An automatic frequency tuning (AFT) system which can effect immediate and accurate automatic frequency tuning of the local oscillator (LO) of a receiver, in order to achieve a stable intermediate frequency (IF) signal while reducing the power consumption and the cost of the system. In the automatic frequency tuning (AFT) system, an analog-to-digital converter (ADC) converts the intermediate frequency (IF) to a digital value which is sent to a microcontroller. A signal sent from the microcontroller accurately and automatically tunes the local oscillator (LO).