Discussion
A receiver's preselector has a quality factor of \( 100 \) at \( 10 \ \mathrm{MHz} \) with a \( 455 \ \mathrm{kHz} \) intermediate frequency. Image rejection is roughly
Answer: D
The image is only \( 910 \ \mathrm{kHz} \) away out of ten megahertz, so the detuning ratio is small:
\[ \begin{aligned} \rho &= \tfrac{10.91}{10} - \tfrac{10}{10.91} \approx 0.18 \\ \text{ratio} &\approx 100 \times 0.18 = 18 \end{aligned} \]
which is about 25 dB, so about 20 dB - poor. The same intermediate frequency that serves the medium wave band well is quite inadequate at ten megahertz, which is the calculation that forces up-conversion on any wide coverage receiver.
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