Here is a schematic of a FM tracking transmitter circuit. The circuit can be operated with 1.5V battery (any size) and it will last longer because the current consumption of the circuit is only 3.7mA. Transmitting range of this circuit is 30 to 50 meters. This transmitter circuit is using LM3909 IC. Although LM3909 ICs are
not manufactured any more but some electronic shops have stock of it and it is still available in some parts of the world and also online on some websites. When you complete the assembling of the circuit apply 1.5 volt to the circuit and you will see that the LED blinking will start in the circuit. Take a good quality FM receiver and tune the transmitter on it. You will hear tak-tak-tak etc beat equal to the flash of LED. If you have found the beat and it will interfering with any radio station then adjust it with the help of variable capacitor in the transmitter and tune it on the blank spot. Use 12-inch wire as an antenna.