FM transmitter having a stable frequency & with a high power (Range)
is a tough task to do , actually you can buy a high power FM transmitter , but
hard to make it due to the restriction as well as parts availability in the certain
areas , in my this circuit the input were taken from the Car MP3 modulator ,
antenna point at the PCB can be easily found , where they always printed the every
point on the PCB , if not found the antenna point then you can use the field strength
meter (FSM) , antenna will be the peak FSM reading ,
this signal were then given to the circuit , sometime the RF power from the MP3
found low which cannot derive the first
transistor , for this biasing required from positive supply to the transistor
base to boost some hove the input signal , 30 k to 56 k resistor can be used
for the biasing ,in first stage I used 2sc2407 transistor ,in the other next
stages both 2sc3950 were used , very cheap transistors ,where all these
transistor can work very nice in the FM range, RFC were used at the transistor
collector which can be easily available in the market RFC for FM rage will be 0.56 mh or 0.68 mh (Micro henry) you don’t have to wound the coil , you can use
2N2219 , 2N3866, 2N2222 instead 2sc2407 , instead of 2sc3905 , you can use
2sc1971 , 2n3553 etc.
