CRAC Class B (2025) — Questions 281–290

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.

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

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.

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.

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).

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".

A signal report is given by naming the station and stating its signal: "BH1ZZZ, 你的信号57" then confirming copy (A). B asks permission oddly; C gives the number without naming the station; D uses "this is BH1ZZZ" which would falsely claim to be the other station. Only A is correct.

QTH means "my location", so "我的QTH是成都" (My QTH is Chengdu) is the correct way to state operating location (A). QRT = shutting down (B), QRO = increasing power (C), QRV = I am ready / equipped (D) — none mean "located at".

"Cheerio" (British English), "Ciao ciao" (Italian), and "Do svidaniya" (Russian) are all friendly farewells. On the air they express mutual good wishes and goodbye between operators of different regions (A). B/C/D only describe the linguistic nature, not the communicative meaning.

Good CW practice is to reply at a speed you can both send and copy well, and never faster than the station you are answering (A). Matching or exceeding the other's speed (B) is rude/uncopyable; the fixed WPM limits in C/D are not the rule.