This SMD FM transmitter has an operating
frequency of about 80 to 115MHz. Under reasonable circumstances you will
be able to receive its signal at a distance of about 200 meters.
Although it is low-power, it might be illegal in your part of the
planet.
Here's the circuit:
Depending on the electret microphone you use,
you might have to tweek R4 to set the gain of the pre-amplifier.
Depending on the Q of the LC-part (usually not very good when using
off-the-shelf SMD parts) you may also have to re-bias the end stage of
the circuit. For the coil you can use a ECM45T
Series Inductor.
