Peltz Oscillator FM Transmitter

426

08:12:13

A simple LC oscillator that produces an ~90Mhz sinusoidal wave using relatively few components. Although the simulated circuit is a bit erratic and the values of the inductor and capacitor likely do not align with real world values, this circuit can be used to produce FM carrier waves that you can modulate by varying the capacitor's capacitance using a varactor diode to transmit an audio signal for example. 

published 7 years ago

hurz

7 years ago

2pF with 10nH is good for 1.1GHz reaonance. But if the cap is increased it does even speedup in oscillation. It does even run without this 2pF capacitor. It looks more like an RL relaxation oscillator and not a harmonic LC one. I wont use it as oscillator for a FM transmitter

hurz

7 years ago

here a finetuned version to run as harmonic oscillator http://everycircuit.com/circuit/4558664401420288

Sheen140

7 years ago

@hurz Yeah I really just spitballed the values for the capacitor and inductor and clearly that came back to bite me! If I recall correctly there is an equation to predict the resonant frequency of an lc tank circuit using the capacitance and inductance values, did you use an equation when you made the fine tuned (ie correct) version of a peltz harmonic Oscillator?

hurz

7 years ago

No, cuz i still remember the LC values for a simple FM oscillator

Sheen140

7 years ago

Also you putting that 110Mhz AC source in the bottom there (not connected to the circuit) is that another trick to get the simulation timing to focus in on the oscillation of the main circuit?

hurz

7 years ago

it helps to get a quicker result, cuz it uses in presence of an ac source a higher oversampling, which you without it just get with a slow simspeed setup

hurz

7 years ago

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