Background
Today it is very popular to connect the Ipod, MP3 or CD player to some kind of FM transmitter. The transmitting signal can the be picked up by any FM radio receiver. Most often used in cars. The problem with most FM transmitter is that they have very weak signal and short transmitting range. Some units are so bad that even when they are placed really close to the receiver, you barely receive the signal.

Ipod FM Transmitter Amplifier Schematic
The schematic show you a RF amplifier with very high gain. The feeding RF signal enter C9 to transistor Q1 which has a self biased working point. The gain and working point is set with the two resistors R1 and R2.

FB1, C5, C6 works as filter for rejecting RF to power line. Q1 has a gain about 15dBm. The output signal can be found a the collector which then enter a second amplifier stage Q2. This stage also has a self biased working point.

The gain is set by the resistors R3//R4 and R5//R6.
Why do I have 2 parallel resistors like that?

It is because I want to be able to change the gain of the amplifier. On the PCB below you will see that I only have 2 pads for the resistors. When I want to resistors I solder the two resistors R5 and R6 on top of each other and the same with R3 and R4.

I advice you to start building without R3 and R5 and test the unit. If you want you can then add R3 and R5 later to obtain max gain of this stage. Q2 has a gain of 12 dBm. FB2, C7, C8 works as filter for rejecting RF to power line.

The last amplifier stage is based around the transistor 2N3866. This transistor has low input impedance.
I match it by using 2 capacitors (C11, C12) and the inductor L1 to about 50 ohm. The transistor has an output impedance match, (C13, C14, and L3) to get best performance for an 50-75 ohm antenna.

# The inductor L1 is made by a wire 2 turns with 5mm diameter.
# The inductor L2 is made by a wire 7-9 turns with 6.5mm diameter.
# The inductor L3 is made by a wire 4 turns with 6.5mm diameter.

Source: Ipod Stereo FM transmitter with 1W output power