FCC E4A - 业余电台实践与测试

#E4A01🔗

Which of the following limits the highest frequency signal that can be accurately displayed on a digital oscilloscope?

以下哪项限制了数字示波器上可以精确显示的最高频率信号？

Sampling rate of the analog-to-digital converter

模数转换器的采样率

✓ 正确答案

Analog-to-digital converter reference frequency

模数转换器参考频率

Q of the circuit

电路的Q值

All these choices are correct

所有这些选项都是正确的

#E4A02🔗

Which of the following parameters does a spectrum analyzer display on the vertical and horizontal axes?

频谱分析仪在垂直轴和水平轴上显示以下哪些参数？

Signal amplitude and time

信号幅度和时间

Signal amplitude and frequency

信号幅度和频率

✓ 正确答案

SWR and frequency

驻波比和频率

SWR and time

驻波比和时间

#E4A03🔗

Which of the following test instruments is used to display spurious signals and/or intermodulation distortion products generated by an SSB transmitter?

以下哪种测试仪器用于显示 SSB 发射机生成的杂散信号和/或互调失真产物？

Differential resolver

差动旋转变压器

Spectrum analyzer

频谱分析仪

✓ 正确答案

Logic analyzer

逻辑分析仪

Network analyzer

网络分析仪

#E4A04🔗

How is compensation of an oscilloscope probe performed?

示波器探头的补偿是如何进行的？

A square wave is displayed, and the probe is adjusted until the horizontal portions of the displayed wave are as nearly flat as possible

显示方波，并调整探头，直到显示波的水平部分尽可能接近平坦

✓ 正确答案

A high frequency sine wave is displayed, and the probe is adjusted for maximum amplitude

显示高频正弦波，并将探头调整至最大幅度

A frequency standard is displayed, and the probe is adjusted until the deflection time is accurate

显示频率标准，调整探头直至偏转时间准确

A DC voltage standard is displayed, and the probe is adjusted until the displayed voltage is accurate

显示直流电压标准，调节探头直至显示电压准确

#E4A05🔗

What is the purpose of using a prescaler with a frequency counter?

使用预分频器和频率计数器的目的是什么？

Amplify low-level signals for more accurate counting

放大低电平信号以实现更准确的计数

Multiply a higher frequency signal so a low-frequency counter can display the operating frequency

乘以较高频率的信号，以便低频计数器可以显示工作频率

Prevent oscillation in a low-frequency counter circuit

防止低频计数器电路中的振荡

Reduce the signal frequency to within the counter's operating range

将信号频率降低到计数器的工作范围内

✓ 正确答案

#E4A06🔗

What is the effect of aliasing on a digital oscilloscope when displaying a waveform?

显示波形时，混叠对数字示波器有何影响？

A false , jittery low - frequency version of the waveform is displayed

显示错误的、抖动的低频版本的波形。

✓ 正确答案

The waveform DC offset will be inaccurate

波形 DC 偏移将不准确

Calibration of the vertical scale is no longer valid

垂直刻度的校准不再有效

Excessive blanking occurs, which prevents display of the waveform

消隐过多，导致波形无法显示

#E4A07🔗

Which of the following is an advantage of using an antenna analyzer compared to an SWR bridge?

与 SWR 电桥相比，使用天线分析仪有以下哪些优势？

Antenna analyzers automatically tune your antenna for resonance

天线分析仪自动调整天线的谐振

Antenna analyzers compute SWR and impedance automatically

天线分析仪自动计算 SWR 和阻抗

✓ 正确答案

Antenna analyzers display a time-varying representation of the modulation envelope

天线分析仪显示调制包络随时间变化的表示

All these choices are correct

所有这些选项都是正确的

#E4A08🔗

Which of the following is used to measure SWR?

以下哪项用于测量 SWR？

Directional wattmeter

定向功率计

Vector network analyzer

矢量网络分析仪

Antenna analyzer

天线分析仪

All these choices are correct

所有这些选项都是正确的

✓ 正确答案

#E4A09🔗

Which of the following is good practice when using an oscilloscope probe?

使用示波器探头时，以下哪一项是好的做法？

Minimize the length of the probe's ground connection

尽量缩短探头接地连接的长度

✓ 正确答案

Never use a high-impedance probe to measure a low-impedance circuit

切勿使用高阻抗探头来测量低阻抗电路

Never use a DC-coupled probe to measure an AC circuit

切勿使用直流耦合探头来测量交流电路

All these choices are correct

所有这些选项都是正确的

#E4A10🔗

Which trigger mode is most effective when using an oscilloscope to measure a linear power supply’s output ripple?

使用示波器测量线性电源的输出纹波时，哪种触发模式最有效？

Single-shot

单发

Edge

边缘

Level

级别

Line

线

✓ 正确答案

#E4A11🔗

Which of the following can be measured with an antenna analyzer?

以下哪项可以使用天线分析仪进行测量？

Velocity factor

速度系数

Cable length

电缆长度

Resonant frequency of a tuned circuit

调谐电路的谐振频率

All these choices are correct

所有这些选项都是正确的

✓ 正确答案

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FCC E4A - 业余电台实践与测试

小节 E4A：业余电台实践与测试