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Subelement T8

SIGNALS AND EMISSIONS

Section T8B

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

What telemetry information is typically transmitted by satellite beacons?

  • The signal strength of received signals
  • Time of day accurate to plus or minus 1/10 second
  • Correct Answer
    Health and status of the satellite
  • All these choices are correct
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What is the impact of using excessive effective radiated power on a satellite uplink?

  • Possibility of commanding the satellite to an improper mode
  • Correct Answer
    Blocking access by other users
  • Overloading the satellite batteries
  • Possibility of rebooting the satellite control computer
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Which of the following are provided by satellite tracking programs?

  • Maps showing the real-time position of the satellite track over Earth
  • The time, azimuth, and elevation of the start, maximum altitude, and end of a pass
  • The apparent frequency of the satellite transmission, including effects of Doppler shift
  • Correct Answer
    All these choices are correct
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What mode of transmission is commonly used by amateur radio satellites?

  • SSB
  • FM
  • CW/data
  • Correct Answer
    All these choices are correct
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What is a satellite beacon?

  • The primary transmit antenna on the satellite
  • An indicator light that shows where to point your antenna
  • A reflective surface on the satellite
  • Correct Answer
    A transmission from a satellite that contains status information
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Which of the following are inputs to a satellite tracking program?

  • The satellite transmitted power
  • Correct Answer
    The Keplerian elements
  • The last observed time of zero Doppler shift
  • All these choices are correct
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What is Doppler shift in reference to satellite communications?

  • A change in the satellite orbit
  • A mode where the satellite receives signals on one band and transmits on another
  • Correct Answer
    An observed change in signal frequency caused by relative motion between the satellite and Earth station
  • A special digital communications mode for some satellites
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What does it mean if a satellite is operating in U/V mode?

  • The satellite uplink is in the 15-meter band and the downlink is in the 10-meter band
  • Correct Answer
    The satellite uplink is in the 70-centimeter band and the downlink is in the 2-meter band
  • The satellite operates using ultraviolet frequencies
  • The satellite frequencies are usually variable
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What causes spin fading of satellite signals?

  • Circular polarized noise interference radiated from the sun
  • Correct Answer
    Rotation of the satellite and its antennas
  • Doppler shift of the received signal
  • Interfering signals within the satellite uplink band
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What does the term LEO mean in reference to communication satellites?

  • Low Energy Orbit, which conserves battery power
  • Low Elevation Orbit, which appears close to the horizon from the earth station
  • Low Equilibrium Orbit, which has a slightly unstable period
  • Correct Answer
    Low Earth Orbit, which has a period of around 100 minutes
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Who is permitted to receive telemetry from an amateur radio satellite?

  • Correct Answer
    Anyone
  • Only the satellite control operator
  • Only the control operator or a licensed radio amateur who has received the encryption key from the control operator
  • Only a licensed radio amateur who has received the encryption key from AMSAT
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Which of the following is a way to determine whether your satellite uplink power into a linear transponder satellite is neither too low nor too high?

  • Check your signal strength report in the telemetry data
  • Listen for distortion on your downlink signal
  • Correct Answer
    Your signal strength on the downlink should be about the same as the beacon
  • Compare your signal to others on the downlink using an internet SDR receiver
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