The following is a simple yet powerful 4W FM transmitter which is tunable to 88-108MHz frequency. Connect to your ipod/computer, etc. When this was first made, I only had a 2N2219A on hand, which resulted in a lower RF output. I have since swapped out the transistor for a 2N3866 for full 4W output at around 15VDC supply. In order to achieve a high output level, you will need a well tuned antenna, and a large heatsink to dissipate the heat from T2 transistor.
Transmitter was mounted in metal enclosure and works extremely well.
Transmitter should be supplied with 12-16V voltage. Regulated DC supply is recommended for improved frequency stability. Current consumption ranges from 100mA at 12V to 400mA at 16V.
R1, R2 = 10K Ohm (1/4 W)
R3 = 47 Ohm (1/4 W)
C1, C2 = 1nF
C3 = 4,7uF/16V
C4, C7, C8 = 0~45pF trimmer
C5, C6 = 10pF
C9 = 100nF
T1 = 2N2219
T2 = 2N3866/2N4427 with heatsink
ANT = Simple dipole l/2.
MIC IN = Microphone dynamic or other type. (It can also connected to MP3 player)
L1 = 4 turns, 7mm diameter *
L3 = 3 turns, 7mm diameter *
L4 = 5 turns, 7mm diameter *
L2 = RFC (10cm of fine magnet wire wrapped around 1 MOhm resistor)