This simple transmitter can send signals to distances up to 200 m, depending on the power supply voltage. The microphone is a 2,5 cm loudspeaker and L1 is formed by 4 turns of 22 to 26 AWG wire in a air core with 1 cm of diameter. Antenna is a piece of wire 20 to 50 cm long. The capacitors must be all ceramic. The transformer is a output transformer found in old transistor radio.
Small FM Transmitter
