What is link margin?
The correct answer is B: The difference between received power level and minimum required signal level at the input to the receiver. What link margin is the difference between received power level and minimum required signal level at the input to the receiver. Link margin shows how much signal strength exceeds the minimum needed. For amateur radio operators, this indicates communication reliability. Understanding this helps when evaluating radio links.
Exam Tip
Link margin = difference between received power and minimum required signal. Think 'L'ink 'M'argin = 'L'ooks at 'M'argin above minimum. Shows how much signal strength exceeds minimum needed. Not opposite of fade margin, not transmit-sensitivity, not sensitivity+3dB - just received minus minimum.
Memory Aid
"Link margin = difference between received power and minimum required signal. Think 'L'ink 'M'argin = 'M'argin above minimum. Shows how much signal strength exceeds minimum needed. Indicates communication reliability."
Real-World Application
Link margin: Received power = -100 dBm, minimum required = -110 dBm. Link margin = -100 - (-110) = 10 dB. This means the received signal is 10 dB above the minimum needed. Higher link margin means more reliable communication. Link margin is the difference between received power and minimum required.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Link margin isn't the opposite of fade margin - fade margin is similar to link margin, not opposite. Fade margin is related, not opposite.
Option C: Incorrect. Link margin isn't transmit power minus receiver sensitivity - it's received power minus minimum required, not transmit minus sensitivity. Transmit power isn't in the calculation.
Option D: Incorrect. Link margin isn't receiver sensitivity plus 3 dB - it's received power minus minimum required, not sensitivity plus 3 dB. Sensitivity plus 3 dB isn't link margin.
题目解析
The correct answer is B: The difference between received power level and minimum required signal level at the input to the receiver. What link margin is the difference between received power level and minimum required signal level at the input to the receiver. Link margin shows how much signal strength exceeds the minimum needed. For amateur radio operators, this indicates communication reliability. Understanding this helps when evaluating radio links.
考试技巧
Link margin = difference between received power and minimum required signal. Think 'L'ink 'M'argin = 'L'ooks at 'M'argin above minimum. Shows how much signal strength exceeds minimum needed. Not opposite of fade margin, not transmit-sensitivity, not sensitivity+3dB - just received minus minimum.
记忆口诀
Link margin = difference between received power and minimum required signal. Think 'L'ink 'M'argin = 'M'argin above minimum. Shows how much signal strength exceeds minimum needed. Indicates communication reliability.
实际应用示例
Link margin: Received power = -100 dBm, minimum required = -110 dBm. Link margin = -100 - (-110) = 10 dB. This means the received signal is 10 dB above the minimum needed. Higher link margin means more reliable communication. Link margin is the difference between received power and minimum required.
错误选项分析
Option A: Incorrect. Link margin isn't the opposite of fade margin - fade margin is similar to link margin, not opposite. Fade margin is related, not opposite. Option C: Incorrect. Link margin isn't transmit power minus receiver sensitivity - it's received power minus minimum required, not transmit minus sensitivity. Transmit power isn't in the calculation. Option D: Incorrect. Link margin isn't receiver sensitivity plus 3 dB - it's received power minus minimum required, not sensitivity plus 3 dB. Sensitivity plus 3 dB isn't link margin.
知识点
Link margin, Received power level, Minimum required signal, Receiver input
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.