One of the key issues with superhet radios is that of the image signal. Having a good image performance will reduce the level of interference from signals on the image frequency. To reduce the image response, RF tuning is applied before the mixer to remove the response on the image frequency, but this tuning will always let some of the unwanted signals through. The key is to reduce this as far as possible. As the image response is removed from the wanted frequency by an amount equal to twice the intermediate frequency, increasing the IF can make a significant improvement. Also improving the RF tuning helps. To describe these issues in detail as well as discussing how the image response is defined, Electronics Notes has made a video.
