An astronomical object is Ascending when it is moving north in latitude with respect to the celestial sphere or "up" with respect to the usual ground map. Descending means moving south or "down" with respect to the map.

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An inverted linear transponder reverses the ordering of frequencies between input and output. The Doppler shift shifts the input and output frequencies the same way, and so there is some cancellation due to the reversing effect of the transponder. USB and LSB signals are likewise swapped, as is signal position.

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Satellites have transponders, which receive the uplink signal and retransmit it as a downlink signal. Unlike your usual repeaters, though, they receive an entire band of signals and retransmit the entire band shifted to another frequency.

Transponders come in both inverting and non-inverting types. The inverting type, which is the subject of this question, "flips" the entire band before retransmitting; thus, the highest frequency in the uplink becomes the lowest frequency in the downlink.

To do this, The signal is passed through a mixer and the difference rather than the sum is transmitted. The base band frequency is chosen such that the proper "shift" occurs, but in the inverting case, the mixer operation calculates offsets from the other side of the baseband compared to the non-inverting case, and the baseband frequency is chosen accordingly.

The other answers are wrong, and this is easy to remember if you just remember that:

• a frequency mixer can produce both sums and differences;

• a mixer is used to invert the signal in this type of transponder.

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Historically OSCAR uplink (transmit to) and downlink (receive from) frequencies were designated using single letter codes.

Mode A: 2 m uplink / 10 m downlink

Mode B: 70 cm uplink / 2 m downlink

Mode J: 2 m uplink / 70 cm downlink

New uplink and downlink designations use sets of paired letters following the structure X/Y where X is the uplink band and Y is the downlink band.

Reference: http://en.wikipedia.org/wiki/OSCAR#Mode_designators

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Historically OSCAR uplink (transmit to) and downlink (receive from) frequencies were designated using single letter codes.

• Mode A: 2 m uplink / 10 m downlink
• Mode B: 70 cm uplink / 2 m downlink
• Mode J: 2 m uplink / 70 cm downlink

New uplink and downlink designations use sets of paired letters following the structure X/Y where X is the uplink band and Y is the downlink band.

Reference: http://en.wikipedia.org/wiki/OSCAR#Mode_designators

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Memory item:

Keplerian elements are a set of numerical parameters that define the motion of an orbiting body or satellite. They are named after Johannes Kepler who first defined the laws governing orbiting planet motion.

See http://en.wikipedia.org/wiki/Orbital_elements

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A linear transponder takes one range of frequencies and directly shifts it to another range, without decoding and re-encoding the signals. Therefore, any signal type that fits in the transponder's bandwidth can be used through it.

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Satellite transponders are power-sharing. If one signal received at the satellite is stronger than the others, all other retransmitted signals will get a smaller portion of the available power.

Memory trick: associate linear with downlink and limited with reducing

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Transponder link designators:

-w3mit

Keeping in mind that V is 2m (the VHF-band on many 2-band hand helds) and U is 70cm (the UHF band on many 2-band hand-helds), think "long and short" -- 23cm is longer than 13cm.

Study Hint: Think "(L)ittle and (S)mall" for 23 and 13 cm. “LS” looks like 23 and "ls" looks like 13.

See the mode designator chart

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A geosynchronous satellite is actually moving along its orbit just like any other satellite. It is at a height and position such that this orbital rotation matches the earth’s rotation and so it appears to be stationary.

LEO means "Low Earth Orbit" and HEO means "Highly Elliptical Orbit" and both are not relevant to this question. A geomagnetic orbit is not a thing, I think.

Hint: It’s the only question with stationary in it.

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Faraday rotation is the change in radio wave polarization due to the presence of a magnetic field, while spin modulation is also a polarization change, but due to the rotation of the signal source or of an object that reflects the radio wave, such as a satellite. Both effects can result in rotating radio waves, which can be minimized by a circularly polarized antenna.

Memory trick: “spin” in a ”circular” motion.

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With a satellite in low earth orbit, the transmit and receive stations may not have a line of sight path to the satellite at the same time. Store and forward allows the transmission to be stored for a while until the receiving station can be “seen” by the satellite.

HINT: Store-and-forward implies a delay; so messages are downloaded later.

Other Answers

• ...upload ... software - doesn't forward anything.
• ...delay download of telemetry... - nothing is initially sent to store; telemetry is initiated in the satellite.
• ...relay messages between satellites - unfortunately this is a store-and-forward use-case, but doesn't apply to HAM satellites since it requires a larger constellation of satellites to work in low earth orbit.

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