CRAC Class C (2025) — Questions 231–240
U0695. In amateur satellite communication, how do you determine that your current transmit power is appropriate?
业余电台在进行业余卫星通信时如何确定当前发射功率是恰当 的？
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The practical rule is to adjust your uplink so your downlink signal is roughly equal to the satellite's beacon — strong enough to be copied, but not stronger (A). Telemetry (B) usually shows whole-transponder status, not your level; audio distortion (C) is a receiver issue; asking others (D) is unreliable. A is the standard method.
U0696. In communication between a ground station and an amateur satellite, the main factor affecting signal strength at VHF/UHF is:
业余电台和业余卫星之间通信，VHF/UHF频段影响信号强度的 主要因素是：
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At VHF/UHF the path to a satellite is essentially line-of-sight through space, so the dominant loss is free-space path loss (which grows with distance and frequency) (A). The ionosphere neither absorbs nor reflects VHF/UHF significantly (B, C are false), and ground absorption (D) is not the main factor for the space link.
U0697. In amateur satellite communication, the modes called A, B, K, JA, JD, S, T, etc. indicate:
业余卫星通信中所说的A、B、K、JA、JD、S、T等工作方 式，表示的是：
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The letter designations (Mode A, B, K, JA, JD, S, T…) specify which amateur bands are used for the uplink and downlink and what modulation the transponder supports (e.g., Mode A = 2 m uplink / 10 m downlink) (A). They are not country prefixes (B), power classes (C), or orbital data (D).
U0698. The concept of "Doppler effect" appears in both amateur satellite communication and amateur radio direction finding. The Doppler effect means:
业余卫星通信和业余无线电测向都会出现"多普勒效应"的概 念。多普勒效应是指：
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The Doppler effect (多普勒效应 / Doppler shift) is a frequency offset produced by the relative motion (changing distance) between source and observer (A). B/C/D describe amplitude fading from propagation or polarization, not the Doppler frequency shift.
U0699. When a ground station conducts amateur satellite communication, the Doppler-shift pattern of the received satellite-signal frequency is:
地面业余电台进行业余卫星通信时，接收到的卫星信号频率的 多普勒频移规律是：
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By the Doppler effect, an approaching satellite compresses the wave so the received frequency is higher; a receding satellite stretches it so it is lower. The rate of change (and thus the instantaneous offset) is greatest near the horizon (largest relative velocity along the line of sight) and passes through zero at the zenith (A). B reverses the approach/recede sign; C/D get the zenith behaviour wrong.
U0700. Amateur radio satellites are generally placed in low or elliptical orbits. The main reason is:
业余无线电卫星一般都选择运行在低轨道或者椭圆轨道上。主 要原因是：
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Amateur (typically small/cubesat) satellites use LEO or elliptical orbits mainly because they are cheap to launch (small launchers, rideshare) (A). Orbital height does not increase transponder power (B) or coverage (D — lower orbits actually reduce coverage), and "stronger gravity" (C) is not a stability benefit. 呼叫程序与守听 Calling Procedure and Listening
U0260. Before initiating a call, an amateur station should listen for a while and then ask "is anyone using the frequency?", only calling after confirming no reply. Which of the following English phrases does NOT correctly express this inquiry?
业余电台在发起呼叫前应先守听一段时间，然后再询问“有人 使用频率吗？”，确认没有应答方可发起呼叫。下列英语短句 中不能正确表达这一询问的是：
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The question asks which phrase does NOT mean "is the frequency in use?". B/C/D all ask whether anyone is on frequency. "Calling you, Roger?" (A) is a directed call to a specific station, not a frequency-check query — so A is the incorrect one and is marked correct per the key.
U0261. The method for amateur station BH1ZZZ to initiate a CQ call in FM or SSB voice is:
业余电台BH1ZZZ用FM或SSB话音发起CQ呼叫的方法为：
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A proper Chinese-voice CQ states "CQ CQ CQ, 这里是BH1ZZZ, [phonetics], BH1ZZZ呼叫CQ, 听到请回答" — exactly option A. B ("please continue") is not a CQ; C truncates the call to "1ZZZ" (incomplete); D ends with "您请讲" (you go ahead) which is not a CQ closing.
U0262. The method for amateur station BH1ZZZ to initiate a CQ call in voice is:
业余电台BH1ZZZ用话音发起CQ呼叫的方法为：
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Option A is the standard English-voice CQ: "CQ CQ CQ, this is <call> <phonetics>, <call> calling CQ and standing by." B lacks the call sign; C truncates the call to "One Zulu Zulu Zulu"; D ends with "Back to you" (improper for a general CQ).
U0263. The method for amateur station BH1ZZZ to call BH8YYY in voice is:
业余电台BH1ZZZ用话音呼叫BH8YYY的方法为：
Exam tips · 考试提示
A directed Chinese-voice call repeats the target's call three times, then "这里是BH1ZZZ [phonetics], BH1ZZZ呼叫, 听到请回 答" — exactly option A. B ends with "您继续" (please continue), C truncates the call to "1ZZZ", and D uses an incomplete "8YYY".