This 3 stage FM transmitter can be use if you want a long range with less power for example 1.5V or 3V. The circuit is consist of three stages first audio preamplifier stage built with transistor Q1, second oscillator stage built with transistor Q2 and the third is RF amplifier stage built with Q3.
The RF amplifier stage is used to increase the output power of the transmitter and separating the antenna with the oscillator to make the transmitter more stable. The Coil L1 is equal to 5 turns of AWG 22 enameled copper wire wound on 3mm form. For antenna use any wire of 75cm length.