Q.What are the important considerations while selecting an IF of a radio receiver?

The intermediate frequency of a superheterodyne receiver is a compromise value. It must be low enough to give good gain and selectivity, yet high enough to reject the image frequency, and it must lie outside the tuning band. …

[!TLDR]

The IF is chosen as a compromise: high enough for good image rejection, low enough for high gain and selectivity, and always outside the tuning band - hence 455 kHz for AM and 10.7 MHz for FM.

In a superheterodyne receiver every incoming station is converted to one fixed intermediate frequency (IF) before the main amplification. Choosing this frequency involves several competing requirements:

1. Image-frequency rejection: The image frequency lies at $f_{image}=f_s+2f_{IF}$. If the IF is too low, the image is very close to the wanted signal and the RF tuned circuits cannot separate them, so image rejection is poor. A higher IF pushes the image far from the signal and makes it easy to reject. This favours a high IF.

2. Selectivity and gain: A lower IF allows tuned circuits with sharper response and stable high gain, giving good selectivity and adjacent-channel rejection. If the IF is too high, it becomes difficult to obtain high, stable gain and the selectivity worsens. This favours a low IF. …