FCC E9H - 天线与传输线系统

#E9H01🔗

When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?

构建饮料天线时，设计中应考虑以下哪些因素，以在所需频率下实现良好的性能？

Its overall length must not exceed 1/4 wavelength

其总长度不得超过1/4波长

It must be mounted more than 1 wavelength above ground

它必须安装在距地面 1 个波长以上的位置

It should be configured as a four-sided loop

应将其配置为四边环

It should be at least one wavelength long

它应该至少有一个波长长

✓ 正确答案

#E9H02🔗

Which is generally true for 160- and 80-meter receiving antennas?

对于 160 米和 80 米接收天线，哪一项通常是正确的？

Atmospheric noise is so high that directivity is much more important than losses

大气噪声如此之高，方向性比损耗重要得多

✓ 正确答案

They must be erected at least 1/2 wavelength above the ground to attain good directivity

它们必须安装在距地面至少 1/2 波长处才能获得良好的方向性

Low loss coax transmission line is essential for good performance

低损耗同轴传输线对于良好的性能至关重要

All these choices are correct

所有这些选项都是正确的

#E9H03🔗

What is receiving directivity factor (RDF)?

什么是接收方向性因子（RDF）？

Forward gain compared to the gain in the reverse direction

正向增益与反向增益的比较

Relative directivity compared to isotropic

与各向同性相比的相对方向性

Relative directivity compared to a dipole

与偶极子相比的相对方向性

Peak antenna gain compared to average gain over the hemisphere around and above the antenna

峰值天线增益与天线周围和上方半球的平均增益相比

✓ 正确答案

#E9H04🔗

What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna?

在小环测向天线周围放置静电屏蔽的目的是什么？

It adds capacitive loading, increasing the bandwidth of the antenna

它增加了电容负载，增加了天线的带宽

It eliminates unbalanced capacitive coupling to the antenna’s surroundings , improving the depth of its nulls

它消除了与天线周围环境的不平衡电容耦合，提高了零点深度

✓ 正确答案

It eliminates tracking errors caused by strong out-of-band signals

它消除了由强带外信号引起的跟踪误差

It increases signal strength by providing a better match to the feed line

它通过提供与馈线更好的匹配来增加信号强度

#E9H05🔗

What challenge is presented by a small wire-loop antenna for direction finding?

用于测向的小型线环天线面临哪些挑战？

It has a bidirectional null pattern

它有一个双向空模式

✓ 正确答案

It does not have a clearly defined null

它没有明确定义的 null

It is practical for use only on VHF and higher bands

仅适用于 VHF 和更高频段

All these choices are correct

所有这些选项都是正确的

#E9H06🔗

What indicates the correct value of terminating resistance for a Beverage antenna?

什么指示饮料天线终端电阻的正确值？

Maximum feed point DC resistance at the center of the desired frequency range

所需频率范围中心的最大馈电点直流电阻

Minimum low-angle front-to-back ratio at the design frequency

设计频率下最小低角度前后比

Maximum DC current in the terminating resistor

终端电阻中的最大直流电流

Minimum variation in SWR over the desired frequency range

所需频率范围内 SWR 的最小变化

✓ 正确答案

#E9H07🔗

What is the function of a Beverage antenna’s termination resistor?

饮料天线终端电阻的作用是什么？

Increase the front-to-side ratio

增加前后比

Absorb signals from the reverse direction

吸收反向信号

✓ 正确答案

Decrease SWR bandwidth

降低 SWR 带宽

Eliminate harmonic reception

消除谐波接收

#E9H08🔗

What is the function of a sense antenna?

感应天线的作用是什么？

It modifies the pattern of a DF antenna to provide a null in only one direction

它修改了 DF 天线的方向图，仅在一个方向上提供零点

✓ 正确答案

It increases the sensitivity of a DF antenna array

它提高了 DF 天线阵列的灵敏度

It allows DF antennas to receive signals at different vertical angles

允许DF天线以不同的垂直角度接收信号

It provides diversity reception that cancels multipath signals

它提供分集接收，消除多径信号

#E9H09🔗

What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?

单匝端接环（例如三角旗天线）会产生什么类型的辐射图？

Cardioid

心形

✓ 正确答案

Bidirectional

双向

Omnidirectional

全向

Hyperbolic

双曲线

#E9H10🔗

How can the output voltage of a multiple-turn receiving loop antenna be increased?

如何提高多匝接收环形天线的输出电压？

By reducing the permeability of the loop shield

通过降低环路屏蔽的磁导率

By utilizing high impedance wire for the coupling loop

利用高阻抗导线作为耦合环路

By increasing the number of turns and/or the area enclosed by the loop

通过增加匝数和/或环路所包围的面积

✓ 正确答案

All these choices are correct

所有这些选项都是正确的

#E9H11🔗

What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?

心形方向图天线的哪些特性使其可用于测向天线？

A very sharp peak

一个非常尖锐的峰

A single null

单个空值

✓ 正确答案

Broadband response

宽带响应

High radiation angle

高辐射角

← 上一节: E9G 📑 返回 E9 大纲下一节: E0A →

FCC E9H - 天线与传输线系统

小节 E9H：天线与传输线系统