Question
When scheduling EME contacts, which of these conditions will generally result in the least path loss?
Answer Options
- A) When the Moon is at perigee
- B) When the Moon is full
- C) When the Moon is at apogee
- D) When the MUF is above 30 MHz
Correct Answer: A
Explanation
The Earth-Moon-Earth (EME) path loss is largely governed by the distance the radio signal must travel (the inverse square law). While the Moon’s orbit is fairly circular, it is elliptical, meaning its distance from the Earth varies over the course of its approximately 28-day cycle. This variation directly impacts the amount of path loss experienced by the EME signal.
The least path loss occurs when the Moon is at perigee-the point in its orbit where it is closest to the Earth. The difference in distance between perigee and apogee (the farthest point) is significant enough to cause a measurable difference in signal strength (around 1 to 2 dB), making perigee a prime time for challenging EME contacts, especially for stations with smaller antenna systems.
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