CRAC Class C (2025) — Questions 1101–1110

U1270. Sometimes we see a function or circuit block abbreviated VXO in a homebrew amateur transceiver or its schematic. It stands for:

有时，我们会在业余自制的收发信机或其电路图中看到缩写为 VXO的功能或电路组件。它代表：

U1271. Sometimes we see a circuit abbreviated VCO in amateur radio literature or a device schematic. It stands for:

有时，我们会在业余无线电文献或某设备的电路图中看到缩写 为VCO的电路。它代表：

U1272. Sometimes we see a component abbreviated XTAL in amateur radio literature or a device schematic. It stands for:

有时，我们会在业余无线电文献或某设备的电路图中看到缩写 为XTAL的元件。它代表：

U1273. To improve the frequency stability of radio equipment, various high-Q (quality factor) piezoelectric resonator elements have been developed. Considering such elements can mostly be made into oscillators, the following common oscillators arranged from lowest to highest frequency stability are:

为提升无线电设备的频率稳定度，人们研制了多种高Q值压电 谐振元件。考虑这类元件多可做成振荡器，则下列常见振荡器 按频率稳定度由低到高可以排列为：

U1274. Regarding TCXO or OCXO mentioned in the manuals of high- end radio communication equipment, the following descriptions are correct: (Choose all that apply.)

关于高配置无线电通信设备的说明书中提到的TCXO或OCXO， 以下描述正确的是：

U1275. Although nonlinear distortion in a circuit mainly comes from active devices, the inductors or transformers in passive filters can also produce the same distortion when their magnetic cores approach saturation. In addition, a signal containing multiple frequency components will also undergo linear distortion after passing through a filter. Such distortion may include: (Choose all that apply.)

虽然电路中的非线性失真主要来自有源器件，但是无源滤波器 中的电感或变压器在其磁芯趋于饱和时也会产生同样的失真。 此外，包含多个频率分量的信号通过滤波器后还会发生线性失 真。这种失真可能包括：

U1276. A circuit's "phase distortion" means the output signal, compared with the input, undergoes the following change:

电路的"相位失真"是指该电路的输出信号与输入信号相比发生 了下列改变：

U1277. A circuit's "frequency distortion" means the output signal waveform, compared with the input, undergoes the following change:

电路的"频率失真"是指该电路的输出信号波形与输入信号相比 发生了如下变化：

U1278. When assembling an amateur transceiver, hams often use resonant circuits (tank circuits) to select signals of a specific frequency. The main components forming a resonant circuit include:

组装业余收发信机时，爱好者常用谐振回路来筛选特定频率的 信号。组成谐振回路的主要元件包括：

U1279. Building a frequency multiplier uses a high-performance band-pass filter or some LC resonant circuit with excellent selectivity. Among the following LC circuits, the one with the best selectivity is:

制作倍频器会用到高性能带通滤波器或是某种选择性优良的LC 谐振回路。下列LC回路中，选择性最佳的是：