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FM transmitter WASP -oscillator working ,rf output stage not working

Discussion in 'Radio and Communications' started by savvej, Jan 14, 2012.

  1. savvej

    savvej Member

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    The FM transmitter circuit is from :
    http://talkingelectronics.com/projects/Wasp/Wasp-P1.html

    I build it on a PCB as is mentioned.I also built RF led power meter from :
    http://talkingelectronics.com/projects/Wasp/Wasp-P4.html

    I used it to check whether the oscillator section is working and the led of the meter light up at the collector of the transistor of the oscillator stage indicating that the oscillator is working.

    But I am getting no output from the 3rd transistor i.e. the rf output stage.
    I checked the transistor(2n2222A) and it is working.Also I checked the volatges as per given on troubleshooting page
    http://talkingelectronics.com/projects/Wasp/Wasp-P2.html
    and the voltages at the base is 0.62V and at the collector is 3.4V which I guess is okay if I consider a 5V supply.

    Also one more thing when I connect the RF led power meter at the base of this (output)transistor I am not getting any output.Neither at the emitter of the oscillator transistor am I getting any ac output..

    Should I connect instead of the emitter,the collector of the oscillator section to the rf output stage? or is there some other problem?

    Please help me.
    I heard that collin55 the author of this circuit is too a registered electro-tech-online user.I wish if he could comment on the same.
     
  2. colin55

    colin55 Well-Known Member

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    You have connected the transistor around the wrong way
     
  3. savvej

    savvej Member

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    I checked the transistor but it is connected correctly.Also I would like to emphasis(as was told earlier) that I am using 5V supply instead of 3V one.
     
  4. dave

    Dave New Member

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  5. savvej

    savvej Member

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    does the collector resistor need to be changed for a 5V supply?
     
  6. colin55

    colin55 Well-Known Member

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    no The transistor is ebc
     
  7. savvej

    savvej Member

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    Sir I agree that the transistor 2n2222A has pins ebc(with flat side facing towards me) and I had confirmed this by referring datasheet before inserting the transistor into the circuit.I even desoldered the transistor to check again if the transistor had not been damaged.But still I am getting no oscillations at the collector of it.
    Today I go 2N3563 (RF transistor) to replace 2N2222A with it.but it too did'nt help.Still am getting no output at its collector.
    Also as far as your LED power meter is concerned too I forgot to mention 1 thing.I am not using it with the multimeter.Just LED indication.Also I added a ground wire so that I can get better indication.Else the output shown is very less.
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi savvej,
    Ref your PM, if you want me to check this circuit in simulation as requested, please post your LTspice 'asc' file.
     
  9. colin55

    colin55 Well-Known Member

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    What is the RF on the collector of the oscillator?
     
  10. savvej

    savvej Member

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    Removed simulation file for avoiding confusion
     
    Last edited: Jan 15, 2012
  11. savvej

    savvej Member

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    @colin55 RF ? I dont have any oscilloscope. I am using your LED power meter only.
     
    Last edited: Jan 15, 2012
  12. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Sorry, those files are not compatible with LTspice.
     
  13. colin55

    colin55 Well-Known Member

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    Put the LED power meter on the colector of the RF stage.
    There is nothing more stupid than trying to simulate this circuit.
     
  14. savvej

    savvej Member

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    @colin55 Sir,I am trying to simulate just Collpitts oscillator(not related to problem I am facing) at much lower frequecnies(not high RF,to be precise 79.5Khz) using pspice alike software which is unable to oscillate in simulation.
     
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    It works as expected in an LTspice sim.
     
  16. savvej

    savvej Member

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    0.042V at the collector of RF stage and 2V at the collector of oscillator stage(reading from multimeter after connecting led power meter to it).
     
  17. savvej

    savvej Member

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    thnx at Erric sir for verifying.Wanted to ask whether you used ideal inductor there? or did you simulate considering its resistance?
     
  18. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    The circuit will oscillate providing that the resistance of the inductor is <=1R
     
  19. savvej

    savvej Member

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    @ erric Sir could you plot the output at the collector of the oscillator and collector of the RF output transistor both on the same graph?
     
    Last edited: Jan 15, 2012
  20. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    look here.

    Please do not use PM's for technical queries.
     
    Last edited: Jan 15, 2012
  21. savvej

    savvej Member

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    So why is the last stage anyways? Is'nt it reducing the output instead of amplifying it?Please correct me if I am wrong.
     
    Last edited: Jan 15, 2012

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