🔍 Key Concepts

• Image frequency in a superheterodyne receiver and how it is related to the RF, LO, and IF frequencies • How tuned RF stages (preselector/front end filters) affect which frequencies can reach the mixer • The goal of selecting an intermediate frequency (IF) to control where the image frequency falls

💭 Think About

• For a given desired receive frequency and IF, where does the image frequency occur in relation to the desired signal? Think about the LO mixing products. • How do additional tuned RF stages ahead of the mixer affect unwanted signals like the image frequency? Do they increase or decrease the image response, and why? • If you can choose the IF, do you want the image frequency to be closer to or farther away from the desired receive frequency, and what effect does that have on filtering it out?

✅ Before You Answer

• Write down the relationship: image frequency is separated from the desired RF by twice the IF and use that to see where the image falls. • Check which options would reduce the strength of image signals reaching the detector, rather than just placing them inside the receiver’s passband. • Confirm which choice(s) both (1) help you filter out the image before mixing and (2) place the image where front-end filters can more easily reject it.