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The range of this FM transmitter is about 100 meters with 9V DC power supply. The circuit consists of three stages. The first stage is a microphone preamplifier built around a BC548 transistor. The next step is to wire the VHF oscillator around another BC548. (BC series transistors are usually used in the low frequency stage. But they also work well in RF stages as an oscillator.) The third stage is a Class A tuned amplifier that amplifies the signals from the oscillator. The use of an additional RF amplifier increases the range of the transmitter.
The L1 coil consists of four turns of 20SWG enameled copper wire 1.5cm long and 4mm in diameter. air core. The L2 coil consists of six turns of 20SWG enameled copper wire wound on a 4mm diameter. air core. Use a 75 cm long cord as an antenna. For maximum range, use a sensitive receiver. VC1 is a frequency regulator. VC2 should be tuned for maximum range. The transmitter is powered by a 9V PP3 battery. It can be combined with an existing FM tuner to form a walkie-talkie.