Which of the following determines ground losses for a ground-mounted vertical antenna operating on HF?
The correct answer is C: Soil conductivity. Soil conductivity determines ground losses for a ground-mounted vertical antenna operating on HF. Higher soil conductivity means lower resistance, which reduces ground losses and improves efficiency.
Ground losses occur because return current flows through the soil. Soil with high conductivity (like saltwater-saturated soil or moist clay) has low resistance, so losses are low. Soil with low conductivity (like dry sand or rock) has high resistance, so losses are high. This is why vertical antennas work much better near saltwater (high conductivity) than in dry desert areas (low conductivity). Soil conductivity is the primary factor determining how much power is lost in the ground versus radiated.
Exam Tip
Ground losses determined by = Soil conductivity. Remember: Soil conductivity determines ground losses for ground-mounted vertical antennas. High conductivity (wet, salty soil) = low losses. Low conductivity (dry, sandy soil) = high losses.
Memory Aid
"**G**round **L**osses = **S**oil **C**onductivity (think 'GL = SC')"
Real-World Application
You install a ground-mounted vertical in dry, sandy soil (low conductivity). Ground losses are high - much of your power is lost as heat in the ground. You move the same antenna to a location with moist, clay soil (higher conductivity). Ground losses decrease, and more power is radiated. The soil conductivity directly determines the ground losses.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Standing wave ratio (SWR) is a measure of impedance match, not a factor that determines ground losses. SWR doesn't cause ground losses.
Option B: Incorrect. Distance from the transmitter doesn't determine ground losses. Ground losses are about the antenna's interaction with the ground, not transmitter distance.
Option D: Incorrect. Take-off angle is the elevation angle of maximum radiation, not a factor that determines ground losses. Take-off angle is a result, not a cause of ground losses.
题目解析
The correct answer is C: Soil conductivity. Soil conductivity determines ground losses for a ground-mounted vertical antenna operating on HF. Higher soil conductivity means lower resistance, which reduces ground losses and improves efficiency. Ground losses occur because return current flows through the soil. Soil with high conductivity (like saltwater-saturated soil or moist clay) has low resistance, so losses are low. Soil with low conductivity (like dry sand or rock) has high resistance, so losses are high. This is why vertical antennas work much better near saltwater (high conductivity) than in dry desert areas (low conductivity). Soil conductivity is the primary factor determining how much power is lost in the ground versus radiated.
考试技巧
Ground losses determined by = Soil conductivity. Remember: Soil conductivity determines ground losses for ground-mounted vertical antennas. High conductivity (wet, salty soil) = low losses. Low conductivity (dry, sandy soil) = high losses.
记忆口诀
**G**round **L**osses = **S**oil **C**onductivity (think 'GL = SC')
实际应用示例
You install a ground-mounted vertical in dry, sandy soil (low conductivity). Ground losses are high - much of your power is lost as heat in the ground. You move the same antenna to a location with moist, clay soil (higher conductivity). Ground losses decrease, and more power is radiated. The soil conductivity directly determines the ground losses.
错误选项分析
Option A: Incorrect. Standing wave ratio (SWR) is a measure of impedance match, not a factor that determines ground losses. SWR doesn't cause ground losses. Option B: Incorrect. Distance from the transmitter doesn't determine ground losses. Ground losses are about the antenna's interaction with the ground, not transmitter distance. Option D: Incorrect. Take-off angle is the elevation angle of maximum radiation, not a factor that determines ground losses. Take-off angle is a result, not a cause of ground losses.
知识点
Ground losses, Soil conductivity, Vertical antenna, HF operation
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.