What weather condition might decrease range at microwave frequencies?
The correct answer is C: Precipitation. Precipitation (rain, snow, fog) can decrease range at microwave frequencies because water droplets absorb and scatter microwave signals. The higher the frequency, the more pronounced this effect becomes.
Microwave signals are particularly affected by water in the atmosphere. Rain, snow, and even heavy fog contain water that absorbs microwave energy, converting it to heat. This absorption reduces signal strength and decreases communication range. This is why microwave links can be affected by weather - heavy rain can significantly reduce range and signal quality. The effect is much more pronounced at higher microwave frequencies (like 10 GHz and above) than at lower frequencies.
Exam Tip
Microwave range decrease = Precipitation. Remember: Precipitation (rain, snow, fog) decreases microwave range because water absorbs microwave signals. Higher frequencies are more affected.
Memory Aid
"**M**icrowave **R**ange **D**ecrease = **M**oisture **R**educes **D**istance (think 'MRD = MRD' = Moisture Reduces Distance)"
Real-World Application
You're operating a 10 GHz microwave link that normally works over 20 miles. During a heavy rainstorm, the link becomes unreliable and range drops to only a few miles. The rain is absorbing your microwave signal energy. When the rain stops, your range returns to normal. This is why microwave links can be weather-dependent.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. High winds don't directly affect microwave propagation. They might move antennas or cause mechanical issues, but they don't absorb signals.
Option B: Incorrect. Low barometric pressure doesn't significantly affect microwave propagation. Weather fronts might, but pressure itself doesn't.
Option D: Incorrect. Colder temperatures don't decrease microwave range. In fact, colder air can sometimes improve propagation slightly.
题目解析
The correct answer is C: Precipitation. Precipitation (rain, snow, fog) can decrease range at microwave frequencies because water droplets absorb and scatter microwave signals. The higher the frequency, the more pronounced this effect becomes. Microwave signals are particularly affected by water in the atmosphere. Rain, snow, and even heavy fog contain water that absorbs microwave energy, converting it to heat. This absorption reduces signal strength and decreases communication range. This is why microwave links can be affected by weather - heavy rain can significantly reduce range and signal quality. The effect is much more pronounced at higher microwave frequencies (like 10 GHz and above) than at lower frequencies.
考试技巧
Microwave range decrease = Precipitation. Remember: Precipitation (rain, snow, fog) decreases microwave range because water absorbs microwave signals. Higher frequencies are more affected.
记忆口诀
**M**icrowave **R**ange **D**ecrease = **M**oisture **R**educes **D**istance (think 'MRD = MRD' = Moisture Reduces Distance)
实际应用示例
You're operating a 10 GHz microwave link that normally works over 20 miles. During a heavy rainstorm, the link becomes unreliable and range drops to only a few miles. The rain is absorbing your microwave signal energy. When the rain stops, your range returns to normal. This is why microwave links can be weather-dependent.
错误选项分析
Option A: Incorrect. High winds don't directly affect microwave propagation. They might move antennas or cause mechanical issues, but they don't absorb signals. Option B: Incorrect. Low barometric pressure doesn't significantly affect microwave propagation. Weather fronts might, but pressure itself doesn't. Option D: Incorrect. Colder temperatures don't decrease microwave range. In fact, colder air can sometimes improve propagation slightly.
知识点
Precipitation, Microwave frequencies, Signal absorption, Range reduction
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.