Question
Which frequency will have the least attenuation for long-distance skip propagation?
Answer Options
- A) Just below the MUF
- B) Just above the LUF
- C) Just below the critical frequency
- D) Just above the critical frequency
Correct Answer: A
Explanation
For long-distance propagation using skywave, a radio wave must be refracted back to Earth by the ionosphere, and it must experience minimal signal absorption. The lowest possible attenuation, and thus the strongest received signal, occurs when the operating frequency is just below the Maximum Usable Frequency (MUF).
At frequencies just below the MUF, the signal travels through the ionosphere with the least amount of loss, primarily because the ray angle is shallowest, resulting in fewer hops for a given distance and less exposure to the lower, absorbing D-region of the ionosphere. Operating too far below the MUF increases absorption, especially on the lower frequencies.
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