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FM transmitter

Discussion in 'Electrical Engineering' started by Adam M, Nov 17, 2003.

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  1. Adam M

    Adam M Guest

    Hi guys,

    My neighbors and I are going to be having a joint flat party. In order to
    keep the music the same throughout, I want to hook up an FM Tx to my PC, and
    tune in both of our Hi-Fis. (I realise this is technically illegal, but I'm
    going to keep the Tx power right down).

    I have an old wireless kit for a guitar which operates at 174.1MHz which I
    want to adapt for the job.

    I've photographed the PCB inside it:

    I have two questions:

    1. Can anyone tell me if this is already a stereo FM transmitter? I couldn't
    quite work the circuit out. (the ICs are a compressor/limiter type thing and
    an RF op-amp package). I see that there are 4 wires on the input (red,
    white, yellow, black) which would suggest stereo.

    2. How should I go about re-assigning the frequency? The crystal osc is
    14.198MHz (how come it broadcasts at 174.1MHz?!). Should I swap for another
    crystal? Or am I better to swap some inductors/capacitors? Incidentally, I
    tried tuning a few of the tunable inductors and caps, but there's not
    sufficient movement to get it to a frequency I can recieve on a stereo.

    I'm aiming for somewhere around 100MHz.

    Thanks in advance!!

  2. Ryan Breai

    Ryan Breai Guest

    "Pratt" is spelt, "P","r","a","t","t", and not, "p","i","r","a","t","e".
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