What happens to power lost in a feed line?
The correct answer is C: It is converted into heat. Power lost in a feed line is converted into heat. Feed line losses occur due to resistance in the conductors and dielectric losses in the insulation. When RF power encounters this resistance, it's converted to heat energy, just like current through a resistor. This heat is dissipated into the surrounding environment. For amateur radio operators, understanding feed line losses helps explain why some power doesn't reach the antenna and why certain feed lines are better than others. Low-loss feed lines minimize this heat generation and power loss.
Exam Tip
Feed line losses = converted to heat. Think 'L'ost power = 'L'ost as heat. Resistance in feed line converts RF power to heat energy. Not radiated, not distortion, not SWR increase - just heat.
Memory Aid
"Feed line losses = converted to heat. Think 'L'ost power = 'L'ost as heat. Resistance converts RF power to heat energy. Not harmonics, not distortion - just heat."
Real-World Application
Your 100-watt transmitter is connected to your antenna through 100 feet of RG-58 coax. Due to feed line losses (about 3 dB), only 50 watts reaches your antenna. The other 50 watts is converted to heat in the feed line - you can sometimes feel the coax getting warm during extended operation. Using lower-loss feed line (like LMR-400) reduces this heat generation and delivers more power to the antenna.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Feed line losses don't increase SWR - SWR is determined by impedance mismatch, not by losses. Losses reduce power, but don't affect the SWR reading.
Option B: Incorrect. Lost power isn't radiated as harmonics - harmonics are generated by non-linear devices, not by feed line losses. Lost power becomes heat.
Option D: Incorrect. Feed line losses don't distort the signal - they just reduce power. Distortion comes from non-linear devices or poor modulation, not from feed line losses.
题目解析
The correct answer is C: It is converted into heat. Power lost in a feed line is converted into heat. Feed line losses occur due to resistance in the conductors and dielectric losses in the insulation. When RF power encounters this resistance, it's converted to heat energy, just like current through a resistor. This heat is dissipated into the surrounding environment. For amateur radio operators, understanding feed line losses helps explain why some power doesn't reach the antenna and why certain feed lines are better than others. Low-loss feed lines minimize this heat generation and power loss.
考试技巧
Feed line losses = converted to heat. Think 'L'ost power = 'L'ost as heat. Resistance in feed line converts RF power to heat energy. Not radiated, not distortion, not SWR increase - just heat.
记忆口诀
Feed line losses = converted to heat. Think 'L'ost power = 'L'ost as heat. Resistance converts RF power to heat energy. Not harmonics, not distortion - just heat.
实际应用示例
Your 100-watt transmitter is connected to your antenna through 100 feet of RG-58 coax. Due to feed line losses (about 3 dB), only 50 watts reaches your antenna. The other 50 watts is converted to heat in the feed line - you can sometimes feel the coax getting warm during extended operation. Using lower-loss feed line (like LMR-400) reduces this heat generation and delivers more power to the antenna.
错误选项分析
Option A: Incorrect. Feed line losses don't increase SWR - SWR is determined by impedance mismatch, not by losses. Losses reduce power, but don't affect the SWR reading. Option B: Incorrect. Lost power isn't radiated as harmonics - harmonics are generated by non-linear devices, not by feed line losses. Lost power becomes heat. Option D: Incorrect. Feed line losses don't distort the signal - they just reduce power. Distortion comes from non-linear devices or poor modulation, not from feed line losses.
知识点
Feed line losses, Power dissipation, Heat generation, Transmission line losses
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.