Technician T3C: Propagation beyond the horizon
These are the 11 official questions in group T3C of the 2026–2030 Technician question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- T3C01Question 1
Why are simplex UHF signals rarely heard beyond their radio horizon?
- AThey are too weak to go very far
- BFCC regulations prohibit them from going more than 50 miles
- CUHF signals are usually not propagated by the ionosphere Correct
- DUHF signals are absorbed by the ionospheric D region
Why: The ionosphere usually doesn't return UHF signals, so they stay near the radio horizon.
- T3C02Question 2
What is a characteristic of HF communication compared with communications on VHF and higher frequencies?
- AHF antennas are generally smaller
- BHF accommodates wider bandwidth signals
- CLong-distance ionospheric propagation is far more common on HF Correct
- DThere is less atmospheric interference (static) on HF
Why: On HF, the ionosphere often bends signals back to Earth, so long-distance contacts are far more common.
- T3C03Question 3
What is one characteristic of VHF signals received via auroral backscatter?
- AThey are often received from 10,000 miles or more
- BThey are distorted, with a characteristic raspy sound Correct
- CThey occur only during winter nighttime hours
- DThey are generally strongest when your antenna is aimed west
Why: Signals reflected from the aurora are distorted and sound raspy.
- T3C04Question 4
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?
- ABackscatter
- BSporadic E Correct
- CD region absorption
- DGray-line propagation
Why: Sporadic E clouds bring occasional strong signals on 10, 6 and 2 meters from beyond the horizon.
- T3C05Question 5
Which of the following effects may allow radio signals to travel beyond obstructions between the transmitting and receiving stations?
- AKnife-edge diffraction Correct
- BFaraday rotation
- CQuantum tunneling
- DDoppler shift
Why: Knife-edge diffraction bends signals over sharp edges like a ridge or building.
- T3C06Question 6
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?
- ATropospheric ducting Correct
- BD region refraction
- CF2 region refraction
- DFaraday rotation
Why: Tropospheric ducting regularly carries VHF and UHF about 300 miles.
- T3C07Question 7
What band is best suited for communicating via meteor scatter?
- A33 centimeters
- B6 meters Correct
- C2 meters
- D70 centimeters
Why: 6 meters is the best band for meteor scatter.
- T3C08Question 8
What causes tropospheric ducting?
- ADischarges of lightning during electrical storms
- BSunspots and solar flares
- CUpdrafts from hurricanes and tornadoes
- DTemperature inversions in the atmosphere Correct
Why: Temperature inversions in the atmosphere create the ducts that carry signals.
- T3C09Question 9
What is generally the best time for long-distance 10-meter band propagation via the F region?
- AFrom dawn to shortly after sunset during periods of high sunspot activity Correct
- BFrom shortly after sunset to dawn during periods of high sunspot activity
- CFrom dawn to shortly after sunset during periods of low sunspot activity
- DFrom shortly after sunset to dawn during periods of low sunspot activity
Why: 10 meters via the F region is best from dawn until shortly after sunset when sunspots are high.
- T3C10Question 10
Which of the following bands may provide long-distance communications via the ionosphere’s F region during the peak of the sunspot cycle?
- A6 and 10 meters Correct
- B23 centimeters
- C70 centimeters and 1.25 meters
- DAll these choices are correct
Why: At the sunspot peak, the F region can support long-distance contacts on both 6 and 10 meters.
- T3C11Question 11
Why is the radio horizon for VHF and UHF signals more distant than the visual horizon?
- ARadio signals move somewhat faster than the speed of light
- BRadio waves are not blocked by dust particles
- CThe atmosphere refracts radio waves slightly Correct
- DRadio waves are blocked by dust particles
Why: The atmosphere bends radio waves slightly, so the radio horizon is a little past the visual one.