CRAC Class C (2025) — Questions 221–230

A geostationary satellite appears nearly fixed over one point on Earth — it is a special case of geosynchronous with a zero- inclination equatorial orbit (A). B is sun-synchronous, C is polar, and D is wrong because not all geosynchronous satellites are geostationary (an inclined geosynchronous satellite is not stationary).

The ascending pass (升轨道) is the arc where the satellite moves northward, crossing the equator at the ascending node (A). Northward motion is "ascending"; southward is "descending" (B).

The descending pass (降轨道) is the arc where the satellite moves southward, crossing the equator at the descending node (A). This is the opposite of the ascending (northbound) pass.

The orbital period is the time for one revolution around the Earth (A). B is the spin (rotation) period, C is the revisit interval over a QTH (longer/irregular), and D is a year — none is the orbital period.

A linear transponder (线性转发器) receives a whole uplink band, translates it in frequency (shift, or shift + inversion for some modes), and retransmits it without demodulating — preserving each signal's modulation (A). Options B/C/D all involve demodulation and re-modulation, which describe a "repeater" type, not a linear transponder.

The defining feature of a linear transponder is that it passes the whole band through without altering modulation, so CW, SSB, FM, digital, etc. can all be relayed (A). B is true of the hardware but not the distinctive system feature asked; C describes demodulate-and-remodulate (not linear); D wrongly limits it to amplitude modes and misstates the principle.

Periodic fast fading of a satellite downlink is typically caused by the satellite (or its antenna) tumbling, so the polarization rotates and no longer matches your fixed antenna (A). The ionosphere (B) causes slower/scintillation effects, not this mechanical periodic fade; C and D are not the cause.

To predict a satellite's position the software must have that satellite's Keplerian elements (TLE/orbital parameters); without them it cannot compute the orbit (A). Magnetic parameters (B), sunspot number (C) and F10.7 flux (D) relate to propagation, not to geometric orbit prediction.

Because an LEO satellite only sees a small area at a time, global messaging is achieved by store-and-forward: the satellite records your uplink and repeats it on a later pass over another station (A). B/C/D do not overcome the limited footprint of a single pass.

A linear transponder has a fixed total power budget; an excessively strong uplink "captures" the transponder (AGC reduces gain), lowering the downlink power available to everyone else and degrading their communications — so overpowering must be opposed (A). B and C are false; D is partly true (waste/pollution) but misses the core harm to other users, and A is the complete correct statement.