Final answer:
The main advantage of a double-conversion receiver over a single-conversion receiver is increased image frequency rejection, which improves the selectivity by ensuring only desired signals are amplified.
Step-by-step explanation:
One of the greatest advantages of the double-conversion over the single-conversion receiver is that it increases image frequency rejection. This is critical for a receiver's ability to discern the intended signal from potential interferences. Image frequencies are signals that are an equal distance away from the receiver's local oscillator frequency but on the opposite side of it. In a double-conversion receiver, the first conversion creates an intermediate frequency (IF) that is sufficiently different from the original frequency, making it less susceptible to these image frequencies. After the first IF stage, the signal is converted again to a second, often lower, IF which improves the image frequency rejection even further.
Image frequency rejection enhances the overall selectivity of the receiver, ensuring that only the desired signal is amplified and processed, while unwanted signals are discarded. This leads to a more accurate and clear reception, which is particularly beneficial in environments where multiple signals of varying frequencies are present.