What is the effect of transmission line loss on SWR measured at the input to the line?
The correct answer is A: Higher loss reduces SWR measured at the input to the line. The effect of transmission line loss on SWR measured at the input to the line is that higher loss reduces SWR measured at the input. Loss absorbs reflected power, making the SWR appear lower at the input than it actually is at the load. For amateur radio operators, this is important when measuring SWR. Understanding this helps when evaluating feed line performance.
Exam Tip
Line loss effect on SWR = higher loss reduces SWR at input. Think 'H'igher 'L'oss = 'H'ides 'L'ower SWR (reduces measured SWR). Loss absorbs reflected power, making SWR appear lower at input than at load. Not increases, not increases accuracy, not no effect - just reduces.
Memory Aid
"Line loss effect on SWR = higher loss reduces SWR at input. Think 'H'igher 'L'oss = 'H'ides 'L'ower SWR. Loss absorbs reflected power, making SWR appear lower at input than at load. Important when measuring SWR."
Real-World Application
A feed line with high loss: The load has 5:1 SWR, but at the input (transmitter end), the SWR might read 3:1. The loss absorbs some of the reflected power, making the SWR appear lower at the input. This is why SWR should be measured at the antenna, not through lossy feed lines. Higher loss reduces measured SWR at input.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Higher loss doesn't increase SWR at input - it reduces it because loss absorbs reflected power. Increase is wrong.
Option C: Incorrect. Higher loss doesn't increase accuracy - it actually makes SWR measurement less accurate (shows lower SWR than actual). Accuracy increase is wrong.
Option D: Incorrect. Transmission line loss does affect SWR measurement - loss reduces the measured SWR at the input. No effect is wrong.
题目解析
The correct answer is A: Higher loss reduces SWR measured at the input to the line. The effect of transmission line loss on SWR measured at the input to the line is that higher loss reduces SWR measured at the input. Loss absorbs reflected power, making the SWR appear lower at the input than it actually is at the load. For amateur radio operators, this is important when measuring SWR. Understanding this helps when evaluating feed line performance.
考试技巧
Line loss effect on SWR = higher loss reduces SWR at input. Think 'H'igher 'L'oss = 'H'ides 'L'ower SWR (reduces measured SWR). Loss absorbs reflected power, making SWR appear lower at input than at load. Not increases, not increases accuracy, not no effect - just reduces.
记忆口诀
Line loss effect on SWR = higher loss reduces SWR at input. Think 'H'igher 'L'oss = 'H'ides 'L'ower SWR. Loss absorbs reflected power, making SWR appear lower at input than at load. Important when measuring SWR.
实际应用示例
A feed line with high loss: The load has 5:1 SWR, but at the input (transmitter end), the SWR might read 3:1. The loss absorbs some of the reflected power, making the SWR appear lower at the input. This is why SWR should be measured at the antenna, not through lossy feed lines. Higher loss reduces measured SWR at input.
错误选项分析
Option B: Incorrect. Higher loss doesn't increase SWR at input - it reduces it because loss absorbs reflected power. Increase is wrong. Option C: Incorrect. Higher loss doesn't increase accuracy - it actually makes SWR measurement less accurate (shows lower SWR than actual). Accuracy increase is wrong. Option D: Incorrect. Transmission line loss does affect SWR measurement - loss reduces the measured SWR at the input. No effect is wrong.
知识点
Transmission line loss, SWR measurement, Input SWR, Loss effect on SWR
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.