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Subelement T8
Modulation modes: amateur satellite operation; operating activities; non-voice communications
Section T8B
Amateur satellite operation; Doppler shift, basic orbits, operating protocols; control operator, transmitter power considerations; satellite tracking; digital modes
Who may be the control operator of a station communicating through an amateur satellite or space station?
  • Only an Amateur Extra Class operator
  • A General Class licensee or higher licensee who has a satellite operator certification
  • Only an Amateur Extra Class operator who is also an AMSAT member
  • Correct Answer
    Any amateur whose license privileges allow them to transmit on the satellite uplink frequency

There are no special requirements as far as licensing goes for talking to a satellite; it's a station like any other, it just happens to be in a very remote location. As long as you are allowed to transmit on the uplink frequency (the frequency the satellite listens on) you can communicate through it.

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Tags: satellite operation control operator space station license class arrl chapter 6 arrl module 14

How much transmitter power should be used on the uplink frequency of an amateur satellite or space station?
  • The maximum power of your transmitter
  • Correct Answer
    The minimum amount of power needed to complete the contact
  • No more than half the rating of your linear amplifier
  • Never more than 1 watt

This is a good rule of thumb in any case; never use more power than you actually need, and particularly not when communicating over a long distance. The reason is that the more power you use the more likely you are to cause inadvertant but harmful interference to other stations.

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Tags: transmit power satellite operation space station arrl chapter 6 arrl module 14

Which of the following are provided by satellite tracking programs?
  • Maps showing the real-time position of the satellite track over the 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 of these answers are correct

Satellite tracking programs tell you where a satellite is at a given time, including its altitude and where it will be at the start and end of a pass, relative to your location.

The tracking programs even tell you how much to change your transmitter's and receiver's frequency to compensate for the Doppler shift you get when the satellite is coming toward you or moving away from you.

So all of these answers are correct.

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Tags: arrl chapter 6 arrl module 14

Which amateur stations may make contact with an amateur station on the International Space Station using 2 meter and 70 cm band amateur radio frequencies?
  • Only members of amateur radio clubs at NASA facilities
  • Correct Answer
    Any amateur holding a Technician or higher class license
  • Only the astronaut's family members who are hams
  • You cannot talk to the ISS on amateur radio frequencies

There are no special requirements as far as licensing goes for talking to a satellite or space station; it's a station like any other, it just happens to be in a very remote location. As long as you are allowed to transmit on the uplink frequency (the frequency the satellite listens on) you can communicate through it.

Since any amateur radio operator with a Technician or higher class license can operate on the 2 meter and 70 cm bands, that means that those operators can also make contact with a station in space.

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Tags: license class 2 meter 70 cm arrl chapter 6 arrl module 14

What is a satellite beacon?
  • The primary transmit antenna on the satellite
  • An indicator light that that shows where to point your antenna
  • A reflective surface on the satellite
  • Correct Answer
    A transmission from a space station that contains information about a satellite

A beacon provides us with a gauge to determine how much power we should use. If you transmit your signal and compare it to the beacon strength, you can then adjust your power up or down to match the beacon. That would be the optimum transmitting power for your station. The next thing that the beacons provide us with is a schedule of the satellite's activity. It might tell you that it is on during a particular time period and off during others.

The beacon can also help us tune our radio to compensate for doppler shift. Since we know the beacon is supposed to be on a certain frequency, we can calculate where our signal will be based on the current reception of the beacon (http://www.amsat.org/articles/houston-net/beacons.html)

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Tags: satellite operation definitions arrl chapter 6 arrl module 14

Which of the following are inputs to a satellite tracking program?
  • The weight of the satellite
  • Correct Answer
    The Keplerian elements
  • The last observed time of zero Doppler shift
  • All of these answers are correct

Keplerian elements, named after Johannes Kepler (1571-1630) and his laws of planetary motion, are the parameters that define the orbit of a satellite. From these elements, a computer program can calculate the time and bearing of a satellite pass, relative to your position on the earth.

The weight of the satellite is not one of the Keplerian elements. The last observed time of zero Doppler shift would be the time that the satellite was moving neither toward you nor away from you (like when it was overhead, for example). While this might be interesting data, it isn't enough to predict where it will be coming from or going to on its next pass, or at what altitudes.

According to AMSAT's "Keplerian Elements Tutorial" the "basic orbital elements are":

  1. Epoch
  2. Orbital Inclination
  3. Right Ascension of Ascending Node (R.A.A.N.)
  4. Argument of Perigee
  5. Eccentricity
  6. Mean Motion
  7. Mean Anomaly
  8. Drag (optional)

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With regard to satellite communications, what is Doppler shift?
  • 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 the earth station
  • A special digital communications mode for some satellites

The most common references to the doppler effect (or doppler shift) refer to sound; one of the most common examples used in highschool science classes involves a fire engine (or other vehicle with a siren) whose siren seems to drop in pitch drastically when the vehicle passes you. The producer of the sound does not actually change frequency, but the relative speed of the vehicle producing the sound to the object (you) receiving the sound makes it seem to you that it does.

The same principle applies to a radio frequency signal; the relative motion between a satellite and the earth station can cause a shift in the frequency at which you can receive the signal depending on what its position and momentum are relative to the receiving station.

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What is meant by the statement that a satellite is operating in mode U/V?
  • 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 cm band and the downlink is in the 2 meter band
  • The satellite operates using ultraviolet frequencies
  • The satellite frequencies are usually variable

"mode U/V" is short for "mode UHF/VHF" -- meaning that the uplink is UHF, meaning 70 cm, and the downlink is VHF, meaning 2 meters. There are of course other UHF bands besides 70cm and other VHF bands besides 2m, but they are not commonly used by amateur radio operators and so the term is understood to mean the standard UHF/VHF bands.

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Tags: 70 cm 2 meter satellite operation arrl chapter 6 arrl module 14

What causes spin fading when referring to 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

Satellites are not stationary in space; they are constantly moving, and generally they are rotating as well. As they turn, the antennas on the satellite change position relative to your location. The signal may fade if the antennas are directional, or even if omnidirectional, if they are obscured by the rest of the satellite.

This is referred to as "spin fading" because the fading is caused by the satellite spinning around.

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What do the initials LEO tell you about an amateur satellite?
  • The satellite battery is in Low Energy Operation mode
  • The satellite is performing a Lunar Ejection Orbit maneuver
  • Correct Answer
    The satellite is in a Low Earth Orbit
  • The satellite uses Light Emitting Optics

Just remember that we are talking about a satellite; this question could be a bit tricky if you haven't seen it before, but LEO refers to the position, not to any operation. It is, as the answer indicates, Low Earth Orbit.

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What is a commonly used method of sending signals to and from a digital satellite?
  • USB AFSK
  • PSK31
  • Correct Answer
    FM Packet
  • WSJT

Most amateur satellite communication takes place on 2 meters or 70 cm, though 15 meters is also used at times. With both 2m and 70cm, FM is the most common mode, and so FM packet is the most logical mode to use.

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