FCC G9D - 天线与馈线系统

#G9D01🔗

Which of the following antenna types will be most effective as a near vertical incidence skywave (NVIS) antenna for short-skip communications on 40 meters during the day?

以下哪种天线类型作为近垂直入射天波 (NVIS) 天线在白天 40 米短跳通信中最有效？

A horizontal dipole placed between 1/ 10 and 1/4 wavelength above the ground

水平偶极子放置在距地面 1/ 10 和 1/4 波长之间

✓ 正确答案

A vertical antenna placed between 1/4 and 1/2 wavelength above the ground

放置在距地面 1/4 和 1/2 波长之间的垂直天线

A horizontal dipole placed at approximately 1/2 wavelength above the ground

水平偶极子放置在距地面约 1/2 波长处

A vertical dipole placed at approximately 1/2 wavelength above the ground

垂直偶极子放置在距地面约 1/2 波长处

#G9D02🔗

What is the feed point impedance of an end-fed half-wave antenna?

端馈半波天线的馈点阻抗是多少？

Very low

很低

Approximately 50 ohms

大约50欧姆

Approximately 300 ohms

约300欧姆

Very high

非常高

✓ 正确答案

#G9D03🔗

In which direction is the maximum radiation from a VHF/UHF “halo” antenna?

VHF/UHF“光环”天线的最大辐射方向是哪个？

Broadside to the plane of the halo

光晕平面的侧面

Opposite the feed point

馈电点对面

Omnidirectional in the plane of the halo

在光环平面内全向

✓ 正确答案

On the same side as the feed point

与馈电点同侧

#G9D04🔗

What is the primary function of antenna traps?

天线陷阱的主要功能是什么？

To enable multiband operation

启用多频段操作

✓ 正确答案

To notch spurious frequencies

陷波杂散频率

To provide balanced feed point impedance

提供平衡馈电点阻抗

To prevent out-of-band operation

防止带外操作

#G9D05🔗

What is an advantage of vertically stacking horizontally polarized Yagi antennas?

垂直堆叠水平极化八木天线有什么优点？

It allows quick selection of vertical or horizontal polarization

它允许快速选择垂直或水平偏振

It allows simultaneous vertical and horizontal polarization

它允许同时垂直和水平偏振

It narrows the main lobe in azimuth

它缩小了方位角的主瓣

It narrows the main lobe in elevation

它缩小了主瓣的高度

✓ 正确答案

#G9D06🔗

Which of the following is an advantage of a log-periodic antenna?

以下哪项是对数周期天线的优点？

Wide bandwidth

宽带宽

✓ 正确答案

Higher gain per element than a Yagi antenna

每个元件的增益比八木天线更高

Harmonic suppression

谐波抑制

Polarization diversity

极化分集

#G9D07🔗

Which of the following describes a log-periodic antenna?

以下哪项描述了对数周期天线？

Element length and spacing vary logarithmically along the boom

元件长度和间距沿吊杆呈对数变化

✓ 正确答案

Impedance varies periodically as a function of frequency

阻抗作为频率的函数周期性变化

Gain varies logarithmically as a function of frequency

增益随频率呈对数变化

SWR varies periodically as a function of boom length

SWR 作为吊杆长度的函数周期性变化

#G9D08🔗

How does a “screwdriver” mobile antenna adjust its feed point impedance?

“螺丝刀”移动天线如何调整其馈点阻抗？

By varying its body capacitance

通过改变其身体电容

By varying the base loading inductance

通过改变基本负载电感

✓ 正确答案

By extending and retracting the whip

通过伸出和缩回鞭子

By deploying a capacitance hat

通过部署电容帽

#G9D09🔗

What is the primary use of a Beverage antenna?

饮料天线的主要用途是什么？

Directional receiving for MF and low HF bands

中频和低高频频段的定向接收

✓ 正确答案

Directional transmitting for low HF bands

低 HF 频段的定向发射

Portable direction finding at higher HF frequencies

较高高频下的便携式测向

Portable direction finding at lower HF frequencies

较低高频下的便携式测向

#G9D10🔗

In which direction or directions does an electrically small loop (less than 1/10 wavelength in circumference) have nulls in its radiation pattern?

电学小环路（周长小于 1/10 波长）的辐射图在哪些方向上有零点？

In the plane of the loop

在环平面内

Broadside to the loop

宽边到循环

✓ 正确答案

Broadside and in the plane of the loop

侧面和环路平面内

Electrically small loops are omnidirectional

电气小环路是全向的

#G9D11🔗

Which of the following is a disadvantage of multiband antennas?

以下哪项是多频段天线的缺点？

They present low impedance on all design frequencies

它们在所有设计频率上均呈现低阻抗

They must be used with an antenna tuner

它们必须与天线调谐器一起使用

They must be fed with open wire line

必须用明线喂食

They have poor harmonic rejection

它们的谐波抑制能力很差

✓ 正确答案

#G9D12🔗

What is the common name of a dipole with a single central support?

具有单个中心支撑的偶极子的通用名称是什么？

Inverted V

倒V型

✓ 正确答案

Inverted L

倒L型

Sloper

斯洛珀

Lazy H

懒惰的H

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FCC G9D - 天线与馈线系统

小节 G9D：天线与馈线系统