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T8B09

SIGNALS AND EMISSIONS · Amateur satellite operation: Doppler shift, basic orbits, operating protocols, modulation mode selection, transmitter power considerations, telemetry, satellite tracking programs, beacons, uplink and downlink mode definitions, spin fading, definition of "LEO", setting uplink power

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What causes spin fading of satellite signals?

  1. ACircular polarized noise interference radiated from the sun
  2. BRotation of the satellite and its antennas
  3. CDoppler shift of the received signal
  4. DInterfering signals within the satellite uplink band
Why Many satellites are spin-stabilized, so the spacecraft and its antennas rotate as the satellite passes overhead. As the antenna turns, the polarization of the arriving signal rotates relative to your fixed antenna, so the signal strength rises and falls in a regular cycle. That periodic flutter is called spin fading, and a circularly polarized or switchable-polarization ground antenna helps smooth it out.
Watch out Doppler shift is a different effect: it changes the received frequency as the satellite moves toward or away from you, not the signal amplitude.
Spin fading = the satellite is spinning. Signal strength cycles because the antenna polarization turns with it.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of T8B

  1. T8B01 What telemetry information is typically transmitted by satellite beacons?
  2. T8B02 What is the impact of using excessive effective radiated power on a satellite uplink?
  3. T8B03 Which of the following are provided by satellite tracking programs?
  4. T8B04 What mode of transmission is commonly used by amateur radio satellites?
  5. T8B05 What is a satellite beacon?
  6. T8B06 Which of the following are inputs to a satellite tracking program?
  7. T8B07 What is Doppler shift in reference to satellite communications?
  8. T8B08 What does it mean if a satellite is operating in U/V mode?
  9. T8B09 What causes spin fading of satellite signals?
  10. T8B10 What does the term LEO mean in reference to communication satellites?
  11. T8B11 Who is permitted to receive telemetry from an amateur radio satellite?
  12. T8B12 Which of the following is a way to determine whether your satellite uplink power into a linear transponder sa…
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