#T3C01🔗
Why are simplex UHF signals rarely heard beyond their radio horizon?
为什么单工 UHF 信号很少在其无线电范围之外听到？
#T3C02🔗
What is a characteristic of HF communication compared with communications on VHF and higher frequencies?
与 VHF 和更高频率的通信相比，HF 通信的特点是什么？
#T3C03🔗
What is one characteristic of VHF signals received via auroral backscatter?
通过极光反向散射接收的 VHF 信号的特征之一是什么？
#T3C04🔗
Which of the following types of propagation is most commonly associated with occasional strong signals on the 10-, 6-, and 2-meter bands from beyond the radio horizon?
以下哪种传播类型最常与来自无线电地平线以外的 10、6 和 2 米波段上的偶尔强信号相关联？
#T3C05🔗
Which of the following effects may allow radio signals to travel beyond obstructions between the transmitting and receiving stations?
以下哪种效应可能允许无线电信号在发射站和接收站之间越过障碍物传播？
#T3C06🔗
What type of propagation is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
哪种类型的传播能够定期在大约 300 英里的范围内进行超视距 VHF 和 UHF 通信？
#T3C09🔗
What is generally the best time for long-distance 10-meter band propagation via the F region?
通过 F 区进行长距离 10 米波段传播的最佳时间通常是在什么时间？
#T3C10🔗
Which of the following bands may provide long-distance communications via the ionosphere’s F region during the peak of the sunspot cycle?
在太阳黑子周期的高峰期，以下哪个频段可以通过电离层的 F 区域提供长距离通信？
#T3C11🔗
Why is the radio horizon for VHF and UHF signals more distant than the visual horizon?
为什么 VHF 和 UHF 信号的无线电地平线比视觉地平线更远？
