What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?
两个间隔 1/2 波长并以 180 度异相馈电的 1/4 波长垂直天线会产生什么类型的辐射方向图？
CA figure-eight broadside to the axis of the array
阵列轴的八字形侧面
DA figure-eight oriented along the axis of the array
沿阵列轴方向的 8 字形
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?
两个间隔 1/4 波长并以 90 度异相馈电的 1/4 波长垂直天线会产生什么类型的辐射方向图？
BA figure-eight end-fire along the axis of the array
沿阵列轴的 8 字形端射
CA figure-eight broadside to the axis of the array
阵列轴的八字形侧面
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?
两个间隔 1/2 波长且同相馈电的 1/4 波长垂直天线会产生什么类型的辐射方向图？
CA figure-eight broadside to the axis of the array
阵列轴的八字形侧面
DA figure-eight end-fire along the axis of the array
沿阵列轴的 8 字形端射
What happens to the radiation pattern of an unterminated long wire antenna as the wire length is increased?
随着导线长度的增加，无端接的长导线天线的辐射方向图会发生什么变化？
AFewer lobes form with the major lobes increasing closer to broadside to the wire
随着主波瓣越来越靠近电线的侧面，形成的波瓣越来越少
BAdditional lobes form with major lobes increasingly aligned with the axis of the antenna
附加波瓣形成，主波瓣逐渐与天线轴对齐
CThe elevation angle increases, and the front-to-rear ratio decreases
仰角增大，前后比减小
DThe elevation angle increases, while the front-to-rear ratio is unaffected
仰角增大，前后比不受影响
What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?
在中心和一端之间而不是在中点之间馈电偏心馈电偶极子 (OCFD) 的目的是什么？
ATo create a similar feed point impedance on multiple bands
在多个频段上创建相似的馈电点阻抗
BTo suppress off-center lobes at higher frequencies
抑制较高频率下的偏心波瓣
CTo resonate the antenna across a wider range of frequencies
使天线在更广泛的频率范围内谐振
DTo reduce common-mode current coupling on the feed line shield
减少馈线屏蔽上的共模电流耦合
What is the effect of adding a terminating resistor to a rhombic or long-wire antenna?
在菱形或长线天线上添加终端电阻有什么影响？
AIt reflects the standing waves on the antenna elements back to the transmitter
它将天线元件上的驻波反射回发射器
BIt changes the radiation pattern from bidirectional to unidirectional
它将辐射方向图从双向更改为单向
CIt changes the radiation pattern from horizontal to vertical polarization
它将辐射方向图从水平偏振更改为垂直偏振
DIt decreases the ground loss
减少接地损耗
What is the approximate feed point impedance at the center of a two-wire half-wave folded dipole antenna?
两线半波折叠偶极天线中心的馈电点阻抗大约是多少？
What is a folded dipole antenna?
什么是折叠偶极子天线？
AA dipole one-quarter wavelength long
四分之一波长长的偶极子
BA center-fed dipole with the ends folded down 90 degrees at the midpoint of each side
两端馈电偶极子在每侧中点向下折叠 90 度
CA half - wave dipole with an additional parallel wire connecting its two ends
半波偶极子，两端有一根附加的平行线连接
DA dipole configured to provide forward gain
配置为提供前向增益的偶极子
Which of the following describes a G5RV antenna?
以下哪项描述了 G5RV 天线？
AA wire antenna center -fed through a specific length of open - wire line connected to a balun and coaxial feed line
通过连接到巴伦和同轴馈线的特定长度的明线进行中心馈电的线天线
BA multi-band trap antenna
多频段陷波天线
CA phased array antenna consisting of multiple loops
由多个环组成的相控阵天线
DA wide band dipole using shorted coaxial cable for the radiating elements and fed with a 4:1 balun
宽带偶极子，使用短路同轴电缆作为辐射元件，并由 4:1 巴伦馈电
Which of the following describes a Zepp antenna?
以下哪项描述了 Zepp 天线？
AA horizontal array capable of quickly changing the direction of maximum radiation by changing phasing lines
能够通过改变相位线快速改变最大辐射方向的水平阵列
BAn end- fed half - wavelength dipole
端馈半波长偶极子
CAn omni-directional antenna commonly used for satellite communications
常用于卫星通信的全向天线
DA vertical array capable of quickly changing the direction of maximum radiation by changing phasing lines
能够通过改变相位线快速改变最大辐射方向的垂直阵列
How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus soil?
安装在海水和土壤上的垂直极化天线的远场仰角方向图如何受到影响？
ARadiation at low angles decreases
低角度辐射减少
BAdditional lobes appear at higher elevation angles
额外的波瓣出现在较高的仰角处
CSeparate elevation lobes will combine into a single lobe
单独的高度波瓣将合并成一个波瓣
DRadiation at low angles increases
低角度辐射增加
Which of the following describes an extended double Zepp antenna?
以下哪项描述了扩展双 Zepp 天线？
AAn end-fed full-wave dipole antenna
端馈式全波偶极子天线
BA center-fed 1.5-wavelength dipole antenna
中心馈电 1.5 波长偶极子天线
CA center-fed 1. 25 -wavelength dipole antenna
中心馈电 1. 25 波长偶极子天线
DAn end-fed 2-wavelength dipole antenna
端馈式 2 波长偶极子天线
How does the radiation pattern of a horizontally polarized antenna vary with increasing height above ground?
水平极化天线的辐射方向图如何随着离地高度的增加而变化？
AThe takeoff angle of the lowest elevation lobe increases
最低仰角的起飞角增加
BThe takeoff angle of the lowest elevation lobe decreases
最低仰角的起飞角减小
CThe horizontal beamwidth increases
水平波束宽度增加
DThe horizontal beamwidth decreases
水平波束宽度减小
How does the radiation pattern of a horizontally-polarized antenna mounted above a long slope compare with the same antenna mounted above flat ground?
安装在长坡上的水平极化天线的辐射方向图与安装在平坦地面上的相同天线相比如何？
AThe main lobe takeoff angle increases in the downhill direction
主瓣起飞角沿下坡方向增大
BThe main lobe takeoff angle decreases in the downhill direction
主瓣起飞角沿下坡方向减小
CThe horizontal beamwidth decreases in the downhill direction
水平波束宽度沿下坡方向减小
DThe horizontal beamwidth increases in the uphill direction
水平波束宽度在上坡方向增加
