# fm transmitter colpitt oscillator

Posted on Feb 5, 2014

C1 takes the DC decoupled voltage from the Microphone, amplifies this via Q1, C2 decouples it again, then R6 and C3 Low Pass Filter it, but once we get to Q2, Secondly how does this circut actually accomplish frequency modulation: Please use math on me! (I know that it should change the delta F term in the equation cos(2*pi*fc*t + F) to achieve FM, or more

correctly: cos(2*pi*fc*t + f* «(messageSignal) Frequency deviation is accomplished by changes to the base voltage. This affects the Base-Collector capacitance. The tuned circuit is also changed when anything gets near the antenna and of course it drifts as the battery wears down. My goal is just to build a simple transistor level FM transmitter for my own amusement. More of an exercise on what I`ve learned as an engineer because I want my masters degree to be in Communications Systems and Signal Processing Edit: My bad, we were discussing a different transmitter in that thread, but some of the discussion might still be useful. I have an article on your transmitter, but I can`t find it right now. If I run across it, I`ll post. My goal is just to build a simple transistor level FM transmitter for my own amusement. More of an exercise on what I`ve learned as an engineer because I want my masters degree to be in Communications Systems and Signal Processing Do your self a favour and analyse the circuit of a REAL FM transmitter, one which has a defined, stable frequency, one which has sensible coupling to a defined antenna and harmonic supression filters. Could you provide me with places that have such clearly explained and defined schematics It becomes rather difficult to find such high level designs. I would really rather work at the transistor level (i. e. , no OPAMPs or ICs, including multipliers)

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