Which term describes the ability of a receiver to detect the presence of a signal?
The correct answer is Sensitivity. Sensitivity describes the ability of a receiver to detect the presence of a signal - specifically, how weak a signal can be and still be detected. Sensitivity is typically measured in microvolts (μV) or decibels relative to a milliwatt (dBm) and represents the minimum signal strength required for the receiver to produce a usable output. For amateur radio operators, high sensitivity is crucial for receiving weak signals, working DX (long-distance contacts), and operating on bands with low signal levels. A more sensitive receiver can detect weaker signals, making it better for weak-signal work. Sensitivity is different from selectivity (ability to separate signals) and linearity (faithful signal reproduction).
Exam Tip
Sensitivity = ability to detect weak signals. Think 'S'ensitivity = 'S'ensing weak signals. Selectivity separates signals, linearity preserves quality, THD measures distortion - none describe detection ability.
Memory Aid
"Sensitivity = Sensing weak signals. Think 'S'ensitivity = 'S'ensing how 'S'mall a signal you can detect. Lower numbers (μV) = better sensitivity."
Real-World Application
When working a weak DX station on 20 meters, your receiver's sensitivity determines whether you can hear them at all. A receiver with 0.5 μV sensitivity might detect the signal, while one with 2.0 μV sensitivity might miss it completely. High sensitivity is essential for weak-signal work, allowing you to copy signals that less sensitive receivers can't detect.
Key Concepts
Why Other Options Are Wrong
Option A (Linearity): Incorrect. Linearity refers to how faithfully a receiver reproduces the input signal without distortion. It's about signal quality, not the ability to detect weak signals.
Option C (Selectivity): Incorrect. Selectivity describes a receiver's ability to discriminate between multiple signals and reject unwanted ones. It's about separating signals, not detecting their presence.
Option D (Total Harmonic Distortion): Incorrect. THD is a measure of distortion in the output signal, indicating how much the signal is altered. It's a quality metric, not a detection capability.
题目解析
The correct answer is Sensitivity. Sensitivity describes the ability of a receiver to detect the presence of a signal - specifically, how weak a signal can be and still be detected. Sensitivity is typically measured in microvolts (μV) or decibels relative to a milliwatt (dBm) and represents the minimum signal strength required for the receiver to produce a usable output. For amateur radio operators, high sensitivity is crucial for receiving weak signals, working DX (long-distance contacts), and operating on bands with low signal levels. A more sensitive receiver can detect weaker signals, making it better for weak-signal work. Sensitivity is different from selectivity (ability to separate signals) and linearity (faithful signal reproduction).
考试技巧
Sensitivity = ability to detect weak signals. Think 'S'ensitivity = 'S'ensing weak signals. Selectivity separates signals, linearity preserves quality, THD measures distortion - none describe detection ability.
记忆口诀
Sensitivity = Sensing weak signals. Think 'S'ensitivity = 'S'ensing how 'S'mall a signal you can detect. Lower numbers (μV) = better sensitivity.
实际应用示例
When working a weak DX station on 20 meters, your receiver's sensitivity determines whether you can hear them at all. A receiver with 0.5 μV sensitivity might detect the signal, while one with 2.0 μV sensitivity might miss it completely. High sensitivity is essential for weak-signal work, allowing you to copy signals that less sensitive receivers can't detect.
错误选项分析
Option A (Linearity): Incorrect. Linearity refers to how faithfully a receiver reproduces the input signal without distortion. It's about signal quality, not the ability to detect weak signals. Option C (Selectivity): Incorrect. Selectivity describes a receiver's ability to discriminate between multiple signals and reject unwanted ones. It's about separating signals, not detecting their presence. Option D (Total Harmonic Distortion): Incorrect. THD is a measure of distortion in the output signal, indicating how much the signal is altered. It's a quality metric, not a detection capability.
知识点
Receiver sensitivity, Signal detection, Receiver performance, Weak signal reception
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.