FM transmitter

Discussion in 'The Projects Forum' started by MusicTech, Jan 4, 2010.

  1. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
    Hey guys, first time posting in a while.

    Anyway... I found this really cool FM transmitter project:
    Quite simply it doesn't work. I checked my breadboarding many times, and I can get any signal to my FM receiver right next to me. I think is has something to do with the small coils relative to capacitance. With that in mind, I was considering throwing in a 10-20 turn coil, but before doing that, I was just wondering if anyone has ever really been as far as decided to do want even look more like 10-20?
  2. Audioguru

    New Member

    Dec 20, 2007
    If it operated at only 1MHz then a breadboard layout will work.
    But it operates at 100MHz so a very compact pcb layout as shown in the project must be used.
    It is missing a supply bypass capacitor. A 0.001uf disc capacitor should be added to the pcb.

    It has very poor performance:
    1) Its antenna is directly connected to its tuned LC circuit so its frequency changes if something moves toward or moves away from its antenna.
    2) Its frequency also changes as its battery runs down.
    3) Its sound that is heard on an FM radio will be muffled without any high audio frequencies.

    I fixed all the problems of an FM transmitter circuit similar to that one.
    Mine is here:
  3. Wendy


    Mar 24, 2008