Question
Why are simplex UHF signals rarely heard beyond their radio horizon?
Answer Options
- A) They are too weak to go very far
- B) FCC regulations prohibit them from going more than 50 miles
- C) UHF signals are usually not propagated by the ionosphere
- D) UHF signals are absorbed by the ionospheric D region
Correct Answer: C
Explanation
UHF signals (300 MHz to 3000 MHz) have wavelengths that are too short to be routinely refracted (bent back toward Earth) by the charged particles in the ionosphere (T3A11). The ionosphere simply lets them pass right through and into space.
Because of this, UHF signals are typically limited to line-of-sight communication, with a small extension due to atmospheric refraction known as the radio horizon (T3C11). Therefore, they are rarely heard beyond this radio horizon, making long-distance communication (DX) on UHF much more difficult than on HF bands.
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