A digital type of TV or VCR tuner is the heart of this receiver wherein through the I2C interface, the received frequency is programmed into the tuner. A second mixer using DDS as oscillator was added because the smallest step size of a tuner is 31.25kHz, 50kHz, or 62.5kHz, which is too wide for narrow band signals. This DDS configuration can perform the smallest step size of 0.01Hz
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