If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is adjusted to present a 1:1 SWR to the transmitter, what is the resulting SWR on the feed line?
The correct answer is B: 5:1. If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end is adjusted to present 1:1 SWR to the transmitter, the resulting SWR on the feed line is still 5:1. The matching network only matches at its location - it doesn't change the SWR on the feed line itself. For amateur radio operators, this is important to understand. Understanding this helps when using matching networks.
Exam Tip
Matching network at transmitter = feed line SWR unchanged (still 5:1). Think 'M'atching 'N'etwork = 'M'atches at 'N'etwork location only. Matching network only matches at its location - it doesn't change SWR on feed line itself. Not 1:1, not between - just 5:1 still.
Memory Aid
"Matching network at transmitter = feed line SWR unchanged (still 5:1). Think 'M'atching 'N'etwork = 'M'atches at 'N'etwork only. Matching network only matches at its location - it doesn't change SWR on feed line. Important to understand."
Real-World Application
Feed line has 5:1 SWR. You add a matching network at the transmitter end, adjusting it to present 1:1 SWR to the transmitter. The matching network matches at its location, but the feed line still has 5:1 SWR - the mismatch still exists on the feed line. The matching network doesn't fix the feed line SWR, it only matches at the transmitter.
Key Concepts
Why Other Options Are Wrong
Option A (1:1): Incorrect. SWR on feed line isn't 1:1 - the matching network only matches at its location, it doesn't change the feed line SWR. 1:1 is only at the matching network.
Option C: Incorrect. SWR isn't between 1:1 and 5:1 depending on characteristic impedance - the feed line SWR is still 5:1. Characteristic impedance doesn't change SWR.
Option D: Incorrect. SWR isn't between 1:1 and 5:1 depending on reflected power - the feed line SWR is still 5:1. Reflected power doesn't change SWR.
题目解析
The correct answer is B: 5:1. If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end is adjusted to present 1:1 SWR to the transmitter, the resulting SWR on the feed line is still 5:1. The matching network only matches at its location - it doesn't change the SWR on the feed line itself. For amateur radio operators, this is important to understand. Understanding this helps when using matching networks.
考试技巧
Matching network at transmitter = feed line SWR unchanged (still 5:1). Think 'M'atching 'N'etwork = 'M'atches at 'N'etwork location only. Matching network only matches at its location - it doesn't change SWR on feed line itself. Not 1:1, not between - just 5:1 still.
记忆口诀
Matching network at transmitter = feed line SWR unchanged (still 5:1). Think 'M'atching 'N'etwork = 'M'atches at 'N'etwork only. Matching network only matches at its location - it doesn't change SWR on feed line. Important to understand.
实际应用示例
Feed line has 5:1 SWR. You add a matching network at the transmitter end, adjusting it to present 1:1 SWR to the transmitter. The matching network matches at its location, but the feed line still has 5:1 SWR - the mismatch still exists on the feed line. The matching network doesn't fix the feed line SWR, it only matches at the transmitter.
错误选项分析
Option A (1:1): Incorrect. SWR on feed line isn't 1:1 - the matching network only matches at its location, it doesn't change the feed line SWR. 1:1 is only at the matching network. Option C: Incorrect. SWR isn't between 1:1 and 5:1 depending on characteristic impedance - the feed line SWR is still 5:1. Characteristic impedance doesn't change SWR. Option D: Incorrect. SWR isn't between 1:1 and 5:1 depending on reflected power - the feed line SWR is still 5:1. Reflected power doesn't change SWR.
知识点
SWR on feed line, Matching network, 1:1 SWR to transmitter, Feed line SWR unchanged
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.