Question 3-46F2

When selecting an Intermediate Frequency (IF) in a superheterodyne receiver, two critical factors are image rejection and selectivity. **Image Rejection:** A superheterodyne receiver has an "image" frequency, which is an unwanted signal that can also mix with the local oscillator to produce the IF. A higher IF places the image frequency further away from the desired signal frequency, making it easier for the receiver's pre-selector (RF filters) to attenuate it before it reaches the mixer, thereby improving image rejection. **Selectivity:** The IF stage provides the bulk of a receiver's selectivity. A lower IF allows for the design of sharper, more stable, and often less expensive filters (e.g., crystal or ceramic filters) to reject adjacent channel interference effectively. Designers often balance these competing needs (higher IF for image rejection, lower IF for selectivity), sometimes employing multiple IF stages (double or triple conversion) to optimize both. The other options describe general receiver performance characteristics, but image rejection and selectivity are the most direct and fundamental considerations tied to the *choice of the IF frequency itself*.