Simple FM Radio Using TBA120S

The Simple FM Radio Using TBA120S is an analog radio receiver designed to capture and demodulate frequency-modulated signals. The circuit is constructed on a 5 x 7 cm Vero board and powered by a 6V power supply. RF signals from the environment are picked up by a 75cm long antenna. The incoming signal is tuned using a combination of capacitors—including a 2-22pF trimmer capacitor, fixed 10pF and 33pF ceramic capacitors—and Inductor L2, which consists of 5 turns of 23 SWG wire on a 5mm air core. The BF 494 transistor (Q1) acts as an active RF component, helping to amplify and process the incoming high-frequency signals. Once the radio frequency stage processes the signal, it is passed to the 5.5 MHz IFT coil and the 5.5 MHz 2-pin ceramic filter to select and isolate the intermediate frequency (IF). The core of the receiver is the TBA120S, a 14-pin IC mounted in a 14-pin IC socket. The TBA120S functions as an IF amplifier and FM detector, taking the 5.5 MHz intermediate frequency and demodulating it into an audible audio signal. Various supporting resistors (such as 470K, 470, 2.2K, and 100 ohms) and capacitors (ranging from 0.001µF to a 22µF/25V electrolytic capacitor) are used for biasing, filtering, and decoupling around the active components to ensure stable operation of the analog circuitry.