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

1. A They are too weak to go very far
2. B FCC regulations prohibit them from going more than 50 miles
3. C UHF signals are usually not propagated by the ionosphere
4. D UHF signals are absorbed by the ionospheric D region

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

1. A HF antennas are generally smaller
2. B HF accommodates wider bandwidth signals
3. C Long-distance ionospheric propagation is far more common on HF
4. D There is less atmospheric interference (static) on HF

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

1. A They are often received from 10,000 miles or more
2. B They are distorted, with a characteristic raspy sound
3. C They occur only during winter nighttime hours
4. D They are generally strongest when your antenna is aimed west

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?

1. A Backscatter
2. B Sporadic E
3. C D region absorption
4. D Gray-line propagation

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

1. A Knife-edge diffraction
2. B Faraday rotation
3. C Quantum tunneling
4. D Doppler shift

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?

1. A Tropospheric ducting
2. B D region refraction
3. C F2 region refraction
4. D Faraday rotation

What band is best suited for communicating via meteor scatter?

1. A 33 centimeters
2. B 6 meters
3. C 2 meters
4. D 70 centimeters

What causes tropospheric ducting?

1. A Discharges of lightning during electrical storms
2. B Sunspots and solar flares
3. C Updrafts from hurricanes and tornadoes
4. D Temperature inversions in the atmosphere

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

1. A From dawn to shortly after sunset during periods of high sunspot activity
2. B From shortly after sunset to dawn during periods of high sunspot activity
3. C From dawn to shortly after sunset during periods of low sunspot activity
4. D From shortly after sunset to dawn during periods of low sunspot activity

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

1. A 6 and 10 meters
2. B 23 centimeters
3. C 70 centimeters and 1.25 meters
4. D All these choices are correct

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

1. A Radio signals move somewhat faster than the speed of light
2. B Radio waves are not blocked by dust particles
3. C The atmosphere refracts radio waves slightly
4. D Radio waves are blocked by dust particles