CRAC Class C (2025) — Questions 461–470
U0808. Generally speaking, the best time period for 10 m band DX communication is:
通常来说，10米波段DX通信的最佳时段是：
Exam tips · 考试提示
The 10 m band (28 MHz) is primarily supported by daytime F2- layer propagation, so daytime is its best DX window. At night (B) and during very low solar flux (D) 10 m goes quiet; CME events (C) are sporadic and not the "usual" best time.
U0809. When applying for the WAS (Worked All States) award, which of the following call-sign cards cannot be used as proof of contact:
申请WAS奖状时，不能用以下哪个呼号的卡片作为通联证明：
Exam tips · 考试提示
WAS requires contacts with the 50 US states. VA3EJ is a Canadian (VE3 area) call, not a US state, so it cannot count. AC6HY (California), N8DX (Ohio), and KC1XX (Maine) are all US calls.
U0810. To apply for the 5-band WAZ award (5BWAZ), at least how many zone cards must be submitted:
申请五波段WAZ奖状（5BWAZ），至少要提交多少个分区的 卡片：
Exam tips · 考试提示
The 5BWAZ award requires confirmed contacts with all CQ zones across five bands; per the official question key the minimum number of zone cards to submit is 198. Note: candidates should follow the published CQ WAZ rule for the exact threshold; the source answer key here specifies 198.
U0811. For amateur radio operators in our country, which of the following stations is the rarest and most difficult to contact:
对于我国爱好者来说，以下电台中最稀有，最不易通联的是：
Exam tips · 考试提示
KP5 is the Desecheo Island prefix — one of the most wanted and rarely activated DXCC entities, hence the hardest to work. VK0HR (Heard Island), AH0K (Northern Mariana), and ZS1EZ (South Africa) are rarer-than-average but far more frequently on the air than KP5.
U0812. To apply for the satellite and 6 m WAZ awards, at least how many zone QSL cards must be submitted?
申请卫星和6米WAZ奖状需要至少提交多少个区的QSL卡片？
Exam tips · 考试提示
The satellite WAZ and 6 m WAZ awards each require confirmation of 25 CQ zones (a reduced threshold compared with the standard 40-zone WAZ, because these modes/(bands cover fewer zones). The keyed answer is 25.
U0813. To apply for the 160 m WAZ award, at least how many zone QSL cards must be submitted?
申请160米WAZ奖状需要至少提交多少个区的QSL卡片？
Exam tips · 考试提示
Like the 6 m and satellite WAZ awards, the 160 m WAZ uses the reduced 25-zone requirement because Top Band propagation reaches fewer CQ zones. The keyed answer is 25.
U0814. On 14022 kHz many stations are eagerly sending their call signs. They are calling a rare station whose transmit frequency is 14020 kHz. If you want to work that station, you may:
在14022kHz有很多电台争相报出自己的呼号。他们是在呼叫 发射频率为14020kHz的一个稀有台。如果你要联络该台，你 可以：
Exam tips · 考试提示
In a "split" DX pile-up, the DX station transmits on 14020 kHz and receives (listens) on 14022 kHz. You monitor its transmit frequency to know when it is ready, then answer on its listening frequency (14022 kHz) with only your own call. Sending on its transmit frequency (B/D) or hammering away (C) would collide with the DX.
U0815. Taking Beijing as the center, the great-circle distances to the DXCC entities 3X, HZ, G, and OE, arranged from farthest to nearest, can be ordered as:
以北京为中心，则与DXCC实体3X、HZ、G、OE的大圆距离由 远及近可排列为：
Exam tips · 考试提示
From Beijing: 3X (Guinea, West Africa) is farthest, then G (United Kingdom), then OE (Austria), then HZ (Saudi Arabia) which is nearest. So the farthest-to-nearest order is 3X, G, OE, HZ.
U0816. When we use a directional antenna to contact amateur stations in Europe, we often point the antenna toward roughly 300° (ten o'clock). Correspondingly, if a European station wants to contact us, its antenna should roughly point toward:
我们使用定向天线联络欧洲的业余电台时常将天线指向大约 300度（十点钟）的方向。相应地，如果某个欧洲电台要联络 我们，其天线应大体指向：
Exam tips · 考试提示
Propagation is reciprocal: a beam pointed from Beijing toward Europe at ~300° must be met by a European beam pointed back toward Beijing. Per the official key, the European station's antenna points toward ~60° (two o'clock) — the reciprocal great-circle bearing from Europe back to Beijing.
U0817. To erect a horizontally polarized half-wave dipole in Beijing in an attempt to contact amateur stations in New York, considering the shortest propagation path, the antenna's orientation should roughly be:
在北京架设一副水平极化的半波长偶极天线以尝试联络纽约的 业余电台，若按最短的传播路径考虑，天线的走向应大致为：
Exam tips · 考试提示
A horizontal half-wave dipole radiates broadside (perpendicular to the wire). The shortest Beijing–New York path (over the North Pole region) runs roughly north–south, so the dipole should be oriented east–west so its broadside points north–south toward New York.