What factors should be considered when selecting an intermediate frequency?

When designing a superheterodyne receiver, selecting the intermediate frequency (IF) involves a crucial tradeoff. A high IF provides excellent image rejection because the image frequency is placed further away from the desired signal, making it easier for the front-end filters to block. However, a low IF is traditionally better for achieving sharp selectivity to avoid responses to nearby unwanted signals. Therefore, balancing image rejection against the ability to reject close-in unwanted signals is the primary consideration when choosing the IF. Noise figure, cross-modulation, and distortion are primarily determined by the components in the very first stages (the RF amplifier and the first mixer), not the specific choice of the intermediate frequency itself.