Any sound can be sent to any FM radio from any room by this simple 2-transistor audio transmitter.
Explanation
During the usage, the radio and the audio transmitter should both be in the same frequency between 80-100MHz. Depending on the quality of the device and the parts used, the range can reach at least 100 feet or longer. With this specific device, a very high quality or solid performance can’t be expected since it is one of the most basic transmitter circuits. The transmitter works like 2 independent stages. Some of the components include a 3V or 9V battery power supply, electret microphone, 6”-12” insulated wire antenna, capacitors, transistors, resistors, and a coil.
Most of the parts can be taken from an on radio, TV, or RF based circuit board to avoid purchasing new ones. Any small signal NPN transistor can be used for the two transistors. It could be generic type for as long as the specification is close enough to the important parameters which can be seen in the datasheet. Only the small adjustable capacitor needs to be purchased but there is also an alternative solution without the need for trimmer capacitor
EmoticonEmoticon