Difficulty: Medium
Correct Answer: Variable sensitivity is used to improve selectivity
Explanation:
Introduction / Context:Receiver design includes multiple techniques to improve selectivity, sensitivity, and image rejection. However, some statements can be misleading if the functions of these features are not understood correctly.
Given Data / Assumptions:
Concept / Approach:Double conversion is a known method to improve both selectivity and image rejection. Variable sensitivity, however, does not improve selectivity; it adjusts receiver gain to handle strong or weak signals. Hence, the claim that variable sensitivity improves selectivity is false.
Step-by-Step Solution:
Selectivity is improved by IF filters, not sensitivity control.Double conversion → better image rejection and narrower IF bandwidth.Variable sensitivity → prevents overload on strong signals but does not affect selectivity.Selective fading is mitigated by diversity reception, not sensitivity adjustment.Verification / Alternative check:
Textbooks confirm: sensitivity control = RF gain control, not selectivity improvement.Why Other Options Are Wrong:
Other statements about double conversion and fading elimination are correct in their contexts.Common Pitfalls:
Confusing sensitivity with selectivity. They are different performance measures.Final Answer:
Variable sensitivity is used to improve selectivity
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