Question T8B09
From subelement T8 - T8B
What causes spin fading of satellite signals?
Why is this correct?
Spin fading occurs when satellites rotate in space, causing their antennas to change orientation relative to Earth stations. As the satellite spins, the antenna pattern sweeps across your location like a lighthouse beam, creating periodic variations in signal strength. This rotation causes the received signal to fade in and out rhythmically. Doppler shift (C) affects frequency, not signal strength. Solar interference (A) and uplink interference (D) are separate phenomena unrelated to the satellite's physical rotation.
Memory tip
Remember the lighthouse analogy: just as a lighthouse beam appears bright when pointing toward you and dim when pointing away, satellite antennas create the same effect as they rotate. Look for 'rotation' or 'spinning' keywords in satellite signal variation questions.
Learn more
Spin fading is a critical consideration in satellite communication system design. Most amateur satellites are small CubeSats or similar spacecraft that spin for thermal regulation or attitude control. This rotation affects link budget calculations and requires operators to account for periodic signal variations during passes. Understanding spin characteristics helps predict communication windows and explains why some satellites have more stable signals than others based on their stabilization methods.
Think about it
Why do you think satellite designers might intentionally allow satellites to spin rather than maintaining a fixed orientation toward Earth?