CRAC Class A (2025) — Questions 221–230
U0220. Voice contacts on the 2 m band are usually found in 144.035– 145.800 MHz. This is also a multi-mode shared sub-band in the IARU Region 3 band plan. Suppose an amateur station is operating in this band using USB, with an emission bandwidth below 3 kHz and a frequency tolerance better than ±2 kHz; then the settable range for the station's main carrier can be:
2米波段的话音联络通常位于144.035-145.800MHz。这也是 IARU第3区波段规划中的一个多模式共用细分频段。假设一部 业余电台正以USB方式在该频段参与通联，发射带宽小于3kHz 并且频率容限优于±2kHz，则该电台的主载波设置范围可以 是：
Exam tips · 考试提示
The station must keep its entire occupied emission inside the 144.035–145.800 MHz sub-band. For USB the occupied bandwidth is below 3 kHz and the frequency tolerance is within ±2 kHz, so the carrier must be offset from each band edge by the tolerance plus the half-bandwidth margin: lower limit = 144.035 + 0.002 = 144.037 MHz, upper limit = 145.800 − 0.002 − 0.003 = 145.795 MHz. Only option A satisfies both limits; B/C/D would push the signal outside the sub-band.
U0221. In the 70 cm band, amateurs often conduct voice communication in 438–440 MHz. This is also a multi-mode shared sub-band in the IARU Region 3 band plan. Suppose an amateur station is operating in this band using FM, with an emission bandwidth below 20 kHz and a frequency tolerance better than ±2 kHz; then the settable range for the station's main carrier can be:
在70厘米波段中，爱好者经常在438-440MHz展开话音通信。 这也是IARU第3区波段规划中的一个多模式共用细分频段。假 设一部业余电台正以FM方式在该频段参与通联，发射带宽小于 20kHz并且频率容限优于±2kHz，则该电台的主载波设置范围 可以是：
Exam tips · 考试提示
For FM the occupied bandwidth is below 20 kHz and the tolerance is within ±2 kHz, so the carrier must stay at least (2 kHz + ~10 kHz half-bandwidth) inside the 438–440 MHz sub- band. Lower limit = 438.000 + 0.002 + 0.010 = 438.012 MHz; upper limit = 440.000 − 0.002 − 0.010 = 439.988 MHz. Only A falls within both limits. B/C/D would place the emission outside the sub-band.
U0222. In the 70 cm band, amateurs often conduct voice communication in 438–440 MHz. This is also a multi-mode shared sub-band in the IARU Region 3 band plan. Suppose an amateur station is operating in this band using USB, with an emission bandwidth below 3 kHz and a frequency tolerance better than ±2 kHz; then the settable range for the station's main carrier can be:
在70厘米波段中，爱好者经常在438-440MHz展开话音通信。 这也是IARU第3区波段规划中的一个多模式共用细分频段。假 设一部业余电台正以USB方式在该频段参与通联，发射带宽小 于3kHz并且频率容限优于±2kHz，则该电台的主载波设置范 围可以是：
Exam tips · 考试提示
With USB, bandwidth below 3 kHz and tolerance within ±2 kHz, the carrier must stay inside 438–440 MHz with a margin of 2 kHz (tolerance) plus 1.5 kHz (half-bandwidth) at each edge. Lower limit = 438.000 + 0.002 + 0.0015 ≈ 438.0035 → rounded to 438.002 MHz; upper limit = 440.000 − 0.002 − 0.0015 ≈ 439.9965 → 439.995/439.998 MHz. Option A (438.002–439.995) is the only choice fully within both edges. B/C/D cross a band edge.
U0223. In the 10 m amateur band, the segment reserved for the amateur-satellite service, which voice and other communication modes should not occupy, is:
10米业余波段中留给卫星业余业务，话音及其他通信方式不应 占用的频段为：
Exam tips · 考试提示
According to the band plan (《中华人民共和国无线电频率划分规 定》 and IARU Region 3), the 10 m band reserves 29.3–29.51 MHz for the amateur-satellite service; voice and other terrestrial modes must not use this segment. Option A is the correct reserved segment; the other ranges are ordinary terrestrial sub-bands.
U0224. In the 144 MHz amateur band, the segment reserved for the amateur-satellite service, which voice and other communication modes should not occupy, is:
144MHz业余频段中留给卫星业余业务，话音及其他通信方式 不应占用的频段为：
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The 2 m (144 MHz) band plan reserves the top end, 145.8–146 MHz, for the amateur-satellite service; terrestrial voice and other modes must avoid it. Option A is correct. B is a repeater/voice segment, C is a CW/weak-signal segment, and D is an invalid (reversed) range.
U0225. In the 430 MHz amateur band, the segment reserved for the amateur-satellite service, which voice and other communication modes should not occupy, is:
430MHz业余频段中留给卫星业余业务，话音及其他通信方式 不应占用的频段为：
Exam tips · 考试提示
The 70 cm (430 MHz) band plan reserves 435–438 MHz for the amateur-satellite service; terrestrial modes must not occupy it. Option A is correct. B/C/D are normal terrestrial voice/repeater or shared segments.
U0226. During a contact, what method lets you clearly convey the English letters in a call sign or important message?
通话时，有什么方法可以让你清晰表述呼号或重要消息中的英 语字母？
Exam tips · 考试提示
To make individual letters unambiguous on air, amateurs use the standard phonetic alphabet (字母解释法, e.g., Bravo, Hotel) where each letter is spoken as a code word. This is the universally accepted method; analogies, Morse, or AI reading are not the standard spoken technique.
U0227. When a call sign, term, or necessary text must be spelled out, amateur radio operators generally use the spelling method prescribed by the ITU phonetic alphabet. The call sign BH1XYZ is spelled as:
需要拼出呼号、术语和必要的文字时，业余无线电爱好者普遍 使用ITU语音字母表中规定的字母拼读法。呼号BH1XYZ可以 拼读为：
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Each character of BH1XYZ maps to the ITU phonetic alphabet: B=Bravo, H=Hotel, 1=One, X=Xray, Y=Yankee, Z=Zulu. Option A is the correct spelling; the others spell different call signs.
U0228. When a call sign, term, or necessary text must be spelled out, amateur radio operators generally use the spelling method prescribed by the ITU phonetic alphabet. The call sign B7CRA is spelled as:
需要拼出呼号、术语和必要的文字时，业余无线电爱好者普遍 使用ITU语音字母表中规定的字母拼读法。呼号B7CRA可以拼 读为：
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B7CRA maps to: B=Bravo, 7=Seven, C=Charlie, R=Romeo, A=Alfa. Option A is the correct spelling; the others correspond to BH1XYZ, 4U1UN, and VR2ZQW respectively.
U0229. When a call sign, term, or necessary text must be spelled out, amateur radio operators generally use the spelling method prescribed by the ITU phonetic alphabet. The call sign 4U1UN is spelled as:
需要拼出呼号、术语和必要的文字时，业余无线电爱好者普遍 使用ITU语音字母表中规定的字母拼读法。呼号4U1UN可以拼 读为：
Exam tips · 考试提示
4U1UN maps to: 4=Four, U=Uniform, 1=One, U=Uniform, N=November. Option A is correct; "4U" prefixes are used by UN/ITU stations. The others spell different call signs.