The AC is rectified and then filtered from C8 and C9. The FM stereo encoder circuitĪC voltage is applied on a classical diodes bridge (BR1). It uses two digital integrated circuits, a classical voltage regulator, a balanced modulator IC, and some operational amplifiers. The electronic circuit is relatively simple. The block diagram and the actual electronic schematic of the stereo encoder are shown in figures 1 and 2, respectively. In the current article we will only deal with a stereo encoder circuit project and its construction details and we will assume that readers of this article are aware of the basic principles of FM stereo broadcasting.įigure 1. For more details on the FM stereo broadcasting technique, please refer to a tutorial, here. At the receiver side, the composite signal is decoded and the two audio channels are retrieved to 2 speakers. The encoder multiplexes the left (L) and right (R) audio channels and produces a composite stereo signal which then, modulates the transmitter. This is achieved with the use of a stereo encoder. That is, they transmit a pair of audio channels through a single carrier. The majority of commercial FM radio stations broadcast in stereo mode. The digital age has not yet conquered the radio and FM radio is still based on classical analogue technology.
Technology evolves year after year, but FM radio is still on the air. The encoder converts any monophonic FM transmitter into a stereo one. FM radio hobbyists will love this classic FM stereo encoder circuit.