continue reading →...

Comments are closed.