What indicates the correct value of terminating resistance for a Beverage antenna?
The correct answer is D: Minimum variation in SWR over the desired frequency range. The correct value of terminating resistance for a Beverage antenna is indicated by minimum variation in SWR over the desired frequency range. When the termination is correct, the SWR is relatively constant across the operating frequency range.
A Beverage antenna is a terminated long-wire antenna. The termination resistor should match the antenna's characteristic impedance. When properly terminated, the antenna acts as a traveling-wave antenna with relatively constant impedance across its operating range, resulting in stable SWR. If the termination is wrong, the SWR will vary significantly with frequency. The correct termination value (typically 400-600 ohms for a Beverage) minimizes SWR variation, indicating proper matching. This is the practical way to determine the correct termination value.
Exam Tip
Beverage termination = Minimum SWR variation. Remember: The correct terminating resistance for a Beverage antenna is indicated by minimum variation in SWR over the desired frequency range - proper termination gives stable SWR.
Memory Aid
"**B**everage **T**ermination = **M**inimum **S**WR **V**ariation (think 'BT = MSWRV')"
Real-World Application
You're tuning your Beverage antenna's termination resistor. You try different values and measure SWR across the frequency range. When the termination is correct (maybe 500 ohms), the SWR is relatively constant (maybe 1.5:1 to 2:1) across the band. With wrong termination, SWR varies widely (maybe 1:1 to 5:1). Minimum SWR variation indicates correct termination.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Maximum feed point DC resistance isn't the indicator. DC resistance and RF impedance are different, and the goal is stable SWR, not maximum DC resistance.
Option B: Incorrect. Minimum front-to-back ratio isn't the indicator. Front-to-back ratio is about pattern, not termination matching.
Option C: Incorrect. Maximum DC current in the terminating resistor isn't the indicator. The goal is proper RF termination for stable SWR, not maximum DC current.
题目解析
The correct answer is D: Minimum variation in SWR over the desired frequency range. The correct value of terminating resistance for a Beverage antenna is indicated by minimum variation in SWR over the desired frequency range. When the termination is correct, the SWR is relatively constant across the operating frequency range. A Beverage antenna is a terminated long-wire antenna. The termination resistor should match the antenna's characteristic impedance. When properly terminated, the antenna acts as a traveling-wave antenna with relatively constant impedance across its operating range, resulting in stable SWR. If the termination is wrong, the SWR will vary significantly with frequency. The correct termination value (typically 400-600 ohms for a Beverage) minimizes SWR variation, indicating proper matching. This is the practical way to determine the correct termination value.
考试技巧
Beverage termination = Minimum SWR variation. Remember: The correct terminating resistance for a Beverage antenna is indicated by minimum variation in SWR over the desired frequency range - proper termination gives stable SWR.
记忆口诀
**B**everage **T**ermination = **M**inimum **S**WR **V**ariation (think 'BT = MSWRV')
实际应用示例
You're tuning your Beverage antenna's termination resistor. You try different values and measure SWR across the frequency range. When the termination is correct (maybe 500 ohms), the SWR is relatively constant (maybe 1.5:1 to 2:1) across the band. With wrong termination, SWR varies widely (maybe 1:1 to 5:1). Minimum SWR variation indicates correct termination.
错误选项分析
Option A: Incorrect. Maximum feed point DC resistance isn't the indicator. DC resistance and RF impedance are different, and the goal is stable SWR, not maximum DC resistance. Option B: Incorrect. Minimum front-to-back ratio isn't the indicator. Front-to-back ratio is about pattern, not termination matching. Option C: Incorrect. Maximum DC current in the terminating resistor isn't the indicator. The goal is proper RF termination for stable SWR, not maximum DC current.
知识点
Beverage antenna, Terminating resistance, SWR variation, Termination matching
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.