FCC G4A - 业余无线电实践与电台操作

#G4A01🔗

What is the purpose of the notch filter found on many HF transceivers?

许多 HF 收发器上的陷波滤波器的用途是什么？

To restrict the transmitter voice bandwidth

限制发射机语音带宽

To reduce interference from carriers in the receiver passband

减少接收机通带中载波的干扰

✓ 正确答案

To eliminate receiver interference from impulse noise sources

消除脉冲噪声源对接收机的干扰

To remove interfering splatter generated by signals on adjacent frequencies

消除相邻频率信号产生的干扰飞溅

#G4A02🔗

What is the benefit of using the opposite or “reverse” sideband when receiving CW?

接收 CW 时使用相反或“反向”边带有什么好处？

Interference from impulse noise will be eliminated

脉冲噪声的干扰将被消除

More stations can be accommodated within a given signal passband

在给定的信号通带内可以容纳更多的站

It may be possible to reduce or eliminate interference from other signals

可以减少或消除其他信号的干扰

✓ 正确答案

Accidental out-of-band operation can be prevented

可以防止意外的带外操作

#G4A03🔗

How does a noise blanker work?

噪声消除器如何工作？

By temporarily increasing received bandwidth

通过暂时增加接收带宽

By redirecting noise pulses into a filter capacitor

通过将噪声脉冲重定向至滤波电容器

By reducing receiver gain during a noise pulse

通过在噪声脉冲期间降低接收器增益

✓ 正确答案

By clipping noise peaks

通过剪切噪声峰值

#G4A04🔗

What is the effect on plate current of the correct setting of a vacuum-tube RF power amplifier’s TUNE control?

真空管射频功率放大器的 TUNE 控制的正确设置对板电流有何影响？

A pronounced peak

明显的峰值

A pronounced dip

明显的下降

✓ 正确答案

No change will be observed

不会观察到任何变化

A slow, rhythmic oscillation

缓慢、有节奏的振荡

#G4A05🔗

Why is automatic level control (ALC) used with an RF power amplifier?

为什么射频功率放大器要使用自动电平控制 (ALC)？

To balance the transmitter audio frequency response

平衡发射机音频响应

To reduce harmonic radiation

减少谐波辐射

To prevent excessive drive

防止过度驱动

✓ 正确答案

To increase overall efficiency

提高整体效率

#G4A06🔗

What is the purpose of an antenna tuner?

天线调谐器的用途是什么？

Reduce the SWR in the feed line to the antenna

降低天线馈线中的 SWR

Reduce the power dissipation in the feedline to the antenna

减少天线馈线的功耗

Increase power transfer from the transmitter to the feed line

增加从发射器到馈线的功率传输

✓ 正确答案

All these choices are correct

所有这些选项都是正确的

#G4A07🔗

What happens as a receiver’s noise reduction control level is increased?

当接收器的降噪控制水平提高时会发生什么？

Received signals may become distorted

接收到的信号可能会失真

✓ 正确答案

Received frequency may become unstable

接收频率可能会变得不稳定

CW signals may become severely attenuated

CW 信号可能会严重衰减

Received frequency may shift several kHz

接收频率可能会偏移几 kHz

#G4A08🔗

What is the correct adjustment for the LOAD or COUPLING control of a vacuum tube RF power amplifier?

真空管射频功率放大器的负载或耦合控制的正确调整是什么？

Minimum SWR on the antenna

天线上的最小驻波比

Minimum plate current without exceeding maximum allowable grid current

最小板电流不超过最大允许电网电流

Highest plate voltage while minimizing grid current

最高板电压，同时最小化栅极电流

Desired power output without exceeding maximum allowable plate current

不超过最大允许板电流的所需功率输出

✓ 正确答案

#G4A09🔗

What is the purpose of delaying RF output after activating a transmitter’s keying line to an external amplifier?

激活发射器到外部放大器的键控线后延迟射频输出的目的是什么？

To prevent key clicks on CW

防止 CW 上的按键点击

To prevent transient overmodulation

防止瞬态过调制

To allow time for the amplifier to switch the antenna between the transceiver and the amplifier output

允许放大器有时间在收发器和放大器输出之间切换天线

✓ 正确答案

To allow time for the amplifier power supply to reach operating level

让放大器电源有时间达到工作水平

#G4A10🔗

What is the function of an electronic keyer?

电子键控器的作用是什么？

Automatic transmit/receive switching

自动发射/接收切换

Automatic generation of dots and dashes for CW operation

自动生成 CW 操作的点和划线

✓ 正确答案

To allow time for switching the antenna from the receiver to the transmitter

留出时间将天线从接收器切换到发射器

Computer interface for PSK and RTTY operation

用于 PSK 和 RTTY 操作的计算机接口

#G4A11🔗

Why should the ALC system be inactive when transmitting AFSK data signals?

为什么在传输 AFSK 数据信号时 ALC 系统应处于非活动状态？

ALC will invert the modulation of the AFSK mode

ALC 将反转 AFSK 模式的调制

The ALC action distorts the signal

ALC 操作会使信号失真

✓ 正确答案

When using digital modes, too much ALC activity can cause the transmitter to overheat

使用数字模式时，过多的 ALC 活动可能会导致发射机过热

All these choices are correct

所有这些选项都是正确的

#G4A12🔗

Which of the following is a common use of the dual-VFO feature on a transceiver?

以下哪项是收发器上双 VFO 功能的常见用途？

To allow transmitting on two frequencies at once

允许同时在两个频率上传输

To permit full duplex operation -- that is, transmitting and receiving at the same time

允许全双工操作——即同时发送和接收

To transmit on one frequency and listen on another

在一个频率上传输并在另一个频率上收听

✓ 正确答案

To improve frequency accuracy by allowing variable frequency output (VFO) operation

通过允许可变频率输出 (VFO) 操作来提高频率精度

#G4A13🔗

What is the purpose of using a receive attenuator?

使用接收衰减器的目的是什么？

To prevent receiver overload from strong incoming signals

防止接收器因强输入信号而过载

✓ 正确答案

To reduce the transmitter power when driving a linear amplifier

驱动线性放大器时降低发射器功率

To reduce power consumption when operating from batteries

减少电池供电时的功耗

To reduce excessive audio level on strong signals

减少强信号下过高的音频电平

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FCC G4A - 业余无线电实践与电台操作

小节 G4A：业余无线电实践与电台操作