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FM transmitter Audioguru

Discussion in 'Circuit Simulation & PCB Design' started by rimEP, May 31, 2017.

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  1. rimEP

    rimEP New Member

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    Hello,
    I've been trying to simulate Audioguru's FM transmitter with Proteus then with LT spice but I have encountered numerous problems. First of all, this is my first try with LT spice. Secondly I can't find the LM2931a regulator. Also I don't know how to run the simulation because I always get a blank diagram as an output.
    I joined my draft on Lt spice and Audioguru's model picture to this message.
    I will be very grateful if you could help me.
     

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  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I do not have it working but some of the errors are fixed.
    I added a 5V and a 9V voltage(s)
    There was a resistor with out value.
    I fixed the two capacitors at 30pF.

    No time now. Maybe some one can make it work.
     

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  3. rimEP

    rimEP New Member

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    Thank you so much RonSimpson.
     
  4. dave

    Dave New Member

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  5. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    R5 is also wrong. (audio problem)
    I do not see any hint of RF. (rf problem)
     
  6. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Right click on each inductor.
    Clear all windows except inductance. 1nH The parallel resistance should be blank. The parallel cap should be 1pF or blank.
     
  7. rimEP

    rimEP New Member

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    like this ?
     

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  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The monsterous very high power inductors you used in your sim do nothing at very high radio frequencies. I made the inductors myself and they work perfectly.

    Here is my sim of the RF circuit with its parts tweaked to work the best:
     

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  9. rimEP

    rimEP New Member

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    I erased all the other values in my components. How can I define what other values to put?
     
  10. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Your TRAN command does not delay the start time to save data so the oscillator is not even oscillating yet when your sim stops. The oscillation is good after a start delay of about 4000ns, look at the TRAN command on my sim.

    Here is my TRAN command:
     

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