Question 6A475

Image response is an undesired signal created when a frequency other than the desired signal (specifically, one located at `f_signal ± 2 * IF`) mixes with the local oscillator and produces a signal at the intermediate frequency. Option A describes using one or more tuned RF stages, or pre-selectors, ahead of the mixer. These stages act as bandpass filters, attenuating signals outside the desired reception band, including potential image frequencies, *before* they can reach the mixer. This significantly reduces image interference. Option C explains the role of IF selection. The image frequency is offset from the desired signal by twice the IF. A larger IF separates the image frequency further from the desired signal, making it easier for the pre-selector filters (as described in option A) to attenuate it. By choosing an IF such that the image frequency falls *outside* the receiver's intended operating range, filtering becomes simpler and more effective. Option B is incorrect because choosing an IF that causes the image frequency to fall *within* the operating range would make it harder to filter, thereby *increasing* image response. Since both pre-selection (A) and a strategic IF choice (C) are effective methods for minimizing image response, option D, which combines both, is the correct answer.