CRAC Class A (2025) — Questions 191–200
U0190. On the 18 MHz band, the frequency range a short-wave amateur station may actually occupy when conducting USB voice contacts is:
短波业余电台在18MHz频段进行USB通话时可以实际占用的频 率为：
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The 18 MHz WARC band is 18.068–18.168 MHz. For USB voice, the carrier is offset above 18.068 by one sideband width and capped at the 18.168 upper edge, giving 18.1105–18.168 MHz (A). B/C/D overreach the band edges.
U0191. On the 21 MHz band, the frequency range a short-wave amateur station may actually occupy when conducting USB voice contacts is:
短波业余电台在21MHz频段进行USB通话时可以实际占用的频 率为：
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On 21 MHz (15 m), USB voice occupies 21.125–21.45 MHz, but must exclude the IARU beacon at 21.150 MHz (±500 Hz → 21.1495– 21.1505) (A). B omits the beacon exclusion; C/D use the wrong lower edge (21.000).
U0192. On the 24 MHz band, the frequency range a short-wave amateur station may actually occupy when conducting USB voice contacts is:
短波业余电台在24MHz频段进行USB通话时可以实际占用的频 率为：
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The 24 MHz WARC band is 24.89–24.99 MHz. USB voice starts above the 24.930 beacon (the 24.930 MHz IARU beacon plus offset) and ends at the 24.99 upper edge, giving 24.9305–24.99 MHz (A). Other options ignore the beacon exclusion or use wrong edges.
U0193. On the ~29 MHz band, the frequency range a short-wave amateur station may actually occupy when conducting USB voice contacts is:
短波业余电台在29MHz频段进行USB通话时可以实际占用的频 率为：
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The 10 m band is 28–29.7 MHz. For USB voice near the top, the usable window is 28.3–29.3 MHz (A) — kept below 29.7 to contain the upper sideband and above 28.3 to keep the lower sideband in- band. B/D use the full band edges (sideband would spill), and C reaches the 29.7 top edge.
U0194. On the ~29 MHz band, the frequency range a short-wave amateur station may actually occupy when conducting FM voice contacts is:
短波业余电台在29MHz频段进行FM通话时可以实际占用的频 率为：
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FM needs a wider bandwidth, so on 10 m it is confined to the top of the band, 29.51–29.7 MHz (A), which is the FM/repeater segment. B is too wide; C and D include the SSB/lower regions. (Note: option C in the source contains a stray character "z", preserved verbatim.)
U0195. When conducting local contacts on the 144 MHz band, the frequencies a VHF amateur station should avoid occupying are:
VHF业余无线电台在144MHz频段进行本地联络时应避免占用 的频率为：
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For local 2 m work you should avoid 144–144.035 MHz (EME / weak-signal / propagation) and 145.8–146 MHz (satellite uplink/downlink) (A). B is the main simplex/voice region you should use; C/D list sub-segments, not the protected edges.
U0196. When conducting local contacts on the 430 MHz band, the frequencies a UHF amateur station should avoid occupying are:
UHF业余无线电台在430MHz频段进行本地联络时应避免占用 的频率为：
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For local 70 cm work you should avoid 431.9–432.240 MHz (satellite uplink) and 435–438 MHz (satellite downlink) (A). The other options list the usable regions or wrong segments.
U0197. Where the lower frequency limit of a band allocated to the amateur service is F1, the actual transmit frequency an amateur station may operate at should be:
分配给业余业务的某频段的频率下限为F1，业余电台实际可以 工作的发信频率应为：
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For a band with lower edge F1, the transmit carrier must sit at F1 plus the lower-sideband width so the signal's lower edge stays at/above F1 (A). Placing the carrier at F1 (B) or below (C/D) would push the lower sideband below the band edge.
U0198. Where the upper frequency limit of a band allocated to the amateur service is F2, the actual transmit frequency an amateur station may operate at should be:
分配给业余业务的某频段的频率上限为F2，业余电台实际可以 工作的发信频率应为：
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For a band with upper edge F2, the carrier must sit at F2 minus the upper-sideband width so the signal's upper edge stays at/below F2 (A). Placing the carrier at F2 (B) or above (C) would push the upper sideband above the band edge.
U0199. The ITU's attitude toward the 5–30 MHz short-wave bands is:
ITU对于5至30MHz短波频段的态度是：
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The ITU Radio Regulations note that the 5–30 MHz bands are particularly suited to long-distance communication and encourage administrations, where practicable, to use other means of communication to avoid harmful interference to that long-distance service (A). B/C/D invert or contradict this policy.