FCC T7C - 电台设备与故障排查

#T7C01🔗

What is the primary purpose of a dummy load?

假负载的主要目的是什么？

To prevent transmitting signals over the air when making tests

进行测试时防止通过空中传输信号

✓ 正确答案

To prevent over-modulation of a transmitter

防止发射机的过度调制

To improve the efficiency of an antenna

提高天线效率

To improve the signal-to-noise ratio of a receiver

提高接收机的信噪比

#T7C02🔗

Which of the following is used to determine if an antenna is resonant at the desired operating frequency?

化碳以下哪项用于确定天线是否谐振在所需的工作频率？

A VTVM

一个VVM

An antenna analyzer

天线分析仪

✓ 正确答案

A Q meter

水质计

A frequency counter

频率计数器

#T7C03🔗

What does a typical RF dummy load consist of?

典型的射频假负载由什么组成？

A low-voltage power supply and an AC relay

低压电源和交流继电器

A 50-ohm non-inductive resistor mounted on a heat sink

安装在散热器上的 50 欧姆无感电阻

✓ 正确答案

A low-voltage power supply and a DC relay

低压电源和直流继电器

A 50-ohm inductive reactance mounted in a shielded enclosure

安装在屏蔽外壳中的 50 欧姆感抗

#T7C04🔗

What reading on an SWR meter indicates a perfect impedance match between the antenna and the feed line?

SWR 表上的什么读数表明天线和馈线之间的阻抗完美匹配？

50:50

Zero

零

1 : 1

✓ 正确答案

Full Scale

满量程

#T7C05🔗

Why do most solid-state transmitters reduce output power as SWR increases beyond a certain level?

为什么大多数固态发射机会随着 SWR 增加超过一定水平而降低输出功率？

To protect the RF output amplifier transistors

保护射频输出放大器晶体管

✓ 正确答案

To comply with FCC rules on spectral purity

遵守 FCC 关于光谱纯度的规定

Because power supplies cannot supply enough current at high SWR

因为电源无法在高 SWR 下提供足够的电流

To lower the SWR on the transmission line

降低传输线上的 SWR

#T7C06🔗

What does an SWR reading of 4:1 indicate?

1 的 SWR 读数表示什么？

Loss of -4 dB

损失 -4 分贝

Good impedance match

良好的阻抗匹配

Gain of +4 dB

+4 分贝的增益

Impedance mismatch

阻抗失配

✓ 正确答案

#T7C07🔗

What happens to power lost in a feed line?

馈线中的功率损失会怎样？

It increases the SWR

它增加了SWR

It is radiated as harmonics

它以谐波形式辐射

It is converted into heat

它转化为热量

✓ 正确答案

It distorts the signal

它使信号失真

#T7C08🔗

Which instrument can be used to determine SWR?

哪种仪器可用于确定 SWR？

Voltmeter

电压表

Ohmmeter

欧姆表

Iambic pentameter

抑扬格五音步

Directional wattmeter

定向功率计

✓ 正确答案

#T7C09🔗

Which of the following causes failure of coaxial cables?

以下哪项会导致同轴电缆出现故障？

Moisture contamination

水分污染

✓ 正确答案

Solder flux contamination

助焊剂污染

Rapid fluctuation in transmitter output power

发射机输出功率的快速波动

Operation at 100% duty cycle for an extended period

长时间以 100% 占空比运行

#T7C10🔗

Why should the outer jacket of coaxial cable be resistant to ultraviolet light?

为什么同轴电缆的外护套要耐紫外线？

Ultraviolet light can increase the resistance of the conductors

紫外线可以增加导体的电阻

Ultraviolet light can increase losses in the cable’s jacket

紫外线会增加电缆护套中的损耗

Ultraviolet and RF signals can mix, causing interference

紫外线和射频信号可以混合，造成干扰

Ultraviolet light can damage the jacket and allow water to enter the cable

紫外线会损坏护套并让水进入电缆

✓ 正确答案

#T7C11🔗

What is an advantage of foam-dielectric versus solid-dielectric coaxial cable?

泡沫电介质同轴电缆与固体电介质同轴电缆相比有何优势？

It is more resistant to moisture contamination

更能抵抗湿气污染

It has higher voltage breakdown

它具有更高的击穿电压

It has less loss per foot

每英尺的损失更少

✓ 正确答案

It has a better impedance match to 50 ohms

它具有更好的 50 欧姆阻抗匹配

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FCC T7C - 电台设备与故障排查

小节 T7C：电台设备与故障排查