In a dual-conversion superheterodyne receiver what are the respective aims of the first and second conversion:

In a dual-conversion superheterodyne receiver, the first conversion steps the incoming signal down to a high first Intermediate Frequency (IF). A high IF places the unwanted "image frequency" far away from the desired signal, allowing the front-end RF filters to easily block it. Therefore, the first conversion is aimed at image rejection. The second conversion steps the high IF down to a much lower second IF. At lower frequencies, it is easier and cheaper to build extremely sharp, narrow filters (like crystal filters) that slice away adjacent interfering stations. Thus, the second conversion is aimed at selectivity. Understanding this sequence—first push the image far away, then slice the final signal precisely at a low frequency—makes it easy to remember the order of aims.