Why are simplex UHF signals rarely heard beyond their radio horizon?

What is a characteristic of HF communication compared with communications on VHF and higher frequencies?

What is one characteristic of VHF signals received via auroral backscatter?

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?

Which of the following effects may allow radio signals to travel beyond obstructions between the transmitting and receiving stations?

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?

What band is best suited for communicating via meteor scatter?

What causes tropospheric ducting?

What is generally the best time for long-distance 10-meter band propagation via the F region?

Which of the following bands may provide long-distance communications via the ionosphere’s F region during the peak of the sunspot cycle?

Why is the radio horizon for VHF and UHF signals more distant than the visual horizon?