Amateur ExtraE3A03
When scheduling EME contacts, which of these conditions will generally result in the least path loss?
A
Answer
Radio wave propagation
Type
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
Answer Notes
Path loss in Earth-Moon-Earth (EME) communications is highly dependent on the physical distance the radio waves must travel. As the signal journeys to the Moon and back, it weakens significantly due to free-space path loss.
The Moon's orbit around the Earth is elliptical rather than perfectly circular. The point in the orbit where the Moon is closest to Earth is called 'perigee', while the farthest point is known as 'apogee'.
Because signal loss increases with distance, scheduling a contact when the Moon is at perigee minimizes the round-trip distance. This naturally results in the least amount of path loss and the strongest possible received signals.
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What characterizes libration fading of an EME signal?
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In what direction does an electromagnetic wave travel?