question about fm transmitter

Discussion in 'Wireless & RF Design' started by tedduz, Sep 22, 2009.

  1. tedduz

    Thread Starter New Member

    Aug 31, 2008
    3
    0
    will it make any diffrence if i use the 2n4401 transistor instead of the 2n3904 that was specified in the circuit that i am trying to build?
    where i bought the transistors i was told that the 2n4401 will work, but i am not sure . i have built the circuit three times and it does not work

    or could it be the inductor , i used a 22 gauge wire not the magnetic type . do i have to remove the insulator from the wire or just leave it. I am getting fustrated need help

    thanks!!
     
  2. flat5

    Active Member

    Nov 13, 2008
    403
    17
    Are you building on a breadboard or on a printed circuit board?
    A breadboard will be unreliable for high frequency circuits.
    Use a copper board and very short connections with a good layout of components.
     
  3. tedduz

    Thread Starter New Member

    Aug 31, 2008
    3
    0
    yes it is on pcb,
     
  4. flat5

    Active Member

    Nov 13, 2008
    403
    17
    Download the data sheets for the two transistors.
    Compare them.

    Using a different wire size will change the frequency expected for a given number of turns.

    You say it does not work. That is too vague to give more advice.
    Do you mean the circuit is off frequency? Does not oscillate?

    Can you attach a clear circuit diagram for us to see what you have built?
     
  5. tedduz

    Thread Starter New Member

    Aug 31, 2008
    3
    0
    update

    the circuit does work, however the transmitting distance is very poor and very unstable
    i will have to place my radio very close to the circuit one foot.
    it transmits at 94.5 fm .when i connect the 9v battery, i will have to move the battery around the circuit for it to transmit without distortion
    how can i improve it

    this is the link

    http://www.reconnsworld.com/transmit/fm_trasm.gif

    thanks
     
  6. aj_silverthunder

    Active Member

    Jun 6, 2009
    116
    0
    check this transmitter,it may help u
     
  7. aj_silverthunder

    Active Member

    Jun 6, 2009
    116
    0
    here is the schematic
     
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