Which term describes the ability of a receiver to discriminate between multiple signals?
The correct answer is Selectivity. Selectivity describes the ability of a receiver to discriminate between multiple signals - to separate a desired signal from unwanted nearby signals. Selectivity is determined by the receiver's filters, particularly the IF (intermediate frequency) filters, which determine how narrow the receiver's response is. High selectivity means the receiver can separate closely spaced signals, while low selectivity means it might receive multiple signals simultaneously. For amateur radio operators, good selectivity is essential when operating in crowded band conditions, near strong local stations, or when trying to copy weak signals near strong ones. Selectivity is different from sensitivity (ability to detect weak signals) and is measured by the receiver's bandwidth and filter characteristics.
Exam Tip
Selectivity = separating signals. Think 'S'electivity = 'S'electing one signal from many. Sensitivity detects weak signals, selectivity separates signals. The key word is 'discriminate between multiple signals.'
Memory Aid
"Selectivity = Selecting one signal from many. Think 'S'electivity = 'S'eparating 'S'ignals. Different from sensitivity (detecting weak signals)."
Real-World Application
When operating on a crowded 2-meter repeater frequency, your receiver's selectivity determines whether you can copy the desired signal or if nearby strong signals interfere. A receiver with good selectivity (narrow filters) can separate signals only 5 kHz apart, while poor selectivity might allow interference from signals 20 kHz away. This is crucial in urban areas with many active stations.
Key Concepts
Why Other Options Are Wrong
Option A (Discrimination ratio): Incorrect. This is not a standard receiver specification. While it sounds similar to selectivity, the correct term is 'selectivity.'
Option B (Sensitivity): Incorrect. Sensitivity describes the ability to detect weak signals, not to separate multiple signals. It's about signal detection, not signal separation.
Option D (Harmonic distortion): Incorrect. Harmonic distortion measures how much the receiver adds unwanted harmonics to the signal. It's a quality metric, not a measure of signal separation ability.
题目解析
The correct answer is Selectivity. Selectivity describes the ability of a receiver to discriminate between multiple signals - to separate a desired signal from unwanted nearby signals. Selectivity is determined by the receiver's filters, particularly the IF (intermediate frequency) filters, which determine how narrow the receiver's response is. High selectivity means the receiver can separate closely spaced signals, while low selectivity means it might receive multiple signals simultaneously. For amateur radio operators, good selectivity is essential when operating in crowded band conditions, near strong local stations, or when trying to copy weak signals near strong ones. Selectivity is different from sensitivity (ability to detect weak signals) and is measured by the receiver's bandwidth and filter characteristics.
考试技巧
Selectivity = separating signals. Think 'S'electivity = 'S'electing one signal from many. Sensitivity detects weak signals, selectivity separates signals. The key word is 'discriminate between multiple signals.'
记忆口诀
Selectivity = Selecting one signal from many. Think 'S'electivity = 'S'eparating 'S'ignals. Different from sensitivity (detecting weak signals).
实际应用示例
When operating on a crowded 2-meter repeater frequency, your receiver's selectivity determines whether you can copy the desired signal or if nearby strong signals interfere. A receiver with good selectivity (narrow filters) can separate signals only 5 kHz apart, while poor selectivity might allow interference from signals 20 kHz away. This is crucial in urban areas with many active stations.
错误选项分析
Option A (Discrimination ratio): Incorrect. This is not a standard receiver specification. While it sounds similar to selectivity, the correct term is 'selectivity.' Option B (Sensitivity): Incorrect. Sensitivity describes the ability to detect weak signals, not to separate multiple signals. It's about signal detection, not signal separation. Option D (Harmonic distortion): Incorrect. Harmonic distortion measures how much the receiver adds unwanted harmonics to the signal. It's a quality metric, not a measure of signal separation ability.
知识点
Receiver selectivity, Signal discrimination, Filter bandwidth, Receiver performance
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.